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Microplitis mediator (Hymenoptera: Braconidae) and Helicoverpa armigera nucleopolyhedrovirus (HearNPV) have been broadly used in field for management of cotton bollworm H. armigera (Lepidoptera: Noctuidae) and they both might share resource in the host larvae when simultaneously applied in the fields. This study explored the interactions between M. mediator and HearNPV in H. armigera through bioassay analysis. The mortality of H. armigera caused by HearNPV inoculation on 2 nd instars showed linear relationship with the concentration of the inoculated HearNPV, but the mortality due to HearNPV infection was reduced when HearNPV was inoculated on the third and fourth day post-parasitism by M. mediator . The mortality due to parasitism separately decreased with the increasing of the parasitism host instar. The performance of M. mediator , including survival rate, development duration and the cocoon weight declined with the reduction of interval between the parasitism and HearNPV inoculation. The analysis of co-toxicity factor demonstrated the antagonistic effect between M. mediator and HearNPV on H. armigera larvae when HearNPV was orally inoculated at 4 d post parasitism, however, additive effects were revealed when the intervals between virus infection and parasitism were 1, 2 or 3 days. These results indicated that the application of the HearNPV was unfriendly to the releasing of parasitoid M. mediator and the existence of M. mediator might weaken the virulence of baculovirus. The both HearNPV and M. mediator for management of H. armigera should not be used coincidently. [ABSTRACT FROM AUTHOR]

The ecological implications on biological control of insecticidal transgenic plants, which produce crystal (Cry) proteins derived from the soil bacterium Bacillus thuringiensis (Bt), remains a contentious issue and affects risk assessment decisions. In this study, we used a unique system of resistant insects, Bt plants and a predator to critically evaluate this issue. The effects of broccoli type (normal or expressing Cry1Ac protein) and insect genotype (susceptible or Cry1Ac-resistant) of Plutella xylostella L. (Lepidoptera: Plutellidae) were examined for their effects on the life history of the predator, Coleomegilla maculata DeGeer (Coleoptera: Coccinellidae) over two generations. Additional behavioral studies were conducted on prey choice. C. maculata could not discriminate between Bt-resistant and susceptible genotypes of P. xylostella , nor between Bt and normal broccoli plants with resistant genotypes of P. xylostella feeding on them. The larval and pupal period, adult weight and fecundity of each female were not significantly different when C. maculata larvae fed on different genotypes (Bt-resistant or susceptible) of insect prey larvae reared on Bt or non-Bt broccoli plants. The life-history parameters of the subsequent generation of C. maculata fed on Bt broccoli-reared resistant P. xylostella were also not significantly different from those on non-Bt broccoli. These results indicated that Cry1Ac did not harm the life history or prey acceptance of an important predator after two generations of exposure. Plants expressing Cry1Ac are unlikely to affect this important predator in the field. [ABSTRACT FROM AUTHOR]

Highlights: [•] The first four of five larval instars of M. separata were parasitized by M. tuberculifer. [•] Second instar hosts were preferred in choice tests and yielded the highest relative suitability index. [•] Regardless of host instar at parasitism, host mass was significantly diminished within 24h of parasitism and ended <10% that of controls. [•] Total plant biomass consumption by host larvae ranged from <10% of controls (first instar parasitized) to ca. 30% (fourth instar parasitized). [Copyright &y& Elsevier]

Highlights: [•] Fructose, glucose and sucrose stimulated feeding by Microplitis mediator. [•] Raffinose, galactose and mannose did not stimulate feeding any more than water. [•] Mated females showed a stronger learning response with glucose than did virgins. [•] Fully fed and starved females preferred host odor and food odor, respectively. [•] Oviposition experience enhanced the response of partially fed females to host odor. [ABSTRACT FROM AUTHOR]

Abstract: Parasitoid adults can directly feed on floral nectar and honeydew containing monosaccharides and disaccharides. Oligosaccharides such as maltose, melezitose and raffinose are also found in honeydew but are rare in floral nectar. The effects of six different sugar resources on the longevity, fecundity and nutrient reserves of Microplitis mediator, a larval endoparasitoid in the cotton bollworm Helicoverpa armigera (Hübner) were determined in our laboratory. The results showed that both food and sex affected longevity of this wasp. Females and males of M. mediator fed with 1M sucrose solution survived longer than controls fed with water (5.7- and 3.7-fold longer, respectively). When provided with sucrose, glucose or fructose solutions, the parasitoid generated 3.6- to 3.7-fold more offspring than controls, and 60–75% of these progenies were produced during the first 5days. When separately given fructose, sucrose or glucose, this wasp accumulated fructose and total sugar at the highest level, which means a high sugar levels might lead to prolonging longevity and more offspring in M. mediator. In addition, compared with organisms fed galactose or raffinose, M. mediator fed sucrose or fructose accumulated high glycogen levels. Furthermore, in M. mediator, the lipid content declined with the advancing age. Females showed the slowest lipid metabolic rates when fed with sucrose, glucose, fructose, mannose and galactose solutions versus when fed with raffinose and control. In addition, only sucrose had a significant effect on lipid levels in males nearing the end of life. [Copyright &y& Elsevier]

Abstract: Microplitis mediator (Haliday) is a solitary endoparasitoid of larvae of the cotton bollworm, Helicoverpa armigera (Hübner) and the oriental armyworm, Mythimna = Leucania separata (Walker). The preference and suitability of different instars of M. separata for M. mediator were determined under laboratory conditions at a constant temperature of 26±1°C, 65±5% RH and L14:D10 photoperiod. The selection coefficient revealed that M. mediator parasitized 1st to 4th instars, but preferred 2nd and 3rd instars. Seventy-one percent of parasitism was achieved within 24h when the 2nd instars were used as hosts at a density of one parasitoid per 20 Larvae. Parasitoid egression and pupation were dependent on the host instar parasitized and occurred from the 1st through the 4th instar. The mean developmental time from egg to prepupae of M. mediator within 1st to 4th instars of the host was 8.27, 8.30, 8.30 and 9.20 days, respectively. Cocoon weights were lower when 1st and 2nd instars served as hosts rather than 3rd and 4th instars. The percentage of host larva that died before parasitoid egression declined as the age of the host increased, ranging from 26% to 2% for 1st–5th instars, respectively. The results of this study suggest that 2nd and 3rd instars of M. separata would be the best host stages for mass production of M. mediator in the laboratory and the best host instars to target for effective control in field releases. [Copyright &y& Elsevier]