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Evaluation of miticides for the control of two-spotted mite Tetranychus urticae Koch on field roses in southern Queensland
Evaluation of miticides for the control of twos p o t t e d m i t e Tetranychus urtlcae K o c h on f i e l d r o s e s in s o u t h e r n Q u e e n s l a n d N. GOUGH
Department of Primary Industries, Agricultural Research Laboratories, Meiers Road, Indooroopil~, Queensland, Australia 4068
ABSTRACT. The potential of miticides to control two-spotted mite (Tetranychus urticae Koch) on field roses in southern Queensland was examined by testing 21 compounds at up to three sites. These populations had extensive past exposure to miticides. Bifenthrin, fluvalinate, azocyclotin and cyhexatin were effective everywhere. Control by fenbutatin oxide varied greatly between sites. Clofentezine and hexythiazox gave excellent control on populations not previously exposed but both were completely ineffective, due to resistance, at one site where clofentezine had been applied repeatedly for 2 years before these trials. Propargite was effective overall whereas bromopropylate, dicofol plus tetradifon, dienochlor and sulphur were largely ineffective. Different organophosphates tested at one site gave highly variable control and here both aldicarb and phorate applied as granules were ineffective. The most important miticides were tested for phytotoxicity. The poor prospects for future chemical control on flower crops are discussed in the light of multiple resistance. KEYWORDS: Two-spotted mite; Tetranychus urticae; roses; miticides; clofentezineand hexythiazox resistance
Introduction Two-spotted mite, Tetranychus urticae Koch, is the major pest of roses in Queensland where it has been controlled traditionally by chemicals. Although the industry is of considerable importance there has never been a thorough examination of the effectiveness of miticides for use on roses (or other flower crops) in Queensland. In addition to the older compounds, new miticides such as clofentezine, hexythiazox, bifenthrin and fluvalinate have recently become available. M a n y miticides are phytotoxic to roses (Mansour and Plaut, 1979) so this aspect must be considered as well as efficacy. Although the ovicides clofentezine (e.g. Bryan, Geering and Reid, 1981; Aveyard, Peregrin and Bryan, 1986; Neal, McIntosh and Gott, 1986) and hexythiazox (Hoy and Ouyang, 1986) have been examined, little of the work has been done on ornamentals. Bifenthrin has been used mainly as an insecticide although Yost, Ferrentino and Parrella (1986) and Robinson and Teetes (1987) found it very effective against Tetranychus spp. Fluvalinate is effective against two-spotted mite (e.g. Price, 1981; Robb, Virzi and Parrella, 1985) and has a low phytotoxicity to ornamentals (Osborne, 1986).
Gough and Abdul Q a y y u m (1987) used clof~ntezine and fluvalinate (among other miticides) against 7-. urticae on fuchsias and examined phytotoxicity. Overall, however, there are insufficient easily accessible data on ornamentals enabling a comparison of these new chemicals with more traditional ones. In Queensland T. urticae reproduces rapidly for most of the year and rose growers may apply 15-20 miticide sprays annually, conditions favouring the swift development of miticide resistance (Overmeer, Van Zon and Helle, 1975). Recently there have been m a n y complaints that chemical control is becoming more difficult. The present work was aimed at evaluating a wide range of miticides tbr efficacy and phytotoxicity on field roses. It was considered important to determine whether control failures were due to inadequate spray application--a factor that could be remedied or to miticide inefficacy. The trials were therefore designed with frequent application of miticide and good spray coverage so that the possibility of failure due to extraneous factors was greatly reduced. The aim was not to simulate commercial spray schedules or to demonstrate residual action but to determine, in this area with a history of intensive usage, which miticides had potential to control T. urlicae.
0261-2194/90/02/1)119 09 ((~) 1990Bmterworth& Co (Publishers) Ltd CROP PROTECTION Vol. 9 April 1990, 119-127
120
Control of mites on field roses
Materials and methods
Effcacy trials Five trials were conducted on three commercial rose farms in which control failures with miticides had been reported. As most Queensland rose growers have problems controlling mites, these farms are not unusual. Trial 1 began in March 1984 in part of a 2 ha rose farm at Redland Bay which had been established for at least 10 years. Trials 2 4 were conducted between September 1986 and M a y 1987 in a rose farm at Advancetown which had been established between 6 and 7 years and Trial 5 was conducted at Cleveland in a patch of roses about 9 years old. Growers do not always keep accurate records so complete spray histories are not available. On all three farms bifenthrin, dienochlor, fluvalinate and hexythiazox had never been used. At Redland Bay clofentezine had never been sprayed. Dicofol had been used in the past and cyhexatin had been applied frequently (almost monthly) for several years immediately before Trial 1. At Advancetown (Trials 2 4), dicofol plus tetradifon had been used briefly some years previously and then again (seven times) in the year before the trials. Cyhexatin had been applied for about four years before the trials. Initially it was sprayed very thoroughly by hand, sometimes two applications close together. This was done two or three times a year. In the year before the trials it was applied singly three times. Although fenbutatin oxide was sprayed five times in the year before the trials it had not been used before. Clofentezine and propargite had never been used. Organophosphorous chemicals had been applied extensively for insect control. The mites at Cleveland (Trial 5) had the heaviest exposure to chemicals. Clofentezine had been used alone or alternated with febutatinoxide or propargite for 2 years before these trials, sprays being applied monthly or more frequently when control was poor. Previously, cyhexatin and propargite formed the basis of the spray schedule, having been used often for at least 5 years. Dicofol had been used early in the life of the plantation. Mature rose bushes (1.5 2 m high and about 5 years old) of the following varieties were used: Trial 1, Queen Elizabeth; Trials 2, 3, 4, M r Lincoln; Trial 5, M r Lincoln (three replicates) and R o u n d a l a y (two replicates). The experimental plan for each trial was a randomized block with five replicates, the experimental unit being a single rose bush. Pretreatment counts were conducted. In some trials these showed systematic variation due to inadequate spray penetration by the growers' equipment (i.e. the inner rows of a bed had more mites than the outside rows) and treatments were blocked along the rows. In Trial 5 blocking was by rose variety. On each sampling occasion five single (not compound) leaves per bush were chosen between waist and
CROP PROTECTION Vol. 9 April 1990
shoulder height. Very young and obviously senescent leaves were avoided to reduce random variation in the numbers of mites. Leaves were examined with a stereomicroscope immediately after being picked and the mites counted. The total number of all motile stages on the five leaves was used for the analysis of variance. Either a x/(x + 0-5) or a log x + 1 transformation was used, depending on the number of mites. The equivalent mean number of mites per leaf was calculated by back transformation. Chemicals tested, and their formulations were as shown in Table 1. The rates at which miticides were applied are given in Tables ~ 6 . In Trial 1 spray was applied using a Cooper-Pegler CP3 Mark 2 knapsack spray operating at about 311097 Newtons m -~ with a hollow conespray nozzle. In all other trials spray was applied with a 51 hand pressurized atomizer (4042 Killaspray 8) with an adjustable nozzle. Chemicals were applied to run off. Wetting agents were used only when recommended by the manufacturer as in Tables 2 6. Untreated bushes were sprayed either with water or water plus wetting agent. Precautions were taken to prevent drift. Dates of spraying are as given in Tables 2 to 6. The manufacturers of some chemicals such as dienochlor (which are effective on active stages but not on eggs) recommend two sprays a week apart in hot weather or on well-established populations (Zoecon Corporation, 1982). This allows eggs surviving the first spray to hatch and the larvae are destroyed by the second spray. This regimen was adopted and was found to be very suitable for determining the potential of miticides. The possibility of inadequate spray coverage was eliminated. The influence of sporadic heavy rain was minimized and ineffective chemicals were quickly recognized. Where both counting and spraying were performed on the same day, the former was done in the morning and the latter in the afternoon. Granules in Trials 2 and 3 were dug into the topsoil (on the date of the first spray) in a square metre around the base of the treated bushes. In Trial 2 aldicarb was reapplied 6 weeks after the beginning of the trial on 24 October. In Trial 3 about 30 1 water was sprinkled on to each plot (bush) after the granules were applied to ensure moist conditions for chemical release and uptake. As trials were conducted on commercial rose farms, treatments recognized as ineffectual in Trials 2 and 3 were terminated early by overspraying with fluvalinate to reduce damage (Tables 3 and 4).
Phytoxicity to leaves and flowers Notes were made on phototoxicity to the leaves in most trials, including a detailed examination during a burst of new growth in Trial 5 at Cleveland. Sprays were applied on 18 and 25 March 1987 and
