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PubMed2002

(Z)-7-dodecenyl acetate: a supernormal stimulus of Trichoplusia ni (Hübner) [Lepidoptera: Noctuidae] sex pheromone behavior.

Males discriminate between the single most important individual component of the sex pheromone of the female cabbage looper, Trichoplusia ni (Hübner), (Z)-7-dodecenyl acetate (Z7-12:Ac), and a mixture containing Z7-12:Ac and the other five putative components. The manifestation of discrimination is not an enhancement of captures by the mixture, rather, it is a reduction of captures in a paired trap baited with Z7-12:Ac by itself. Previous experiments showed that either or both of (Z)-7-tetradecenyl acetate (Z7-14:Ac) and (Z)-9-tetradecenyl acetate (Z9-14:Ac) were responsible for this discrimination. This report provides evidence that Z7-14:Ac is more active than Z9-14:Ac, which appears to have no demonstrable effect on behavior. The results are discussed with reference to the behavior that is effected by the above three components, the composition of the native sex pheromone, and whether or not Z7-12:Ac might be a supernormal releaser of behavior.

Acetates↗
PubMed2002

Spatial representation of odours in the antennal lobe of the moth Spodoptera littoralis (Lepidoptera: Noctuidae).

Glomeruli within the antennal lobe (AL) of moths are convergence sites for a large number of olfactory receptor neurons (ORNs). The ORNs target single glomeruli. In the male-specific cluster of glomeruli, the macroglomerular complex (MGC), the input is chemotypic in that each glomerulus of the MGC receives information about a specific component of the conspecific female sex pheromone. Little is known about how neurons that detect other odorants arborize in and amongst glomeruli. The present study focuses on how sex pheromones and biologically relevant semiochemicals are represented in the ALs of both sexes of the moth Spodoptera littoralis. To assess this, we optically measured odour-evoked changes of calcium concentration in the ALs. Foci of calcium increase corresponded in size and shape with anatomical glomeruli. More than one glomerulus was normally activated by a specific non-pheromonal odorant and the same glomerulus was activated by several odorants. All odorants and pheromone components tested evoked unique patterns of glomerular activity that were highly reproducible at repeated stimulations within an individual. Odour-evoked patterns were similar between individuals for a given odorant, implicating a spatial olfactory code. In addition, we demonstrated that activity patterns evoked by host-plant related volatiles are similar between males and females.

Animals↗
PubMed2004

The role of heliothine hairpencil compounds in female Heliothis virescens (Lepidoptera: Noctuidae) behavior and mate acceptance.

Studies on numerous insect species suggest that male-produced sex pheromones play a role in attracting females; as aphrodisiacs, making females more quiescent; or as a means of inhibiting competing males. Male heliothine moths display abdominal hairpencils during courtship, but the specific effects of the odors released on female behavior have not yet been elucidated. This study investigates the role of male hairpencil compounds in female Heliothis virescens mating behavior. Female H. virescens were exposed to filter paper loaded with hairpencil extracts of male H. virescens, Heliothis subflexa and Helicoverpa zea, and observed for behavioral responses to odors. Single synthetic compounds found in the H. virescens hairpencil blend were also tested. In mating assays between single male and female H. virescens it was found that: (i) antennectomized females mated less frequently than sham-operated females; (ii) females mated less frequently with males whose hairpencils had been surgically removed; (iii) females mated with males with ablated hairpencils if a filter paper loaded with one male equivalent of H. virescens hairpencil extract was presented simultaneously; and (iv) this effect was species-specific, as presentation of H. subflexa or H. zea hairpencil extracts did not restore mate acceptance. This study suggests that odors released by male hairpencils are important in mate acceptance by female H. virescens, and may play a role in mate choice and species isolation.

Animals↗
PubMed1989

Comparison between in vivo and in vitro cutaneous penetration of fenvalerate in tobacco budworm (Lepidoptera: Noctuidae).

In vivo and in vitro penetration of fenvalerate were compared in the 3-d-old fifth-instar tobacco budworm, Heliothis virescens (F). In the in vitro studies, a piece of cuticle was excised and mounted on a diffusion cell, and the amount of radioactivity present in the cuticle and medium was determined at various time intervals. At 24 h, approximately 7.4% of the dose was located in the cuticle, whereas only 1.6% actually penetrated. In the in vivo studies, approximately 7.4% of the radioactivity was recovered from the body after cuticular wash.

