Toxicity and deterrency of depitched tall oil to the green peach aphid, Myzus persicae

Toxicity and deterrency of depitched tall oil to the green peach aphid, Myzus persicae Yongshou

Xie* and Murray B. Isman’

Department

of Plant Science,

University

of British Columbia,

Vancouver, Canada, V6T 124

The comparative toxicity and dcterrency of depitched tall oil, a by-product of the kraft process for pulping softwood, and Superior 70 oil, a common horticultural oil, to the green peach aphid, Myzus persicae (Sulzcr), were investigated. Leaf disc choice bioassays using second-instar M. persicae indicated that both depitchcd tall oil and Superior 70 oil deter aphids in a dose-dependent manner. Effective concentrations resulting in 50% deterrence (ECs,, values) (with 95% confidence interval) for dcpitched tall oil and Superior 70 oil were 0.88% (0.78-0.98) and 1.39% (1.17-1.60), respectively. Depitchcd tall oil was significantly (p < 0.05) more deterrent to aphids than Superior 70 oil. Depitched tall oil and Superior 70 oil were equally toxic to second-instar M. persicae when leaf discs were treated with the test materials. Concentrations causing 50% mortality (LCso values) for depitchcd tall oil and for Superior 70 oil were 1.OS and 1. IO%, respectively. At a concentration of 1%) depitchcd tall oil applied to leaf discs reduced aphid survival to 28% after 5 days, whereas survival of controls was 78%. When topically applied at a dose of 0.1 ul per aphid, the lethal doses of dcpitchcd tall oil resulting in 50% mortality (LDSo values) at 72 h for second-instar and adult M. persicae were 0.16 and 0.20 ug per aphid, respectively. When sprayed at a dose of 5 ul cmm2,the LCso values at 72 h for emulsified depitched tall oil to second-instar and adult M. persicue were 1.08 and 0.80%, respectively. The deterrent effect of dcpitched tall oil on M. persicue persisted for at least 3 days under greenhouse conditions. Keywords:

tall oil; horticultural oil; lMyzus persicae

Integrated pest management (IPM) has become the predominant philosophy for insect pest control in the 1990s. Major tenets of IPM are the reduced use of pesticides and the use of those pesticides least disruptive to the environment. It is well known that oils (plant oils, animal oils, and/ or mineral oils) can kill insects, both physically by interfering with insect respiration, and chemically (Martin and Woodcock, 1983). Mineral oils, especially petroleum oils, have been used as insecticides in agriculture for over two centuries (Miller, 1983), and continue to play a crucial role in pest management in tree fruits in the United States (Riehl, 1981), Australia (Furness, 1981), Israel (Neubauer, 1981), Japan (Ohkubo, 1981) and Canada (Anonymous, 1991a). In the exploration of plant natural products as insecticides, tall oil, a by-product of the kraft process for pulping softwood, has attracted attention (Cousin, 1989; Xie and Isman, 1992a, b). Physically, tall oil possesses properties somewhat similar to those of horticultural oils. However, major constituents of tall oil are resin acids (37.2% by weight), which are known insect antifeedants and growth inhibitors (Elliger et al., 1976; Wagner et al., 1983; Schuh and Benjamin, 1984; Xie et al., 1993). Tall oil could, therefore, be useful as a crop protectant because of its toxic and/or deterrent properties in addition to its physical properties. *Present address: Agriculture Canada Research Station, 195 Dafoe Road, Winnipeg, Manitoba, Canada R3T 2M9; ‘to whom

correspondence

should be addressed

The purpose of the investigation described here was to evaluate the toxic and deterrent properties of depitched tall oil, a derivative of tall oil, to the green peach aphid, Myzus persicae (Sulzer). The residual activity of depitched tall oil to M. persicae was also evaluated under laboratory and greenhouse conditions. For comparative purposes, Superior 70 oil, a common horticultural oil for insect control, was included in some experiments.