N. GOUGH TABLE 1.
121
Chemicals tested
Common name
Formulation°
Aldicarb Azocyclotin Bifenthrin
10 % G WP25 EC 10
Bromopropylate Chlorpyrifos Clofentezine Cyhexatin Demeton-S-methyl Dicofol Dienochlor Dimethoate Fenbutatin oxide Fluvalinate Hexythiazox Methidathion Monocrotophos Phorate
EC50 EC50 WP50 ; F50 F60; WP50 EC25 EC24 F48 EC30 F55 F48 WP10 EC40 EC40 10%G in inert plastic polymer ~ WP30 WP25 WP80 EC7.5
Propargite Quinomethionate Sulphur Tctradifon
IUPAC chemical name 2-Methyl-2- (methylthio)propionaldehyde O-methylcarbamoyloxime tri(Cyclohexyl)- 1H- 1,2,4-triazol-l-yhin 2-Methylbiphenyl-3-ylmethyl (Z)-(IRS,3RS)-3-(2-chloro-3,3,3-triflu°r°pr°p-l-enyl)-2,2-dimethylcycl°pr°panecarboxylate Isopropyl 4,4'-dibromobenzilate O,O-Diethyl O-3,5,6-trichloro-2-pyridyl phosphorothioate 3,6-bis(2-Chlorophenyl)- 1,2,4,5-tetrazine Tricyclohexyhin hydroxide S-2-Ethyhhioethyl O,O-dimethyl phosphorothioate 2,2,2-Trichloro- 1,1-bis(4-chlorophenyl)ethanol Perchloro- 1, l'-bicyclopenta-2,4-diene O,O-Dimethyl S-methylcarbamoylmethyl phosphorodithioate bis[tris(2-Methyl-2-phenylpropyl) tin] oxide (RS)-~-Cyano-3-phenoxybenzyl N- (2-chloro-~,~,~-trifluoro-p-tolyl-D-valinate (4RS, 5RS)-5- (4-Chlorophenyl)-N-cyclohexyl-4-methyl-2-oxo-1,3-thiazolidine-3-carboxamide S-2,3-Dihydro-5-methoxy-2-oxo-l,3,4-thiadiazol-3-ylmethyl O,O-dimethyl phosphorodithioate Dimethyl (E)-l-methyl-2-(methylcarbamoyl)vinyl phosphate O,0-Diethyl S-ethyhhiomethyl phosphorodithioate
2-(4-tert-Butylphenoxy)cyclohexyl
prop-2-ynyl sulphite 6-Methyl- 1,3-dithiolo [4,5-b] quinoxalin-2-one Sulphur 4-Chlorophenyl 2,4,5-trichlorophenyl sulphone
" G, granules; WP, wettable powder; EC, emulsifiable concentrate; F, flowable; h Suscon Controlled Release Granules: Suscon is the Registered Trade Name of C.F.L., an I ncitec Company
TABLE 2. The cfl'ects of various miticides on the number of motile T. urticae per leaf Trial 1, Redland Bay Chemical treatment and concentratitm (g a.i. 1 I:
Fluvalinate 0-09 Propargite 0.6 Azocyclotin 0.2 Dicofol plus tetradifon 0.5 + 0.2 Cyhexatin ~ 0.2 Clofentezine h 0.3 Oxythioquin(~x (I. 13 Dicofol 0.5 Dienochlt)r' (}.3 Fenl)utatin oxide 0.2 Water + welling agent'
Synthetic pyrethroids
Equivalent mean number of mites per leaf Pretreatment 7March 1984
12March 1984
Results
19March 1984
55-1 38-5 74-6 83.2
a a a a
5.2 6.0 11.8 9.0
a a abe ab
0.1 0.3 1.0 1.1
a ab ab ab
84.6 66.3 59.5 105-4 66.0 86-7 84"2
a a a a a a a
5.5 10.0 11.9 21.4 30.1 49.0 91"3
a abc abc bcd cde de e
1.4 1-8 1.9 10-6 11-7 14.7 20"2
ab b b c c c c
Sprays applied all 7. 14 March 1984; numbers followed by different letters difl'er at P = (I.05 Method (ffleast significant difl~rence, log x + 1 transformation used for analysis of variance; " flowable formulation; bwettable powder formulation; ' wetting agcm iAgral 60) used at the rate of 0-18 ml 1 i
damage was assessed on 26 March. Flowers and mature buds of M r Lincoln were removed ti~om the bushes immediately after being sprayed and held in the shade for a day before examination. Phytotoxicity to the longer-lasting flowers of the varieties Samantha and Gabriella was also assessed. Three newly opened flowers and three buds (commercial maturity) were picked from a glasshouse and tested against the miticides used in Trial 5. They were placed in a bucket of water and sprayed tbr 3 s with the pressurized hand applicator as for the main trial. Damage to the open flowers was assessed 1 day and damage to the buds 1 and 2 days after spray application.
Fluvalinate was used on all three populations and always gave outstanding chemical control (Tables 2-4 and 6). Bifenthrin was also highly effective (Tables 5 and 6).
Organotins On all three populations cyhexatin produced acceptable control (Tables 2, 3 and 6) as did azocyclotin where it was used (Tables 2 and 6). Fenbutatin oxide was as effective as cyhexatin at Advancetown ( Table 4) but was completely ineffective at Redland Bay Table 2) and Cleveland (Table 6).
Propargite Propargite was extremely effective at Redland Bay ( Table 2) and Advancetown ( Table 3), equalling cyhexatin and fluvalinate and generally reducing numbers of mites to one or less per leaf. It was less effective at Cleveland ( Table 6) where it was significantly inferior to the synthetic pyrethroids, cyhexatin and azocyclotin.
Clofentezine Clofentezine applied at 0.3 g a.i. 1 - 1 at Redland Bay ( Table 2) and Advancetown ( Table 3) or at 0-2 g a.i. 1-1 (Advancetown, Table 4) was as effective as cyhexatin in reducing and suppressing two-spotted mite. At Cleveland (Table 6) it was completely ineffective.
CROP
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Vol. 9 April 1990
Control o f mites on f i e l d roses
122 TABLE 3.
T h e effects o f v a r i o u s miticides o n the n u m b e r o f motile T. urticae p e r leaf. T r i a l 2, A d v a n c e t o w n
Chemical treatment and concentration (g a.i. 1 - 1)
E q u i v a l e n t m e a n n u m b e r o f mites p e r l e a f Pretreatment 12 S e p t e m b e r 1986 a
H e x y t h i a z o x 0.05 C y h e x a t i n c 0-2 F l u v a l i n a t e 0.1 BromopropylateO.75 Clofentezine ~ 0.3 P r o p a r g i t e 0.3 D i e n o c h l o r 0.36 Dicofol plus t e t r a d i f o n 0.5 + 0.2 Aldicarb0-75 ga.i.m -2 Water only
0.4 0.6 0.6 0-9 1.9 1.4 0.6 0.8
26 S e p t e m b e r 1986 a
a a a a a a a a
0.2 0.1 0 a 0.3 0.3 0.1 0.4 0.2
0.8a 1.3 a
10 O c t o b e r 1986 a
ab a
0.2 0-5 0.6 1.1 1.2 1-2 3.9 4.5
ab ab a ab ab
1.6bc 3.6 c
24 O c t o b e r 1986 b
a a a ab ab ab b b
7.5bc 19-5 c
0.25 0.03 0-1 0.8 0-9 0.2 2.3 3.1
a a ab b b ab b bc
11.3 c 44.4 d
6 November 1986" 0.9 0.4 0.3 5.2 0.8 1-0 15.9 10-1
13 N o v e m b e r 1986 b
ab a a b ab ab bc b
0.9 a b 0-2 a b 0.1 a 1.9 b 0.6 a b 0.7 a b 26.8 c 2-4 b
5.1 b 78.0 c
21 N o v e m b e r 1986 ° 0.4 0.7 0-4 17.7 1-0 0.2
2 December 1986 a
ab a ab c b ab
0-2 a 0.2 a 0.2 a 1.4 a 1.7 a
19.2 c
18.1 c
Sprays applied on 12, 19 September, I0, 17 October, 6, 21 November 1986; granules applied 12 September and 24 October; numbers followed by different letters differ at P = 0-05; method of least significant difference; " x/~ + 0-5, and b log x + 1 transformation used for analysis of variance; c WP formulation; d flowable formulation
TABLE 4. T h e effects o f v a r i o u s miticides o n the n u m b e r o f motile 7-. urticae p e r leaf. T r i a l 3, A d v a n c e t o w n
TABLE 5. T h e effects o f v a r i o u s c h e m i c a l s o n the n u m b e r of motile T. urticae p e r leaf. T r i a l 4, A d v a n c e t o w n
Chemical treatment and concentration (g a.i. 1 - l)
Chemical treatment and concentration (g a.i. 1 I)
E q u i v a l e n t m e a n n u m b e r o f mites p e r l e a f Pretreatment 1 D e c e m b e r 22 D e c e m b e r 1986 ~ 1986 a
F l u v a l i n a t e 0-1 F e n b u t a t i n o x i d e 0.2 M o n o c r o t o p h o s 0.6 Clofentezine ~ 0-2 S u l p h u r 3.1 A l d i c a r b 1 g a.i. m - 2 P h o r a t e 0-8 g a.i. m - 2 P h o r a t e 1.6 g a.i. m - 2 Water only
9.5 20-4 12.6 19.6 15.9 13-0 14-5 12.5 13.3
a a a a a a a a a
0.2 0-4 0.5 2.2 69-1 69-3 104.7 125.3 67.2
a ab ab b c c c c c
9January 1987 a 1.4 0.9 0.7 2.4
23January 1987 b
a a a a
Pretreatment 13 M a y '87
0.4 a 0 a 0.9 a 0.1 a --
Bifenthrin" 0-04 M o n o c r o t o p h o s ~ 0.6 C h l o r p y r i f o s " 0.75 M e t h i d a t h i o n b 0-5 D i m e t h o a t e b 0.3 Demeton-S-methyl ~ 0.25 Water only h
75.2 b -
6.2 11.3 5.7 17.1 8.5
a a a a a
11.3 a 9.9 a
25 M a y '87
0-4 0.3 0.5 10-5 8-2
a a a b b
2 June '87 0 a 0.6 1.6 2.1 7.3
21.6 b 9.5 b
a bc bc cd
13.5 d 10.0 d
"Sprays applied on 18 May 1987; bsprays applied on 18 and 25 May 1987; numbers followed by different letters differ at P = 0.05; method of least significant difference; log x + 1 transformation used for analysis of variance
Sprays applied on 3, I l, 22 December 1986, 9 J a n u a r y I987; granules applied with the first spray; numbers followed by different letters differ at P = 0.05; method of least significant difference; " log x + 1 and b ~/x + 0.5 transformations used for analysis of variance; ' flowable formulation
TABLE 6.
E q u i v a l e n t m e a n n u m b e r o f mites p e r leaf
T h e effects o f v a r i o u s miticides o n the n u m b e r of motile 7-. urticae p e r leaf. T r i a l 5, C l e v e l a n d
Chemical treatment and concentration (g a.i. 1 - 1)
B i f e n t h r i n 0.04 F l u v a l i n a t e 0.1 C y h e x a t i n 0.2 A z o c y c l o t i n 0-2 P r o p a r g i t e 0.3 D i e n o c h l o r 0.36 a B r o m o p r o p y l a t e 0.5 Dicofol plus t e t r a d i f o n O-5 + 0.2 Dicofol 0.5 F e n b u t a t i n oxide 0-2 H e x y t h i a z o x 0-05 Clofentezine 0.2 Water only a
E q u i v a l e n t m e a n n u m b e r o f mites p e r l e a f Pretreatment 16 F e b r u a r y 1987
26 F e b r u a r y 1987
15.1 13.5 7.4 17.3 13.2 4.4 5.2 12.4
a a a a a a a a
0.4 1.7 2.3 0.7 9.3 6.7 4-3 6.2
a b bc ab cd c bc c
3.8 8.7 10-8 6.9 9.3
a a a a a
16-I 17.8 16.6 23.4 23.6
cd cd cd d d
4 March 1987 0.03 a 0-1 a 0.1 a 0.2 a 4.0 b 5.8 bc 4.8 b 3.7 b 15-7 25.3 15.9 52.7 55-8
cd de d e e
16 M a r c h 1987 0.3 0.3 1.0 2.2 5-3 7.7 7.0 10-5
a a ab b bc cd bcd cd
12.2 6-4 17.3 18.7 20.8
ce bcd cd cd d
1 April 1987
9 April 1987
22 April 1987
0.1 0.2 0.5 0.9 6.1 7.6 9.8 5-5
a a ab b c cd cde c
1-9 1-0 1.8 6.0 9.3 11.0 24.3 18.3
a a a b bc bc cd cd
0.03 a 0.2 a b 1.4 c 0.9 bc 5-3 d 11.4 de 5.7 d 16.1 ef
22-8 ef 16.7 d e f 26.6 f 24.8 f 44.8 f
32-1 41.9 41.4 32-7 40.8
d d d d d
18.7 57.6 52.8 44-0 47.0
efg h gh fgh gh
Sprays applied on 18, 26 February, 18, 25 March, 13 April 1987; ~ wetting agent (0-1 ml Agral 60 1 J) used from 18 March; numbers followed by different letters differ at P = 0-05; method of least significant difference; log x + 1 transformation used for analysis of variance
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123
N. GOU6H
Hexythiazox
Aldicarb
Hexythiazox at Advancetown was very effective ( Table 3). At Cleveland ( Table 6) it produced a slight decline in mite numbers 2 weeks after the start of spraying but after that it was completely ineffective.
