Mortality Of First Instar Larvae Research Articles

Earias vittella management by utilizing obnoxious weeds extracts of Jammu and Kashmir Himalayas, India

All the three agro-ecological zones (sub-tropical, intermediate and temperate) of the Jammu province were surveyed for potential pesticidal plants. Methanol extracts of all the thirteen plants / plant parts and fractions were assessed for insecticidal activity. Eight treatments (T3 –Boerhavia diffusa stem methanolic extract, T6 –Boerhavia diffusa roots methanolic extract, T7 –Boerhavia diffusa roots hexane fraction, T12 –Arisaema flavum stem + leaves methanol extract, T13 –Arisaema flavum stem + leaves hexane fraction, T14 –Arisaema flavum stem + leaves acetone fraction, T15 –Arisaema flavum roots / tubers methanol extract and T17 –Arisaema flavum roots / tubers acetone fraction) recorded cent percent mortality of first instar larvae, within four hours. All the extracts / fractions evaluated against Earias vitella exhibited contact toxicity, and ovicidal action. The growth indices were also affected. Few extracts / fractions were so toxic that they exhibited 100% control. When larvae were fed on extract / fraction treated food for growth indices studies, in many cases larvae died. These extracts/ fractions have great potential to be developed as botanical pesticide. Active pesticidal compounds from few promising plants may be extracted and further studied for their pesticidal activity. The present studies suggest that the plant extract may be fractionated for better results.

Susceptibility of Chilo partellus Swinhoe, 1885 (Lepidoptera: Crambidae) to some commonly used insecticides

Chilo partellus Swinhoe, 1885 (Lepidoptera: Crambidae), a destructive pest of maize, was recently recorded in the Mediterranean Region of Turkey. The pest is considered to be an invasive species, displacing indigenous stem borers in many parts of the world. The aim of the study was to determine the effect of commonly used insecticides in a maize production system in Turkey on egg hatch and mortality of first instar larvae of C. partellus under laboratory conditions (27±2ºC, 70% RH and 14:10 h L:D photoperiod) at the Plant Protection Department, Faculty of Agriculture, University of Çukurova. Eight insecticides registered for indigenous lepidopteran pests were used at the recommended rates. The percentage of hatched egg masses were significantly different. The smallest percentage was 30.6% with deltamethrin. The percentages of hatched egg masses were greater than 80% for all other insecticides. Mortality of hatched larvae was significantly different. The highest and lowest mortalities of hatched larvae were 84.5% and 38.2% with emamectin-benzoate and lambda-cyhalothrin, respectively. Seventy-two h after exposure of the first instar larvae to sprayed maize leaf disks, the lowest and highest mortalities were 62.6% and 96.7% with indoxacarb and emamectin-benzoate, respectively. Survival analyses revealed that hazard ratios ranged from 4.91 (95% CI: 1.66-14.6) to 15.6 (95% CI: 5.33-45.6) with chlorpyrifos-ethyl and emamectin-benzoate, respectively. The mortality of first instar larvae was about 16, 10 and 9 times that of the control with emamectin-benzoate, lambda-cyhalothrin and deltamethrin, respectively. Feeding activity of larval stage was reduced by all treatments. The implications of this study are discussed.

Activity of Selected Formulated Biorational and Synthetic Insecticides Against Larvae of Helicoverpa armigera (Lepidoptera: Noctuidae).

This work studied 17 insecticides belonging to nucleopolyhedrovirus (NPV), Bacillus thuringiensis (Bt kurstaki and Bt aizawai), benzoylureas (insect growth regulators [IGRs]), carbamates, organophosphates, spinosyns, and diamides against larvae of Helicoverpa armigera (Hübner), invasive species in the South American continent. Larvae of different instars were fed for 7 d with untreated or insecticide-treated diets. Mortality was recorded daily for 7 d, and surviving larvae were individually weighed on the seventh day. The NPV and Bt insecticides caused 100% mortality of first-instar larvae and first-instar and second-instar larvae, respectively. However, both NPV and Bt-based products caused low mortality of third-instar larvae and did not kill older larvae. The IGR lufenuron was highly effective against all three ages of larvae tested, whereas teflubenzuron and triflumuron produced maximum 60% mortality of second-instar larvae and lower than 50% to older larvae. Thiodicarb, chlorantraniliprole, indoxacarb, chlorpyrifos, and chlorfenapyr, irrespective of tested age, caused 100% mortality of larvae, with the last two insecticides reaching 100% mortality within 2 d of feeding on the treated diet. Flubendiamide caused lower mortality but significantly affected the weight of surviving larvae, whereas neither spinosad nor methomyl produced significant mortality or affected the weight of larvae. Based on the results, the age of H. armigera larvae plays an important role in the recommendation of NPV and Bt insecticides. Furthermore, there are potential options between biological and synthetic insecticides tested against H. armigera, and recording larval size during monitoring, in addition to the infestation level, should be considered when recommending biological-based insecticides to control this pest.