Materials and methods Oils

Depitched tall oil (code J-30) was supplied by B.C. Chemicals Limited, Prince George, British Columbia, Canada.. Superior 70 oil (code 61920, United Agri Products, London, Ontario, Canada) was supplied by the B.C. Ministry of Agriculture, Food and Fisheries, Kelowna, B.C., Canada. Depitched tall oil is somewhat more viscous than Superior 70 oil (26 mm2 s-’ at 60°C vs 12.2 mm* s-’ at 40°C); depitched tall oil also has a higher boiling point (>25O”C vs >97”C) and specific gravity (0.97 vs 0.87). Plants and insects Mustard cabbage, Brassica chinensis L., cv. Pak-choi, was grown in plastic pots (10 cm diameter) containing a mixture of sandy loam soil and peatmoss (5:l). Pots were kept in a greenhouse at 20°C with supplemental

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1995 Volume 14 Number 1

51

Effects of depitched tall oil on AIyzus persicae: Y. Xie and M.B. lsman

lighting supplied by sodium vapour lamps (- 1500 lux) , and watered once a day. After 5 weeks, fully expanded leaves were removed for bioassays. Green peach aphids, Myzus persicue (Sulzer), were from a natural infestation on cabbage (Brussica olerucea cupitutu L. var. Stonehead) in the greenhouse.

Deterrent

activity of depitched tall oil and

Superior 70 oil

Deterrent activity of depitched tall oil and Superior 70 oil was assessed using leaf disc choice and no-choice tests. In the former case, discs (3.5 cm’) were removed from mustard cabbage leaves and dipped in aqueous emulsions at concentrations of 0,0.50,0.75, 1.00, 1.25, 1.50 and 2.00% of the test materials. Depitched tall oil was emulsified with 1% I-Sol RB emulsifier (LeoChem Inc., Oakville, Ontario, Canada). After discs had dried at room temperature (-21”C), two leaf discs treated with the test material and two discs treated with emulsifier alone were placed alternately in a plastic Petri dish (9 by 50 mm) with their edges touching. Twenty second-instar aphids were introduced in the centre of the dish; ten replicates were prepared for each treatment. Dishes were kept in clear plastic containers lined with several layers of moist Kimwipe, and held in a growth chamber at 17 f l”C, under constant, indirect fluorescent light. After 24 h, the number of aphids on each disc (treated and control) was recorded. The deterrency index (%) for each treatment was calculated as (C - 7’)I(C + 7’) X 100, where C is the number of aphids on control discs and T is the number of aphids on treated discs (Isman et al., 1990). Each experiment was repeated twice, for a total of 20 replicates. The leaf disc no-choice test was performed by placing one treated disc or one control disc in the centre of a plastic Petri dish (9 by 50 mm). Leaf discs were dipped in aqueous emulsions at concentrations of 0, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0% of the test materials. After the leaf discs had dried, ten second-instar nymphs were placed on the disc. Other conditions were as described above. The percentage of total aphids remaining on the discs was recorded at 24 h. Each experiment was repeated twice. Deterrent activity of depitched tall oil to adult aphids was also evaluated by the above-mentioned leaf disc choice and no-choice bioassay. All conditions were the same as those for second-instar nymphs.

Toxic action of depitched tall oil and Superior 70 oil (treated leaf discs)

Leaf discs were dipped in aqueous emulsions of depitched tall oil or Superior 70 oil at concentrations of 0, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0%. After the leaf discs had dried, ten second-instar nymphs were placed on each disc. Because leaf discs began to dessicate under the experimental conditions within 48 h, new treated and control discs were provided and experimental insects were transferred from the old discs to the new discs at 48 h. All other conditions were as described for the deterrent leaf disc choice tests. Mortality was determined at 72 h. In an additional experiment using depitched tall oil at 1 .O and 2.0%) aphid (second-instar)

52

Crop Protection 1995 Volume 14 Number 1

mortality was monitored daily for 5 days under the conditions mentioned above. Toxic action of depitched tall oil (topical application and spray)

