- Email: [email protected]
Control of apple diseases and pests with low spray volumes and reduced chemical rates
CROP PROTECTION (1986) 5 (4), 283-287
Control of apple diseases and pests with low spray v o l u m e s and r e d u c e d c h e m i c a l rates T. J. WICKS AND L. F. NITSCHKE
South Australian Department of Agriculture, GPO Box 1671, Adelaide, South Australia 5001 ABSTRACT. Fungicides applied in volumes of either 100, 200 or 800 1/ha controlled apple scab in large-scale field experiments from 1982 to 1985. Either Sonax C, a formulated mixture ofetaconazole and captan applied at 1 kg/ha (one-third the recommended rate), or fenarimol at 112 ml/ha (one-quarter the recommended rate), controlled scab when applied in 100 or 200 1/ha respectively. Scab was controlled with either eight protectant or at least five eradicant applications of Sonax C at either 3 or 1 kg/ha in 200 1of water per hectare. In all years, weather conditions favoured the development of scab. In unsprayed trees the incidence of scabbed fruit ranged from 60% in cv. Granny Smith to 26°70in cv. Jonathan. In sprayed trees fruit infection rarely exceeded 1°7o. The control of powdery mildew was unsatisfactory with Sonax C applied at 1 kg in 100 1/ha. Better control was achieved by either increasing the spray volume or the rate of fungicide per hectare. Two-spotted and European mites were controlled with propargite at the recommended rate of 5.5 kg/ha at either 200 or 800 1/ha. Codling moth was controlled with 160 ml/ha ofazinphos-methyl (one-quarter the recommended rate) applied in 800 1/ha.
Introduction In Australia most apple growers apply up to 12 sprays each season to control codling (Cydia pomonella L.) and light brown apple moths (Epiphyas postvittana Walk.), mites, apple scab (Venturia inaequalis (Cke) Wint.) and powdery mildew (Podosphaera leucotricha (Ell. & Ev.) Salm.). A wide variety of machines are used to apply the pesticides (Johnson, 1965), but most operate using water volumes of 900-2700 1/ha. Few Australian orchardists apply low spray volumes (less than 2001/ha, Matthews, 1979) although the technique potentially offers considerable cost saving, both in time and in chemicals. A possible reason for this is that there have been few reported studies evaluating low-volume spraying in Australian orchards except for the work of Whan, Smith and Morgan (1983). This paper reports the studies conducted in South Australia from 1982 to 1985 evaluating spray programmes based on the use of reduced spray volumes and reduced pesticide rates.
Materials and methods
e.c.), and Sonax C, a formulated mixture of 2% etaconazole ((___)-l-[2-(2,4-dichlorophenyl)-4-ethyl1,3-dioxolan-2-ylmethyl]-lH-1,2,4-triazole) and 50°70 captan (N-(trichloromethylthio)cyclohex-4-ene- 1,2dicarboximide). They were applied at either the recommended rate, one-half, one-third or one-quarter of that rate in spray volumes of 100, 200 and 800 1/ha. The combinations of chemical rates and spray volumes are shown in Tables 1-3, As the standard South Australian practice for the control of apple scab, copper oxychloride was applied at normal rates to all trees at bud break. The other fungicides were applied at either 10-14-day intervals or within five days from the start of an infection period. A 'DeWit' leaf wetness recorder was used to indicate the start of apple scab infection periods as calculated from 'Mills' periods (Mills and La Plante, 1951). During the 1984/85 season the miticide propargite (2-(4-tert-butylphenoxy)cyclohexl prop-2-ynyl sulphite) was used at the recommended rate of 5.Skg/ha in 200 and 800 1/ha. In all years 160ml/ha (one-quarter of the recommended rate) of azinphosmethyl (S-(3,4-dihydro-4-oxobenzo[d][ 1,2,3]triazin-3ylmethyl) O,O-dimethyl phosphorodithioate, 50°70 e.c.) was applied in 800 l/ha to control codling moth.
Pesticides The fungicides used were Rubigan (fenarimol; (___)-2,4' dichloro-ot-(pyrimidin-5-yl)benzhydryl alcohol; 12°7o 0261-2194/86104/0283-05 $03.00 © 1986 Butterworth & Co (Publishers) Ltd
Equipment T w o spray machines were used in these experiments.
