Evaluation of Bacillus thuringiensis, aminocarb and fenitrothion against jack pine budworm (Lepidoptera: Tortricidae) in Northern Ontario

Evaluation of Bacillus thuringiensis, aminocarb and fenitrothion against jack pine budworm (Lepidoptera: Tortricidae) in Northern Ontario B. L. Cadogan Forestry Canada, Forest Pest Management Institute, PO Box 490, Sault Sainte Marie, Ontario, Canada P6A 5M7

A field trial was conducted in Northern Ontario to evaluate the efficacy of Sumithion 20F (fenitrothion, 200 g l-l), Matacil 180F (aminocarb, 180 g l-I) and Futura XLV [Bacillus thuringensis (Bt), 14.4 billion (109) international units (BIU) I-I] against jack pine budworm, Choristoneura pinus pinus Freeman. Fcnitrothion at 210 g ha -1 and aminocarb at 70 g ha i were mixed with water and applied twice by aerial spraying at 1.5 1ha t. Bt was applied undiluted at 20 and 30 BIU ha-1 in 1.4 and 2.1 I ha-~, respectively. Fenitrothion, and Bt (30 BIU), reduced budworm populations by 89% and 72%, respectively, to satisfactory levels of < 2.6 larvae per 60 cm branch, whereas populations treated with aminocarb and Bt at 20 BIU declined by 67% and 45%, respectively, to 5-8 larvae per 60 cm branch. All the treatments provided some measure of foliage protection to the host tree, Pinus banksiana Lamb. Fenitrothion and Bt at 30 BIU provided 64% and 60% foliage protection, respectively. These levels of protection were significantly better (p = 0.05) than the 39% and 23% protection afforded by aminocarb, and Bt at 20 BIU, respectively. Thus, a single application of Bt at 30 BIU ha -~ or fcnitrothion applied twice at 210 g ha -~ controlled jack pine budworm and protected the host tree from severe defoliation. Aminocarb at 70 g ha ~ and Bt at 20 BIU ha -t wcrc only marginally effective.

Key~ords: Choristoneura pinus pinus; Pinus banksiana; Bacillus thuringiensis; aminocarb; fenitrothion

The jack pine budworm, Choristoneura pinus pinus Freeman (JPBW), is one of the most important defoliators of jack pine, Pinus banksiana Lamb., in central Canada and the Lake States Region of the United States. Although e p i d e m i c i n f e s t a t i o n s o f J P B W are usually of short duration, lasting from 1 to 4 years ( D e b o o and Hildahl, 1967), sustained attacks by this insect can result in extensive top kill of target trees and some tree mortality, particularly in stands of low vigour

the forest manager should have more than one insecticidal option to cope with different pest/host-tree situations, this research was conducted to evaluate the efficacy of Futura XLV (a microbial insecticide), Sumithion 20F (a new flowable formulation) and Matacil 180F (also a flowable formulation) against JPBW, with the aim of having them registered for aerial application against the species in Canada.

(Clancy et al., 1980; Howse, 1986). In 1985, for the second consecutive year, infestations of JPBW increased markedly in Ontario (Applejohn and Howse, 1985) and in Manitoba (K. Knowles, personal communication).Theseinfestationsthreatened large areas of jack pine and jeopardized certain sectors of the Canadian pulp and paper industry that depend on jack pine as their major wood supply. Thus, protection of these forests from further insect damage was of paramount importance, Previous studies assessed the efficacy of aerial applications of D D T , Matacii (aminocarb) and Sumithion (fenitrothion) against J P B W in Manitoba ( D e B o o and Hildahl, 1967). However, in 1985, fenitrothion technical was the only insecticide registered in Canada for aerial application againstJPBW. Because

Materials and methods The research was conducted in 1985, - 2 5 km west of the village of Shining Tree in Northern Ontario. Six blocks (each 75-100 ha), four for treatments and two as controls, were selected in naturally regenerated jack pine stands, 25-35 years old. Three plots (each 10-15 ha) were replicated within each block and 24 uniformly sized trees (height 14.8 + 0.45 m; diameter at breast height 20.9 + 2.3 cm) were randomly selected as sample trees in each plot. Spray application Two synthetic chemical insecticides, namely Matacil 180F (aminocarb) and Sumithion 20F (fenitrothion),