Direct contact toxicity of depitched tall oil on secondinstar and adult M. persicue was determined by topical application of oil and acetone solutions and by spraying aqueous emulsions of the test material. For topical applications, depitched tall oil in 0.1 ~1 acetone was applied to the dorsum of second-instar or adult aphids using a fine 5 ~1 syringe (7105 series syringe, Hamilton Co., Reno, Nevada, USA) attached to a repeating dispensor (PB-600, Hamilton Co.). Six concentrations (O-16 pg ~1~‘) were tested (acetone alone as control), with 100 aphids treated at each concentration in groups of ten per Petri dish. Dishes were placed in plastic containers and kept in a growth chamber as outlined previously. Treated aphids were reared on leaf discs for 72 h. Leaf discs were changed and mortality determined daily. For spray application, the micro-spray tower consisted of a Plexiglass tube (15.5 by 8.8 cm diameter) with the nozzle from a hair spray bottle (Fixatif Aussie Sprunch Spray, Redmond Product Inc., Chanhassen, Minnesota, USA) fastened at the top. One hundred aphids (second-instar and adult, respectively) were placed on a section of cabbage leaf outlined with fluon (Northern Products Inc., Woonsocket, Rhode Island, USA) to prevent escape. The leaf with aphids was placed in a Petri dish (8.8 cm diameter), which was placed under the tower. Depitched tall oil emulsion (300 ~1) was delivered as a fine mist per 60.8 cm* (-5 ~1 cm”) of leaf surface area. Six concentrations (O-8%) were prepared (1% emulsifier as control). After spraying was completed, treated aphids were transferred to fresh leaf discs in Petri dishes, with ten aphids per dish and ten replicates. Other conditions were as outlined previously for topical applications. Residual activity of depitched tall oil

Persistence of the deterrent activity of depitched tall oil to second-instar M. persicue was evaluated under greenhouse (for plants) and laboratory (for insects) conditions. Six concentrations (0.5-3.0%) of depitched tall oil aqueous emulsions (0.5% I-Sol RB emulsifier) were prepared and sprayed on mustard cabbage plants until run-off. Thirty minutes after application of the treatments (= day 0), leaf discs were removed from treated plants and a leaf disc choice bioassay using second-instar aphids was conducted as previously described (n = 20 with 20 aphids per replicate). Bioassays were conducted daily for 4 days using leaf discs treated at day 0. Effective concentrations resulting in 50% deterrency were calculated. Statistical

analysis

An arcsin transformation was performed for all percentage data before analysis (Steel and Torrie, 1980; Zar, 1984; Anonymous, 1991b). Transformed values were subjected to analysis of variance (ANOVA) and linear regression (Anonymous, 1991b). Inverse prediction

Effects of

was used to determine the effective concentration required to result in a deterrency index of 50% (EC,“). ANOVA and least significant difference (1.s.d.) test were used to evaluate the effect of depitched tall oil on survivorship of second-instar M. persicae (Anonymous, 1991b). To compare regression slopes for depitched tall oil and Superior 70 oil (Figure I), analysis of covariance (ANCOVA) was used to test equality of regression coefficients (Zar, 1984). Probit analysis was used for all mortality data to calculate LCsO (lethal dose to cause 50% mortality) values. Abbott’s formula (Abbott, 1925) was used to correct for control mortality.

depitched tall oil on Myzus persicae: Y. Xie and M.B. lsman

a

70

60

Results Deterrent 70 oil

activity

of depitched

50

tall oil and Superior

Leaf disc choice tests with second-instar M. persicae indicated that both depitched tall oil and Superior 70 oil deter aphids in a dose-dependent manner. Deterrency index (%) was significantly 0, < concentration of depitched tall oil (

b

a go-

0 l

0

80 0

0 0

90

-

80

-

70

-

60

-

a

70

-

60

-

0.0

0.5

1.0

1.5

Concentration

0.0 70

I

I

I

I

0.5

1.0

1.5

2.0

I

I

l

50 0 0

40 0

30

0

20 0

10 I

0.0

0.5

I

1.0

Concentration

2.5

3.0

(X)