Compositional analysis and toxicity of four plant essential oils to different stages of Mediterranean flour moth, Ephestia kuehniella Zeller (Lepidoptera: Pyralidae)

Experiments were conducted to investigate the biological effects of essential oils from basil ( Ocimum basilicum L.), paprika ( Capsicum annuum L.), peppermint ( Mentha x piperita L.) and rosemary ( Rosmarinus officinalis L.) on the different stages of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae). Essential oils were obtained by Clevenger-type water distillation and analyzed by capillary gas chromatography-mass spectrometry. The doses of the essential oils applied were 0.1, 1, 5, 10, 20, 50 and 100 μl L -1 air. The major compounds of the essential oils were detected as linalool (63.1%), capsaicin (35.4%), menthol (28.3%) and cineole (25.7%), in basil, paprika, peppermint, and rosemary oils, respectively. The essential oil of paprika caused the highest mortality of first instar larvae of E. kuehniella at a dose of 5 μl L -1 air after 24 h exposure . Among the tested different stages, larvae of E. kuehniella were the most tolerant of essential. Basil, paprika, peppermint and rosemary oils exhibited toxicity to adult stages of E. kuehniella with 100% mortality obtained after 24 h at dose of 100, 5, 20 and 10 µl L -1 air, respectively. Increasing the doses of essential oils resulted in increased toxicity to all stages of E. kuehniella. In conclusion , the four plants essential oils tested in this study have potential for use in the management of the stored-product pest, E. kuehniella .

Repellent, antifeedant and toxic effects of Ageratum conyzoides (Linnaeus) (Asteraceae) extract against Helicovepra armigera (Hübner) (Lepidoptera: Noctuidae)

Repellent, antifeedant and toxic effect of crude hexane extract of Ageratum conyzoides were investigated against Helicoverpa armigera. In orientation bioassay, the extract exhibited dose-dependent repellency against neonates. Extract significantly increased the mortality and decreased growth of different larval stages when administrated orally in artificial diet. EC50 value was at 0.11% for larval growth inhibition. Toxicity of the extract was manifested by high mortality of first instar larvae after 7 days of feeding on diet containing 0.05–0.4% of extract with LC50 of 0.17%. Under choice bioassay, extract showed strong antifeedant activity against fifth instar larvae with DI50 of 0.21%. In nutritional bioassay, extract significantly reduced RCR, RGR, ECI and ECD of fifth instar larvae with increased AD. When RGR were plotted against RCR, the growth efficiency of larvae fed on treated diet was significantly lower than the control fed larvae suggesting the antifeedant and toxic effect of extract.

Patogenisitas Beberapa Isolat Cendawan Entomopatogen Metarhizium spp. terhadap Telur Spodoptera litura Fabricius (Lepidoptera: Noctuidae)

Metarhizium spp. merupakan salah satu jenis cendawan entomo-patogen yang dapat digunakan untuk mengendalikan hama Spodoptera litura. Tujuan dari penelitian ini adalah untuk mempelajari patogenisitas isolat Metarhizium spp. terhadap telur Spodoptera litura. Isolat Metarhizi-um spp. dikoleksi dari rizosfer tanaman kubis, bawang merah, bawang daun dan cabai. Hasil penelitian menunjukkan bahwa semua isolat yang diuji bersifat patogen terhadap telur S. litura. Mortalitas telur S. litura berkisar antara19,79%-75,70%, tergantung pada isolat. Larva instar I mati setelah 3 hari keluar dari telur dengan mortalitas tertinggi sekitar 58,65%. Isolat Mt-Kb merupakan isolat yang paling virulen dengan mortalitas telur dan larva instar I tertinggi dibandingkan dengan isolat lain.

EFFECT OF SOME BIOINSECTICIDES ON THE PREDATOR Chrysoperla carnea (STEPHENS).