Aldicarb was used only at Advancetown. It could neither prevent the build-up of mites (Table 3) nor reduce established populations (Table 4). Although the mean number of mites per leaf was significantly less than the untreated, on 6 November (Table 3) two of the five trees were showing obvious mite damage. By 13 November mite damage was widespread on three of the five trees. This was despite a second application of aldicarb on 24 October. Rainfall and irrigation were adequate in this trial to allow good chemical uptake from the granules (68 mm in the latter half of September, 122 mm in October and 42 mm in the first two weeks of November). In Trial 3 aldicarb showed no sign of controlling the mites three weeks after the trial began and the treatment was oversprayed to prevent damage (Table 4).
Organochlorines and tetradifon Although dicofol plus tetradifon and bromopropylate delayed the build-up of mites at both Advancetown and Cleveland (Tables 3 and 6) they soon proved ineffective. Leaf damage occurred after about 8 weeks and when spraying ceased even for a period of 2 weeks large populations built up. Dicofol plus tetradifon was more effective than dicofol at Redland Bay (Table 2) and for parts of the trial at Cleveland (Table 6).
Organophosphorous chemicals Organophosphorous chemicals were used only at Advancetown. In Trial 3 monocrotophos produced outstanding control whereas phorate applied as granules did not reduce numbers at all (Table 4). Because of this apparent contradiction a larger range of organophosphates was used in Trial 4. Single sprays of monocrotophos and chlorpyrifos were highly effective whereas two sprays of methidathion were necessary to achieve the same level of control. Dimethoate and demeton-S-methyl were completely ineffective ( Table 5).
Dienochlor Dienochlor was relatively ineffective, with or without a wetting agent, in either suppressing established populations to an acceptably low level ( Table 2) or in preventing their build up ( Tables 3 and 6). In Trials 2 and 5 leaf damage occurred after 7-8 weeks despite four sprays of dienochlor applied according to the manufacturer's instructions. The mean number of mites per leaf estimated by log transformation was sometimes misleading and in Trial 5 on 22 April 1987 two of the five trees were heavily infested although the overall mean number per leaf was not high ( Table 6).
Quinomethionate Quinomethionate was as effective as cyhexatin in Trial 1 (Table 2). It was not used more widely because of its known phytoxicity which raised doubts about its commercial potential for ornamentals.
Sulphur Sulphur was used once (Table 4) and was ineffective.
Phytotoxicity to leaves and flowers Symptoms induced by the formulations can be divided into two categories (Table 7). O f the miticides causing negligible damage, bromopropylate (EC) was the most phytotoxic, occasionally causing a yellow mottling of young leaves of M r Lincoln. In the second category, where there was pronounced damage, propargite (WP) marked the flowers but had little effect on the leaves. Dicofol (EC) (alone or in mixture) had the opposite action, sometimes severely damaging very young growth but with little effect on the flowers. Cyhexatin flowable was more phytotoxic than the wettable powder formulation and azocyclotin (WP) was severely phytotoxic. M a n y growers avoided cyhexatin flowable and none used azoeyclotin as they were considered too phytotoxic. With many miticides, damage occurred only to very young, reddish leaves. When more mature leaves were sprayed, damage was greatly reduced. Phytotoxicity in glasshouses is more severe, with many more compounds unacceptable.
Discussion The most striking feature of the data is that so many miticides were shown to be ineffective. Adequate spray coverage was apparently achieved in all the trials, as fluvalinate, to which populations had never been exposed, was always highly effective. Fluvalinate has been found to be consistently effective on two-spotted mite on fuchsias (Gough and Q a y y u m , 1987) and other ornamental crops in Queensland (N. Gough, unpublished data). Trial 5 was the only one influenced by heavy rainfall and the decline in numbers on the untreated leaves between 4 March (55.8 mites leaf -1) and 16 March (20-8 mites leaf -~) was probably due to 92 mm of rain which fell in that period. U p to 6 mm of rain fell a few hours after the second spray on 26 February but this seems to have little influence on the results. T. urticae
CROP PROTECTION Vol. 9 April 1990
Control of mites on field roses
124
TABLE7. Synopsisof the effectsofmiticideson the leaves (varietyMr Lincoln)and flowersand buds of roses (Gabriella,Mr Lincoln,Samantha) under field conditions Miticide formulationand concentration (g a.i. 1- 1)
Effecton leaves
Effect on flowersand buds
Category 1. Negligibleor slight damage Bifenthrin EC 0-04 BromopropylateEC 0.5 DienochlorF 0-36 Fenbutatin oxide F 0.2 Fluvalinate F 0.1 HexythiazoxWP 0.05
Little damage, minor leaf distortion or dimpling when applied to very young leaves
Negligible damage, insignificantshine or residues where spray landed on petals. Buds perfect
Category 2. Noticeableor pronounceddamage DicofolEC 0-5 Dicofol EC plus tetradifon EC 0.5 + 0.2
Moderate to severeleaf distortion and reduced leaf size on veryyoung growth. Leaf dimpling
Slight damage, residue and a few shiny spots on flowers
Propargite WP 0.3 Cyhexatin WP 0.2 Cyhexatin F 0-2
Propargite has little effecton leaves, cyhexatinF causes severe leaf distortion
Petals of all varieties pock-marked,as buds open petal tips are damaged. Propargite damage is least severe
AzocyclotinWP 0.2
Severe dimpling and leaf distortion
Severe damage to flowersand buds
is notorious for its ability to develop resistance to miticides ( C r a n h a m and Helle, 1985). Rosegrowers in Q u e e n s l a n d are a m o n g the heaviest users o f miticides in the world. F u r t h e r m o r e , their roses h a r b o u r p e r m a n e n t populations o f mites which exist as long as the plantings (up to 10 years or more) and are thus exposed to a great a r r a y o f chemicals. As there was no p a t t e r n o f r a n d o m spray failure, resistance seems the most logical e x p l a n a t i o n for the p o o r p e r f o r m a n c e o f m a n y chemicals to which T. urticae has b e c o m e resistant in the past. Clofentezine was surprisingly effective w h e n used in the u n o r t h o d o x m a n n e r o f two sprays a week a p a r t on p o p u l a t i o n s which h a d not previously been exposed to it at R e d l a n d Bay and A d v a n c e t o w n . A v e y a r d et al. (1986) showed that clofentezine was very effective on eggs, larvae and p r o t o n y m p h s , b u t caused only 2 0 % m o r t a l i t y to d u e t o n y m p h s a n d was ineffective against adults. At 25-5°C, female T. urticae have an average longevity of 18.3 days (Bengston, 1969). W i t h high d e u t o n y m p h a l survival one would not expect the virtual elimination o f p o p u l a tions within 12 (Table 2) or 14 days (N. G o u g h , u n p u b l i s h e d d a t a on o t h e r o r n a m e n t a l s ) as freq u e n t l y occurred. H e x y t h i a z o x was similarly effective at A d v a n c e t o w n (Table 3). T h e failure o f b o t h chemicals at C l e v e l a n d was shown by l a b o r a t o r y bioassay to be due to high-level resistance (V.E. Edge, personal c o m m u n i c a t i o n , 1987) as clofentezine h a d been used regularly and intensively for two years before the trials (N. G o u g h , u n p u b l i s h e d d a t a ) . T h e c o n c e r n o f Croft, H o y t a n d Westigard (1987) a b o u t the misuse o f ovicides such as clofentezine and h e x y t h i a z o x alone as regular miticides is justified by this study. A l t h o u g h clofentezine and h e x y t h i a z o x do not a p p e a r to be c h e m i c a l l y related, resistance to the f o r m e r conferred a v e r y high level o f cross-resistance to the latter. Since this study, clofen-
CROP PROTECTION Vol. 9 April 1990
t e z i n e / h e x y t h i a z o x resistance has also been r e c o r d e d in T. urticae from roses g r o w n in the S y d n e y region o f New S o u t h Wales (V.E. Edge, personal c o m m u n i c a tion, 1988). These c o m p o u n d s are selective, being almost harmless to m a n y i m p o r t a n t phytoseiids ( H o y and O u y a n g , 1986). T h e i r retention as sprays to correct t e m p o r a r y p o p u l a t i o n imbalances between predators and prey in I P M systems is therefore o f p a r a m o u n t i m p o r t a n c e . Dicofol resistance was r e c o r d e d in Australia by H o o p e r (1968) and U n w i n (1973). It occurs widely in T. urticae in New C a l e d o n i a (Brun, Edge and Gutierrez, 1983) and elsewhere ( C r a n h a m and Helle, 1985). T e t r a d i f o n resistance also o c c u r r e d widely and quickly in Australia (Unwin, 1973). Resistance to b o t h these c o m p o u n d s is stable and is m a i n t a i n e d for long periods even w h e n they are not applied ( O v e r m e e r et al., 1975). As dicofol and b r o m o p r o p y l a t e are chemically related, cross-resistance to the latter c o m p o u n d can also be expected. T h e i r failure is p r o b a b l y due to resistance as dicofol and tetradifon have been extensively used on roses in Q u e e n s l a n d , including the three populations e x a m i n e d here. O r g a n o p h o s p h o r o u s chemicals were tested only at A d v a n c e t o w n w h e r e various chemicals from this g r o u p (including d i m e t h o a t e ) had long been used as insecticides. Usage here is similar to that on o t h e r o u t d o o r flower crops in Q u e e n s l a n d . Ii'9 view o f the widespread and quick d e v e l o p m e n t o f O P resistance by T. urticae in Australia (Kerr, 1964; U n w i n , 1973) and elsewhere (Helle and van de Vrie, 1974; Brun et al., 1983; C r a n h a m and Helle, 1985), the failure o f d e m e t o n - S - m e t h y l , d i m e t h o a t e and p h o r a t e can p r o b a b l y be a t t r i b u t e d to resistance. D i m e t h o a t e h a d been used 14 times for thrip control in the previous y e a r at A d v a n c e t o w n . Some OPs have been shown actually to stimulate r e p r o d u c t i o n once resis-