0261-2194/93/05/0351 --06

© 1993 Butterworth-HeinemannLtd

Crop Protection 1993 Volume 12 Number 5 351

Jack pine budworm control: B.L. Cadogan and one bacterial insecticide, Futura XLV (Bacillus thuringiensis; Bt), were applied aerially as treatments between June and July. Futura XLV, with a potency of 14.4 billion (14.4 x 109) international units per litre (14.4 BIU !-1), was sprayed undiluted as single applications at 20 BIU (1.4 1) 1 ha-1 and 30 BIU (2.1 0 -1 ha -1, hereafter referred to as Bt-20 and Bt-30, respectively, each to a block. These dosages required flow rates of 16.8 and 25.2 1 min l, respectively. Sumithion 20F (200 g a.i. I-I) and Matacil 180F (180 g a.i. 1-1) were applied twice, with the second application 5 days after the first, Sumithion 20F (210 g a.i. ha -I) was mixed with water (64.5:35.5% v/v) and applied at 1.5 1ha i (18.3 1min-1). The Matacii (70 g a.i. ha-1) tank mix comprised Matacil 180F:water:Atlox 3409F (an emulsifier) in volumetric proportions of 25.9:71.85:1.25 and was sprayed at 1.5 1 ha -t (18.3 1 min-t), To facilitate deposit assessments, the Bt was dyed with Erie acid red dye (0.1% w/v) (St Lawrence Aniline Co., Ontario, Canada). The Matacil and Sumithion tank mixes were dyed with Rhodamine B red dye (1.0% v/v) (C.I.L., Willowdale, Ontario, Canada). The spray aircraft, a Cessna 188 Agtruck fitted with four AU-3000 Micronair rotary atomizers, flew at 160 km h -1 (44.45 m s-I) and released the sprays --10 m above the canopy using swath intervals of 45 m. Sprays were conducted in the morning (05:30-07:00 hours) under inve:sion to neutral stable conditions with winds < 10 km h-1 (< 2.8 m s-1) and a relative humidity between 80 and 95%). Sampling A clearing was made around each sample tree (Cadogan et al., 1984), and a deposit sample unit (Randall, 1980) was placed in each clearing 1 h before the sprays started; these sample units were retrieved 1 h after each spray. In addition, two mid-crown branch tips (each 20 cm) were removed from each sample tree to assess deposit on foliage. The foliage was examined immediately for droplets, whereas the Kromekote cards from the deposit sample units were examined later at the Forest Pest Management Institute, Sault Ste Marie (Zylstra, 1980; Cadogan et al., 1986). Diameters of the aerodynamic droplets that produced the stains captured on the Kromekote cards and from which volume median diameters and number median diameters were calculated, were derived by applying spread factor equations (Haliburton, 1978). In this study the spread factor equations were determined to be as follows: X = (Y/3.7816) 11729 for the Futura XLV, X = (Y/0.7876) °s3°7 for the Sumithion tank mix and X = (Y-- 7.6330)/2.4496 for the Matacil tank mix, where X is the drop diameter and Y is the stain diameter (and Y/> X). Prespray assessments of larval JPBW were made in each block and three or four postspray assessments were made at intervals of 3-8 days. At each sampling, two branch tips (each 60 cm) were taken at random from the midcrown of each sample tree using pole