Low-volume spraying of apple trees
284
TABLE 1. Effect of different spray volumes and fungicide rates on the incidence of apple scab, 1982/83, using Micron X7 spray heads Infection (%) Fungicide
Rate of product per hectare
Spray volume (1/ha)
Leaves
Fruit
Block
Cultivar
C
Jonathan Red Delicious Granny Smith Golden Delicious
Sonax C Sonax C Sonax C Sonax C
3 kg* 3 kg 3 kg 3 kg
200 200 200 200
0 2 0 0
0 0 0 0
E
Jonathan Jonathan Granny Smith Granny Smith
Rubigan Rubigan Rubigan Rubigan
450 ml* 225 ml 450 ml 225 ml
200 200 200 200
0 0 0 0
0 0 0 0
E
Jonathan Granny Smith
Unsprayed Unsprayed
---
---
31 67
26 60
*Recommended rate
TABLE 2. Effect of different spray volumes and fungicide rates on the incidence of apple scab and powdery mildew during 1984/85 Infection (%)
Block
Rate of Spray product volume per hectare ( 1 / h a )
Cultivar
Fungicide
Golden Delicious Golden Delicious Granny Smith Granny Smith Jonathan Jonathan
Sonax C Sonax C Sonax C Sonax C Sonax C Sonax C
1 kg 1 kg 1 kg I kg i kg 1 kg
D
Red Delicious Red Delicious
Rubigan Rubigan
H
Jonathan Jonathan Golden Delicious Golden Delicious
C
Apple scab
Powdery mildew
Leaves
Fruit
Nov. 1984
800 200 800 200 800 200
2.6 1- 0 3- 0 i-2 3.0 0.6
0.0 0.0 0.3 0.1 0.3 0.0
----12.5 21.0
225ml 112 ml
200 200
3.0 2.0
0-1 0-1
---
Sonax C Sonax C Sonax C Sonax C
2-0 kg 1-0kg 2.0 kg 1.0 kg
100 100 100 100
0-4 0-8 0 2.5
0 0 0 0.5
10.5 44.0 ---
June 1985:~
(X21 = 5- 23)*
4.3 11.0
(X21= 13"36)**
1.5 7.8
(X21= 19" 3)***
(X21-- 59"8)***
E
Jonathan Granny Smith
Unsprayed Unsprayed
---
---
23.6 45- 6
24.2 48.9
100 --
39.3
F
Jonathan Golden Delicious
Unsprayed Unsprayed
---
---
44- 5 56.0
56.5 78.0
62 --
61.0
t% Secondary mildew. ~Primary mildew-silvered extension shoots. *P=0'05; **P=O'O1; ***P=0.001
TABLE 3. Incidence of apple scab after protectant or eradicant spray schedules Infection (%) Number of sprays per season* Cultivar Jonathan Jonathan Jonathan Granny Smith Granny Smith Granny Smith
Leaves
Fruit
tSchedule
1983/84
1984/85
1983/84
1984/85
1983/84
1984/85
P E U P E U
8 4 0 8 4 0
8 5 0 8 5 0
0.8 0- 3 20.0 3.3 1.5 42.0
1.2 3.2 31.0 2- 4 2.4 67- 0
NA* NA NA NA NA NA
0 0 26.0 0 1' 0 60.0
*SonaxC applied at 3 kg/ha(1983/84) and 1kg/ha(1984/85) in 2001/ha. t p :I:NA= not assessed
=
protectant, applied before infection. E eradicant, applied within 5 days from infection. U unsprayed.
During 1982/83 a modified three-point linkage airassisted sprayer (Model AF3 Metters MBP) was used. The main modifications were the replacement of the hydraulic nozzles with four sets of Micron X7 spinning-disc atomizers and the addition of baffles to direct an even air flow (110km/h and 1.5m3/s) to the spinning nozzles so that each nozzle spun within the range of 13 000-15 000 rev/min. Rotation speed was
=
=
checked periodically during the season using an electronic counter. Other modifications included replacing the 5501 tank with a 2201 tank and replacing the original diaphragm pump with a low-pressure centrifugal pump. The pump was replaced to give better agitation of the spray tank needed when spraying concentrated spray mixtures. The unit was calibrated to apply 200 l/ha with a tractor ground speed of
T. J. WICKSANDL. F. NITSCHKE 3" 8 km/h. This machine was only used for one season as the micron X7 atomizers required considerable maintenance and spare parts were difficult to obtain. During 1983/84 and 1984/85, a three-point linkage Pony Kinkelder sprayer with air-shear nozzles and electrostatic attachments that induced electrical charges on the droplets was used. Descriptions of the sprayer are given by Keil et al. (1980) and Inculet et al. (1981). The machine was calibrated to apply either 100, 200 or 800 1/ha. The spray volumes used were recorded after each spraying period so the accuracy of the applied volume could be checked throughout the spray season. The tractor travelled at 3.8 km/h and in all treatments the spray machine was used with the electrostatics switched on.