Figure 2. Deterrency of oils to Myzus persicae in leaf disc nochoice bioassays, based on percentage of aphids remaining on treated leaf discs. (a) Effect of depitched tall oil (0; slope = -13.07, i! = 0.98, p = 0.0001) and Superior 70 oil (0; ? = 0.48, p = 0.0855) on second-instar nymphs; (b) effect of depitched tall oil on adult aphids (i! = 0.11, p = 0.4755)

I

I

b

60

2.5

2.0

I

I

1.5

2.0

2.5

(X)

Figure 1. Deterrency of oils to Myzus persicae in leaf disc choice bioassays. (a) Effect of depitched tall oil (0; E& = 0.88%, slope = 36.13, r’ = 0.98, p = 0.0001) and Superior 70 oil (0; E& = 1.39%, slope = 20.63, /2 = 0.92, p = 0.0026) on second-instar nymphs; (b) effect of depitched tall oil on adult aphids (r’ = 0.44, p = 0.1534)

Superior 70 oil (3 = 0.92) (Figure la). Effective concentrations resulting in 50% deterrency (EC,,) (with 95% confidence interval) for depitched tall oil and Superior 70 oil were 0.88% (0.78-0.98) and 1.39% (1.17-l .60), respectively (Figure Za). Depitched tall oil showed a significantly (p < 0.05) stronger deterrent effect on aphids than Superior 70 oil based on the lack of overlap of confidence intervals for their respective ECso values. This conclusion received further support from the regression coefficients. Slopes of deterrency curves for depitched tall oil and for Superior 70 oil were 36.13 and 20.63, respectively, which were significantly different (p < 0.05) by ANCOVA (t = 3.410, co.05(2j,8 = 2.306) (Figure la). Leaf disc no-choice bioassays with second-instar M. persicae also demonstrated that depitched tall oil deterred aphids in a dose-dependent manner. When aphids were provided with only tall oil-treated leaf discs for 24 h, the proportion of aphids remaining on leaf discs was negatively and significantly (p < 0.05) correlated to depitched tall oil concentration (? = 0.98). In contrast, Superior 70 oil showed only a

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1995 Volume 14 Number 1

53

Effects of depitched tall oil on Myzus persicae: Y. Xie and M.B. lsman moderate deterrent effect in the no-choice test, but no significant correlation was found between proportion of aphids on treated leaf discs and concentration of oil used (3 = 0.48, p = 0.0855) (Figure 2a). Both leaf disc choice and no-choice bioassays with adult M. persicae indicated that adult aphids were insensitive to the deterrent action of depitched tall oil. No significant correlations were found between deterrency index and depitched tall oil concentration in the choice test (3 = 0.44, p = 0.1534) (Figure lb), or between the proportion of aphids on treated leaf discs and depitched tall oil concentration in the no-choice test (12 = 0.11, p = 0.4755) (Figure 2b).

A

I

g

20

C

b

n.

b

Toxic action of depitched tall oil and Superior 70 oil (treated leaf discs) When leaf discs were treated with depitched tall oil and Superior 70 oil, it caused mortality of second-instar M. persicae at 72 h. LCso values (with 95% confidence interval) for depitched tall oil and for Superior 70 oil were 1.05% (0.73-1.50) and 1.10% (0.67-1.82), respectively (Figure 3). Slopes of mortality curves for depitched tall oil and Superior 70 oil were 1.07 and 0.74, respectively (Figure3). The lack of significant (p > 0.05) difference between L& values and slopes for depitched tall oil and for Superior 70 oil indicated that these materials are equally toxic to second-instar M. persicae.