352 Crop Protection 1993 Volume 12 Number 5

pruners with attached baskets (Churcher, 198l). The living budworms on each branch were either handpicked and counted or removed using a branch-beating technique (Martineau and Benoit, 1973). The population decline in each sample tree was calculated and block mean reductions were established. Where relevant, the decline in JPBW population in each treated block was corrected for natural mortality (Abbott, 1925; Cadogan, 1987) by using populations that were not signficantly different (the appropriate check blocks). Defoliation In October 1985, all the sample trees were re-examined to determine the extent of defoliation. Two midcrown branch tips (60 cm) were again taken from each sample tree and assessed, using the method described by Cadogan etal. (1986). Data analysis The data were analysed using SAS GLM (SAS Institute, Inc., 1985) and BMDP P7D (Dixon, 1983) software. To calculate the percentage foliage protection that can be attributed to the treatments (%PAT) (Cadogan et al., 1986), the data from the untreated plots were grouped into six classes (0, 1-20, 21-30, 31-40, 41-50 and > 50) based upon their mean prespray JPBW populations (x). Their corresponding defoliation values (y) recorded in October, were regressed x against y. The resulting equation (y = 27.84 + 13.76x; R 2 = 0.47) provided the basis from which 'expected' levels of defoliation in the treated blocks could be calculated. With these values, the percentageexpecteddefoliationwasdeterminedfor individual sample trees in the treated plots and then the %PAT was calculated. Results and discussion Spray deposit The synthetic chemical pesticides were rapidly incorporated into the cuticular layers of the jack pine foliage, thus preventing visual enumeration of these droplets; spray deposits on foliage were, therefore, not evaluated. In general, aminocarb and fenitrothion sprays deposited more droplets per unit area on Kromekote cards than did the Bt sprays (Table 1). Both Bt and the synthetic chemical insecticides were applied with narrow spray droplet spectra (Table I), suggesting that the spray comprised primarily droplets < 100 ~tm in diameter. No statistical analyses were conducted on the spray deposit because many uncontrollable variables (such as different spray application times and different weather at spray times) might lead to incorrect or invalid inferences. Population reduction Reductions in JPBW populations are presented in Table 2 and Figure 1. With one exception, no significant

J a c k pine b u d w o r m control: B.L. C a d o g a n

differences (p = 0.05) were o b s e r v e d b e t w e e n the p o o l e d m e a n p r e s p r a y p o p u l a t i o n s that were represe n t a t i v e of the blocks. F u r t h e r m o r e (also with o n e e x c e p t i o n ) , no significant differences were o b s e r v e d b e t w e e n p r e s p r a y p o p u l a t i o n m e a n s within i n d i v i d u a l blocks. J P B W p o p u l a t i o n s in the plots t r e a t e d with f e n i t r o t h i o n a n d Bt-30 d e c l i n e d to satisfactory levels ( < 2.6 larvae per 60 cm b r a n c h ) ; these levels c o r r e s p o n d to m e a n t r e a t m e n t r e d u c t i o n s of 89% a n d 7 2 % , respectively. T h e J P B W p o p u l a t i o n s in the blocks t r e a t e d with Bt-20 a n d a m i n o c a r b d e c l i n e d to 7.8 per 60 cm b r a n c h a n d 5.2 p e r 60 cm b r a n c h , respectively. T h e s e levels of larval s u r v i v o r s h i p indicate that these two t r e a t m e n t s were only m a r g i n a l l y effective in suppressing JPBW populations. Figure la shows that the larval p o p u l a t i o n in the Bt20 block r e a c h e d its lowest level 10 days after the t r e a t m e n t , w h e r e a s the larval p o p u l a t i o n s in the f e n i t r o t h i o n , Bt-30 a n d a m i n o c a r b blocks (Figure lb±d) r e a c h e d their lowest levels by the first postspray s a m p l i n g 5 days after the t r e a t m e n t s . I n g e n e r a l , J P B W p o p u l a t i o n s did n o t decline f u r t h e r after 10 days postt r e a t m e n t ; thus, it a p p e a r s that a single J P B W p o p u l a -

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Figure 1. Rate of decline of jack pine budworm population

reducing the population,

using three or four postspray sampling dates (shown as days of Julian year) after aerial application of (a) Bacillus thuringiensis (Bt) at 20 billion (109) international units (BIU) ha-~, (b) fenitrothion at 210 g a.i. ha-~, (c) Bt at 30 BIU ha-~, and (d) aminocarb at 70 g a.i. ha-~. Regression equations: (a) y = 20.32 - 0.95x; t 2 = 0.72; (b) y = 29.5 - 2.31x; r2 = 0.80*; (c) y = 13.44 - 0.72x; t 2 = 0.70*; (d) y = 21.77 - 1.36x; t2 = 0.80*. *Significant at p = 0.05. Arrows indicate spray dates

and could replace the multiple

p o s t s p r a y a s s e s s m e n t s , e x t e n d i n g for 15-20 days, that are now routinely

practised.