285
1984, by recording the number of extension shoots with one or more mildewed leaves, and in early June 1985 by recording the number of 'pinched' mildewed terminal shoots. Both assessments were made on 100 shoots chosen at random on each of five trees. The incidences of European red mite, Panonychus ulmi Koch, and two-spotted mite, Tetranychus urticae Koch, were monitored in cv. Red Delicious in Block C during 1984/85. The presence or absence of mites was recorded at weekly intervals on 100 leaves chosen at random from the bottom half of ten sprayed trees for each treatment (Pielou, 1960; Zalom et al., 1984). Codling moth infestation was assessed as the fruit was graded. Results
Orchard design
Apple scab control
All experiments were conducted on the Lenswood Research Centre situated at Lenswood in the main apple-growing area of South Australia, approximately 30km east of Adelaide. The blocks were planted between 1968 and 1972 and varied in planting distance and cultivar as described in Table 4. Blocks of at least 80 trees were used in these experiments to facilitate the use of commercial machinery and reduce the spray drift between treated blocks. For assessment a minimum of five replicated trees were selected at random from the middle of each block. Assessment rows were surrounded on either side of one or more (mainly three) barrier rows. In block E, unsprayed trees were approximately 20m away from sprayed trees in the same block. Block F was a separate unsprayed area approximately 200 m from block H. Disease and pest assessment Apple scab leaf infection was assessed approximately 2 weeks after each infection period and at harvest. As there was little difference in these assessments except for the unsprayed plots, only final counts are reported. Apple scab incidence was assessed by counting the number of infected leaves per treatment in 100 leaves in 1982/83 and 200 leaves in 1984/85, collected from four positions selected randomly around each of the five trees (Jeger, 1981). Between 1300 and 6000 fruit were assessed from each treatment at harvest. Powdery mildew was assessed only in the 1984/85 experiments on Jonathan which is the most susceptible apple cultivar grown on the Research Centre. Incidence of powdery mildew was assessed in November TABLE 4. Block C D E F H
At least five apple scab infection periods were recorded in each year, resulting in high levels of apple scab infection in the unsprayed blocks. For example 67% and 49% of unsprayed Granny Smith fruit were infected in block E in 1982/83 and 1984/85 respectively (Tables 1, 2). All combinations of spray rate and spray volume tested controlled apple scab. Efficacy was not reduced by either cultivar, planting distance or training systems (Tables 1, 2). The incidence of scab was commercially acceptable and considerably less than 1% in all treatments in all years. Reducing the rate of Sonax C to one-third and that of Rubigan to one-quarter of that recommended did not reduce the effectiveness of either material. At the lowest rate of Sonax C, excellent control of apple scab was achieved in spray volumes of either 800, 200 or 100 l/ha (Table 2). In all seasons the incidence o f apple scab was similar in trees sprayed on a protectant schedule and those sprayed only within 5 days of an infection period. For example in 1984/85 eight protectant sprays controlled apple scab on both cvs Jonathan and Granny Smith, and was similar to the control achieved with five sprays applied after infection (Table 3). Powdery mildew control Infection-levels of powdery mildew were high during the 1984185 experiments as secondary mildew was detected on 100°7o and 62% of the unsprayed shoots of Jonathan trees in blocks E and F respectively (Table 2).
Orchard blocks used for spray evaluation
Cultivar Golden Delicious, Granny Smith, Jonathan, Red Delicious Red Delicious Jonathan, Granny Smith Jonathan Jonathan, Golden Delicious, Red Delicious
Planting distance 5.5 m x 5.5 m Average 3- 0 m x 5.0 m Average 3.0 m x 5.0 m 5.5 m x 5.5 m 3" 0 m x 5.0 m
Training system Plant height (m) Vase Vase Central leader Vase Central leader
4--4.5 2.5--3 2.5 2.5
286
Low-volume spraying of apple trees
10090-
than 85% of leaves throughout summer, with severe leaf drop in early autumn.
'~"
80 o~ 70
.~
•~
9
60
e-
•~
Codling moth control Less than 0.05% of fruit was infested despite three codling moth flights being recorded in the orchard with lure traps in 1984/85. Although codling moth was not assessed in other seasons, it caused no economic loss during this period and in two previous seasons in which the low rates of aziphos-methyl were used.
o.
50
~> 4 0
..J
; '
3020
~
Discussion
10.
-11
.~-r---r--r---
-3~ii 3
10
17
24
31
38 44
5'1
58
6'6 72
Days from spraying
FIGURE 1. Response of two-spotted mite to propargite applied at 200 ( • - - -- - - • ) and 800 ( • • ) 1/ha using a 'Pony' Kinkelder sprayer in 1985.
Powdery mildew was controlled by Sonax C but the incidence of the disease was greatest in those trees sprayed with low volumes and a low rate of fungicide (Table 2). At the 1 kg/ha rate ofSonax C the incidence of powdery mildew declined with an increase in the spray volume applied (Table 2).
Contol of two-spotted and European red mites At both 200 l/ha and 800 1/ha good mite control was achieved immediately and up to 30 days after spraying. There was, however, a marked increase in European red mite 6 weeks after spraying trees at 200 1/ha compared with those sprayed with 800 1/ha. Similar differences were not observed for two-spotted mite (Figures 1 and 2). Although the incidence of mites in unsprayed trees was not assessed in this experiment, assessments in other seasons detected mites on more 100
90 ¸ 80 ¸
70 P 60
•~
j
i-
A .o
O
I
,
,
e
50
40 i
30 20 10
-1'1 -3~,Lz.., 3 10 17 2'4:31 3'8 4~1 5'1 5'8 6'6 72 ,-.
Days from
spraying
FIGURE 2. Response of European red mite to propargite applied at 200 ( • - - -- -- • ) and 800 ( • • ) 1/ha using a 'Pony' Kinkelder sprayer in 1985.
