Microdroplet application for determination of comparative topical and residual efficacy of formulated permethrin to two populations of diamond back moth (plutella xylostella L.)

An on-demand, uniform droplet generator was used to apply 120 μm diameter drops of formulated permethrin either directly onto 3rd-instar Plutella xylostella, of two Ohio populations, or onto the abaxial surface of leaf discs (1-1000 drops cm^?2) to which those larvae were subsequently exposed. Incorporating a fluorescent tracer (Saturn Yellow GT-17N) in the spray mixture confirmed that ?direct hit”? larvae had received a topical dose from a single droplet. There was little difference in the LC₅₀/LD₅₀ for either population of P. xylostella when 24 and 48 h mortality assessments from direct hits were compared, but the LD₅₀ of Celeryville larvae was 6-8 times greater than that of Fremont larvae. Residual deposits of 120 μm drops containing approximately the LC₅₀, based on the topical assays, revealed that a droplet density providing a dose per cm² leaf surface of more than 1000 times the LD₅₀ was required to cause median mortality. The efficiency of utilisation, based on the topical LD₉₅ values, was 0.0006% and 0.072% for Fremont and Celeryville larvae, respectively.     

Toxicity of pyrethroids to larvae of the Egyptian cotton leafworm,Spodoptera littoralis (Boisd.). II. Factors determining the effectiveness of permethrin at ultra-low volume

Factors determining theeffectiveness of permethrinat ultra-low volume against larvae of Spodoptera littoralis (Boisd.) were investigated using a modified Potter tower. Higher mass application rates for 95 % control were necessary when permethrin was used as a residual deposit compared with direct contact plus residual deposit action. Mortality was increased by adjusting droplet density, although the optimum number of drops/ unit area depended on the mass application rate. When mass application rate and droplet density were held constant, mortality increased inversely with the mean droplet diameter. The implications of these results for field applications are discussed.     

Droplet size and efficacy of an adulticide-larvicide ultralow-volume formulation on Aedes aegypti using different solvents and spray application methods

BACKGROUND: When cases of dengue are reported or the density of adult Aedes aegypti (L.) becomes too high, ultralow-volume (ULV) application of insecticides is the recommended control method. The droplet size of an aerosol insecticide influences its efficiency in killing adult mosquitoes. Many studies have been carried out to determine the optimum droplet size that maximises vector control efforts, but only a few have determined droplet-size spectra for specific equipment using different solvents and comparing thermal and non-thermal aerosols. RESULTS: The present study showed that the droplet size for a water-based adulticide–larvicide formulation was larger than for the same formulation diluted in gasoil or biodiesel. No significant differences in adult mortality were observed between sprayers and solvents, but efficacy decreased with distance from the sprayer nozzle. Adult emergence inhibition was more than 90% when using water as a solvent for both thermal and cold foggers, and the efficacy did not decrease with distance from the sprayer nozzle. On the other hand, oil-based solvents became less effective with distance. CONCLUSION: The use of water as a solvent with both thermal and cold foggers improves the efficacy of the studied formulation containing permethrin as adulticide and pyriproxyfen as larvicide in scaled-up assays. Moreover, it reduces the environmental impact and costs of spraying by comparison with formulations using oil solvents. Copyright © 2011 Society of Chemical Industry     

Distribution and activity of spray deposits in an oak canopy following aerial application of diluted and undiluted formulations of Bacillus thuringiensis Berliner against the gypsy moth,Lymantria dispar L. (Lepidoptera: Lymantriidae)

The distribution and biological activity of spray deposits resulting from aerial applications of diluted and undiluted Bacillus thuringiensis, ‘Dipel 64AF’ against the gypsy moth, Lymantria dispar L., were examined in oak stands in south-eastern Ontario, Canada. The sprays were applied by fixed-wing aircraft equipped with four ‘Micronair AU4000’ atomizers. Application of diluted formulation at 30 BIU ha^?1 in 6.0–6.4 litre generally resulted in a higher droplet density (10–28 cm ^?2 leaf) than application of undiluted product at the same dosage rate in 1.8 litre ha^?1 (4–10 cm ^?2). However, spray deposits of undiluted product with a volume median diameter (D_v.5) of 90–130 μm caused as much mortality of gypsy moth larvae in bioassays of sprayed foliage as deposits of diluted product with a D_v.5 of 150–350 μm despite a two- to three-fold reduction in droplet density. Our data suggest that by using fine spray atomization, undiluted application of these formulations can offer the same efficacy against gypsy moth as coarsely atomized sprays of diluted product.     