Table 1. Deposition, on Kromekote cards from deposit sample units, of aerially applied insecticides for the control of jack pine budworm 11985)

Treatment" (a.i. ha ')

Flow rate Drops cm 2 VMDb (1 min ') (2 +_ s.e.m.) (~tm)

Bt (20 BIU) Bt (3(1 BIU) Sumithion 20F(210g)

16.7 25.0 18.3

5.7 8.5 8.6 51.7

+ 11.8 +_ 0.8 + 0.5 + 2.5

M a t a c i l 180F (7(I g)

18.3

19.2 _+ 1.2 18.4 _+ 1.2

NMD' (~m)

57 62 73 66

12 36 29 29

72 72

11 8

W h e n the slopes of the linear regressions were c o m p a r e d , b o t h a m i n o c a r b a n d f e n i t r o t h i o n were s h o w n to r e d u c e J P B W p o p u l a t i o n s m o r e rapidly than the Bt t r e a t m e n t s (Figure 11. T w o a p p l i c a t i o n s of f e n i t r o t h i o n showed the steepest slope, with a m i n o c a r b b e i n g the next most effective. H o w e v e r , if the confidence intervals a b o u t the slopes were t a k e n into c o n s i d e r a t i o n , there were no significant differences (at

"Bt, Bacillus thuringiensis; 20 BIU. 20 billion (20 X 109) international units; 311 BIU, 30 billion international units; Sumithion 20F, fenitrothion (200 g I ~);

Matacill80F, aminocarb(lg0gl,);hVMD, volumcmediandiameter;,NMD, numbermediandiameter

the 0.01 level) in the rate of J P B W p o p u l a t i o n r e d u c t i o n b e t w e e n a m i n o c a r b a n d the Bt t r e a t m e n t s .

Table 2. Reductions in jack pine budworm populations and the protection given to jack pine in treated and untreated blocks

Larvae per 60 cm branch (£ _+ s.e.m.) Treatment" (a.i. ha t) Bt (20 BIU) Bt (311BIU) Sumithion 20F (21(1g) Matacil 180F (70 g) Untreated A B

Prespray 17.0 _+ 1.4 a' 12.2 +_ 2.4 a 23.11 + 3.80 ab 18.5 +_ 3.41 a 40.5 _+ 5.47 b 15.9 + 2.42 a

Postspray 7.8 2.5 2.1 5.2

± 11.54 a +_ 0.31 b _+ 0.31 b + (I.50 c

15.9 + 1.04 d 15.8 + 1.54 d

Percentage corrected population reduction (2 + s.e.m.) 45.5 72.5 89.0 66.3

± 3.54 a + 2.84 b _+ 0.58 b _+ 5.66 ab ---

Percentage defoliation (2 + s,e.m.) Expected

Observed

73 64 81 74

58 28 29 48

+ 2.47 a _+ 2.82 b _+ 2.46 b ± 3.33 a

---

91 _+ 1.88 c 87 _+ 2.44 c

% PATt' 23 + 3.01 a 60 _+ 3.58 b 64 ± 2.98 b 39 ± 3.85 c ---

"Treatments as in Table I; b,,/o PAT, percentage foliage protection that can be attributed to the treatments; ' m e a n s in the same column followed by unlike Icttcrs arc significantly different (p = 0.05) using BMDP comparison of means with the Bonferroni inequality (Dixon, 1983)

C r o p P r o t e c t i o n 1993 V o l u m e 12 N u m b e r 5

353

Jack pine b u d w o r m control: B.L. Cadogan

The J P B W populations all stabilized after a given time following their respective treatments; thus, it might not have been necessary to carry out the July samplings, except in the Bt-20 block. When those data sets shown in Figure 1 were regressed using only three sample points, the reduction slopes (Figure 2b-d) were similar to those with four points, confirming that sampling at 10 days after spraying might be sufficient for population reduction assessments. In the check blocks, the natural rate of J P B W population reduction was directly related to the size of the initial insect population (Table 2; Figure 3). The block with a mean initial population ~< 20 larvae per 60 cm branch a p p e a r e d not to have any significant natural population decline, whereas the block with a mean initial population of - 4 0 larvae per branch showed a natural population decline that differed significantly (p = 0.05) from that in the low population blocks (Figure 3). Trends in the decline of 'natural' populations are influenced by the availability of food and habitat niches, which in turn are influenced by population size, disease, natural enemies and adverse weather. In this study neither disease nor unusual natural e n e m y activity was evident and the weather was not unusual; the rate of natural decline in untreated J P B W populations was, therefore, probably caused primarily b y a t t r i t i o n d u e to lack o f h a b i t a t niches.