Our results clearly demonstrate that efficient pest and scab control is achievable with reduced spray volumes, reduced rates of chemicals and fewer applications than those commonly used in Australian orchards. In our experiments, spray volumes as low as one-tenth of that currently used by most orchardists and rates of fungicides up to one-quarter of the label recommendation were used. Adoption of reduced spray volumes and pesticide rates similar to those used in our experiments should, in most seasons, result in considerable cost saving to Australian orchardists. Further cost savings are possible with scab control if the number of spray applications is reduced by spraying only after infection rather than spraying on a regular basis. This technique has been adequately evaluated in Australia (Wicks and Moiler, 1970; Penrose et aL, 1985) and our latest results show that the effectiveness of sprays applied after infection is not reduced by using low spray volumes and reduced rates of fungicide. Work elsewhere has shown that reductions in spray volume and pesticide rates greater than those evaluated in our experiments are possible without reducing the degree of disease control. For example Barrat et al. (1981) controlled scab with normal rates of fungicides applied at 9.4 1/ha and Morgan (1974) using a 'hand directed spinning disk sprayer' reported good scab control with one-tenth the conventional amount of benomyl. In addition, Matthee, Thomas and Nel (1976) controlled apple scab with half the normal rate of benomyl applied at 30 1/ha. Although the control of apple scab has been excellent in most cases where low-volume spraying and reduced pesticide rates have been evaluated, the control of powdery mildew in the same or similar experiments has been variable. In our experiments, poor mildew control was achieved with eight Sonax C applications at one-third the recommended rate in 1001/ha. Better control was obtained either with higher spray volumes or by increasing the rate of fungicide. Similar results have been reported by Gunn (1980) and Umpelby (1984) where reduced rates of fungicide with low volumes resulted in poor mildew control. By way of contrast, good control of powdery mildew at reduced rates or low volumes has been reported by
TI J. WICKSANDL. F. NITSCHKE Matthee et aL (1974), Keil et al. (1980) and Whan et al. (1983). These differences illustrate the difficulty of comparing experiments conducted at different sites. Factors such as planting distances, tree height and shape, spray machines, pesticides and spray additives and climatic conditions at the time and after spraying, all affect spray deposition and efficacy and at least some of these factors will differ between sites. Much more work needs to be done to evaluate and refine low-volume and electrostatic spraying in tree crops. However, as our experiments were conducted in large commercial blocks of trees and sprayed with commercial machines, we believe that similar spraying techniques could readily be adopted by the majority of Australian orchardists.
Acknowledgements We thank all staff at the Lenswood Research Centre for co-operating in these experiments and in particular Mr H. H. van Dam for his assistance in planning and monitoring the spray programmes. Also Mr D. R. C. Traeger and Mr R. H. Allen for assistance in assessing spray programmes, Mrs B. Hall for preparing the figures and Mr P. M. McCloud for analysing the data.
References BARRAT, R. E., MASS, J. L., RETZER, H. J. AND ADAMS, R. E. (1981). Comparisons of spray droplet size, pesticide deposition and drift with ultralow-volume, low-volume, and dilute pesticide application on apple. Plant Disease 65, 872-875. GUNN, E. (1980). Pesticide application on top fruit--a review. In:
Spraying Systems for the 1980s. British Crop Protection Council Monograph No. 24, pp. 253-260 (ed. by J. O. Walker). Croydon: BCPC. INCULET, I. I., CASTLE, G. S. P., MENZIES, D. m. AND FRANK, R. (1981 ). Deposition studies with a novel form of electrostatic crop sprayer. Journal of Electrostatics 10, 65-72. JEGER, M. J. (1981). Disease measurements in a study of apple scab
287
epidemics. Annals of Applied Biology 99, 43-51. JOHNSON, J. F. (1965). Developments in orchard spraying machinery. Agricultural Gazette, New South Wales 76, 226232. KEIL, H. L., RETZER, H. J., EARRAT, R. E. AND MASS, J. L. (1980). Ultra-low volume spray control of three apple diseases. Plant Disease 64, 681-684. MATTHEE, F. N., THOMAS, A. C. AND NEL, E. W. (1976). Efficacy of low volume, very low volume and ultra-low volume sprays against apple scab. DeciduousFruit Grower 26, 104-110. MATTHEE, F. N., THOMAS, A. C., SCHWABE, W. F. S. AND NEL, E. W. (1974). Control of apple mildew (Podosphaera leucotricha) by applying low and ultra-low-volume sprays. Deciduous Fruit Grower 24, 174-179. MATTHEWS, G. A. (1979). Pesticide Application Methods, pp. 33-34. London: Longmans. MILLS,W. D. AND LA PLANTE,A. A. (1951). Control of diseases and insects in the orchard. New York AgriculturalExperimental Station (Ithaca) Extension Bulletin, pp. 18-22. MORGAN,N. G. (1974). Some BiologicalRequirements in the U.L. V.
Spraying of Top Fruit. British Crop Protection CouncilMonograph No. 11. Croydon: BCPC. PENROSE, L. J., HEATON,J. B., WASHINGTON,W. S. ANDWICKS, T. J. (1985). Australian evaluation of an orchard-based electronic device to predict apple scab infections. Journal of the Australian Institute of Agriculture Science 51, 74-78. PIELOU, D. P. (1960). Contagious distribution in the European red mite, Panonychus ulmi (Koch), and a method for grading population densities for a count of mite-free leaves. Canadian Journal of Zoology 38, 645-653. UMPELBY, R. A. (1984). Pest and disease control with medium and reduced volume spraying of apples, Luddington, 1981-1984.
Proceedings 1984 British Crop Protection Conference--Pests and Diseases 3, 1075-1082. WHAN, J. H., SMITH, I. R. AND MORGAN,N. G. (1983). Effect of spraying techniques on the brown rot of peach fruit and on black spot, powdery mildew and two-spotted mite of apple trees. PesticideScience 14, 609-614. WICKS, T. J. AND MOLLER, W. J. (1970). Benomyl as a spring eradicant for apple scab. Experimental Record 5, 25-27. ZALOM,F. G., HoY, M. A., WILSON,L. T. ANDBARNETT,W. W. (1984). Presence-absence sequential sampling for Tetranychus mite species. Hilgardia 52 (7), 14-24.