N, GOUGH
tance has occurred (Leigh and Wynholds, 1980; Dittrich, 1987). Although the numbers of mites per leaf in the phorate treatments in Table 4 are not significantly greater than those on the untreated trees, there is a strong trend in that direction. There was a marked contrast in efficacy among the OPs, with chlorpyrifos and monocrotophos giving excellent control. Monocrotophos has been effective for many years against T. urticae in cotton in NSW, in spite of moderate levels of resistance (V.E. Edge, personal communication, 1988). However, highlevel resistance has occurred in T. urticae on roses in New Caledonia after prolonged exposure to mevinphos (Brun et al., 1983). Although some OPs may be effective at present, the only possible conclusion is that they have no long-term future as miticides on roses. Aldicarb was ineffective at Advancetown and would appear to have limited potential on fieldgrown roses. Dienochlor is the one chemical to which T. urticae has never developed resistance, despite extensive use in glasshouses (Helle and van de Vrie, 1974; Cranham and Helle, 1985) so resistance is unlikely to be the reason for poor performance here. It is widely used in European glasshouses and is known to be effective under cover in America (Allen, Ota and Gehring, 1964) and in Queensland (N. Gough, unpublished data). However, there have been other reports of its lower efficacy on outdoor crops (Allen et al., 1964). Streu (1982) examined reported failures of dienochlor which he attributed to formulation (wettable powder being less effective than the flowable formulation) and inadequate spray coverage. He showed that high temperatures per se (46°C) were not responsible for the breakdown of the chemical on glass plates. In the present trials a flowable formulation was used and wetting agents did little to increase the compound's effectiveness. There is no reason to assume inadequate coverage. Worthing and Walker (1983) noted that direct sunlight or ultraviolet radiation may cause dienochlor to break down. Whatever the reason, dienochlor was not as effective on outdoor roses in Queensland as it is in protected situations. Azocyclotin and cyhexatin were effective against all populations of mites despite the long previous usage of cyhexatin at Cleveland and Redland Bay; indeed, the population at Cleveland was found by laboratory bioassay to have an eightfold resistance factor to cyhexatin (V.E. Edge, personal communication, 1987). Edge and James (1982) first detected cyhexatin resistance in T. urticae in Australia with a 7.5-fold resistance factor at the LCs0 level. Subsequent bioassays showed that field levels of resistance had not risen above 15-fold (Edge and James, 1986). The authors concluded that, in apple and pear orchards, resistance may have reached a plateau which would not readily be exceeded. T h e y also found the immature stages of resistant strains to be
125
much more susceptible than the adult females. These findings may explain the present results, for despite moderate levels of resistance in the Cleveland population, good control was obtained by frequent use of cyhexatin and azocyclotin. These chemicals presumably caused heavy mortality to the immature stages. Fenbutatin oxide gave highly variable results. It was completely ineffective at Redland Bay and Cleveland, against populations which had a long history of intensive exposure to organotins, but was highly effective at Advancetown where cyhexatin had been used less. Fenbutatin oxide has a reputation for reduced activity in cold weather, but as the trials above were all performed in summer this can not explain the differences in effectiveness. The extreme variability makes recommendation of this important chemical difficult in commercial flower crops. Further work is urgently required to evaluate the effects of organo-tin resistance on the performance of fenbutatin oxide against T. urticae. Propargite was very effective at Advancetown (where it had not been used betbre), at Redland Bay and on ornamentals in shade houses (N. Gough, unpublished data). During the trials at Advancetown, numbers of mites were generally below one per leaf (Table 3). At Cleveland, even only a week or so after spraying (e.g. 4 March 1987, 1 and 22 April 1987), numbers always exceeded four mites per leaf, sufficient to allow a very quick population build-up. A resistance factor to propargite of approximately fivefold, due to prolonged exposure before the trial, was detected in this population by bioassay (V.E. Edge, personal communication, 1987). Propargite has some of the advantages of cyhexatin in that it is compatible with phytoseiids, but these results suggest that its long-term effectiveness on roses is doubtful, because of resistance. The bleak propects for future chemical control of mites on Queensland roses are evident from the trial at Cleveland (Table 6) where clofentezine, hexythiazox, fenbutatin oxide, dicofol plus tetradifon, bromopropylate and dienochlor all failed. Only four compounds were very effective and two of these, cyhexatin and azocyclotin, have now been withdrawn from sale. Bifenthrin and fluvalinate are synthetic pyrethroids. Although they have low phytotoxicity and are currently very effective, they have two drawbacks. Resistance to this group of chemicals has quickly developed in a wide range of insects (Georghiou, 1986) and will almost certainly occur in T. urticae. Secondly, synthetic pyrethroids are very toxic to phytoseiids. In contrast, as pointed out by Croft et al. (1987), cyhexatin is physiologically selective, being relatively benign to phytoseiids although killing tetranychids. In addition, as discussed previously, resistance of a very high order was not recorded in field populations in Australia. It seems certain that moderate levels of resistance, such as that at Cleveland, are widespread in southern Queensland rose farms, where cyhexatin has been
CROP PROTECTION Vol. 9 April 1990
126
Control of mites on field roses
used intensively, b u t h a v e b e e n u n r e c o g n i z e d as growers w e r e able to control the mites b y r e g u l a r a p p l i c a t i o n s o f the chemical. Its u n a v a i l a b i l i t y will p u t e n o r m o u s pressure on the few r e m a i n i n g miticides, i n c l u d i n g p r o p a r g i t e . O n A u s t r a l i a n cut flower crops, w h e r e miticide usage is e x t r e m e l y h e a v y , I n t e g r a t e d M i t e C o n t r o l is still in its i n f a n c y b u t there are p r o m i s i n g d e v e l o p m e n t s . Phytoseiulus persimilis A t h i a s - H e n r i o t has b e e n used to control T. urticae in s o m e rose tunnels in s o u t h e r n Q u e e n s l a n d for u p to 3 years with a l m o s t no use o f a u x i l i a r y miticides (N. G o u g h , u n p u b l i s h e d d a t a ) a n d in N S W it has also b e e n successful (J.F. R e a d s h a w , p e r s o n a l c o m m u n c i a t i o n , 1987). I n such systems, occasional use o f clofentezine a n d h e x y t h i a z o x m a y be e n o u g h to regain control o f 7-. urticae. T h e use o f P. persimilis on o u t d o o r roses is m o r e p r o b l e m a t i c because o f the necessity to control l a r v a e o f Heliothis spp. ( L e p i d o p t e r a : N o c t u i d a e ) w h i c h feed on the buds. T h e m o t h s are e x c l u d e d f r o m the rose tunnels. T h e m o s t effective c h e m i c a l s for control o f these l a r v a e are inimical to P. persimilis. T h e future o f the o u t d o o r rose industry, a n d o t h e r similar flower crops in Q u e e n s l a n d , m a y well d e p e n d on o u r ability to control Heliothis l a r v a e while allowing P. persimilis to r e m a i n effective.
Acknowledgements T h e a u t h o r t h a n k s D r V. E. E d g e , N S W D e p a r t m e n t o f A g r i c u l t u r e a n d Fisheries, R y d a l m e r e , w h o b i o a s s a y e d the C l e v e l a n d strain for resistance to clofentezine, h e x y t h i a z o x , c y h e x a t i n a n d p r o p a r g i t e a n d for his c o m m e n t s on the m a n u s c r i p t . S u z a n n e R a y n e r assisted with the field trials a n d L a r r y C o o p e r with p r e p a r a t i o n o f d a t a . T h a n k s also to rose growers K e n a n d the late M a x M c K a v a n a g h , G e o r g e M a r s h a l l , G r a h a m Mitchell a n d Bob a n d B r a d S k i n n e r for their c o m p l e t e c o o p e r a t i o n . T h i s w o r k was f u n d e d in p a r t b y g r a n t s f r o m the Q u e e n s l a n d N u r s e r y I n d u s t r y Association a n d the A u s t r a lian C o m m o n w e a l t h G o v e r n m e n t t h r o u g h the A u s t r a l i a n Special R u r a l R e s e a r c h F u n d .
References ALLEN, W. W., OTA, A. K. AND GEHRING, R. D. (1964). The
effectiveness of various pesticides against resistant two-spotted mites on greenhouse roses. Journal of Economic Entomology 57, 187-192. AVEYARD,C. S., PEREGRINE,D.J. ANDBRYAN,K. M. G. (1986). Biological activity of clofentezine against egg and motile stages of tetranychid mites. Experimental and Applied Acarology 2, 223-229 BENGSTON, M. (1969) Effect of Various Temperatures and Humidities on the Population Growth Potential of Tetranychus urticae Koch. Division of Plant Industry Bulletin No. 497. Queensland Department of Primary Industries. 78 pp. BRUN, L. O., EDGE, V. E. AND GUTIERREZ, J. (1983). The occurrence of five Tetranychus spp. (Acari: Tetranychidae) in New Caledonia and their responses to acaricides. Tropical Pest Management 29, 371-377.