Survival time curves for second-instar M. persicae exposed to 1 .O% and 2.0% depitched tall oil are shown in Figure 4. Survivorship of second-instar aphids was significantly (p < 0.05) reduced even after 1 day of exposure to leaf discs treated with depitched tall oil at concentrations of 1.0% (86% survival) or 2.0% (75% survival), compared with controls (97% survival) (Figure 4). After 5 days, only 19% of the aphids had survived on discs treated with 2.0% depitched tall oil, and 28% had survived on discs treated with l.O%, whereas 78% had survived on control discs (Figure 4).

c,

*

0.5

1.0

1.5

2.0

Concentration

2.5

3.0

(X)

Figure 3. Mortality of second-instar Myz~s persicae nymphs after 72 h feeding on leaf discs treated with depitched tall oil (0; LCSO= 1.05%, slope = 1.07), or Superior 70 oil (0; LCSO= 1 .lO%, slope = 0.74)

Crop

1

2

Day after

3

4

5

treatment

Figure 4. Survival of second-instar Myzus persicae nymphs exposed to leaf discs treated with 1.0% (m) and 2.0% (A) depitched tall oil; 0 = control. For each day, values surmounted by the same letter do not differ significantly (least significant difference test)

Toxic action of depitched tall oil (topical application and spray) When acetone solutions of depitched tall oil were applied topically to second-instar M. persicae, the LD50 values at 24,48 and 72 h were 0.35,0.25 and 0.16 pg per (Table I). Adult aphids were aphid, respectively similarly susceptible to the toxic action of topically applied depitched tall oil, with LDsO values at 24, 48 and 72 h of 0.39, 0.34 and 0.20 pg per aphid respectively (Table I). The L&, values for emulsified depitched tall oil s rayed on second-instar M. persicae at a dose of 5@cm- g were3.11,1.75andl.O8%,at24,48and72h, respectively (Table I). LCsO values for adult aphids at 24,48 and 72 h were 2.64,0.84 and 0.80%) respectively (Table 2). There were no significant differences between nymph and adult mortality caused by either topical applied or sprayed depitched tall oil solutions, as 95% confidence intervals for their respective LD50 and/or L&o values overlapped under both treatment conditions (Table I). Residual activity of depitched tall oil

65.0

G

54

0

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1995 Volume

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1

Regression analyses revealed that deterrence of depitched tall oil remained significantly (p < 0.05) dose dependent for at least 2 days after application to plants (Table 2). For bioassays conducted 3 days after treatment, a correlation coefficient of 0.86 gives a coefficient of determination of 0.74 (Table 2)) indicating that 74% of the deterrent activity could be attributed to the depitched tall oil spray, although the regression line was not significant at the p = 0.05 level (p = 0.0628). These results suggest that the deterrent activity of depitched tall oil toward M. persicae nymphs persists for at least 3 days when sprayed on mustard cabbage plants in the greenhouse (Table 2). Discussion

Spray oils can be highly effective in controlling a wide range of arthropod pests, including mites, scales,

Effects of depitched tall oil on Myzus persicae: Y. Xie and M.B. lsman Table 1. Contact toxicity of depitched tall oil to Myzus

persicae Time after treatment (h)

24 Aphid stage

Treatment Topical application

95% CI’

2nd instar

0.35

0.2W.48

Adult

0.39

0.29-0.55

[3.11]

1.75-5.51

2nd instar

Spray

Adult

(5 ~1 cm-‘)

48

1.92-3.63

[2.64]

Slope (se.)* 1.89 (0.19) 1.66 (0.18) 1.08 (0.20) 1.15 (0.20)

95% CI 0.25

0.18-0.35

0.34

0.254.47

[I.751

1.19-2.57

Slope (se.) 1.82 (0.20) 1.75 (0.19)

0.16

0.1 l-0.25

0.20

0.13~).31

1.65

[ 1.081

0.74-t

.57

[0.80]

0.5&l

.33

w;) [0.84]

0.47-l Sl (0.20)