Accepted 3 February 1986
Control of apple diseases and pests with low spray v o l u m e s and r e d u c e d c h e m i c a l rates T. J. WICKS AND L. F. NITSCHKE
South Australian Department of Agriculture, GPO Box 1671, Adelaide, South Australia 5001 ABSTRACT. Fungicides applied in volumes of either 100, 200 or 800 1/ha controlled apple scab in large-scale field experiments from 1982 to 1985. Either Sonax C, a formulated mixture ofetaconazole and captan applied at 1 kg/ha (one-third the recommended rate), or fenarimol at 112 ml/ha (one-quarter the recommended rate), controlled scab when applied in 100 or 200 1/ha respectively. Scab was controlled with either eight protectant or at least five eradicant applications of Sonax C at either 3 or 1 kg/ha in 200 1of water per hectare. In all years, weather conditions favoured the development of scab. In unsprayed trees the incidence of scabbed fruit ranged from 60% in cv. Granny Smith to 26°70in cv. Jonathan. In sprayed trees fruit infection rarely exceeded 1°7o. The control of powdery mildew was unsatisfactory with Sonax C applied at 1 kg in 100 1/ha. Better control was achieved by either increasing the spray volume or the rate of fungicide per hectare. Two-spotted and European mites were controlled with propargite at the recommended rate of 5.5 kg/ha at either 200 or 800 1/ha. Codling moth was controlled with 160 ml/ha ofazinphos-methyl (one-quarter the recommended rate) applied in 800 1/ha.
Introduction In Australia most apple growers apply up to 12 sprays each season to control codling (Cydia pomonella L.) and light brown apple moths (Epiphyas postvittana Walk.), mites, apple scab (Venturia inaequalis (Cke) Wint.) and powdery mildew (Podosphaera leucotricha (Ell. & Ev.) Salm.). A wide variety of machines are used to apply the pesticides (Johnson, 1965), but most operate using water volumes of 900-2700 1/ha. Few Australian orchardists apply low spray volumes (less than 2001/ha, Matthews, 1979) although the technique potentially offers considerable cost saving, both in time and in chemicals. A possible reason for this is that there have been few reported studies evaluating low-volume spraying in Australian orchards except for the work of Whan, Smith and Morgan (1983). This paper reports the studies conducted in South Australia from 1982 to 1985 evaluating spray programmes based on the use of reduced spray volumes and reduced pesticide rates.
Materials and methods
e.c.), and Sonax C, a formulated mixture of 2% etaconazole ((___)-l-[2-(2,4-dichlorophenyl)-4-ethyl1,3-dioxolan-2-ylmethyl]-lH-1,2,4-triazole) and 50°70 captan (N-(trichloromethylthio)cyclohex-4-ene- 1,2dicarboximide). They were applied at either the recommended rate, one-half, one-third or one-quarter of that rate in spray volumes of 100, 200 and 800 1/ha. The combinations of chemical rates and spray volumes are shown in Tables 1-3, As the standard South Australian practice for the control of apple scab, copper oxychloride was applied at normal rates to all trees at bud break. The other fungicides were applied at either 10-14-day intervals or within five days from the start of an infection period. A 'DeWit' leaf wetness recorder was used to indicate the start of apple scab infection periods as calculated from 'Mills' periods (Mills and La Plante, 1951). During the 1984/85 season the miticide propargite (2-(4-tert-butylphenoxy)cyclohexl prop-2-ynyl sulphite) was used at the recommended rate of 5.Skg/ha in 200 and 800 1/ha. In all years 160ml/ha (one-quarter of the recommended rate) of azinphosmethyl (S-(3,4-dihydro-4-oxobenzo[d][ 1,2,3]triazin-3ylmethyl) O,O-dimethyl phosphorodithioate, 50°70 e.c.) was applied in 800 l/ha to control codling moth.
Pesticides The fungicides used were Rubigan (fenarimol; (___)-2,4' dichloro-ot-(pyrimidin-5-yl)benzhydryl alcohol; 12°7o 0261-2194/86104/0283-05 $03.00 © 1986 Butterworth & Co (Publishers) Ltd
Equipment T w o spray machines were used in these experiments.