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Day Figure 2. Rate of decline of jack pine budworm population

using three sampling dates (shown as days of Julian year) after aerial application of (a) Bt (20 BIU ha-~), (b) fenitrothion (210 g a.i. ha-~, (c) Bt (30 BIU ha-~), and (d) aminocarb (70 g a.i. ha-~). Regression equations: (a) y = 25.61 - 0.446x; t2 = 0.78; (b) y = 39.8 - 3.95x; t2 = 0.93*; (c)y = 15.1 - 0.948x; r2 = 0.74; (d)y = 25.0 - 1.94x; r2 = 0.92*. *Significant at p = 0.05. Arrows indicate

spray dates

354

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15

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Figure 3. Rate of decline of jack pine budworm population in check (untreated) blocks with different initial population levels [a, - 4 0 larvae per branch (60 cm); b, ~< 20 larvae per branch]. Regression equations: (a)y = 43.26 - 0.713x; r2 = 0.96*; (b)y = 17.0 - 0.022x; t2 = 0.013. *Significant at p = 0.05

2s b

201x~

s0 a

Crop Protection 1993 Volume 12 Number 5

T h e r e is no consensus as to what n u m b e r of pests that survived a treatment constitutes excellent, good, acceptable or p o o r control. Traditionally, most field trials focus on percentage population reduction as the primary evaluation criterion; however, the density and, to some degree, the health of the population surviving a treatment are influential in how quickly the pest again reaches epidemic proportions within the target area, and these should also be considered as criteria for assessing efficacy. Cadogan et al. (1986), in a study with spruce budworm (C. fumiferana), arbitrarily chose a density of two or fewer larvae per 45 cm branch as a measure of good control; however, these levels might not be equally appropriate for JPBW. Nevertheless, in this study both Bt-30 and a double application of fenitrothion at 210 g ha ~ reduced J P B W to what the author considers to be acceptable levels ( < 2.5 larvae per 60 cm branch; Table 2). Two applications of aminocarb at 70 g ha ~ and a single Bt-20 spray were not as effective in limiting survivorship as Bt-30 and fenitrothion. It is possible that Bt-30 was more effective than Bt-20 primarily because ~ 3 3 % more droplets w e r e r e c o r d e d as h a v i n g the p o t e n t i a l to d e p o s i t in the B t - 3 0 b l o c k t h a n in the B t - 2 0 b l o c k . I t is n o t easy t o e x p l a i n w h y a m i n o c a r b was n o t as e f f i c a c i o u s as was anticipated on

the basis o f t h e p r o d u c t ' s

reported

field efficacy against spruce budworm (Cadogan, 1987)

Jack pine budworm control: B.L. Cadogan

and1975).its

laboratory

toxicity against J P B W

(Nigam,

100B0

Defoliation

60

T h e levels of defoliation in the various blocks are p r e s e n t e d in Table 2. Based on the J P B W populations, all of the t r e a t m e n t s afforded s o m e m e a s u r e of protection to jack pine. Nevertheless, in the t r e a t m e n t blocks generally p o o r relationships were f o u n d b e t w e e n p r e s p r a y populations and defoliation (Figure 4). This differs f r o m earlier findings with spruce b u d w o r m , w h e r e defoliation in S u m i t h i o n - t r e a t e d plots was directly related to p r e s p r a y populations ( C a d o g a n , 1986) w h e n the application was timed satisfactorily. H o w e v e r , better relationships were f o u n d b e t w e e n J P B W survivorship and defoliation (Figure 5). This finding supports the hypothesis that the J P B W p o p u l a lions that survive are m o r e i m p o r t a n t than p r e s p r a y p o p u l a t i o n s in influencing defoliation. T h e defoliation o b s e r v e d in the fenitrothion block did not differ significantly (p = 0 . 0 5 ) f r o m that in the B t - 3 0 b l o c k , but was significantly less than that seen in the Bt-20 and a m i n o c a r b blocks (Table 2). O n the basis of e x p e c t e d defoliation values, it was postulated that if no t r e a t m e n t s were applied, defoliation in the fenitrothion block would be higher than in the Bt-30 block, but not significantly different from that in the o t h e r 100