Effect of Formulation and Application Method on the Efficacy of Aerial and Submerged Conidia of Metarhizium flavoviride for Locust and Grasshopper Control

A study was carried out to investigate the relative infectivity of aerial and submerged conidia of Metarhizium flavoviride to Schistocerca gregaria and Zonocerus variegatus. The effect of formulation and application method on initial infectivity and field persistence of these conidia was investigated. Strain IMI 330189 was highly virulent to S. gregaria but showed relatively low virulence to Z. variegatus. Direct contact with conidia from the initial spray application resulted in 100% mortality of S. gregaria for all formulation and application combinations. The mean survival time of infected locusts was significantly shorter for treatments using a knapsack sprayer containing submerged conidia in water plus 10 ml litre⁻¹ ‘Codacide’™ (seven days), than treatments with aerial conidia in oil using ULV techniques (8.9 days) or submerged conidia in modified (water plus adjuvants) ULV (MULV) (nine days) or in water-based (VLV) applications (9·3 days). Both aerial and submerged conidia persisted long enough in the environment to effect significant mortality via secondary pick-up of spray residue from vegeta-tion. Persistence was greatest in the ULV and MULV treatments, where the oil component of the formulations provided greater protection of the conidia from environmental stresses. The consequences of secondary pick-up of conidia from the different treatments on total mortality from a single application were examined using a simple host–pathogen model. This predicted that the ULV treatment would be much more effective than the other treatments under conditions where direct contact with the spray was limited. The results of these investigations are discussed in the context of development of optimum spray strategies for control of locusts and grasshoppers, and other pests, under different environmental conditions.     

The interactions between routes of exposure and physicochemical properties of four water-dilutable permethrin formulations in relation to their activities against Trichoplusia ni (Hubner)

A series of laboratory experiments were undertaken to compare the activities of four water-dilutable permethrin formulations against the cabbage looper Trichoplusia ni (Hubner). The formulations used were “Pounce 3.2 EC”, “Ambush 2.0 EC” and two novel formulations (containing evaporation retardants) supplied, for comparison, by Roussel Uclaf Environmental Health Ltd, Berkhamsted, UK (formerly Wellcome Environmental Health Ltd). Bioassays were developed to investigate the activity of the insecticides via topical, residual and residual/dietary routes of exposure. The test insects were exposed to insecticide droplets, of 200 μm diameter, either directly or indirectly (on cabbage leaves or parafilm) using an on-demand droplet generator. Following exposure to insecticide, the test species were confined in petri dishes and mortality assessments were made at 24 h after treatment. The results were analyzed using probits. The results indicated that up to 15-fold differences in activity between formulations may occur when exposure is via residual contact on an artificial waxy surface (parafilm). The novel formulations were found to be far more active than the standard EC formulations. These differences in activity were significantly correlated with the dynamic surface tension and droplet spread upon cabbage leaves of the formulations. The results are discussed in terms of the bioavailability of pyrethroids upon waxy surfaces and also in terms of the potential for manipulating the pick-up of pesticides from plant surfaces.     

Speed of action and toxicity of acylurea insect growth regulators against Spodoptera exempta (Walk.) and Spodoptera littoralis (Boisd.) larvae: Effect of inter-moult age

Ultra-low volume (ULV) spray bioassays at droplet densities (20–80 drops cm^?2) corresponding to field deposits were used to determine the efficacy of two acylurea insect growth regulators, teflubenzuron (‘Nomolt®’) and flufenoxuron (‘Cascade®’) against three different age groups of third-instar Spodoptera exempta and Spodoptera littoralis larvae. While no response (mortality and/or abnormal moulting with impaired ability to feed) was observed with one-day-old larvae until 48 h after treatment, two-day-old larvae showed some response (27–93% abnormal moulting and 3–10% mortality when larvae were sprayed; 80–100% abnormal moulting and up to 83% mortality when larvae and plants were sprayed) after 24 h and up to 100% mortality at 120 h. Studies with non-feeding, pre-moult larvae showed that cuticular uptake of acylureas was sufficient to affect an appreciable proportion of larvae after 24 h, with up to 100% mortality at 120 h. More detailed studies with pre-moult S. littoralis larvae showed that, while a few larvae which moulted between 1 and 5 h after treatment showed abnormal moulting to the L4 stage, a much larger proportion of larvae which moulted 6–20 h after treatment were affected. Previous studies with S. exempta have shown that different larval instars show similar levels of sensitivity to acylureas. The present work suggests that, while the age distribution within instars has little influence on the end-point mortality of acylureas, it can profoundly modify the speed of response, the majority of larvae within an instar being effectively controlled at the moult following treatment. The significance of these observations in relation to the crop protection activity of acylureas against field populations of Spodoptera larvae is discussed.     