Low-volume spraying of apple trees
284
TABLE 1. Effect of different spray volumes and fungicide rates on the incidence of apple scab, 1982/83, using Micron X7 spray heads Infection (%) Fungicide
Rate of product per hectare
Spray volume (1/ha)
Leaves
Fruit
Block
Cultivar
C
Jonathan Red Delicious Granny Smith Golden Delicious
Sonax C Sonax C Sonax C Sonax C
3 kg* 3 kg 3 kg 3 kg
200 200 200 200
0 2 0 0
0 0 0 0
E
Jonathan Jonathan Granny Smith Granny Smith
Rubigan Rubigan Rubigan Rubigan
450 ml* 225 ml 450 ml 225 ml
200 200 200 200
0 0 0 0
0 0 0 0
E
Jonathan Granny Smith
Unsprayed Unsprayed
---
---
31 67
26 60
*Recommended rate
TABLE 2. Effect of different spray volumes and fungicide rates on the incidence of apple scab and powdery mildew during 1984/85 Infection (%)
Block
Rate of Spray product volume per hectare ( 1 / h a )
Cultivar
Fungicide
Golden Delicious Golden Delicious Granny Smith Granny Smith Jonathan Jonathan
Sonax C Sonax C Sonax C Sonax C Sonax C Sonax C
1 kg 1 kg 1 kg I kg i kg 1 kg
D
Red Delicious Red Delicious
Rubigan Rubigan
H
Jonathan Jonathan Golden Delicious Golden Delicious
C
Apple scab
Powdery mildew
Leaves
Fruit
Nov. 1984
800 200 800 200 800 200
2.6 1- 0 3- 0 i-2 3.0 0.6
0.0 0.0 0.3 0.1 0.3 0.0
----12.5 21.0
225ml 112 ml
200 200
3.0 2.0
0-1 0-1
---
Sonax C Sonax C Sonax C Sonax C
2-0 kg 1-0kg 2.0 kg 1.0 kg
100 100 100 100
0-4 0-8 0 2.5
0 0 0 0.5
10.5 44.0 ---
June 1985:~
(X21 = 5- 23)*
4.3 11.0
(X21= 13"36)**
1.5 7.8
(X21= 19" 3)***
(X21-- 59"8)***
E
Jonathan Granny Smith
Unsprayed Unsprayed
---
---
23.6 45- 6
24.2 48.9
100 --
39.3
F
Jonathan Golden Delicious
Unsprayed Unsprayed
---
---
44- 5 56.0
56.5 78.0
62 --
61.0
t% Secondary mildew. ~Primary mildew-silvered extension shoots. *P=0'05; **P=O'O1; ***P=0.001
TABLE 3. Incidence of apple scab after protectant or eradicant spray schedules Infection (%) Number of sprays per season* Cultivar Jonathan Jonathan Jonathan Granny Smith Granny Smith Granny Smith
Leaves
Fruit
tSchedule
1983/84
1984/85
1983/84
1984/85
1983/84
1984/85
P E U P E U
8 4 0 8 4 0
8 5 0 8 5 0
0.8 0- 3 20.0 3.3 1.5 42.0
1.2 3.2 31.0 2- 4 2.4 67- 0
NA* NA NA NA NA NA
0 0 26.0 0 1' 0 60.0
*SonaxC applied at 3 kg/ha(1983/84) and 1kg/ha(1984/85) in 2001/ha. t p :I:NA= not assessed
=
protectant, applied before infection. E eradicant, applied within 5 days from infection. U unsprayed.
During 1982/83 a modified three-point linkage airassisted sprayer (Model AF3 Metters MBP) was used. The main modifications were the replacement of the hydraulic nozzles with four sets of Micron X7 spinning-disc atomizers and the addition of baffles to direct an even air flow (110km/h and 1.5m3/s) to the spinning nozzles so that each nozzle spun within the range of 13 000-15 000 rev/min. Rotation speed was
=
=
checked periodically during the season using an electronic counter. Other modifications included replacing the 5501 tank with a 2201 tank and replacing the original diaphragm pump with a low-pressure centrifugal pump. The pump was replaced to give better agitation of the spray tank needed when spraying concentrated spray mixtures. The unit was calibrated to apply 200 l/ha with a tractor ground speed of
T. J. WICKSANDL. F. NITSCHKE 3" 8 km/h. This machine was only used for one season as the micron X7 atomizers required considerable maintenance and spare parts were difficult to obtain. During 1983/84 and 1984/85, a three-point linkage Pony Kinkelder sprayer with air-shear nozzles and electrostatic attachments that induced electrical charges on the droplets was used. Descriptions of the sprayer are given by Keil et al. (1980) and Inculet et al. (1981). The machine was calibrated to apply either 100, 200 or 800 1/ha. The spray volumes used were recorded after each spraying period so the accuracy of the applied volume could be checked throughout the spray season. The tractor travelled at 3.8 km/h and in all treatments the spray machine was used with the electrostatics switched on.
