Pseudoplusia Includens Larvae Research Articles

Virulence and pathogenesis of the baculovirus Autographa californica M nucleopolyhedrovirus (AcMNPV) in Pseudoplusia includens larvae

Virulence and pathogenesis of the baculovirus Autographa californica M nucleopolyhedrosis virus were quantified in penultimate instar Pseudoplusia includens (soybean looper) larvae using a recombinant encoding the lacZ reporter gene (AcMNPV-hsp70/lacZ). Larvae inoculated orally with AcMNPV-hsp70/lacZ occlusion bodies (OB) or intrahemocoelically with budded virus (BV) were susceptible to fatal infection (LD50=40.8 OB; 13.8 BV plaque forming units). Pseudoplusia includens displayed increased developmental resistance as larvae were orally inoculated with OB at later times during the penultimate instar. The optical brightener M2R, an inhibitor of the apoptotic processes that drive developmental resistance, did not significantly affect the virulence of AcMNPV-hsp70/lacZ OB. To study pathogenesis, newly molted penultimate instar P. includens were orally inoculated with 60 OB and examined from 0.5 to 96h post inoculation (h.p.i). Infection in the midgut was first detected at 4h.p.i in 32% of the larvae and was apparent in cells of the tracheal system at 8h.p.i. LacZ-positive (LacZ+) hemocytes were first observed 2h later. At 18h.p.i, a low proportion of the hemocytes were LacZ+ (5.6%). However, flow cytometry analysis of cell surface expression of the viral protein GP64 showed that 84.5% of the hemocytes collected at 18h.p.i were infected with AcMNPV, suggesting that flow cytometry may be a more sensitive method for identifying AcMNPV-infected cells. Because P. includens display no physiological barriers to AcMNPV OB and is permissive to fatal infection, this species could be controlled in organic cropping systems using naturally occurring strains of AcMNPV.

Microplitis demolitor bracovirus genome segments vary in abundance and are individually packaged in virions

Polydnaviruses (PDVs) are distinguished by their unique association with parasitoid wasps and their segmented, double-stranded (ds) DNA genomes that are non-equimolar in abundance. Relatively little is actually known, however, about genome packaging or segment abundance of these viruses. Here, we conducted electron microscopy (EM) and real-time polymerase chain reaction (PCR) studies to characterize packaging and segment abundance of Microplitis demolitor bracovirus (MdBV). Like other PDVs, MdBV replicates in the ovaries of females where virions accumulate to form a suspension called calyx fluid. Wasps then inject a quantity of calyx fluid when ovipositing into hosts. The MdBV genome consists of 15 segments that range from 3.6 (segment A) to 34.3 kb (segment O). EM analysis indicated that MdBV virions contain a single nucleocapsid that encapsidates one circular DNA of variable size. We developed a semi-quantitative real-time PCR assay using SYBR Green I. This assay indicated that five (J, O, H, N and B) segments of the MdBV genome accounted for more than 60% of the viral DNAs in calyx fluid. Estimates of relative segment abundance using our real-time PCR assay were also very similar to DNA size distributions determined from micrographs. Analysis of parasitized Pseudoplusia includens larvae indicated that copy number of MdBV segments C, B and J varied between hosts but their relative abundance within a host was virtually identical to their abundance in calyx fluid. Among-tissue assays indicated that each viral segment was most abundant in hemocytes and least abundant in salivary glands. However, the relative abundance of each segment to one another was similar in all tissues. We also found no clear relationship between MdBV segment and transcript abundance in hemocytes and fat body.

Effect of Bt-cotton expressing Cry1A(c) on the survival and fecundity of two hymenopteran parasitoids (Braconidae, Encyrtidae) in the laboratory

