Susceptibility of North Carolina Chloridea (Heliothis) virescens (Lepidoptera: Noctuidae) Populations From Flue Cured Tobacco to Chlorantraniliprole

The tobacco budworm, Chloridea (Heliothis) virescens (F.), has evolved resistance to numerous insecticides in the field. In tobacco, chlorantraniliprole can be applied as either a preventative systemic soil application at or near transplant, or a foliar application timed to current treatment thresholds. With a novel mode of action chlorantraniliprole provides an option for rotation with other insecticides to reduce the probability of insecticide resistance development. However, specific usage patterns in tobacco have the potential to increase the risk of resistance development to this insecticide. In particular, soil applied treatments may expose C. virescens to sublethal concentrations of the insecticide. We studied chlorantraniliprole susceptibility in nine field populations and one laboratory strain of C. virescens using a diet incorporation bioassay. Mortality was measured at 7, 10, and 14 d after exposure. Our results demonstrated that bioassays should be evaluated at 14 d after exposure to optimize interpretation of the dose–response due to the antifeeding properties of chlorantraniliprole. We observed low variation within field-collected populations. Field populations were as susceptible as the laboratory strain; the resistance ratio at the 14-d evaluation for field-collected populations ranged from 1.01 to 1.05. A discriminating dose of 0.117, 0.080, and 0.070 μg a.i./g diet could be used at 7, 10, and 14 d, respectively. Larval growth varied between field populations. Two field populations continued growing on diet containing chlorantraniliprole and differed in size from the laboratory and other populations. Further evaluation of growth inhibition will be necessary.

Role of Ovarian Proteins Secreted by Toxoneuron nigriceps (Viereck) (Hymenoptera, Braconidae) in the Early Suppression of Host Immune Response

Toxoneuron nigriceps (Viereck) (Hymenoptera, Braconidae) is an endophagous parasitoid of the larval stages of the tobacco budworm, Heliothis virescens (Fabricius) (Lepidoptera, Noctuidae). During oviposition, T. nigriceps injects into the host body, along with the egg, the venom, the calyx fluid, which contains a Polydnavirus (T. nigriceps BracoVirus: TnBV), and the Ovarian Proteins (OPs). Although viral gene expression in the host reaches detectable levels after a few hours, a precocious disruption of the host metabolism and immune system is observed right after parasitization. This alteration appears to be induced by female secretions including TnBV venom and OPs. OPs, originating from the ovarian calyx cells, are involved in the induction of precocious symptoms in the host immune system alteration. It is known that OPs in braconid and ichneumonid wasps can interfere with the cellular immune response before Polydnavirus infects and expresses its genes in the host tissues. Here we show that T. nigriceps OPs induce several alterations on host haemocytes that trigger cell death. The OP injection induces an extensive oxidative stress and a disorganization of actin cytoskeleton and these alterations can explain the high-level of haemocyte mortality, the loss of haemocyte functionality, and so the reduction in encapsulation ability by the host.

Comparison of in Vitro and in Planta Toxicity of Vip3A for Lepidopteran Herbivores

Agricultural pest infestation is as old as domestication of food crops and contributes a major share to the cost of crop production. In a transgenic pest control approach, plant production of Vip3A, an insecticidal protein from Bacillus thuringiensis, is effective against lepidopteran pests. A synthetic Vip3A gene was evaluated for efficacy against Spodoptera litura Fabricius (Lepidoptera: Noctuidae; cotton leafworm), Spodoptera exigua Hübner (Lepidoptera: Noctuidae; beet armyworm), Spodoptera frugiperda Smith (Lepidoptera: Noctuidae; fall armyworm), Helicoverpa armigera Hübner (Lepidoptera: Noctuidae; cotton bollworm), Helicoverpa zea Boddie (Lepidoptera: Noctuidae; corn earworm), Heliothis virescens Fabricius (Lepidoptera: Noctuidae; tobacco budworm), and Manduca sexta L. (Lepidoptera: Sphingidae; tobacco hornworm) in tobacco. In artificial diet assays, the concentration required to achieve 50% mortality was highest for H. zea followed by H. virescens > S. exigua > H. armigera > M. sexta > S. frugiperda > S. litura. By contrast, in bioassays with detached leaves from Vip3A transgenic tobacco, the time until 50% lethality was M. sexta > H. virescens > S. litura > H. zea > H. armigera > S. exigua. There was no significant correlation between the artificial diet and transgenic plant bioassay results. Notably, the two insect species that are best-adapted for growth on tobacco, M. sexta and H. virescens, showed the greatest time to 50% mortality on Vip3A-transgenic tobacco. Together, our results suggest that artificial diet assays may be a poor predictor of Vip3A efficacy in transgenic plants, lepidopteran species vary in their sensitivity to Vip3A in diet-dependent manner, and host plant adaptation of the targeted herbivores should be considered when designing transgenic plants for pest control.