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Figure 5. Relationship between surviving jack pine budworm populations and jack pine defoliation in sprayed blocks after aerial application of (a) Bt (20 BIU ha-l), (b) fenitrothion (210 g a.i. ha-l), (c) Bt (30 BIU ha-1) or (d) aminocarb (70 g a.i. ha-~).

40~- , . . . . ~' . 2o~ . ~"~ , , , r ' 28 56 84 112 140 0 45

blocks (Table 2). C o n s e q u e n t l y , 6 4 % and 6 0 % o f the jack p i n e f o l i a g e p r o t e c t i o n c o u l d be a t t r i b u t e d to

fenitrothion and Bt-30, respectively. A m i n o c a r b and Bt-20 were shown to be responsible for 39% and 23% foliage protection, respectively, significantly less than that in the Bt-30 and fenitrothion blocks. T h e s e results confirm earlier findings ( C a d o g a n et

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Regression equations: (a) y = 40.36 + 2.304x; r2 = 0.258*; (b) y = 20.48 + 4.095x; t2 = 0.271"; (c) y = 15.68 + 4.663x; r2 = 0.26*; (d) y = 27.06 + 3.976x; r2 = 0.362*. *Significant at p = 0.05

00

a

a. .".'"..:."~' '.

'

9% 135 ' 180 ' 225

al., 1986) t h a t

showed

Bt-30 to be more

effective than

Bt-20 in protecting jack pine foliage. F u r t h e r m o r e , the results from this study indicate that a single application of Bt at 30 B I U h a - ' was as effective in protecting jack pine foliage from heavy d a m a g e as two applications of fenitrothion at 210 g ha i. T h e defoliation o b s e r v e d in the a m i n o c a r b plots r a n g e d from 28°/,, to 70% and these values a p p e a r e d to be directly related to the n u m b e r of J P B W larvae that survived the treatment. In general, it c a n n o t readily be explained why a m i n o c a r b was not as effective as was anticipated. C o n s e q u e n t l y , these insecticides were reviewed favourably and were registered by A g r i c u l t u r e C a n a d a for aerial use against

Initial l a r v a e (no.

per b r a n c h }

J P B W in C a n a d a .

Figure 4. Relationship between populations of jack pine budworm before spraying and jack pine defoliation in sprayed blocks after aerial application of (a) Bt (20 BIU ha-~), (b) fenitrothion (210 g a.i. ha -~, (c) Bt (30 BIU ha -~) and (d) aminocarb (70 g a.i. ha-l). Regression equations: (a) y =

Acknowledgements

42.55 + 0.075x; ta = 0.24; (b) y = 22.8 + 0.279x; r2 = 0.19; (c) y =

The

22.6 + 0.405x; t2 = 0.12; (d) y = 44.57 + 0.177x; t2 = 0.03

C h e m i c a l A m e r i c a Inc. and C h e m a g r o L t d . T e c h n i c a l

field

research

was

supported

by

Sumitomo

Crop Protection 1993 Volume 12 Number 5

355

Jack pine budworm control: B.L. Cadogan

assistance was provided by B. Zylstra, C. Nystrom, P. E b l i n g a n d R . S c h a r b a c h . T h e a u t h o r is g r a t e f u l to

to frequency of infested vegetative and staminate flower buds. Entomol. News 91, 75-77

C. Davis, Ontario Ministry of Natural Resources, for

Deboo,R. F. and Hildahl, V. (1967) Aerial spraying for the control of

p e r m i s s i o n t o u s e t h e r e s e a r c h sites a n d f a c i l i t i e s at t h e

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Received 20 October 1992 Revised 4 January 1993 Accepted 5 January 1993

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Crop Protection 1993 Volume 12 Number 5