CROP PROTECTION Vol. 9 April 1990
BRYAN, K. M. G., GEERING, 0~. A. AND REID, J. (1981)
NC21314, a novel compound for control of phytophagous mites. In: Proceedings 1981 British Crop Protection Conference --Pests and Diseases 1, 67-74. CRANHAM,J. E. AND HELLE, W. (1985). Pesticide resistance in Tetranychidae. In: Spider Mites: Their Biology, Natural Enemies and Control, Vol 1B, pp. 405-421 (ed. by W. Helle and M. W. Sabelis). Amsterdam: Elsevier. CROFT, B. A., HOYT, S. C. ANDWESTIGARD,P. H. (1987). Spider mite management on pome fruits, revisited: organotin and acaricide resistance management. Journal of Economic Entomology 80, 304-311. DITTRICH, V. (1987). Resistance and hormoligosis as driving forces behind pest outbreaks. In: Rational Pesticide Use, pp. 169-181 (ed. by K. J. Brent and R. K. Atkin). Cambridge: Cambridge University Press. EDGE, V. E. AND JAMES, D. G. (1982). Detection of cyhexatin resistance in twospotted mite, Tetranychus urticae Koch (Acarina: Tetranychidae) in Australia. Journal of the Australian Entomological Society 21, 198. EDGE, V. E. ANDJAMES, D. G. (1986) Organo-tin resistance in Tetranychus urticae (Acari: Tetranychidae) in Australia. Journal of Economic Entomology 79, 1477-1483. GEORGmOU, G. P. (1986). The magnitude of the resistance problem. In: Pesticide Resistance: Strategies and Tacticsfor Management, pp. 14-43. Washington DC: National Academy Press. GOUGH, N. AND QAYYUM, ABDUL (1987). Trials of miticides against twospotted mite and broad mite on fuchsias with comments on phytotoxicity. QueenslandJournal of Agricultural and Animal Sciences 44, 21-30. HELLE, W. AND VAN DE VRIE, M. (1974). Problems with spider mites. Outlook on Agriculture 8, 119 125. HOOPER, G. H. S. (1968). A review of the problem of insecticide resistance in Australia. Journal of the Australian Entomological Society 1, 67-76. HoY, M. A. AND OUYANG, Y. L. (1986). Selectivity of the acaricides clofentezine and hexythiazox to the predator Metaseiulus occidentalis (Acari:Phytoseiidae). Journal of Economic Entomology 79, 1377-1380. KERR, R. W. (1964). Notes on arthropod resistance to chemicals used in their control in Australia. Journal of the Australian Institute of Agricultural Science 30, 33-38. LEIGH,T. F. ANDWYNHOLDS,P. F. (1980). Insecticides enhance spider mite reproduction. California Agriculture 34, 14-15. MANSOUR, F. A. AND PLAUT, H. N. (1979). The effectiveness of various acaricides against resistant and susceptible carmine spider mites. Phytoparasitica 7, 185-193. NEAL, J. W., MCINTOStt, M. S. AND GOTT, K. M. (1986). Toxicity of clofentezine against twospotted and carmine spider mites (Acari:Tetranychidae). Journal of Economic Entomology 79, 479-483. OSBORNE, L. (1986) Dip treatment of tropical ornamental foliage cuttings in fluvalinate to prevent spread of insect and mite infestations. Journal of Economic Entomology 79, 465-470. OVERMEER, W. P. J., VAN ZON, A. Q. AND HELLE, W. (1975). The stability of acaricide resistance in spider mite (Tetranychus urticae) populations from rose houses. Entomologia experimentalis et applicata 18, 68-74. PRICE, J. F. (1981). Response of twospotted spider mites, leaf miners and their parasitoids and other arthropods to newly developed pesticides in chrysanthemums. Proceedings of the Florida State Horticultural Society 94, 80-83. ROBB, K. L., VIRZI,J. K. ANDPARRELLA,M. P. (1985). Control of twospotted mite on chrysanthemums, California, 1984. Insecticide and Acaricide Tests 10, 284. ROBINSON, J. R. C. AND TEETES, G. L. (1987). Insecticides for suppression of carmine mites on cotton, 1986. Insecticide and Acaricide Tests 12, 297. STREU, H. T. (1982). Pesticide 'facts' often inaccurate. Greenhouse Manager, August, 46-47.
N. GOUGH UNWIN, B. (1973). Chemical resistance in populations of Tetranychus urticae (Koch) (Acarina: Tetranychidae) from apple orchards in New South Wales, Australia. Journal of the Australian Entomological Society 12, 59-67. WORTH1NG,C. R. AND WALKER, S. B. (eds) (1983). The Pesticide Manual, A World Compendium, 7th edn. Croydon: British Crop Protection Council. 695 pp. YOST, J. T., FERRENTINO, G. W. AND PARRtSLLA,M. P. (1986). Control of twospotted mite on hydrangea, 1985. Insecticide and Acaricide Tests 10, 409.
127
ZOECON CORPORATION (1982). PentacAquaflow. TechnicalBulletin. Palo Alto, California 1260-3-82-1: Zoecon Corporation, Agricultural Chemicals Division. 4 pp.
Received 6 March 1989 Revised 22 August 1989 Accepted 12 September 1989
CROP P R O T E C T I O N Vol. 9 April 1990
Department of Primary Industries, Agricultural Research Laboratories, Meiers Road, Indooroopil~, Queensland, Australia 4068
ABSTRACT. The potential of miticides to control two-spotted mite (Tetranychus urticae Koch) on field roses in southern Queensland was examined by testing 21 compounds at up to three sites. These populations had extensive past exposure to miticides. Bifenthrin, fluvalinate, azocyclotin and cyhexatin were effective everywhere. Control by fenbutatin oxide varied greatly between sites. Clofentezine and hexythiazox gave excellent control on populations not previously exposed but both were completely ineffective, due to resistance, at one site where clofentezine had been applied repeatedly for 2 years before these trials. Propargite was effective overall whereas bromopropylate, dicofol plus tetradifon, dienochlor and sulphur were largely ineffective. Different organophosphates tested at one site gave highly variable control and here both aldicarb and phorate applied as granules were ineffective. The most important miticides were tested for phytotoxicity. The poor prospects for future chemical control on flower crops are discussed in the light of multiple resistance. KEYWORDS: Two-spotted mite; Tetranychus urticae; roses; miticides; clofentezineand hexythiazox resistance
Introduction Two-spotted mite, Tetranychus urticae Koch, is the major pest of roses in Queensland where it has been controlled traditionally by chemicals. Although the industry is of considerable importance there has never been a thorough examination of the effectiveness of miticides for use on roses (or other flower crops) in Queensland. In addition to the older compounds, new miticides such as clofentezine, hexythiazox, bifenthrin and fluvalinate have recently become available. M a n y miticides are phytotoxic to roses (Mansour and Plaut, 1979) so this aspect must be considered as well as efficacy. Although the ovicides clofentezine (e.g. Bryan, Geering and Reid, 1981; Aveyard, Peregrin and Bryan, 1986; Neal, McIntosh and Gott, 1986) and hexythiazox (Hoy and Ouyang, 1986) have been examined, little of the work has been done on ornamentals. Bifenthrin has been used mainly as an insecticide although Yost, Ferrentino and Parrella (1986) and Robinson and Teetes (1987) found it very effective against Tetranychus spp. Fluvalinate is effective against two-spotted mite (e.g. Price, 1981; Robb, Virzi and Parrella, 1985) and has a low phytotoxicity to ornamentals (Osborne, 1986).
Gough and Abdul Q a y y u m (1987) used clof~ntezine and fluvalinate (among other miticides) against 7-. urticae on fuchsias and examined phytotoxicity. Overall, however, there are insufficient easily accessible data on ornamentals enabling a comparison of these new chemicals with more traditional ones. In Queensland T. urticae reproduces rapidly for most of the year and rose growers may apply 15-20 miticide sprays annually, conditions favouring the swift development of miticide resistance (Overmeer, Van Zon and Helle, 1975). Recently there have been m a n y complaints that chemical control is becoming more difficult. The present work was aimed at evaluating a wide range of miticides tbr efficacy and phytotoxicity on field roses. It was considered important to determine whether control failures were due to inadequate spray application--a factor that could be remedied or to miticide inefficacy. The trials were therefore designed with frequent application of miticide and good spray coverage so that the possibility of failure due to extraneous factors was greatly reduced. The aim was not to simulate commercial spray schedules or to demonstrate residual action but to determine, in this area with a history of intensive usage, which miticides had potential to control T. urlicae.
0261-2194/90/02/1)119 09 ((~) 1990Bmterworth& Co (Publishers) Ltd CROP PROTECTION Vol. 9 April 1990, 119-127
120
Control of mites on field roses
Materials and methods
Effcacy trials Five trials were conducted on three commercial rose farms in which control failures with miticides had been reported. As most Queensland rose growers have problems controlling mites, these farms are not unusual. Trial 1 began in March 1984 in part of a 2 ha rose farm at Redland Bay which had been established for at least 10 years. Trials 2 4 were conducted between September 1986 and M a y 1987 in a rose farm at Advancetown which had been established between 6 and 7 years and Trial 5 was conducted at Cleveland in a patch of roses about 9 years old. Growers do not always keep accurate records so complete spray histories are not available. On all three farms bifenthrin, dienochlor, fluvalinate and hexythiazox had never been used. At Redland Bay clofentezine had never been sprayed. Dicofol had been used in the past and cyhexatin had been applied frequently (almost monthly) for several years immediately before Trial 1. At Advancetown (Trials 2 4), dicofol plus tetradifon had been used briefly some years previously and then again (seven times) in the year before the trials. Cyhexatin had been applied for about four years before the trials. Initially it was sprayed very thoroughly by hand, sometimes two applications close together. This was done two or three times a year. In the year before the trials it was applied singly three times. Although fenbutatin oxide was sprayed five times in the year before the trials it had not been used before. Clofentezine and propargite had never been used. Organophosphorous chemicals had been applied extensively for insect control. The mites at Cleveland (Trial 5) had the heaviest exposure to chemicals. Clofentezine had been used alone or alternated with febutatinoxide or propargite for 2 years before these trials, sprays being applied monthly or more frequently when control was poor. Previously, cyhexatin and propargite formed the basis of the spray schedule, having been used often for at least 5 years. Dicofol had been used early in the life of the plantation. Mature rose bushes (1.5 2 m high and about 5 years old) of the following varieties were used: Trial 1, Queen Elizabeth; Trials 2, 3, 4, M r Lincoln; Trial 5, M r Lincoln (three replicates) and R o u n d a l a y (two replicates). The experimental plan for each trial was a randomized block with five replicates, the experimental unit being a single rose bush. Pretreatment counts were conducted. In some trials these showed systematic variation due to inadequate spray penetration by the growers' equipment (i.e. the inner rows of a bed had more mites than the outside rows) and treatments were blocked along the rows. In Trial 5 blocking was by rose variety. On each sampling occasion five single (not compound) leaves per bush were chosen between waist and
CROP PROTECTION Vol. 9 April 1990
shoulder height. Very young and obviously senescent leaves were avoided to reduce random variation in the numbers of mites. Leaves were examined with a stereomicroscope immediately after being picked and the mites counted. The total number of all motile stages on the five leaves was used for the analysis of variance. Either a x/(x + 0-5) or a log x + 1 transformation was used, depending on the number of mites. The equivalent mean number of mites per leaf was calculated by back transformation. Chemicals tested, and their formulations were as shown in Table 1. The rates at which miticides were applied are given in Tables ~ 6 . In Trial 1 spray was applied using a Cooper-Pegler CP3 Mark 2 knapsack spray operating at about 311097 Newtons m -~ with a hollow conespray nozzle. In all other trials spray was applied with a 51 hand pressurized atomizer (4042 Killaspray 8) with an adjustable nozzle. Chemicals were applied to run off. Wetting agents were used only when recommended by the manufacturer as in Tables 2 6. Untreated bushes were sprayed either with water or water plus wetting agent. Precautions were taken to prevent drift. Dates of spraying are as given in Tables 2 to 6. The manufacturers of some chemicals such as dienochlor (which are effective on active stages but not on eggs) recommend two sprays a week apart in hot weather or on well-established populations (Zoecon Corporation, 1982). This allows eggs surviving the first spray to hatch and the larvae are destroyed by the second spray. This regimen was adopted and was found to be very suitable for determining the potential of miticides. The possibility of inadequate spray coverage was eliminated. The influence of sporadic heavy rain was minimized and ineffective chemicals were quickly recognized. Where both counting and spraying were performed on the same day, the former was done in the morning and the latter in the afternoon. Granules in Trials 2 and 3 were dug into the topsoil (on the date of the first spray) in a square metre around the base of the treated bushes. In Trial 2 aldicarb was reapplied 6 weeks after the beginning of the trial on 24 October. In Trial 3 about 30 1 water was sprinkled on to each plot (bush) after the granules were applied to ensure moist conditions for chemical release and uptake. As trials were conducted on commercial rose farms, treatments recognized as ineffectual in Trials 2 and 3 were terminated early by overspraying with fluvalinate to reduce damage (Tables 3 and 4).