Chrysoperla carnea (Stephens), (aphid lion, green lacewing) larvae active predators and feed on aphids and other small insects. It has been used in the biological control of insect pests on crops. While The adults feed on nectar, pollen and aphid honeydew and are not predatory Tracer (Spinosad) is primarily a stomach poison with some contact activity and is particularly active against Lepidoptera and Diptera. In this study, tested the effect of bio-pesticide Tracer on percentage of mortality on different larval instars of aphid lion, The results showed 63% mortality of first instar larvae after 72 h of exposure in high concentration when recorded 52% and 30% mortality of second and third instars larvae after the same time The study has proved that, the mortality percentages for the first instar larvae were high, But they modularity in second instar and no significant in third instar.

Biocontrol efficacy of protoplast fusants between Bacillus thuringiensis and Bacillus subtilis against Spodoptera litura Fabr.

Bacillus thuringiensis (Bt) is a microbial pesticide widely used to control crop pests. Its strains have good biocontrol activity against crop insect pest, but lack some desirable characteristics that are found in Bacillus subtilis. An attempt has been made to combine those desirable characteristics; we used a highly effective biocontrol strain of B. thuringiensis in protoplast fusions with a strain of B. subtilis. The fusants were identified through cell culture and stained with crystal violet. The Bt and B. subtilis protoplasts were induced to fuse by PEG 6000. The fusants were produced almost 95% mortality in first instar larvae of Spodoptera litura. The lethal doses (The LC50 and LC90) for mortality of S. litura values were significantly in lower level in the fusant-treated larvae, when compared with Bt and B. subtilis individual treatment. The consumption and digestion of S. litura significantly decreased after treatment with fusant. Also the approximate digestibility of S. litura increased significantly.

Laboratory evaluation of entomopathogenic fungi against the white grubs, Holotrichia oblita and Anomala corpulenta (Coleoptera: Scarabaeidae) from the field of peanut, Arachis hypogaea

We evaluated the pathogenicity of nine isolates of entomopathogenic fungi, including six isolates of Metarhizium anisopliae, one of Beauveria bassiana, and two of Beauveria brongniartii, against eggs and various larval instars of two scarab-beetle species, Holotrichia oblita and Anomala corpulenta, under laboratory conditions. The fungal isolates differed in pathogenicity. Generally, the isolates were more pathogenic to A. corpulenta than to H. oblita. Some of the isolates prevented egg hatching and caused larval death. Isolates M2-2 and Br5-8 caused 39 and 27% egg mortality, respectively, and produced 23 and 24% viewable fungal-infection rates in H. oblita. Three isolates had no significant effect on egg hatchability. Three isolates (Br5-8, Br232818, and M200614) caused about 40% mortality in H. oblita first instars. In A. corpulenta, all isolates except M200614 caused more than 60% egg mortality, and M2-2, Br232818 and Br5-8 caused egg-infection rates greater than 50%. M2-2 caused 47% infection and 100% mortality in first-instar larvae of A. corpulenta, while Br5-8 and Br232818 yielded over 80% mortality of the larvae. The three most virulent isolates, M2-2, Br232818 and Br5-8, were selected for further bioassays against second- and third-instar larvae. In addition, seven graduated concentrations of a Br5-8 conidial suspension were assayed against H. oblita second instars. Larval mortality was positively correlated with fungal dosage, and the LC50 was 4.49×106 conidia/mL. These three virulent isolates may be used to prevent H. oblita and A. corpulenta larval infestations in field crops.

Constructing life‐tables for the invasive maize pestDiabrotica virgifera virgifera(Col.; Chrysomelidae) in Europe

Abstract: The western corn rootworm (Diabrotica virgifera virgiferaLeConte, Col.; Chrysomelidae) is an alien invasive species in Europe. It is a univoltine species with eggs that overwinter in the soil and larvae that hatch in spring. Three larval instars feed on maize roots, which can cause plant lodging and yield loss of economic importance. Adults emerge between mid‐June and early August and can reduce yields through intensive silk feeding. In order to provide a thorough understanding of the population dynamics of this invasive pest species in the invaded European region, complete age specific life‐tables were constructed in two maize fields in southern Hungary assessing the significance of natural mortality factors acting onD. v. virgiferapopulations. This information provides a rational basis for devising sustainable integrated pest management programmes, in particular, by enabling the identification of vulnerable pest age intervals for the timely application of various management tools. The life‐table forD. v. virgiferain Europe resulted in a total mortality of about 99% from the egg stage in the autumn to the emergence of adult females in the following year (KTotal = 2.48), which is comparable with North America. The highest reduction ofD. v. virgiferanumbers resulted from the mortality in first instar larvae (94% marginal death rate) and from the unrealized fecundity (80%). However, only the variation in mortality between years can change the generational mortality and thus influence population growth. High variation in the marginal death rate between fields and years was found in the second and third instar larval stages, and in the overwintering egg stage. These mortality factors therefore have the potential to cause changes in the total generational mortality. Furthermore, the life‐table suggested that a high fecundity could compensate for a high generational mortality and would lead to population increase.