Animals↗
PubMed1994

Simple method for monitoring dispersal of Heliothis (Lepidoptera: Noctuidae) backcross sterility genes.

Release of sterile backcross males from [Heliothis subflexa (F.) X H. virescens (Guenée) females X H. virescens males] has been suggested as a means of reducing populations of H. virescens. A simple method is needed to measure the persistence or dispersal of the backcross sterility genetic factors. Backcross male sterility is transmitted via maternal inheritance. The mitochondrial DNA (mtDNA) also is inherited maternally; therefore, the mtDNA in the backcross is from H. subflexa. Several regions of the mtDNA were amplified using polymerase chain reaction (PCR), then were cut with restriction enzymes to generate restriction fragment length polymorphisms (RFLP). Differences between H. virescens and backcross mtDNA were observed for 16S (ribosomal DNA (rDNA)), 12S-16S rDNA, and the COI-COII (cytochrome oxidase) regions. This is attributed to species-specific differences between H. virescens mtDNA and H. subflexa mtDNA carried by the backcross. Therefore, mtDNA provides a convenient marker for tracking the progress of backcross sterility. Developmental stages from eggs through adults are suitable for use.

Animals↗
PubMed1994

Toxicity, penetration, tissue distribution, and metabolism of methyl parathion in Helicoverpa armigera and H. punctigera (Lepidoptera: Noctuidae).

Toxicity of C14-ring-methyl parathion in penetration, tissue absorption, and metabolism by susceptible Helicoverpa armigera (Hübner) and Helicoverpa punctigera (Wallengren) larvae was compared. C14 methyl parathion penetrated the cuticle of H. punctigera more rapidly than of H. armigera, leading to initially higher internal insecticide concentrations in H. punctigera. The same methyl-parathion metabolites were recovered from H. armigera and H. punctigera. However, larger quantities of methyl paraoxon and p-nitrophenol-glucoside were extracted from H. punctigera. These results are discussed in terms of the history of insecticide resistance in H. punctigera and H. armigera in Australia.

Absorption↗
PubMed1997

Interactions of recombinant and wild-type baculoviruses with classical insecticides and pyrethroid-resistant tobacco budworm (Lepidoptera: Noctuidae).

In tests with neonate Heliothis virescens (F.), we characterized interactions of all combinations of a recombinant Autographa californica (Speyer) nuclear polyhedrosis virus (AcAaIT) that expresses an insect-selective neurotoxin (AaIT) and wild-type AcNPV when combined with low concentrations of several conventional insecticides. All combinations of the recombinant virus AcAaIT and insecticides showed a positive interaction (decrease in the median lethal time (LT50) compared with the LT50 for either component alone). A type II pyrethroid (cypermethrin, which modifies currents of sodium channels) and a carbamate (methomyl, an inhibitor of acetylcholinesterase) were synergistic in combination with AcAaIT. Other insecticides also showed a positive interaction when tested in combination with the recombinant virus, but joint activity was slightly antagonistic (i.e., less than predicted activity when combined) with wild-type AcNPV. We also characterized the effectiveness of AcAaIT against pyrethroid-resistant H. virescens larvae. Our results show that a resistant strain of H. virescens is more sensitive to the recombinant virus compared with a susceptible strain. Results of these studies should be useful in planning of future field trials to increase the effectiveness of nuclear polyhedrosis viruses and to manage resistance to pyrethroids and other insecticides.

Animals↗
PubMed1997

Efficacy of a dehydrated steinernematid nematode against black cutworm (Lepidoptera: Noctuidae) and diamondback moth (Lepidoptera: Plutellidae).