Phytoxicity to leaves and flowers Notes were made on phototoxicity to the leaves in most trials, including a detailed examination during a burst of new growth in Trial 5 at Cleveland. Sprays were applied on 18 and 25 March 1987 and
N. GOUGH TABLE 1.
121
Chemicals tested
Common name
Formulation°
Aldicarb Azocyclotin Bifenthrin
10 % G WP25 EC 10
Bromopropylate Chlorpyrifos Clofentezine Cyhexatin Demeton-S-methyl Dicofol Dienochlor Dimethoate Fenbutatin oxide Fluvalinate Hexythiazox Methidathion Monocrotophos Phorate
EC50 EC50 WP50 ; F50 F60; WP50 EC25 EC24 F48 EC30 F55 F48 WP10 EC40 EC40 10%G in inert plastic polymer ~ WP30 WP25 WP80 EC7.5
Propargite Quinomethionate Sulphur Tctradifon
IUPAC chemical name 2-Methyl-2- (methylthio)propionaldehyde O-methylcarbamoyloxime tri(Cyclohexyl)- 1H- 1,2,4-triazol-l-yhin 2-Methylbiphenyl-3-ylmethyl (Z)-(IRS,3RS)-3-(2-chloro-3,3,3-triflu°r°pr°p-l-enyl)-2,2-dimethylcycl°pr°panecarboxylate Isopropyl 4,4'-dibromobenzilate O,O-Diethyl O-3,5,6-trichloro-2-pyridyl phosphorothioate 3,6-bis(2-Chlorophenyl)- 1,2,4,5-tetrazine Tricyclohexyhin hydroxide S-2-Ethyhhioethyl O,O-dimethyl phosphorothioate 2,2,2-Trichloro- 1,1-bis(4-chlorophenyl)ethanol Perchloro- 1, l'-bicyclopenta-2,4-diene O,O-Dimethyl S-methylcarbamoylmethyl phosphorodithioate bis[tris(2-Methyl-2-phenylpropyl) tin] oxide (RS)-~-Cyano-3-phenoxybenzyl N- (2-chloro-~,~,~-trifluoro-p-tolyl-D-valinate (4RS, 5RS)-5- (4-Chlorophenyl)-N-cyclohexyl-4-methyl-2-oxo-1,3-thiazolidine-3-carboxamide S-2,3-Dihydro-5-methoxy-2-oxo-l,3,4-thiadiazol-3-ylmethyl O,O-dimethyl phosphorodithioate Dimethyl (E)-l-methyl-2-(methylcarbamoyl)vinyl phosphate O,0-Diethyl S-ethyhhiomethyl phosphorodithioate
2-(4-tert-Butylphenoxy)cyclohexyl
prop-2-ynyl sulphite 6-Methyl- 1,3-dithiolo [4,5-b] quinoxalin-2-one Sulphur 4-Chlorophenyl 2,4,5-trichlorophenyl sulphone
" G, granules; WP, wettable powder; EC, emulsifiable concentrate; F, flowable; h Suscon Controlled Release Granules: Suscon is the Registered Trade Name of C.F.L., an I ncitec Company
TABLE 2. The cfl'ects of various miticides on the number of motile T. urticae per leaf Trial 1, Redland Bay Chemical treatment and concentratitm (g a.i. 1 I:
Fluvalinate 0-09 Propargite 0.6 Azocyclotin 0.2 Dicofol plus tetradifon 0.5 + 0.2 Cyhexatin ~ 0.2 Clofentezine h 0.3 Oxythioquin(~x (I. 13 Dicofol 0.5 Dienochlt)r' (}.3 Fenl)utatin oxide 0.2 Water + welling agent'
Synthetic pyrethroids
Equivalent mean number of mites per leaf Pretreatment 7March 1984
12March 1984
Results
19March 1984
55-1 38-5 74-6 83.2
a a a a
5.2 6.0 11.8 9.0
a a abe ab
0.1 0.3 1.0 1.1
a ab ab ab
84.6 66.3 59.5 105-4 66.0 86-7 84"2
a a a a a a a
5.5 10.0 11.9 21.4 30.1 49.0 91"3
a abc abc bcd cde de e
1.4 1-8 1.9 10-6 11-7 14.7 20"2
ab b b c c c c
Sprays applied all 7. 14 March 1984; numbers followed by different letters difl'er at P = (I.05 Method (ffleast significant difl~rence, log x + 1 transformation used for analysis of variance; " flowable formulation; bwettable powder formulation; ' wetting agcm iAgral 60) used at the rate of 0-18 ml 1 i
damage was assessed on 26 March. Flowers and mature buds of M r Lincoln were removed ti~om the bushes immediately after being sprayed and held in the shade for a day before examination. Phytotoxicity to the longer-lasting flowers of the varieties Samantha and Gabriella was also assessed. Three newly opened flowers and three buds (commercial maturity) were picked from a glasshouse and tested against the miticides used in Trial 5. They were placed in a bucket of water and sprayed tbr 3 s with the pressurized hand applicator as for the main trial. Damage to the open flowers was assessed 1 day and damage to the buds 1 and 2 days after spray application.
Fluvalinate was used on all three populations and always gave outstanding chemical control (Tables 2-4 and 6). Bifenthrin was also highly effective (Tables 5 and 6).
Organotins On all three populations cyhexatin produced acceptable control (Tables 2, 3 and 6) as did azocyclotin where it was used (Tables 2 and 6). Fenbutatin oxide was as effective as cyhexatin at Advancetown ( Table 4) but was completely ineffective at Redland Bay Table 2) and Cleveland (Table 6).
Propargite Propargite was extremely effective at Redland Bay ( Table 2) and Advancetown ( Table 3), equalling cyhexatin and fluvalinate and generally reducing numbers of mites to one or less per leaf. It was less effective at Cleveland ( Table 6) where it was significantly inferior to the synthetic pyrethroids, cyhexatin and azocyclotin.
Clofentezine Clofentezine applied at 0.3 g a.i. 1 - 1 at Redland Bay ( Table 2) and Advancetown ( Table 3) or at 0-2 g a.i. 1-1 (Advancetown, Table 4) was as effective as cyhexatin in reducing and suppressing two-spotted mite. At Cleveland (Table 6) it was completely ineffective.
CROP
PROTECTION
Vol. 9 April 1990
Control o f mites on f i e l d roses
122 TABLE 3.
T h e effects o f v a r i o u s miticides o n the n u m b e r o f motile T. urticae p e r leaf. T r i a l 2, A d v a n c e t o w n
Chemical treatment and concentration (g a.i. 1 - 1)
E q u i v a l e n t m e a n n u m b e r o f mites p e r l e a f Pretreatment 12 S e p t e m b e r 1986 a
H e x y t h i a z o x 0.05 C y h e x a t i n c 0-2 F l u v a l i n a t e 0.1 BromopropylateO.75 Clofentezine ~ 0.3 P r o p a r g i t e 0.3 D i e n o c h l o r 0.36 Dicofol plus t e t r a d i f o n 0.5 + 0.2 Aldicarb0-75 ga.i.m -2 Water only
0.4 0.6 0.6 0-9 1.9 1.4 0.6 0.8
26 S e p t e m b e r 1986 a
a a a a a a a a
0.2 0.1 0 a 0.3 0.3 0.1 0.4 0.2
0.8a 1.3 a
10 O c t o b e r 1986 a
ab a
0.2 0-5 0.6 1.1 1.2 1-2 3.9 4.5
ab ab a ab ab
1.6bc 3.6 c
24 O c t o b e r 1986 b
a a a ab ab ab b b
7.5bc 19-5 c
0.25 0.03 0-1 0.8 0-9 0.2 2.3 3.1
a a ab b b ab b bc
11.3 c 44.4 d
6 November 1986" 0.9 0.4 0.3 5.2 0.8 1-0 15.9 10-1
13 N o v e m b e r 1986 b
ab a a b ab ab bc b
0.9 a b 0-2 a b 0.1 a 1.9 b 0.6 a b 0.7 a b 26.8 c 2-4 b
5.1 b 78.0 c
21 N o v e m b e r 1986 ° 0.4 0.7 0-4 17.7 1-0 0.2
2 December 1986 a
ab a ab c b ab
0-2 a 0.2 a 0.2 a 1.4 a 1.7 a
19.2 c
18.1 c
Sprays applied on 12, 19 September, I0, 17 October, 6, 21 November 1986; granules applied 12 September and 24 October; numbers followed by different letters differ at P = 0-05; method of least significant difference; " x/~ + 0-5, and b log x + 1 transformation used for analysis of variance; c WP formulation; d flowable formulation
TABLE 4. T h e effects o f v a r i o u s miticides o n the n u m b e r o f motile 7-. urticae p e r leaf. T r i a l 3, A d v a n c e t o w n
TABLE 5. T h e effects o f v a r i o u s c h e m i c a l s o n the n u m b e r of motile T. urticae p e r leaf. T r i a l 4, A d v a n c e t o w n
Chemical treatment and concentration (g a.i. 1 - l)
Chemical treatment and concentration (g a.i. 1 I)
E q u i v a l e n t m e a n n u m b e r o f mites p e r l e a f Pretreatment 1 D e c e m b e r 22 D e c e m b e r 1986 ~ 1986 a
F l u v a l i n a t e 0-1 F e n b u t a t i n o x i d e 0.2 M o n o c r o t o p h o s 0.6 Clofentezine ~ 0-2 S u l p h u r 3.1 A l d i c a r b 1 g a.i. m - 2 P h o r a t e 0-8 g a.i. m - 2 P h o r a t e 1.6 g a.i. m - 2 Water only
9.5 20-4 12.6 19.6 15.9 13-0 14-5 12.5 13.3
a a a a a a a a a
0.2 0-4 0.5 2.2 69-1 69-3 104.7 125.3 67.2
a ab ab b c c c c c
9January 1987 a 1.4 0.9 0.7 2.4
23January 1987 b
a a a a
Pretreatment 13 M a y '87
0.4 a 0 a 0.9 a 0.1 a --
Bifenthrin" 0-04 M o n o c r o t o p h o s ~ 0.6 C h l o r p y r i f o s " 0.75 M e t h i d a t h i o n b 0-5 D i m e t h o a t e b 0.3 Demeton-S-methyl ~ 0.25 Water only h
75.2 b -
6.2 11.3 5.7 17.1 8.5
a a a a a
11.3 a 9.9 a
25 M a y '87
0-4 0.3 0.5 10-5 8-2
a a a b b
2 June '87 0 a 0.6 1.6 2.1 7.3
21.6 b 9.5 b
a bc bc cd
13.5 d 10.0 d
"Sprays applied on 18 May 1987; bsprays applied on 18 and 25 May 1987; numbers followed by different letters differ at P = 0.05; method of least significant difference; log x + 1 transformation used for analysis of variance
Sprays applied on 3, I l, 22 December 1986, 9 J a n u a r y I987; granules applied with the first spray; numbers followed by different letters differ at P = 0.05; method of least significant difference; " log x + 1 and b ~/x + 0.5 transformations used for analysis of variance; ' flowable formulation
TABLE 6.