Variation among Accessions of Pisum fulvum for Resistance to Pea Weevil

ABSTRACTThe pea weevil, Bruchus pisorum (L.) (Coleoptera: Bruchidae), is one of the most intractable pest problems of cultivated pea, Pisum sativum L. The availability of resistant cultivars would give growers more pest management options. Searches for plant resistance to pea weevil were expanded to the Pisum secondary gene pool (P. fulvum Sm.) because seed resistance had not been located in P. sativum and subspecies. The objectives of this study were to determine the extent of pod and seed resistance to pea weevil in P. fulvum, and to use the life table format to characterize weevil stage‐specific mortality and survivorship on different P. fulvum accessions. Mortality of first instar larvae on pods, mortality of all weevil stages within seed, adult emergence from seed, and seed damage levels were quantified. In two greenhouse trials, more larvae died (14 to 50% averages) on pods of P. fulvum accessions than on pods of ‘Alaska 81’ (6% average), and mortality of first instar larvae entering seed of P. fulvum accessions averaged 83.7%. Seed damage ratings (1 = feeding scar on seed testa, 0‐1% cotyledon tissue eaten, dead first instar larva; 5 = extensive damage, live adult) averaged <3.0 for 26 P. fulvum accessions, compared with mean ratings of 4.9 for Alaska 81. Using weevil mortality and survivorship values in life tables and adult emergence rates, entries were classified as susceptible (two controls and five accessions), moderately resistant (14 accessions), and resistant (12 accessions). Antibiosis resistance was based on the death of weevil larvae on pods and seed testa and cotyledon tissues. The results identify sources of natural weevil resistance in the Pisum genome (26 moderately resistant and resistant accessions of P. fulvum) to endow pea cultivars with pod and/or seed resistance to B. pisorum.

Cloning and characterization of an insecticidal crystal protein gene from Bacillus thuringiensis subspecies kenyae.

A sporulating culture of Bacillus thuringiensis subsp. kenyae strain HD549 is toxic to larvae of lepidopteran insect species such as Spodoptera litura, Helicoverpa armigera and Phthorimaea operculella, and a dipteran insect, Culex fatigans. A 1.9-kb DNA fragment, PCR-amplified from HD549 using cryII-gene-specific primers, was cloned and expressed in E. coli. The recombinant protein produced 92% mortality in first-instar larvae of Spodoptera litura and 86% inhibition of adult emergence in Phthorimaea operculella, but showed very low toxicity against Helicoverpa armigera, and lower mortality against third-instar larvae of dipteran insects Culex fatigans, Anopheles stephensi and Aedes aegypti. The sequence of the cloned crystal protein gene showed almost complete homology with a mosquitocidal toxin gene from Bacillus thuringiensis var. kurstaki, with only five mutations scattered in different regions. Amino acid alignment with different insecticidal crystal proteins using the MUTALIN program suggested presence of the conserved block 3 region in the sequence of this protein. A mutation in codon 409 of this gene that changes a highly conserved phenylalanine residue to serine lies in this block.

Evaluation of insecticides for the control of Helicoverpa armigera (Hübner) and Helicoverpa punctigera (Wallengren) (Lepidoptera: Noctuidae) on soybean, and the implications for field adoption

AbstractSeven insecticides were evaluated against first‐, third‐ and fifth‐instar Helicoverpa armigera (Hübner) and Helicoverpa punctigera (Wallengren) larvae using a leaf‐disc bioassay of field‐treated soybean. Significant differences were detected in age‐specific mortality, time to effect (LT50) and field persistence of the insecticides tested. With the exception of trichlorfon, the mortality of first‐instar larvae was similar in the different treatments to the commercial standard, methomyl. The mortality of third‐ and fifth‐instar larvae in the spinosad and chlorpyrifos treatments was also similar to that in the methomyl treatment, while the age‐specific mortality of the insecticides based on Bacillus thuringiensis and nucleopolyhedrovirus declined more rapidly, resulting in low mortality to fifth‐instar larvae. The LT50 of the biological‐based products were significantly greater than those of the conventional products. Only chlorpyrifos showed significant activity 1 week after treatment. The results suggest the need for a user education program to highlight the likely differences in the field performance of the newer biological‐based products compared with the conventional chemicals with which growers are familiar.

