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Interactions between the cotton bollworm,Helicoverpa armigera(Hübner) (Lepidoptera: Noctuidae), its larval parasitoidMicroplitis mediator(Haliday) (Hymenoptera: Braconidae), and the Cry1Ac toxin ofBacillus thuringiensisBerliner were evaluated under laboratory conditions. The growth ofH. armigeralarvae was delayed and its pupal rate and pupal weight decreased when they were fed on a diet containing Cry1Ac toxin. Due to the lowered growth rate of the host larvae, the time available for parasitization ofH. armigerabyM. mediatorincreased when the host larvae were reared on a diet containing Cry1Ac toxin at concentrations of 0.5, 1, 2, and 4 µg g−1. The longevity of female and male parasitoids was not significantly affected when newly emerging wasps fed on honey solutions containing three different concentrations of Cry1Ac toxin (125, 250, and 500 µg ml−1). When female parasitoids were fed on honey solutions containing Cry1Ac, their offsprings’ egg and larval development period, pupal weight, length of pupation, adult weight, and adult longevity did not change significantly in most of the treatments compared with controls. When the female parasitoids parasitized host larvae that had been fed on a diet containing 0.5, 1, 2, 4, and 8 µg g−1 Cry1Ac toxin, their offsprings’ eggs and larvae were significantly delayed. Their pupal weight, adult weight, and adult longevity were also significantly less than controls. [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]

Diapause in Microplitis mediator Haliday (Hymenoptera: Braconidae) is manifested during the pupal stage and normally occurs during the winter season because of a photoperiodic response that is highly dependent on temperature. No diapause was observed at temperatures above 20°C regardless of the photoperiod. Only a small part of the population entered diapanse at 20°C under short daylengths of fight:dark 8:16-12:12. In contrast, when larvae were exposed to 16, 18, and 20°C combined with a photoperiod of 10:14, the percentages of parasitoids that entered pupal diapause was 97.9, 87.8, and 26.2%, respectively. Critical photoperiods were determined to be 7.03:16.97 and 12.21:11.79 at 16°C and 6.75:17.25 and 12.03:11.97 at 18°C. The second instar of the parasitoid was the most sensitive to diapause induction for the photoperiods and temperatures tested. [ABSTRACT FROM AUTHOR]

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]