E q u i v a l e n t m e a n n u m b e r o f mites p e r leaf
T h e effects o f v a r i o u s miticides o n the n u m b e r of motile 7-. urticae p e r leaf. T r i a l 5, C l e v e l a n d
Chemical treatment and concentration (g a.i. 1 - 1)
B i f e n t h r i n 0.04 F l u v a l i n a t e 0.1 C y h e x a t i n 0.2 A z o c y c l o t i n 0-2 P r o p a r g i t e 0.3 D i e n o c h l o r 0.36 a B r o m o p r o p y l a t e 0.5 Dicofol plus t e t r a d i f o n O-5 + 0.2 Dicofol 0.5 F e n b u t a t i n oxide 0-2 H e x y t h i a z o x 0-05 Clofentezine 0.2 Water only a
E q u i v a l e n t m e a n n u m b e r o f mites p e r l e a f Pretreatment 16 F e b r u a r y 1987
26 F e b r u a r y 1987
15.1 13.5 7.4 17.3 13.2 4.4 5.2 12.4
a a a a a a a a
0.4 1.7 2.3 0.7 9.3 6.7 4-3 6.2
a b bc ab cd c bc c
3.8 8.7 10-8 6.9 9.3
a a a a a
16-I 17.8 16.6 23.4 23.6
cd cd cd d d
4 March 1987 0.03 a 0-1 a 0.1 a 0.2 a 4.0 b 5.8 bc 4.8 b 3.7 b 15-7 25.3 15.9 52.7 55-8
cd de d e e
16 M a r c h 1987 0.3 0.3 1.0 2.2 5-3 7.7 7.0 10-5
a a ab b bc cd bcd cd
12.2 6-4 17.3 18.7 20.8
ce bcd cd cd d
1 April 1987
9 April 1987
22 April 1987
0.1 0.2 0.5 0.9 6.1 7.6 9.8 5-5
a a ab b c cd cde c
1-9 1-0 1.8 6.0 9.3 11.0 24.3 18.3
a a a b bc bc cd cd
0.03 a 0.2 a b 1.4 c 0.9 bc 5-3 d 11.4 de 5.7 d 16.1 ef
22-8 ef 16.7 d e f 26.6 f 24.8 f 44.8 f
32-1 41.9 41.4 32-7 40.8
d d d d d
18.7 57.6 52.8 44-0 47.0
efg h gh fgh gh
Sprays applied on 18, 26 February, 18, 25 March, 13 April 1987; ~ wetting agent (0-1 ml Agral 60 1 J) used from 18 March; numbers followed by different letters differ at P = 0-05; method of least significant difference; log x + 1 transformation used for analysis of variance
CROP
PROTECTION
Vol. 9 April 1990
123
N. GOU6H
Hexythiazox
Aldicarb
Hexythiazox at Advancetown was very effective ( Table 3). At Cleveland ( Table 6) it produced a slight decline in mite numbers 2 weeks after the start of spraying but after that it was completely ineffective.
Aldicarb was used only at Advancetown. It could neither prevent the build-up of mites (Table 3) nor reduce established populations (Table 4). Although the mean number of mites per leaf was significantly less than the untreated, on 6 November (Table 3) two of the five trees were showing obvious mite damage. By 13 November mite damage was widespread on three of the five trees. This was despite a second application of aldicarb on 24 October. Rainfall and irrigation were adequate in this trial to allow good chemical uptake from the granules (68 mm in the latter half of September, 122 mm in October and 42 mm in the first two weeks of November). In Trial 3 aldicarb showed no sign of controlling the mites three weeks after the trial began and the treatment was oversprayed to prevent damage (Table 4).
Organochlorines and tetradifon Although dicofol plus tetradifon and bromopropylate delayed the build-up of mites at both Advancetown and Cleveland (Tables 3 and 6) they soon proved ineffective. Leaf damage occurred after about 8 weeks and when spraying ceased even for a period of 2 weeks large populations built up. Dicofol plus tetradifon was more effective than dicofol at Redland Bay (Table 2) and for parts of the trial at Cleveland (Table 6).
Organophosphorous chemicals Organophosphorous chemicals were used only at Advancetown. In Trial 3 monocrotophos produced outstanding control whereas phorate applied as granules did not reduce numbers at all (Table 4). Because of this apparent contradiction a larger range of organophosphates was used in Trial 4. Single sprays of monocrotophos and chlorpyrifos were highly effective whereas two sprays of methidathion were necessary to achieve the same level of control. Dimethoate and demeton-S-methyl were completely ineffective ( Table 5).
Dienochlor Dienochlor was relatively ineffective, with or without a wetting agent, in either suppressing established populations to an acceptably low level ( Table 2) or in preventing their build up ( Tables 3 and 6). In Trials 2 and 5 leaf damage occurred after 7-8 weeks despite four sprays of dienochlor applied according to the manufacturer's instructions. The mean number of mites per leaf estimated by log transformation was sometimes misleading and in Trial 5 on 22 April 1987 two of the five trees were heavily infested although the overall mean number per leaf was not high ( Table 6).
Quinomethionate Quinomethionate was as effective as cyhexatin in Trial 1 (Table 2). It was not used more widely because of its known phytoxicity which raised doubts about its commercial potential for ornamentals.
Sulphur Sulphur was used once (Table 4) and was ineffective.
Phytotoxicity to leaves and flowers Symptoms induced by the formulations can be divided into two categories (Table 7). O f the miticides causing negligible damage, bromopropylate (EC) was the most phytotoxic, occasionally causing a yellow mottling of young leaves of M r Lincoln. In the second category, where there was pronounced damage, propargite (WP) marked the flowers but had little effect on the leaves. Dicofol (EC) (alone or in mixture) had the opposite action, sometimes severely damaging very young growth but with little effect on the flowers. Cyhexatin flowable was more phytotoxic than the wettable powder formulation and azocyclotin (WP) was severely phytotoxic. M a n y growers avoided cyhexatin flowable and none used azoeyclotin as they were considered too phytotoxic. With many miticides, damage occurred only to very young, reddish leaves. When more mature leaves were sprayed, damage was greatly reduced. Phytotoxicity in glasshouses is more severe, with many more compounds unacceptable.
Discussion The most striking feature of the data is that so many miticides were shown to be ineffective. Adequate spray coverage was apparently achieved in all the trials, as fluvalinate, to which populations had never been exposed, was always highly effective. Fluvalinate has been found to be consistently effective on two-spotted mite on fuchsias (Gough and Q a y y u m , 1987) and other ornamental crops in Queensland (N. Gough, unpublished data). Trial 5 was the only one influenced by heavy rainfall and the decline in numbers on the untreated leaves between 4 March (55.8 mites leaf -1) and 16 March (20-8 mites leaf -~) was probably due to 92 mm of rain which fell in that period. U p to 6 mm of rain fell a few hours after the second spray on 26 February but this seems to have little influence on the results. T. urticae
CROP PROTECTION Vol. 9 April 1990
Control of mites on field roses
124
TABLE7. Synopsisof the effectsofmiticideson the leaves (varietyMr Lincoln)and flowersand buds of roses (Gabriella,Mr Lincoln,Samantha) under field conditions Miticide formulationand concentration (g a.i. 1- 1)
Effecton leaves
Effect on flowersand buds
Category 1. Negligibleor slight damage Bifenthrin EC 0-04 BromopropylateEC 0.5 DienochlorF 0-36 Fenbutatin oxide F 0.2 Fluvalinate F 0.1 HexythiazoxWP 0.05
Little damage, minor leaf distortion or dimpling when applied to very young leaves
Negligible damage, insignificantshine or residues where spray landed on petals. Buds perfect
Category 2. Noticeableor pronounceddamage DicofolEC 0-5 Dicofol EC plus tetradifon EC 0.5 + 0.2
Moderate to severeleaf distortion and reduced leaf size on veryyoung growth. Leaf dimpling
Slight damage, residue and a few shiny spots on flowers
Propargite WP 0.3 Cyhexatin WP 0.2 Cyhexatin F 0-2
Propargite has little effecton leaves, cyhexatinF causes severe leaf distortion
Petals of all varieties pock-marked,as buds open petal tips are damaged. Propargite damage is least severe
AzocyclotinWP 0.2
Severe dimpling and leaf distortion
Severe damage to flowersand buds
is notorious for its ability to develop resistance to miticides ( C r a n h a m and Helle, 1985). Rosegrowers in Q u e e n s l a n d are a m o n g the heaviest users o f miticides in the world. F u r t h e r m o r e , their roses h a r b o u r p e r m a n e n t populations o f mites which exist as long as the plantings (up to 10 years or more) and are thus exposed to a great a r r a y o f chemicals. As there was no p a t t e r n o f r a n d o m spray failure, resistance seems the most logical e x p l a n a t i o n for the p o o r p e r f o r m a n c e o f m a n y chemicals to which T. urticae has b e c o m e resistant in the past. Clofentezine was surprisingly effective w h e n used in the u n o r t h o d o x m a n n e r o f two sprays a week a p a r t on p o p u l a t i o n s which h a d not previously been exposed to it at R e d l a n d Bay and A d v a n c e t o w n . A v e y a r d et al. (1986) showed that clofentezine was very effective on eggs, larvae and p r o t o n y m p h s , b u t caused only 2 0 % m o r t a l i t y to d u e t o n y m p h s a n d was ineffective against adults. At 25-5°C, female T. urticae have an average longevity of 18.3 days (Bengston, 1969). W i t h high d e u t o n y m p h a l survival one would not expect the virtual elimination o f p o p u l a tions within 12 (Table 2) or 14 days (N. G o u g h , u n p u b l i s h e d d a t a on o t h e r o r n a m e n t a l s ) as freq u e n t l y occurred. H e x y t h i a z o x was similarly effective at A d v a n c e t o w n (Table 3). T h e failure o f b o t h chemicals at C l e v e l a n d was shown by l a b o r a t o r y bioassay to be due to high-level resistance (V.E. Edge, personal c o m m u n i c a t i o n , 1987) as clofentezine h a d been used regularly and intensively for two years before the trials (N. G o u g h , u n p u b l i s h e d d a t a ) . T h e c o n c e r n o f Croft, H o y t a n d Westigard (1987) a b o u t the misuse o f ovicides such as clofentezine and h e x y t h i a z o x alone as regular miticides is justified by this study. A l t h o u g h clofentezine and h e x y t h i a z o x do not a p p e a r to be c h e m i c a l l y related, resistance to the f o r m e r conferred a v e r y high level o f cross-resistance to the latter. Since this study, clofen-
CROP PROTECTION Vol. 9 April 1990