Abstract We examined the effect of Bt-cotton (Event 531) plants expressing the Bacillus thuringiensis δ-endotoxin CryIA(c) on two hymenopteran endoparasitoids, Cotesia marginiventris and Copidosoma floridanum . In the laboratory, parasitized and unparasitized Pseudoplusia includens larvae were reared on foliage from a conventional soybean cultivar (Pioneer 97B61), a conventional cotton cultivar (DPL 5415), or a Bt-cotton cultivar (NuCotn 33B). C. marginiventris developed significantly faster within P. includens larvae feeding on Pioneer 97B61 and DPL 5415 compared to those feeding on NuCotn 33B. C. marginiventris that developed inside P. includens larvae feeding on NuCotn 33B suffered reduced longevity, and females had fewer ova. NuCotn 33B also affected the growth and development of P. includens parasitized with C. floridanum and life history parameters of adult C. floridanum . Parasitized and unparasitized P. includens developed more slowly when they were fed NuCotn 33B and the prepupae weighed less. Survival of parasitized and unparasitized P. includens was lower when larvae were fed NuCotn 33B and some evidence points to higher susceptibility of parasitized caterpillars to intoxication by NuCotn 33B. Fewer C. floridanum adults emerged from hosts fed NuCotn 33B, but pupal weight and adult longevity were unaffected. Analysis comparing the two experiments conducted with C. floridanum suggests that older NuCotn 33B plants (90–120 days after planting) may affect parasitoid development and adult survival less than younger NuCotn 33B plants (60–90 days after planting). Feeding on NuCotn 33B by P. includens affected the survival and development of the two hymenopteran endoparasitoids studied here, and the degree of the effect was similar to that observed with natural resistance found in soybean plants. It remains to be determined if the effects demonstrated here are less than, equal to, or greater than the impact of conventional insecticide applications used in conventional, non-transgenic, cotton.

Separation and behavior in vitro of hemocytes from the moth, Pseudoplusia includens.

Hemocytes collected from larvae of Pseudoplusia includens (Lepidoptera:Noctuidae) were separated by centrifugation on Percoll cushions. The procedure resulted in 95% purity of plasmatocytes and greater than 99% purity of granular and spherule cells. Medium supplemented with chicken serum enhanced cell viability and promoted spreading of plasmatocytes. Cell-free plasma and medium preconditioned by plasmatocytes or granular cells stabilized cells in vitro and also accelerated spreading of plasmatocytes relative to medium supplemented with chicken serum. Oenocytoids were the only morphotype that exhibited endogenous phenoloxidase activity, while granular cells and plasmatocytes were the only cells that endocytosed fluorescent beads in vitro. Granular cells and plasmatocytes ingested fluorescently labelled beads, both in mixed populations of hemocytes and after separation. Plasmatocytes were the only morphotype that encapsulated large foreign targets in vitro following separation. Separated granular cells attached and spread on the surface of foreign targets but never formed a multilayered capsule.

Persistence and expression of Microplitis demolitor polydnavirus in Pseudoplusia includens.

Persistence and expression of Microplitis demolitor polydnavirus (MdPDV) was examined in parasitized and virus-injected Pseudoplusia includens larvae. Viral DNA persisted in P. includens larvae for 6 days, but no increase in the amount of viral DNA present was detected. Viral transcripts were observed in parasitized and virus-injected larvae 4 h post-parasitism and expression continued for 6 days. When specific host tissues were examined, more viral DNA and RNA was detected in haemocytes than in the gut, nervous system and fat body. 32P-labelled MdPDV DNA hybridized to approximately six different size classes of mRNAs on Northern blots of RNA from haemocytes of parasitized larvae. MdPDV transcription was first detected in haemocytes at 4 h post-parasitism and continued for 6 days. Similar transcripts were observed in haemocytes from larvae that had been injected with calyx fluid or MdPDV plus venom. First-strand cDNA probes of haemocyte-specific MdPDV transcripts hybridized to only certain MdPDV viral DNAs, suggesting that only part of the MdPDV genome is expressed in this host cell type.

The growth and role of Microplitis demolitor teratocytes in parasitism of Pseudoplusia includens

The growth and function of Microplitis demolitor teratocytes in Pseudoplusia includens larvae was investigated. An average of 542 teratocytes was produced per M. demolitor egg. The number of teratocytes present per host declined during the course of parasitoid development, but the size of individual cells increased. The ploidy levels of teratocytes ranged from 2 to 8C at hatching, but had increased to 128–256C at the completion of parasitoid development. Injection of in vitro cultured teratocytes into fourth stadium P. includens larvae had an inconsistent effect on development. Most larvae pupated without delay when injected with a physiological dose of 600 teratocytes, but 54% of larvae failed to pupate when injected with a superphysiological dose of 2400 teratocytes. Examination of teratocytes indicated most cells were encapsulated by P. includens haemocytes within 24 h of injection. However, prior injection of larvae with M. demolitor calyx fluid or polydnavirus plus venom suppressed the encapsulation response. Further, 87% of larvae injected with polydnavirus plus venom and 600 teratocytes exhibited alterations in growth that were very similar to parasitism by M. demolitor.