285
1984, by recording the number of extension shoots with one or more mildewed leaves, and in early June 1985 by recording the number of 'pinched' mildewed terminal shoots. Both assessments were made on 100 shoots chosen at random on each of five trees. The incidences of European red mite, Panonychus ulmi Koch, and two-spotted mite, Tetranychus urticae Koch, were monitored in cv. Red Delicious in Block C during 1984/85. The presence or absence of mites was recorded at weekly intervals on 100 leaves chosen at random from the bottom half of ten sprayed trees for each treatment (Pielou, 1960; Zalom et al., 1984). Codling moth infestation was assessed as the fruit was graded. Results
Orchard design
Apple scab control
All experiments were conducted on the Lenswood Research Centre situated at Lenswood in the main apple-growing area of South Australia, approximately 30km east of Adelaide. The blocks were planted between 1968 and 1972 and varied in planting distance and cultivar as described in Table 4. Blocks of at least 80 trees were used in these experiments to facilitate the use of commercial machinery and reduce the spray drift between treated blocks. For assessment a minimum of five replicated trees were selected at random from the middle of each block. Assessment rows were surrounded on either side of one or more (mainly three) barrier rows. In block E, unsprayed trees were approximately 20m away from sprayed trees in the same block. Block F was a separate unsprayed area approximately 200 m from block H. Disease and pest assessment Apple scab leaf infection was assessed approximately 2 weeks after each infection period and at harvest. As there was little difference in these assessments except for the unsprayed plots, only final counts are reported. Apple scab incidence was assessed by counting the number of infected leaves per treatment in 100 leaves in 1982/83 and 200 leaves in 1984/85, collected from four positions selected randomly around each of the five trees (Jeger, 1981). Between 1300 and 6000 fruit were assessed from each treatment at harvest. Powdery mildew was assessed only in the 1984/85 experiments on Jonathan which is the most susceptible apple cultivar grown on the Research Centre. Incidence of powdery mildew was assessed in November TABLE 4. Block C D E F H
At least five apple scab infection periods were recorded in each year, resulting in high levels of apple scab infection in the unsprayed blocks. For example 67% and 49% of unsprayed Granny Smith fruit were infected in block E in 1982/83 and 1984/85 respectively (Tables 1, 2). All combinations of spray rate and spray volume tested controlled apple scab. Efficacy was not reduced by either cultivar, planting distance or training systems (Tables 1, 2). The incidence of scab was commercially acceptable and considerably less than 1% in all treatments in all years. Reducing the rate of Sonax C to one-third and that of Rubigan to one-quarter of that recommended did not reduce the effectiveness of either material. At the lowest rate of Sonax C, excellent control of apple scab was achieved in spray volumes of either 800, 200 or 100 l/ha (Table 2). In all seasons the incidence o f apple scab was similar in trees sprayed on a protectant schedule and those sprayed only within 5 days of an infection period. For example in 1984/85 eight protectant sprays controlled apple scab on both cvs Jonathan and Granny Smith, and was similar to the control achieved with five sprays applied after infection (Table 3). Powdery mildew control Infection-levels of powdery mildew were high during the 1984185 experiments as secondary mildew was detected on 100°7o and 62% of the unsprayed shoots of Jonathan trees in blocks E and F respectively (Table 2).
Orchard blocks used for spray evaluation
Cultivar Golden Delicious, Granny Smith, Jonathan, Red Delicious Red Delicious Jonathan, Granny Smith Jonathan Jonathan, Golden Delicious, Red Delicious
Planting distance 5.5 m x 5.5 m Average 3- 0 m x 5.0 m Average 3.0 m x 5.0 m 5.5 m x 5.5 m 3" 0 m x 5.0 m
Training system Plant height (m) Vase Vase Central leader Vase Central leader
4--4.5 2.5--3 2.5 2.5
286
Low-volume spraying of apple trees
10090-
than 85% of leaves throughout summer, with severe leaf drop in early autumn.
'~"
80 o~ 70
.~
•~
9
60
e-
•~
Codling moth control Less than 0.05% of fruit was infested despite three codling moth flights being recorded in the orchard with lure traps in 1984/85. Although codling moth was not assessed in other seasons, it caused no economic loss during this period and in two previous seasons in which the low rates of aziphos-methyl were used.
o.
50
~> 4 0
..J
; '
3020
~
Discussion
10.
-11
.~-r---r--r---
-3~ii 3
10
17
24
31
38 44
5'1
58
6'6 72
Days from spraying
FIGURE 1. Response of two-spotted mite to propargite applied at 200 ( • - - -- - - • ) and 800 ( • • ) 1/ha using a 'Pony' Kinkelder sprayer in 1985.
Powdery mildew was controlled by Sonax C but the incidence of the disease was greatest in those trees sprayed with low volumes and a low rate of fungicide (Table 2). At the 1 kg/ha rate ofSonax C the incidence of powdery mildew declined with an increase in the spray volume applied (Table 2).
Contol of two-spotted and European red mites At both 200 l/ha and 800 1/ha good mite control was achieved immediately and up to 30 days after spraying. There was, however, a marked increase in European red mite 6 weeks after spraying trees at 200 1/ha compared with those sprayed with 800 1/ha. Similar differences were not observed for two-spotted mite (Figures 1 and 2). Although the incidence of mites in unsprayed trees was not assessed in this experiment, assessments in other seasons detected mites on more 100
90 ¸ 80 ¸
70 P 60
•~
j
i-
A .o
O
I
,
,
e
50
40 i
30 20 10
-1'1 -3~,Lz.., 3 10 17 2'4:31 3'8 4~1 5'1 5'8 6'6 72 ,-.
Days from
spraying
FIGURE 2. Response of European red mite to propargite applied at 200 ( • - - -- -- • ) and 800 ( • • ) 1/ha using a 'Pony' Kinkelder sprayer in 1985.