t e z i n e / h e x y t h i a z o x resistance has also been r e c o r d e d in T. urticae from roses g r o w n in the S y d n e y region o f New S o u t h Wales (V.E. Edge, personal c o m m u n i c a tion, 1988). These c o m p o u n d s are selective, being almost harmless to m a n y i m p o r t a n t phytoseiids ( H o y and O u y a n g , 1986). T h e i r retention as sprays to correct t e m p o r a r y p o p u l a t i o n imbalances between predators and prey in I P M systems is therefore o f p a r a m o u n t i m p o r t a n c e . Dicofol resistance was r e c o r d e d in Australia by H o o p e r (1968) and U n w i n (1973). It occurs widely in T. urticae in New C a l e d o n i a (Brun, Edge and Gutierrez, 1983) and elsewhere ( C r a n h a m and Helle, 1985). T e t r a d i f o n resistance also o c c u r r e d widely and quickly in Australia (Unwin, 1973). Resistance to b o t h these c o m p o u n d s is stable and is m a i n t a i n e d for long periods even w h e n they are not applied ( O v e r m e e r et al., 1975). As dicofol and b r o m o p r o p y l a t e are chemically related, cross-resistance to the latter c o m p o u n d can also be expected. T h e i r failure is p r o b a b l y due to resistance as dicofol and tetradifon have been extensively used on roses in Q u e e n s l a n d , including the three populations e x a m i n e d here. O r g a n o p h o s p h o r o u s chemicals were tested only at A d v a n c e t o w n w h e r e various chemicals from this g r o u p (including d i m e t h o a t e ) had long been used as insecticides. Usage here is similar to that on o t h e r o u t d o o r flower crops in Q u e e n s l a n d . Ii'9 view o f the widespread and quick d e v e l o p m e n t o f O P resistance by T. urticae in Australia (Kerr, 1964; U n w i n , 1973) and elsewhere (Helle and van de Vrie, 1974; Brun et al., 1983; C r a n h a m and Helle, 1985), the failure o f d e m e t o n - S - m e t h y l , d i m e t h o a t e and p h o r a t e can p r o b a b l y be a t t r i b u t e d to resistance. D i m e t h o a t e h a d been used 14 times for thrip control in the previous y e a r at A d v a n c e t o w n . Some OPs have been shown actually to stimulate r e p r o d u c t i o n once resis-
N, GOUGH
tance has occurred (Leigh and Wynholds, 1980; Dittrich, 1987). Although the numbers of mites per leaf in the phorate treatments in Table 4 are not significantly greater than those on the untreated trees, there is a strong trend in that direction. There was a marked contrast in efficacy among the OPs, with chlorpyrifos and monocrotophos giving excellent control. Monocrotophos has been effective for many years against T. urticae in cotton in NSW, in spite of moderate levels of resistance (V.E. Edge, personal communication, 1988). However, highlevel resistance has occurred in T. urticae on roses in New Caledonia after prolonged exposure to mevinphos (Brun et al., 1983). Although some OPs may be effective at present, the only possible conclusion is that they have no long-term future as miticides on roses. Aldicarb was ineffective at Advancetown and would appear to have limited potential on fieldgrown roses. Dienochlor is the one chemical to which T. urticae has never developed resistance, despite extensive use in glasshouses (Helle and van de Vrie, 1974; Cranham and Helle, 1985) so resistance is unlikely to be the reason for poor performance here. It is widely used in European glasshouses and is known to be effective under cover in America (Allen, Ota and Gehring, 1964) and in Queensland (N. Gough, unpublished data). However, there have been other reports of its lower efficacy on outdoor crops (Allen et al., 1964). Streu (1982) examined reported failures of dienochlor which he attributed to formulation (wettable powder being less effective than the flowable formulation) and inadequate spray coverage. He showed that high temperatures per se (46°C) were not responsible for the breakdown of the chemical on glass plates. In the present trials a flowable formulation was used and wetting agents did little to increase the compound's effectiveness. There is no reason to assume inadequate coverage. Worthing and Walker (1983) noted that direct sunlight or ultraviolet radiation may cause dienochlor to break down. Whatever the reason, dienochlor was not as effective on outdoor roses in Queensland as it is in protected situations. Azocyclotin and cyhexatin were effective against all populations of mites despite the long previous usage of cyhexatin at Cleveland and Redland Bay; indeed, the population at Cleveland was found by laboratory bioassay to have an eightfold resistance factor to cyhexatin (V.E. Edge, personal communication, 1987). Edge and James (1982) first detected cyhexatin resistance in T. urticae in Australia with a 7.5-fold resistance factor at the LCs0 level. Subsequent bioassays showed that field levels of resistance had not risen above 15-fold (Edge and James, 1986). The authors concluded that, in apple and pear orchards, resistance may have reached a plateau which would not readily be exceeded. T h e y also found the immature stages of resistant strains to be
125
much more susceptible than the adult females. These findings may explain the present results, for despite moderate levels of resistance in the Cleveland population, good control was obtained by frequent use of cyhexatin and azocyclotin. These chemicals presumably caused heavy mortality to the immature stages. Fenbutatin oxide gave highly variable results. It was completely ineffective at Redland Bay and Cleveland, against populations which had a long history of intensive exposure to organotins, but was highly effective at Advancetown where cyhexatin had been used less. Fenbutatin oxide has a reputation for reduced activity in cold weather, but as the trials above were all performed in summer this can not explain the differences in effectiveness. The extreme variability makes recommendation of this important chemical difficult in commercial flower crops. Further work is urgently required to evaluate the effects of organo-tin resistance on the performance of fenbutatin oxide against T. urticae. Propargite was very effective at Advancetown (where it had not been used betbre), at Redland Bay and on ornamentals in shade houses (N. Gough, unpublished data). During the trials at Advancetown, numbers of mites were generally below one per leaf (Table 3). At Cleveland, even only a week or so after spraying (e.g. 4 March 1987, 1 and 22 April 1987), numbers always exceeded four mites per leaf, sufficient to allow a very quick population build-up. A resistance factor to propargite of approximately fivefold, due to prolonged exposure before the trial, was detected in this population by bioassay (V.E. Edge, personal communication, 1987). Propargite has some of the advantages of cyhexatin in that it is compatible with phytoseiids, but these results suggest that its long-term effectiveness on roses is doubtful, because of resistance. The bleak propects for future chemical control of mites on Queensland roses are evident from the trial at Cleveland (Table 6) where clofentezine, hexythiazox, fenbutatin oxide, dicofol plus tetradifon, bromopropylate and dienochlor all failed. Only four compounds were very effective and two of these, cyhexatin and azocyclotin, have now been withdrawn from sale. Bifenthrin and fluvalinate are synthetic pyrethroids. Although they have low phytotoxicity and are currently very effective, they have two drawbacks. Resistance to this group of chemicals has quickly developed in a wide range of insects (Georghiou, 1986) and will almost certainly occur in T. urticae. Secondly, synthetic pyrethroids are very toxic to phytoseiids. In contrast, as pointed out by Croft et al. (1987), cyhexatin is physiologically selective, being relatively benign to phytoseiids although killing tetranychids. In addition, as discussed previously, resistance of a very high order was not recorded in field populations in Australia. It seems certain that moderate levels of resistance, such as that at Cleveland, are widespread in southern Queensland rose farms, where cyhexatin has been
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Control of mites on field roses
used intensively, b u t h a v e b e e n u n r e c o g n i z e d as growers w e r e able to control the mites b y r e g u l a r a p p l i c a t i o n s o f the chemical. Its u n a v a i l a b i l i t y will p u t e n o r m o u s pressure on the few r e m a i n i n g miticides, i n c l u d i n g p r o p a r g i t e . O n A u s t r a l i a n cut flower crops, w h e r e miticide usage is e x t r e m e l y h e a v y , I n t e g r a t e d M i t e C o n t r o l is still in its i n f a n c y b u t there are p r o m i s i n g d e v e l o p m e n t s . Phytoseiulus persimilis A t h i a s - H e n r i o t has b e e n used to control T. urticae in s o m e rose tunnels in s o u t h e r n Q u e e n s l a n d for u p to 3 years with a l m o s t no use o f a u x i l i a r y miticides (N. G o u g h , u n p u b l i s h e d d a t a ) a n d in N S W it has also b e e n successful (J.F. R e a d s h a w , p e r s o n a l c o m m u n c i a t i o n , 1987). I n such systems, occasional use o f clofentezine a n d h e x y t h i a z o x m a y be e n o u g h to regain control o f 7-. urticae. T h e use o f P. persimilis on o u t d o o r roses is m o r e p r o b l e m a t i c because o f the necessity to control l a r v a e o f Heliothis spp. ( L e p i d o p t e r a : N o c t u i d a e ) w h i c h feed on the buds. T h e m o t h s are e x c l u d e d f r o m the rose tunnels. T h e m o s t effective c h e m i c a l s for control o f these l a r v a e are inimical to P. persimilis. T h e future o f the o u t d o o r rose industry, a n d o t h e r similar flower crops in Q u e e n s l a n d , m a y well d e p e n d on o u r ability to control Heliothis l a r v a e while allowing P. persimilis to r e m a i n effective.
Acknowledgements T h e a u t h o r t h a n k s D r V. E. E d g e , N S W D e p a r t m e n t o f A g r i c u l t u r e a n d Fisheries, R y d a l m e r e , w h o b i o a s s a y e d the C l e v e l a n d strain for resistance to clofentezine, h e x y t h i a z o x , c y h e x a t i n a n d p r o p a r g i t e a n d for his c o m m e n t s on the m a n u s c r i p t . S u z a n n e R a y n e r assisted with the field trials a n d L a r r y C o o p e r with p r e p a r a t i o n o f d a t a . T h a n k s also to rose growers K e n a n d the late M a x M c K a v a n a g h , G e o r g e M a r s h a l l , G r a h a m Mitchell a n d Bob a n d B r a d S k i n n e r for their c o m p l e t e c o o p e r a t i o n . T h i s w o r k was f u n d e d in p a r t b y g r a n t s f r o m the Q u e e n s l a n d N u r s e r y I n d u s t r y Association a n d the A u s t r a lian C o m m o n w e a l t h G o v e r n m e n t t h r o u g h the A u s t r a l i a n Special R u r a l R e s e a r c h F u n d .
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Received 6 March 1989 Revised 22 August 1989 Accepted 12 September 1989
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