Studies on granular formulations of Bacillus thuringiensis berliner

Survival of the spores of Bacillus thuringiensis in granular formulations has been tested under storage conditions in the laboratory and also outdoor conditions exposed to weather. The granular formulations were prepared with attapulgite and aqueous and non-aqueous carriers. The virulence of the spore formulation was tested on Bombyx mori larvae. A 0.4% spore concentration, with an initial count of 64 × 10⁶, gave ultimately 0.3 to 0.4 × 10⁶ viable spores/g of the granule after 248 days of storage in the room. The viable count of spores in the granules exposed to outdoor weather conditions fell rapidly within two days; at the end of 65 days, it was maintained at between 3 × 10⁴ and 12 × 10⁴/g of the granules. Optimum concentrations required in granules for 100% mortality of the test insect was found to be 0.4 × 10⁶ spores/g, at the rate of 50 mg of granules per 85 cm² of leaf surface. The granular formulation of B. thuringiensis was found to be more virulent than “Thuricide” formulation on B. mori larva.     

Spray application factors and plant growth regulator performance: III. Interaction of daminozide uptake,translocation and phytotoxicity in bean seedlings

Effects of droplet size and carrier volume on foliar uptake and transport of daminozide were investigated. A constant dose of daminozide (100 µg per leaf) was applied to both primary leaves of 10‐day‐old Phaseolus vulgaris (cv Nerina) in droplet sizes of 1–10 µl and carrier volumes of 10 to 200 µl per leaf. Decreasing droplet size or increasing carrier volume decreased daminozide penetration, but increased translocation. Plotting the logarithm of the leaf surface/droplet interface area vs daminozide uptake yielded a negative linear relationship, but for translocation an optimum quadratic type relationship was obtained. Some phytotoxicity occurred at low carrier volumes and large droplet sizes. The degree of phytotoxicity was positively related to the amount of daminozide deposited per unit wetted area above 0.7 µg daminozide mm⁻². Below this threshold, there was no visual evidence of phytotoxicity. At the breakpoint, the deposit covered an area of 276 mm² on both primary bean leaf surfaces. Since the maximum in the relationship of translocation with interface area was in close agreement with the threshold amount of deposit above which phytotoxicity occurred, the inverse relationship between daminozide uptake and translocation at low interface areas was attributed to phytotoxicity. © 2000 Society of Chemical Industry     

The persistence of insecticide spray deposits on woven polypropylene and jute sacking

In a trial, simulating the spray treatment of bags, the persistence and biological activity of insecticide spray deposits on jute and woven polypropylene sheets have been compared; in addition, the build-up of residues in thin layers of maize under the sprayed sheets has been measured. The insecticides were found to have a much shorter persistence on polypropylene than on jute and this was coupled with higher residues on the grain. However, the deposits on polypropylene retained equal or greater activity against Sitophilus zeamais Motsch. and Tribolium castaneum (Herbst) than the deposits on jute, despite the loss of surface deposit. Wettable powder formulations had a slightly greater surface persistence than emulsifiable concentrates and resulted in smaller residues in the grain. There would seem to be more usefulness in using insecticide sprays on woven polypropylene than on jute bags, and a wettable powder formulation of a non-volatile insecticide of low mammalian toxicity would be the best choice. Of the insecticides tested, the pyrethroid permethrin (cis: trans ratio= 25:75) was the most effective and gave the least residue in the grain.     