“LD,,, = dose (pg per aphid) resulting in 50% mortality; bLCT,)(values in square brackets) = percentage concentrations interval; ‘s.e. = + standard error (in parentheses)

Table 2. Residual activity of depitched Myzus persicae nymphs Time after application

tall oil on second-instar

EC,,,” (%)

Slope (s.e.)

r2

P

0

0.79

0.92

0.0090

1

1.26

0.96

0.0033

2

1.88

0.95

0.0045

3

2.31

25.39 (4.19) 32.31 (3.77) 31.33 (4.06) 17.35 (5.99) -

0.74

0.0628

0.28

0.3551

4

(day)

-

“EC,,, = effective concentration

resulting in a deterrency

index of 50%

aphidsandothercommonlyoccurringinsects(Baxendale and Johnson, 1988; Davidson et al., 1991; Lawson and Weires, 1991). In the present study, we provide evidence that depitched tall oil, an inexpensive and abundant by-product of the kraft pulping process of softwoods, has both deterrent effects and toxicity against M. persicae. The mechanisms of action of oils are thought to be mainly physical, i.e. oils kill pests by suffocation. However, our study demonstrated that depitched tall oil possesses significant deterrent activity on M. persicae nymphs in addition to contact toxicity. In leaf disc choice bioassays, which are more sensitive than nochoice tests for detecting differences in host acceptability (Schoonhoven, 1982), both depitched tall oil and Superior 70 oil rendered leaves relatively unacceptable to M. persicae nymphs. The deterrent action of depitched tall oil was significantly (p < 0.05) higher than that of Superior 70 oil (Figure I). Furthermore, in nochoice bioassays, which are more realistic in the practical sense, the deterrent activity of Superior 70 oil lacked linear dose dependence (Figure 2). Considering that depitched tall oil typically contains 40% fatty acids and 37% diterpene resin acids (Xie et al., 1993), we suggest that chemical toxicity, in addition to physical action, is involved in the insecticidal activity of depitched tall oil to M. persicae. Adult aphids were not significantly deterred by

Slope (s.e.) 1.89 (0.25) 1.68 (0.23) 1.93 (0.24) 1.94 (0.25)

causing 50% mortality; ‘CI = confidence

depitched tall oil, but this result is not surprising in that sensitivity to allelochemicals frequently appears inversely related to insect age or development stage (Isman et al., 1989). Deterrents/repellents offer a novel approach for pest management by rendering plants unattractive or unacceptable to pest insects (Jermy, 1990). The deterrent activity of depitched tall oil should contribute to the utility of this material as an insect control agent. It may also aid in the control of plant viruses vectored by aphids. Depitched tall oil possesses physical specifications similar to those of other commercial horticultural oils, such as Superior 70 oil. It is not surprising, therefore, to find that both depitched tall oil and Superior 70 oil are equally toxic to M. persicae nymphs (Figure 3). When aphids contact oil-treated leaves, they may themselves become contaminated. Direct contact toxicity bioassays, in which depitched tall oil was topically applied or sprayed on aphids, also caused mortality (Tub/e 1). Survival of second-instar M. persicae on leaf discs treated with depitched tall oil at concentrations of 1.0 and 2.0% was 28 and 19% at day 5, respectively (Figure 4). We believe that, in this situation, mortality may be a consequence of both deterrent (starvation) and toxic actions of the test material. It is often desirable for an insect control agent to persist in the field for at least several days. Oils are normally considered to be non-persistent compared with many synthetic insecticides. Our residual activity experiments indicate that the deterrent activity of depitched tall oil to M. persicae persists for at least 3 days under greenhouse conditions (Table 2). Such activity would probably be very short-lived under true field conditions. Phytotoxicity is a major limitation of horticultural oils as crop protectants. In greenhouse and field trials on chrysanthemum and cabbage, we have not observed any phytotoxicity following three applications (once a week) of emulsified depitched tall oil at a concentration of 1% (unpublished data). This concentration could cause 50% mortality (Figure 3, Table I), and result in over 50% deterrency (Figure I) of M. persicae. A pest control product based on depitched tall oil, or a derivative thereof, could therefore be promising for the control of aphids and other soft-bodied insects.