We compared the ability of in vitro-produced, commercially formulated with in vivo-produced, nonformulated Steinernema carpocapsae (Weiser) Poinar. All strain to infect and kill larvae of black cutworm, Agrotis ipsilon (Hufnagel), and diamondback moth, Plutella xylostella (L.). In vitro-produced nematodes formulated in wettable dispersible granules, which were stored dry, were rehydrated in water for 0-72 h before application. Against black cutworms, the efficacy of nematodes was (from most to least effective): in vivo > in vitro rehydrated for 72 h > in vitro rehydrated for 48 h > in vitro rehydrated for 24 h > dehydrated (0 h). Nematodes rehydrated for 72 h in water or moist soil were equally effective against black cutworm larvae, and both were significantly more effective than nematodes without rehydration. These results indicated that nematodes in the wettable dispersible granule formulation required time to rehydrate in the soil before infecting black cutworm larvae. Nematode treatments described above were applied to radish plants held at 100 or 75% RH and tested against diamondback moth larvae. At 100% RH, nematode efficacy was (from most to least effective): in vitro rehydrated for 72 h > in vivo > in vitro rehydrated 48 h > in vitro rehydrated 24 h > dehydrated (0 h). The efficacy of all treatments was lower at 75% than at 100% RH, and the ranking of in vivo and in vitro nematodes rehydrated for 72 h was reversed. The nematodes in the wettable dispersible granule formulation were effective for foliar treatments when humidity was high and nematodes were rehydrated for at least 48 h before application. The data show that nematode infectivity was reduced unless nematodes were rehydrated.

Animals↗
PubMed1997

Effect of ecdysteroid UDP-glucosyltransferase gene deletion on efficacy of a baculovirus against Heliothis virescens and Trichoplusia ni (Lepidoptera: Noctuidae).

Laboratory, greenhouse, and field studies were conducted to characterize the biological activity of a genetically altered form of Autographa californica (Speyer) nucleopolyhedrosis virus (AcNPV). The altered baculovirus (vEGTDEL) had a deletion in the ecdysteroid UDP-glucosyltransferase gene. Results from bioassays conducted with neonate and 3rd-instar tobacco budworm, Heliothis virescens (F.), as well as with 3rd-instar cabbage looper, Trichoplusia ni (Hübner), showed vEGTDEL caused larval death slightly, but significantly, quicker than AcNPV. Based on supposition (LT50 values were not calculated), it appeared that larval mortality occurred 0.5-1.0 d faster following exposure to vEGTDEL versus AcNPV. Greenhouse studies conducted against H. virescens on cotton showed that hastened virulence exhibited by vEGTDEL led to improved plant protection versus AcNPV. For example, following 5 weekly sessions of foliar application and H. virescens artificial infestation, cotton treated with wettable powder formulations of vEGTDEL or AcNPV at 2.5 x 10(12) OB/ha averaged 25.7 and 61.8% damaged flower buds, respectively. Although vEGTDEL tended to provide more consistent control of T. ni than AcNPV in greenhouse and field trials conducted on leafy vegetables, differences in efficacy between the 2 baculoviruses were marginal and usually not statistically significant. Generally, results from these studies suggest that genetic modification of NPVs to hasten their lethal effect may be a promising strategy for improving the insecticidal properties of the insect-specific pathogens.

Animals↗
PubMed1999

Evaluation of transgenic sweet corn hybrids expressing CryIA (b) toxin for resistance to corn earworm and fall armyworm (Lepidoptera: Noctuidae).

Many of the lepidopterous insects which attack sweet corn, Zea mays L., are susceptible to insecticidal proteins produced by Bacillus thuringiensis ssp. kurstaki (Berliner) (Btk). Transgenic sweet corn expressing a synthetic cry gene for production of a Btk-insecticidal protein may provide a more environmentally acceptable means of sweet corn production. Eight transgenic sweet corn hybrids containing a synthetic gene for CryIA(b) protein production (BT11 event) were evaluated for resistance to the corn earworm, Helicoverpa zea (Boddie), and fall armyworm, Spodoptera frugiperda (J. E. Smith). Laboratory tests revealed that all Btk sweet corn hybrids were highly resistant to leaf and silk feeding by neonate 3 and 6 d old corn earworm larvae. Ear damage in the field to the Btk sweet corn hybrids caused by corn earworm was negligible. All Btk sweet corn hybrids, except Btk 95-0901, were moderately resistant to leaf and silk feeding by the fall armyworm. Survival and weight gain were reduced when neonates were fed excised whorl leaves of the Btk plants. Weight gain, but not survival, was reduced when 3- and 6-d-old fall armyworm larvae were fed excised whorl leaves of the Btk plants. Btk sweet corn hybrids appear to be ideal candidates for use in integrated pest management (IPM) programs for both the fresh and processing sweet corn markets, and their use should drastically reduce the quantity of insecticides currently used to control these pests in sweet corn. With appropriate cultural practices, it is highly unlikely that Btk sweet corn will contribute to the development of resistance to Btk proteins in these insects because of the high toxicity of the Cry proteins expressed in these sweet corn hybrids and the harvest of sweet corn ears from fields before larvae can complete development.