Survival and behavioral responses of larvae of the caddisfly Hydropsyche angustipennis to copper and diazinon

AbstractThis study reports on newly developed short‐term survival and behavioral tests with larvae of the caddisfly Hydropsyche angustipennis using two model toxicants, copper and diazinon. Mortality of first instar larvae was shown to be a reliable endpoint, and it was demonstrated that H. angustipennis is among the more sensitive aquatic insects in terms of both copper and diazinon. In addition, short‐term behavioral responses were found to be indicative of adverse effects of ecologically relevant low doses of copper. Using the tests developed in this study, hydropsychid species are excellent tools for discerning the effects of individual toxicants present in large European rivers, and these species may help in defining the conditions for ecological rehabilitation.

Comparative ecotoxicity of NPAHs to larvae of the midge Chironomus riparius

Acute toxicity of seven azaarenes (NPAHs) has been determined using larvae of the midge Chironomus riparius. Clear dose-response relationships for mortality of first instar larvae were observed, but surviving larvae grew as equally well as the controls. LC 50 values (96 h) for a two-ringed structure (quinoline), four three-ringed structures (acridine, phenanthridine, benzo[ f]quinoline and benzo[ h]quinoline) and two four-ringed structures (benz[ a]acridine and benz[ c]acridine) were generally one order lower than the few values reported for other aquatic species in the literature. Dibenz[ a,i]acridine, a five-ringed structure, was not acutely toxic at its maximum dissolved concentration. Acute toxicity increased with increasing number of aromatic rings of the compound; accordingly, correlations between the LC 50 values and size, shape and topology-related molecular properties were strong. However, between the four benzoquinoline isomers tested also differences in toxicity were observed: acridine was significantly more toxic than the other benzoquinoline isomers tested. This is most likely caused by transformation of acridine under UV light, indicated by a HOMO–LUMO gap in the highly phototoxic region, a high correlation between isomer toxicity and heat of formation and a low recovery of acridine in the water during the experiment.

Growth-inhibitory effects of proteinaceous fractions from resistant wild bean accessions on the bean weevil, Acanthoscelides obtectus

—This study was conducted to identify the individual biochemical factors involved in the resistance observed in a few Mexican bean accessions against the bean weevil, Acanthoscelides obtectus (Say) (Coleoptera: Bruchidae). Soluble proteins from different bean genotypes were separated by fractionated acetone precipitation. Insects were reared on artifical seeds composed of a susceptible background bean flour enriched with the different protein fractions. At low doses (2% w/w), the 0–20% and 20–40% acetone fractions of the resistant bean accessions G 12954 and G 12880 inhibited larval growth of the bean weevil, but not of a related species, the Mexican bean weevil, Zabrotes subfasciatus (Boheman). The 0–20% fraction caused the highest mortality of first instar larvae. The 60–80% acetone fraction contains general resistance factors, like a-amylase and protease inhibitors, which when enriched in artifical seeds led to a strong depression of insect growth for resistant and susceptible bean accessions alike. These factors should also be taken into account in breeding for multigenic, durable resistance, in order to exploit the synergism between general and specific resistance factors.