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Effects of depitched

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Acknowledgements

Jerry, T. (1990) Prospects of antifeedant approach to pest control a critical review. J. Chem. Ecol. 16, 3151-3166

We thank Yanfen Zheng and Nancy Brard for technical assistance, BC Chemicals Ltd, Prince George, B.C. Canada for supplying depitched tall oil and Mr. Hugh Philip, B.C. Ministry of Agriculture, Food and Fisheries, Kelowna, B.C., Canada for supplying Superior 70 oil. We also thank Dr. Ken Naumann for comments on the manuscript. Supported by grants from NSERC (CRD 112262), Forestry Canada, and BC Chemicals Ltd.

Lawson, D. S. and Weires, R. W. (1991) Management of European red mite (Atari: Tetranychidae) and several aphid species on apple with petroleum oils and an insecticidal soap. J. Econ. Entomol. 84, 1550-1557

Martin, H. and Woodcock, D. (1983) The Scientific Principles Protection. Edward Arnold, London, 486 pp

ofCrop

Miller, R. L. (1983) Spray oil insecticides effectively control some insect and mites. Am. Nurseryman 158, 37-43 Neubauer, I. (1981) Low volume oil sprays to control the soft scale, Ceroplustes floridensis Comstock, in citrus trees in Israel. Proc. Int. Sot. Citric. 2, 614-615

Ohkubo, N. (1981) Role of petroleum oil sprays in an integrated pest management system of citrus crops in Japan. Proc. Int. Sot. Citric. 2, 61 l-614

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(1991a) Canada 1991 Pesticide Service Ltd, London, UK, 50 pp

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Isman, M. B., Brard, N. L., Nawrot, J. and Harmatha, J. (1989) Antifeedant and growth inhibitory effects of bakkenolide-A and other sesquiterpene lactones on the variegated cutworm, Peridroma saucia Hiibner (Lep., Noctuidae). J. Appt. Entomol. 107, 524-529 M. B., Koul, O., Luczynski, A. and Kaminski, J. (1990) Insecticidal and antifeedant bioactivities of neem oils and their relationship to azadirachtin content. J. Agric. Food Chem. 38, 1046-

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Schuh, B. A. and Benjamin, D. M. (1984) Evaluation of commercial resin acids as feeding deterrents against Neodiprion dubiosus, N. lecontei, and N. rugifrons (Hymenoptera: Diprionidae). J. Econ. Entomol.

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Wagner, M. R., Benjamin, D. M., Clancy, K. M. and Scbuh, B. A. (1983) Influence of diterpene resin acids on feeding and growth of larch sawfly, Pristiphoru erichsonii (Hartig). J. Chem. Ecol. 9, 119127 Y. S. and Isman, M. B. (1992a) Antifeedant and growth inhibitory effects of tall oil and derivatives against the variegated cutworm, Peridroma saucia Hiibner (Lepidoptera: Noctuidae). Can.

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Xie, Y. S. and Isman, M. B. (1992b) A note of the chronic effects of tall oil on the variegated cutworm, Peridroma sauciu Htibner (Lepidoptera: Noctuidae). Phytoprotection 73, 119-121

Xie, Y. S., Isman, M. B., Feng, Y. and Wong, A. (1993) Diterpene resin acids: major active principles in tall oil against variegated cutworm, Peridroma sauciu (Lepidoptera: Noctuidae). J. Chem. Ecol. 19, 1073-1082 Zar, J. H. (1984) Biostatistical Analysis, Prentice-Hall,

Cliffs, New Jersey, 718 pp

Isman,

1411

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Ento-

mologia exp. appl. 31, 57-69

Received 3 May 1993 Revised 2.5 January 1994 Accepted 23 April 1994

Englewood