Reductions in Consumption., Utilization, and Growth Rate of Soybean Looper (Lepidoptera: Noctuidae) Larvae Fed Foliage of Soybean Genotype PI 227687

Larvae of Pseudoplusia includens (Walker) reared on the resistant plant introduction (PI) 227687 exhibited reduced growth and high mortality relative to those reared on the susceptible cultivar ‘Davis.’ These effects were most pronounced in the last instar and resulted from an acute action on this instar. The plant genotype consumed during instars one through four had no effect on the maximum larval weight attained, pupal weight, or total mortality during larval development, but did affect the duration of larval development. Measurement of food consumption and utilization by larvae of P. includens fed on PI 227687 or ‘Davis’ foliage indicated that reduced growth on PI 227687 was primarily due to feeding deterrence or the lack of feeding stimulation. A lower efficiency of conversion of digested food to body tissue, not attributable to reduced consumption, also contributed to reduced P. includens growth rate on PI 227687.

Influence of Resistant Soybeans on the Susceptibility of Lepidopterous Pests to Insecticides1

In the laboratory, Heliothis zea (Boddie) larvae that were fed foliage of ED73–371, a genotype resistant to the Mexican bean beetle, Epilachna varivestis Mulsant, weighed less and were more susceptible to methomyl and Bacillus thuringiensis Berliner compared to larvae fed foliage of the ‘Bragg’ variety. No difference was detected in the LD50, of methyl parathion when H. zea larvae were reared on Bragg and ED73–371. Larvae of Pseudoplusia includens (Walker) weighed less and were significantly more susceptible to methyl parathion when fed ED73–371 foliage than when fed Bragg foliage, whereas LD60’s of methomyl and B. thuringiensis were similar on the 2 genotypes. Percent control of field populations of H. zea was greater in ED73–371 than in Bragg soybeans when plots of each genotype were treated with similar rates of methyl parathion or B. thuringiensis . Fewer larvae were found in untreated plots of ED73–371 than in Bragg, indicating a lower natural population in the resistant soybeans.

Imprisonment of Entomophages to Increase Effectiveness: Evaluation of a Concept

In laboratory experiments, de-winged Campoletis flavicincta (Ashmead) placed on soybean plants parasitized 14× more larvae of Pseudoplusia includens (Walker) than their winged counterparts. Likewise, de-winged female Podisus maculiventris (Say), a larval predator of Trichoplusia ni (Hubner) laid ca. 5× more eggs on potted soybeans than their counterparts, and predation eggs of Heliothis zea (Boddie) on potted soybeans by de-winged Hippodamia convergens Guerin-Meneville was ca. 22× greater than that of winged adults. Moreover, more de-winged than winged entomophages (better than 3-fold more) were still on the plants 24 h after release Similar results were obtained in field experiments; ca. 85% of de-winged adult P. maculiventris were still on field soybeans 72 h after the release vs. only 12% of winged adults, and ca, 9× more eggs were counted in plots infested with the de-winged females. Also, less than 1% of winged H. convergens adults, but ca. 50% of de-winged adults, were found on field soybeans one day after the release. Egg predation, within 24 h, by de-winged H. convergens was ca. 3× that of winged adults.

Biological Studies of a Predator Sycanus indagator: I. Life History and Feeding Habits

Sycanus indagator Stal eggs held at 72-78@*F hatched 18 days after being laid and nymphal development averaged 82 days. Starvation of newly hatched nymphs for 8 days and adults for 21 days resulted in death or no egg production. Nymphs fed on several insect species, but cannibalism was uncommon. Larvae of Pseudoplusia includens (Walker) were quickly paralyzed after beak penetration by the nymphal or adult predator.