Our results clearly demonstrate that efficient pest and scab control is achievable with reduced spray volumes, reduced rates of chemicals and fewer applications than those commonly used in Australian orchards. In our experiments, spray volumes as low as one-tenth of that currently used by most orchardists and rates of fungicides up to one-quarter of the label recommendation were used. Adoption of reduced spray volumes and pesticide rates similar to those used in our experiments should, in most seasons, result in considerable cost saving to Australian orchardists. Further cost savings are possible with scab control if the number of spray applications is reduced by spraying only after infection rather than spraying on a regular basis. This technique has been adequately evaluated in Australia (Wicks and Moiler, 1970; Penrose et aL, 1985) and our latest results show that the effectiveness of sprays applied after infection is not reduced by using low spray volumes and reduced rates of fungicide. Work elsewhere has shown that reductions in spray volume and pesticide rates greater than those evaluated in our experiments are possible without reducing the degree of disease control. For example Barrat et al. (1981) controlled scab with normal rates of fungicides applied at 9.4 1/ha and Morgan (1974) using a 'hand directed spinning disk sprayer' reported good scab control with one-tenth the conventional amount of benomyl. In addition, Matthee, Thomas and Nel (1976) controlled apple scab with half the normal rate of benomyl applied at 30 1/ha. Although the control of apple scab has been excellent in most cases where low-volume spraying and reduced pesticide rates have been evaluated, the control of powdery mildew in the same or similar experiments has been variable. In our experiments, poor mildew control was achieved with eight Sonax C applications at one-third the recommended rate in 1001/ha. Better control was obtained either with higher spray volumes or by increasing the rate of fungicide. Similar results have been reported by Gunn (1980) and Umpelby (1984) where reduced rates of fungicide with low volumes resulted in poor mildew control. By way of contrast, good control of powdery mildew at reduced rates or low volumes has been reported by
TI J. WICKSANDL. F. NITSCHKE Matthee et aL (1974), Keil et al. (1980) and Whan et al. (1983). These differences illustrate the difficulty of comparing experiments conducted at different sites. Factors such as planting distances, tree height and shape, spray machines, pesticides and spray additives and climatic conditions at the time and after spraying, all affect spray deposition and efficacy and at least some of these factors will differ between sites. Much more work needs to be done to evaluate and refine low-volume and electrostatic spraying in tree crops. However, as our experiments were conducted in large commercial blocks of trees and sprayed with commercial machines, we believe that similar spraying techniques could readily be adopted by the majority of Australian orchardists.
Acknowledgements We thank all staff at the Lenswood Research Centre for co-operating in these experiments and in particular Mr H. H. van Dam for his assistance in planning and monitoring the spray programmes. Also Mr D. R. C. Traeger and Mr R. H. Allen for assistance in assessing spray programmes, Mrs B. Hall for preparing the figures and Mr P. M. McCloud for analysing the data.
References BARRAT, R. E., MASS, J. L., RETZER, H. J. AND ADAMS, R. E. (1981). Comparisons of spray droplet size, pesticide deposition and drift with ultralow-volume, low-volume, and dilute pesticide application on apple. Plant Disease 65, 872-875. GUNN, E. (1980). Pesticide application on top fruit--a review. In:
Spraying Systems for the 1980s. British Crop Protection Council Monograph No. 24, pp. 253-260 (ed. by J. O. Walker). Croydon: BCPC. INCULET, I. I., CASTLE, G. S. P., MENZIES, D. m. AND FRANK, R. (1981 ). Deposition studies with a novel form of electrostatic crop sprayer. Journal of Electrostatics 10, 65-72. JEGER, M. J. (1981). Disease measurements in a study of apple scab
287
epidemics. Annals of Applied Biology 99, 43-51. JOHNSON, J. F. (1965). Developments in orchard spraying machinery. Agricultural Gazette, New South Wales 76, 226232. KEIL, H. L., RETZER, H. J., EARRAT, R. E. AND MASS, J. L. (1980). Ultra-low volume spray control of three apple diseases. Plant Disease 64, 681-684. MATTHEE, F. N., THOMAS, A. C. AND NEL, E. W. (1976). Efficacy of low volume, very low volume and ultra-low volume sprays against apple scab. DeciduousFruit Grower 26, 104-110. MATTHEE, F. N., THOMAS, A. C., SCHWABE, W. F. S. AND NEL, E. W. (1974). Control of apple mildew (Podosphaera leucotricha) by applying low and ultra-low-volume sprays. Deciduous Fruit Grower 24, 174-179. MATTHEWS, G. A. (1979). Pesticide Application Methods, pp. 33-34. London: Longmans. MILLS,W. D. AND LA PLANTE,A. A. (1951). Control of diseases and insects in the orchard. New York AgriculturalExperimental Station (Ithaca) Extension Bulletin, pp. 18-22. MORGAN,N. G. (1974). Some BiologicalRequirements in the U.L. V.
Spraying of Top Fruit. British Crop Protection CouncilMonograph No. 11. Croydon: BCPC. PENROSE, L. J., HEATON,J. B., WASHINGTON,W. S. ANDWICKS, T. J. (1985). Australian evaluation of an orchard-based electronic device to predict apple scab infections. Journal of the Australian Institute of Agriculture Science 51, 74-78. PIELOU, D. P. (1960). Contagious distribution in the European red mite, Panonychus ulmi (Koch), and a method for grading population densities for a count of mite-free leaves. Canadian Journal of Zoology 38, 645-653. UMPELBY, R. A. (1984). Pest and disease control with medium and reduced volume spraying of apples, Luddington, 1981-1984.
Proceedings 1984 British Crop Protection Conference--Pests and Diseases 3, 1075-1082. WHAN, J. H., SMITH, I. R. AND MORGAN,N. G. (1983). Effect of spraying techniques on the brown rot of peach fruit and on black spot, powdery mildew and two-spotted mite of apple trees. PesticideScience 14, 609-614. WICKS, T. J. AND MOLLER, W. J. (1970). Benomyl as a spring eradicant for apple scab. Experimental Record 5, 25-27. ZALOM,F. G., HoY, M. A., WILSON,L. T. ANDBARNETT,W. W. (1984). Presence-absence sequential sampling for Tetranychus mite species. Hilgardia 52 (7), 14-24.
Accepted 3 February 1986