An experimental study of early stage survival of Helicoverpa armigera (Lepidoptera: Noctuidae) on cotton

AbstractThe pattern and cause of mortality of the early stages of Helicoverpa armigera (Hübner) on cotton was investigated in both field and glasshouse situations for two seasons. In 1987, egg losses were high (32–88%) over days 1–3 following oviposition, more so from the lower than upper leaf surface. The mortality of first instar larvae was 93–100% over days 4–5 following oviposition, and losses were higher from seedling stage than squaring cotton. Wind, rain (or watering), aerial predators, dispersal of first instar larvae, and host plant effects (including leaf orientation) were important mortality factors. In 1988 trials, egg losses over days 1 to 3 after oviposition on plants in glasshouse and field situations, respectively, were 0–1% and 5–6% due to changing leaf orientation alone; 4–22% and 16–32% due to rain/watering and changing leaf orientation combined; 14–31% and 12–31% for wind and changing leaf orientation combined; and 4–38% and 23–52% for the combination of wind, rain/watering and changing leaf orientation. Mortality of first instar larvae on day 4 was 32% and 29% on plants in glasshouse and field, respectively, from which the action of such mortality factors had been excluded. Mortality on plants with changing leaf orientation alone was 30% and 68%, with rain/watering and changing leaf orientation combined 48% and 74%; with wind and changing leaf orientation combined 40% and 63%; and with all factors combined 45% and 69%, respectively. The highest losses (of eggs) occurred on day 1 after oviposition, and similarly for first instar larvae on day 4, which coincided with hatching.

MORTALITY OF FALL ARMYWORM, SPODOPTERA FRUGIPERDA (LEPIDOPTERA: NOCTUIDAE) EGGS, LARVAE AND ADULTS EXPOSED TO SEVERAL INSECTICIDES ON COTTON

Mortality of eggs, first, third, and fifth instars and adults of fall army worm (FAW), Spodoptera frugiperda (J. E. Smith), after exposure to several insecticides on cotton indicated that the FAW is susceptible to most insecticides currently used to control Heliothis spp. Most insecticides tested exhibited ovicidal activity. High mortality of first instar larvae was observed for most treatments, including the biological insecticide, Bacillus thuringiensis (Berliner). More variation in mortality among treatments was observed in third and fifth instars than in first instars. Pyrethroid, carbamate, and organophosphorous insecticides resulted in higher mortality than did B. thuringiensis. Diflubenzuron, an insect growth regulator, was as effective as commonly used insecticides against third and fifth instar larvae when mortality was observed at pupation. Third instar FAW placed on plant tissue from the upper section of cotton plants sprayed in field situations suffered higher mortality than those placed on plant tissue from lower sections in the plant canopy. Inadequate deposition of insecticide in the lower portions of the cotton plant appears to be a limiting factor in control of FAW larvae on cotton.

Distribution of Oviposition Sites and Characteristics of Egg Development in the 'Blandford Fly' Simulium posticatum (Diptera: Simuliidae)

(1) Eggs of Simuliumposticatum have previously been found in bankside soil above the water surface. This study investigated the distribution of oviposition sites on the River Stour, U.K., in relation to a local medical problem caused by the bites of the females. (2) The characteristics of the river bank were noted. Sites with a vertical bank profile and loamy soil in the shade were favoured by the females. Aspect and water velocity were not related to oviposition site., (3) Four weeks of exposure to low temperature was required to break the diapause of the eggs and the minimum total time taken to hatching was 8 weeks. High temperatures, after the diapause had been broken, inhibited hatching (4% hatch after 9 days at 14WC, compared with 48% at 5QC). (4) Larvae were seen to hatch on damp soil but hatching success was greater among eggs immersed in water. Mortality of first-instar larvae was low at 5?C (6% after 7 days, compared with > 70% at 9?C and 14?C). This may be an adaptation to the time required to find a suitable feeding site at the ambient temperature of the river. (5) Eggs were not resistant to desiccation even though they normally remain in soil from early summer to the following February. At relative humidities of 97%). (6) It was concluded that high relative humidity and the presence of capillary water in soil produced favourable conditions for egg development and survival.

Behavioral and physiological responses of cabbage looper,Trichoplusia ni (H�bner), to steam distillates from resistant versus susceptible soybean plants

Soybean plant volatiles, extracted as steam distillates, significantly affected the behavior and biology of the cabbage looper,Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae). Distillates from the susceptible Davis variety attractedT. ni larvae and female adults, whereas those from resistant PI 227687 plants repelled them. When mixed in an artificial diet, steam distillates from PI 227687 plants caused mortality of first-instar larvae. Adults emerging from pupae topically treated with 5 μg of such PI 227687 extractable showed developmental abnormalities. Larval feeding was significantly less on Davis leaves treated with PI 227687 volatiles as compared to solvent (acetone) or such Davis extractables. However, Davis volatiles on PI 227687 leaves did not increase larval feeding. HPLC analyses of steam distillates from susceptible Davis versus resistant PI 227687 indicated differences.