Antifeeding effect of cypermethrin and permethrin at sub-lethal levels against Pieris brassicae larvae

An antifeeding (feeding deterrent) response by first- and fifth-instar larvae of Pieris brassicae was shown to be significant at sub-lethal levels of cypermethrin and permethrin, using leaf-discs treated with the pyrethroids by dipping. Permethrin was slightly more effective than cypermethrin both as an insecticide and as an antifeedant against fifth-instar larvae, but the reverse order of effectiveness was observed, with a marked difference in mortality, against newly-hatched larvae. When 1-day-old fifth-instar larvae were continuously given leaf discs treated with a solution of the pyrethroid (1 mg litre^?1), up to the time of pupation, both cypermethrin and permethrin induced a significant extension of the larval period, with a reduction in the maximum larval and pupal weights, as well as a reduction in the total leaf-area consumed. However, at higher levels of both pyrethroids, lowering the temperature induced some irritancy, as indicated by regurgitation and frequent uncoordinated wriggling movements of the fifth-instar larvae. The advantages of cypermethrin as a protectant and as an antifeedant over permethrin are discussed.     

Evaluation of field resistance in field-collected mosquito Culex quinquefasciatus Say through quantification of ULV permethrin/PBO formulation in field bioassays

BACKGROUND

Pyrethroids are among the most applied adulticides worldwide to control mosquito vectors for prevention of arboviral diseases transmission. However, pesticide resistance development in a mosquito population could lead to decreased control efficacy. While most studies investigate the resistant genotype (i.e. kdr, CYP450, etc.) as explanatory variables, few field efficacy studies have measured pesticide quantities deposited at different distances from the sprayer in association with observed mosquito mortality. The current study determined field delivered amounts of an applied ULV permethrin/PBO formulation (31% permethrin + 66% piperonyl butoxide) by GC/MS and estimated practical resistance ratios using caged mosquito females.

RESULTS

For field samples, the extraction method recovered 78 ± 3.92–108 ± 8.97% of the permethrin/PBO formulation when utilizing the peaks of PBO from GC/MS to estimate the concentrations of adulticide deposited near the mosquito cages. The field bioassay showed that the spatial distribution of permethrin/PBO formulation was heterogeneous among three pseudo-replicates within the same distance. Within the quantifiable permethrin/PBO range of 15.7–51.4 ng/cm², field-collected mosquito mortalities started at 64% and linearly increased reaching 100% only in two areas, while all Sebring susceptible mosquitoes died. The field LC₉₅ resistance ratio (RR) of F₀ Cx. quinquefasciatus ranged from 2.65–3.51, falling within the 95% CI of RR₉₅ estimated by laboratory vial assays. Tests with and without PBO indicated P450's enzymes contributed to field resistance.

CONCLUSION

Results showed the suitability of the collection and quantification method to estimate the field resistance ratio at the applied pesticide rate. Pesticide quantification would also allow the association of the known frequencies of resistance mechanisms (e.g. kdr, CYP450) with field mortalities to estimate the resistance level conferred by such mechanisms. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Deposit structure and efficacy of pesticide application. 1: Interactions between deposit size,toxicant concentration and deposit number

Application of pesticides through a hydraulic nozzle produces deposits on a plant surface which have a spatial structure with elements of deposit size, number per area, and toxin per deposit. To investigate the relative contributions of these elements to the interaction of deposit structure and toxicant efficacy, we used a stochastic cellular automaton model of diamondback moth feeding on Bacillus thuringiensis (Bt)-treated cabbage – the Pesticide Dose Simulator (PDS) model. Data were analyzed using a specialized response surface approach called a mixture design. The advantage of this design was that it integrated the effects of deposit size, number per area and toxin per deposit on toxicant efficacy. Results from PDS simulations led to the following conclusions: (1) Deposit structure plays a major role in toxin efficacy. (2) Small deposits are not always the most efficacious. (3) Uniform coverage is not the best deposit structure if one is forced to limit application rates and field persistence. (4) Since uniform deposit structures allow an insect to live longer, uniform deposit structures should result in more insects acquiring sub-lethal doses. This may result in an interaction between ‘uniform coverage’ and the development of pesticide resistance in insect populations. (5) Percentage mortality and the level of crop protection are not necessarily correlated. Overall, these results help reconcile laboratory observations that small droplets are more efficacious with field observations that application of small droplets (eg from spinning disk sprayers) does not necessarily increase field efficacy. © 1999 Society of Chemical Industry     

Feeding behavior of Plutella xylostella and Leptinotarsa decemlineata on leaves treated with Bacillus thuringiensis and esfenvalerate