Elucidating Efficacy of Ingested Positively Charged Zein Nanoparticles Against Noctuidae

A meridic diet overlay bioassay using empty, positively charged zein nanoparticles ((+)ZNP) was performed on soybean looper (Chrysodeixis includens (Walker)), tobacco budworm (Heliothis virescens (F.)), and velvetbean caterpillar (Anticarsia gemmatalis Hübner) (Lepidoptera: Noctuidae). Assessment of effects on mortality and development weights 7 d after ingestion of (+)ZNP were evaluated on larvae of each species. Treatments involved different concentrations, with H. virescens and A. gemmatalis offered 0 and 3,800 ppm (+)ZNP, whereas C. includens colonies were offered 0, 630, 1,260, and 2,520 ppm (+)ZNP. Mortality of A. gemmatalis and C. includens increased after ingestion of the highest (+)ZNP concentrations, while H. virescens neonate mortality was unaffected. Neonate and third-instar weights of A. gemmatalis and C. includens, and neonate H. virescens, decreased with high (+)ZNP concentrations. Following mortality results from A. gemmatalis neonates, a concentration response test was performed using a range of (+)ZNP concentrations. The LC50 for A. gemmatalis was 1,478 ppm. The potential of (+)ZNP as a pest management tactic is discussed.

POTENSI BEBERAPA JENIS TUMBUHAN LIAR SEBAGAI SUMBER INFESTASI HeUcoverpa armigera Hbn. PADA TANAMAN TEMBAKAU DELI

<p>Penelitian ketahanan hidup serangga hama pcmakan daun tembakau deli HeUcoverpa armigera (Ix'pidoplera: Noetuidac) dilakukan di pertanaman tembakau deli, Medan selama tahun 1999. Penelitian meliputi dua kegiatan. yailu kegiatan lapang dan laboratorium. Kegiatan lapang terdiri atas identifikasi dan padal populasi tumbuhan liar selama tidak ada petanaman tembakau deli (Agustusl)cscmbcr), seta pada padat populasi // armigera pada tumbuhan tersebul Penelitian laboratorium meliputi ketahanan hidup dan kcragaan reproduksi // armigera pada tumbuhan inang Selama tidak ada petanaman lembakau cerutu deli, serangga hama pcmakan daun ini bertahan hidup sedikitnya pada 10 spesies tumbuhan liar yang terdapat di sekitar lahan petanaman lembakau deli Pada umumnya, ketahanan hidup pada tumbuhan liar tersebut lebih rendah (30-70%) dibandingkan kalau hidup pada tanaman lembakau Walaupun larva //. armigera dapat menggunakan Ageratum conyzoides, Amaranthus spinosus. Mimosa pigra, dan M, pudica sebagai tanaman inangnya. tetapi serangga ini tidak dapal mencapai dewasa Pada tanaman Phylunthus amarus dan Euphorbia hirta. keperidian (masa reproduksi. fckunditas dan lertililas lelur yang dihasilkan) //. armigera lebih baik (masing-masing 1 190 dan 1 1 59 butir) danpada individu yang hidup pada tanaman tembakau (949 butir). tetapi fctililas telur yang dihasilkan lidak berbeda (masing-masing 84%) Pemanfaatan tumbuhan liar, terutama /.'. hirta, oleh //. armigera selama tidak ada petanaman tembakau deli berpotensi sebagai sumber infestasi hama ini pada tanaman tembakau deli pada musim tanam bcrikutnya.</p><p>Kata kunci: Tembakau deli, HeUcoverpa armigera, ketahanan hidup, tumbuhan liar</p><p> </p><p><strong>ABSTRACT </strong></p><p><strong>Potency of wild plants as infestation sources of Hclicoverpa armigera on deli tobacco plants </strong></p><p>Research on the survival of tobacco budworm HeUcoverpa armigera (l-epidoptcra: Noetuidac) was conducted in deli tobacco field, Medan, in 1999 The research consisted of ield and laboratory activities. Field activity was conducted by observing wild plants used by //. armigera for surviving during off-season of deli tobacco This activity included identiication of the plants, population density in the area and larval population on the plants Laboratory activity included the effects of the wild plants on the budworm survival and reproduction performance During off-season of deli tobacco. //. armigera survives on, al least, 10 species of wild plants surrounding the tobacco ield In general, the survival of //. armigera on the wild plants was lower (30-70%) than that on tobacco Although larvae of //. armigera used A. conyzoides, A. spinosus. M. pigra, and M. pudica as their host plants, the insect failed to reach adult stage. The use of P. amarus and E. hirta by //. armigera as host plants resulted in a higher fecundity (1 190 and 1 159 eggs, respectively) than those of tobacco (949 eggs), however the fetility of the eggs was not different (84%). The use of wild plants by //. armigera, especially E. hirta during off-season of deli tobacco could be a potential infestation source of the pest on tobacco ield in the next season.</p><p>Key words: Deli tobacco, HeUcoverpa armigera, survival rate, wild plants</p>