Animals↗
PubMed1999

Interplant movement of Heliothis virescens (Lepidoptera: Noctuidae) larvae in pure and mixed plantings of cotton with and without expression of the Cry1Ac delta-endotoxin protein of Bacillus thuringiensis Berliner.

Laboratory and field studies were conducted during 1993 and 1994 to quantify interplant movement of Heliothis virescens (F.) larvae in pure and mixed plantings of cotton, Gossypium hirsutum L., with ('Event 531') and without ('Coker 312') the expression of Cry1Ac delta-endotoxin protein of Bacillus thuringiensis Berliner. Field studies were conducted with neonate, 4-, and 7-d-old larvae placed on 3-plant experimental units and observed at 24, 48, 72, and 96 h after inoculation of larvae. Combining larval movement across observations of neonates, 4-, and 7-d-old larvae, an estimated 52% of the larvae on pure plantings of Coker 312 had moved at least 1 plant by the cumulative time required to reach the age of 10 d. More larvae placed on Event 531 cotton moved to an adjacent plant (13% of the neonates had moved at least 1 plant within 24 h) than those placed on Coker 312 (0% of the neonates had moved at least 1 plant within 24 h). When larvae were placed on Event 531 plants, an estimated 82% of the larvae had moved to an adjacent plant by cumulative age of 10 d. Collectively, these data indicate that movement of larvae from plant to plant increases with larval age and occurs more rapidly for larvae placed on Event 531 cotton than on Coker 312. Previous studies have suggested that resistance to B. thuringiensis could develop more rapidly in insects exposed to seed mixtures of plants with and without endotoxin if larvae move between plants and if an external refuge exists. These data provide evidence of larval movement between plants in seed mixtures.

Animals↗
PubMed2000

Development of diagnostic concentrations for insecticide resistance monitoring in soybean looper (Lepidoptera: Noctuidae) larvae using an artificial diet overlay bioassay.

Diagnostic concentrations for several standard and experimental insecticides were determined for a laboratory reference strain of soybean looper, Pseudoplusia includens (Walker), using an insecticide diet overlay bioassay to evaluate the relative susceptibility of field (P) and F1 generations of four field-collected strains of third-, fourth-, and fifth-instar soybean loopers in 1996 and 1997. Diagnostic concentrations were defined as concentrations that killed 90-95% of the susceptible individuals and were 5 ppm for permethrin, 1,300 ppm for thiodicarb, 60 ppm for chlorfenapyr, 5 ppm for emamectin benzoate, and 60 ppm for spinosad. Field strains exhibited significantly greater percentage survival than the laboratory reference strain in the permethrin bioassays in 1996 and 1997 in both the P and F1 generation bioassays and in the thiodicarb bioassays in 1997. Larvae exposed to diagnostic concentrations of the experimental insecticides chlorfenapyr, emamectin benzoate, and spinosad usually did not exhibit significantly higher percentage survival than the reference strain.

Animals↗
PubMed2002

Antibiosis of the pith maize to Sesamia nonagrioides (Lepidoptera: Noctuidae).

Thirteen inbred lines of maize (Zea mays L.) with different levels of stem resistance to the stem borer Sesamia nonagrioides Lefevbre were evaluated in the field and the laboratory to determine the antibiotic resistance to this pest. Inbreds CM151, CO125, and EP39 had antibiotic pith as well as stem resistance, so the pith could play a role in stem resistance. Inbreds A509, F473, and PB130 did not have antibiotic pith but had stem resistance; therefore, other mechanisms could confer stem resistance. Finally, the inbred MS1334 had antibiotic pith and did not show stem resistance; thus, other factors could compensate the effect of the pith. Therefore, although pith antibiotic compound seems to play a role in the defense against S. nonagrioides attack, it is not the only possible mechanism of defense.

Animals↗