Studies were conducted to examine interactions between esfenvalerate and Bacillus thuringiensis Berl. in their effects on feeding behavior of larvae of Plutella xylostella L. and Leptinotarsa decemlineata Say. Droplets containing esfenvalerate, B. thuringiensis, the two in combination, and water controls were individually applied to leaf disks. Third-instar P. xylostella larvae were allowed to feed for 24 h on cabbage disks and third-instar L. decemlineata larvae were allowed to feed for approximately 18 h on potato leaf disks. For each insect species and each treatment, the proportion of leaf area removed during the feeding period was regressed on the proportion of droplets removed during that period to test for avoidance of droplet residues. No significant differences were found between treatments in these regressions for L. decemlineata. In contrast, B. thuringiensis, either alone or in combination with esfenvalerate, significantly affected the relationship of leaf and droplet consumption for P. xylostella. No evidence of individual droplet avoidance, i.e. a consistently greater proportion of leaf than droplets consumed, was found for any of the treatments. Proportions of leaf consumed and proportions of droplets consumed were compared among treatments to test for effects on feeding rate. B. thuringiensis significantly reduced feeding rate, both alone and in combination with esfenvalerate for P. xylostella and alone for L. decemlineata. We found no statistically significant differences in feeding rate due to esfenvalerate. The species studied can be expected to consume the same amount of B. thuringiensis whether it is mixed with esfenvalerate or not, whereas esfenvalerate dose by ingestion would be reduced if it were mixed with B. thuringiensis.     

‘Universal’ spray droplet adhesion model – accounting for hairy leaves

The adhesion of a spray droplet upon initial contact with a leaf surface is extremely important to spray efficacy and is dependent on dynamic interactions between droplets (formulation, size, velocity) and leaf (micro‐topography, surface chemistry, veininess, hairiness and orientation). A ‘universal’ spray droplet adhesion model has previously been developed, using 50% aqueous acetone contact angles as a measure of leaf surface properties; this model satisfactorily predicts initial adhesion over a range of formulation surface tensions, droplet sizes and velocities. However, it failed to fit data from hairier leaves. This study investigates initial spray droplet adhesion on hairy leaves. Two categories of hairy leaves were identified by how the droplets penetrate the leaf hairs, Wenzel (hairy) and Cassie–Baxter (super hairy). For the Wenzel‐type, a simple constant accounted for the increased droplet shatter caused by the hairs. For the Cassie–Baxter‐type, a cushioning factor was introduced to account for the absorption of kinetic energy at impact by the hair mat. The cushioning factor was estimated by measuring the relative height of the hair mat. By including these two parameters, the new model successfully predicted the mean adhesion of non‐hairy, hairy and super‐hairy plants (R² = 0.96). This model and the underlying principles determining hairy leaf adhesion developed in this article will help develop spray formulations effective at targeting hairy‐leaved weed and crop species.     

Influence of formulation properties on droplet size spectra and ground deposits of aerially-applied pesticides

The influence of the physical properties of the spray liquid on droplet size spectra and ground deposits of aerially-applied pesticides was studied using heavy (high-viscosity) oil- and water-based suspensions of wettable powders (w.p.), a clear solution in a light (low-viscosity) oil, and an emulsion-suspension containing a bacterial control agent. The heavy oil provided a highly viscous spray medium, 52 to 64 mPa s (at a shear rate of 480 s^?1), resulting in large droplet sizes and a high deposit on the ground sampling units. When the spray medium was thickened with petroleum jelly to keep the w.p. in suspension during overnight storage, the viscosity became excessively high (102 mPa s at 480 s^?1), and the droplet spectrum was undesirably coarse and resulted in poor coverage of the spray plot and low deposits. The light-oil-based solution (ca 4 mPa s), provided a finer droplet spectrum and lower deposits than the heavy-oil-based formulations. The water-based suspensions of the w.p. (ca 2 mPa s), showed Newtonian behaviour, whereas the emulsion-suspension (ca 240 mPa s at 480 s^?1) showed pseudoplastic behaviour. Consequently, the emulsion-suspension provided a markedly different droplet spectrum from that of the suspensions of the w.p. Nevertheless, all three aqueous media provided deposits comparable to those of the light-oil-based solution, markedly lower than the heavy-oil-based suspensions. The study indicated that highly viscous Newtonian formulations should be avoided in pesticide applications using Micronair AU3000 atomisers at the volume rate (4–7 litre ha^?1) used here if high atomisation efficiency is required.     