Identification of the Differences in Olfactory System Between Male and Female Oriental Tobacco Budworm Helicoverpa assulta

Background: The olfactory system of insects facilitates their search for host and mates, hence it plays an essential role for insect survival and reproduction. Insects recognize odor substances through olfactory neurons and olfactory genes. Previous studies showed that there are significant sex-specific differences in how insects identify odorant substances, especially sex pheromones. However, whether the sex-specific recognition of odorant substances is caused by differences in the expression of olfaction-related genes between males and females remains unclear. Results: In order to clarify this problem, the whole transcriptome sequence of the adult Helicoverpa assulta, an important agricultural pest of tobacco and other Solanaceae plants, was obtained using PacBio sequencing. RNA-seq analysis showed that there were 27 odorant binding proteins (OBPs), 24 chemosensory proteins (CSPs), 4 pheromone-binding proteins (PBPs), 68 odorant receptors (OR) and 2 sensory neuron membrane proteins (SNMPs) genes that were expressed in the antennae of male and female H. assulta. Females had significantly higher expression of GOBP1-like, OBP, OBP3, PBP3 and SNMP1 than males, while males had significantly higher expression of GOBP1, OBP7, OBP13, PBP2 and SNMP2. Conclusions: Our findings improve our understanding of olfactory genes in H. assulta, and can be used to further study pheromone identification, mate search, and sex differences in an insect’s ability to search for hosts. These results improve our understanding of mate search and host differentiation in H. assulta.

Response of Bt and Non-Bt Cottons to High Infestations of Bollworm (Helicoverpa zea Boddie) and Tobacco Budworm (Heliothis virescens (F.)) under Sprayed and Unsprayed Conditions

Early-maturing and full-season Bt and non-Bt cottons were exposed to high densities of tobacco budworm (Heliothis virescens (F.)) and bollworm (Helicoverpa zea Boddie) in 0.04 ha field cages during the summers of 2011 and 2012 to measure the possible need for supplemental use of insecticides on Bt cotton. Fruit survival within-season and at-harvest was carefully mapped on individual plants within comparative plots of all cottons untreated and sprayed with lambda-cyhalothin (0.0448 kg a.i./ha) or chlorantraniliprole (0.1009 kg a.i./ha) following insect infestations. Differences in lint yields among cotton maturity groups were not always detected, but early-maturing Bt cottons were among the higher yielding experimental plots for both years. Depending on the insecticide treatment, average harvested fruit ranged from 0.3 to 7.1 open bolls per plant for non-Bt cotton plots, while Bt cotton plots ranged from 1.8 to 7.5 open bolls per plant during the two-year study. Bt cottons generally protected fruit from insect damage and resulted in final yields comparable to those of insecticide sprayed Bt and non-Bt cottons. Unsprayed non-Bt cottons were significantly damaged by insects in these high-infestation environments.