The Experimental Application of Insecticides from a Helicopter for the Control of Riverine Populations of Glossina tachinoides in West Africa. IV. Evaluation of Insecticides Applied as Aerosols

Abstract

The effects of aerosol dosages of different categories of insecticide were tested against Glossina tachinoides when applied by helicopter to riverine forest habitats of the River Komoe, Upper Volta, West Africa. The method of application, droplet characteristics of the aerosols and meteorological conditions are described in accompanying papers. Comparative trials based on field dosages calculated initially from dosage mortality curves obtained from topical application studies in the laboratory were carried out. Endosulfan applied at 5.4 g a.i./ha and 9.0 g a.i./ha reduced G. tachinoides populations (determined by Challier/Laveissière traps) by more than 90% in all age and sex categories and evidence is presented which indicates a residual effect at the higher of these dosages. Good results were also obtained with the synthetic pyrethroid decamethrin at a dosage of 0.36 g a.i./ha; another synthetic pyrethroid, permethrin, gave promising results at a dosage of 1.9 g a.i./ha. At the higher dosage of 4.3 g a.i./ha disappointing results were obtained, which were considered to be more attributable to a weakness in the application technique under challenging field conditions, than to a limitation of the insecticide. The organophosphate compounds tested, fenthion, azamethiphos and tetrachlorvinphos although known from laboratory tests to be appreciably toxic to G. tachinoides, performed poorly under field conditions. This was thought to be due to the formulations employed and the authors feel that further small-scale field testing of different formulations of these compounds is warranted. The compounds considered most worthy of larger scale field evaluation were endosulfan and permethrin. Although decamethrin was also very toxic to G. tachinoides it was considered inadvisable to field test this compound on a larger scale, until more information was available on its impact on aquatic food chains. The trials demonstrated that it is not always possible to extrapolate from laboratory-obtained comparative dosage/mortality data (in ng/fly) the field dosages of insecticides (in g a.i./ha) required to produce a certain level of mortality in target populations of G. tachinoides.     

Spray application factors and plant growth regulator performance: II. Foliar uptake of gibberellic acid and 2,4-D

Effects of droplet size and carrier volume on foliar uptake and translocation of gibberellic acid (GA₃) and 2,4-D were investigated. Simulated spray droplets were applied to primary leaves of 10-day-old Phaseolus vulgaris (cv Nerina) in droplet sizes and carrier volumes ranging from 0.5 to 10 μl and 10 to 200 μl per leaf, respectively. Doses of GA₃ (2 μg per leaf) and 2,4-D (100 μg per leaf) were held constant. Total uptake of GA₃ approached a penetration equilibrium within 24 h after application, but uptake of 2,4-D continued to increase. Decreasing droplet size and/or increasing carrier volume increased GA₃ and 2,4-D uptake. Translocation to stem and roots was positively related to total uptake. A positive linear relationship between the logarithm of the total droplet/leaf surface interface area and 2,4-D uptake or translocation was found, but for GA₃ this relationship was quadratic. Potential mechanisms of the effects of spray application factors on foliar uptake are discussed. © 1999 Society of Chemical Industry     

Sublethal effects of insecticides on the diamondback moth Plutella xylostella (L.)

The effect of sublethal concentrations (LC₁ and LC₅₀) of permethrin, fenvalerate, methamidophos and carbaryl on diamondback moth development, female fecundity and insect behaviour was investigated. All the insecticides had deleterious effects on the number of larvae surviving to pupae, the duration of the pupal period, the number of pupae surviving to adulthood, and cocoon formation in pupae. Prolonged duration of the larval period, from third instar to pupation, and deformed pupae were also observed. Permethrin, fenvalerate and carbaryl caused latent toxicity and deformed wings in the adults. Pyrethroids and methamidophos reduced the longevity of the adults whereas carbaryl increased it. Except for permethrin, the insecticides inhibited female fecundity. At LC₁ and LC₅₀ concentrations, the pyrethroids showed both repellent and antifeedant activity against larvae, and female moths preferred to oviposit on untreated leaf discs rather than on those treated with the pyrethroids at concentrations equal to their LC₅₀ values.