Bio-efficacy of the indigenous entomopathogenic fungus, Beauveria bassiana in conjunction with desiccant dust to control of coleopteran stored product pests.

The insecticidal activity and effects of sublethal combinations of the fungus, Beauveria bassiana-IRAN441C and commercial diatomaceous earth (DE) were assessed on adult coleopterans, Callosobruchus maculatus (F.) (Chrysomelidae), and Oryzaephilus surinamensis (L.) (Silvanidae). Dry conidia and DE were applied singly or in combination. The agents produced acceptable mortality, however, results were not affected by species of host plant seeds fed to the beetles. F1 progeny reduction was notably increased in both beetle species when mixtures of the fungus and DE were each at the LC50 level. In addition to avoidance behavior, different combinations of fungus/DE dosages induced winged morphs (non-reproductive phase) in the C. maculatus population after 50 d exposure. Our results demonstrated that a combination of B. bassiana and DE resulted in high mortality of both beetle species and co-application of B. bassiana and DE is feasible in a stored product pest management program.

Sub-lethal concentrations of the entomopathogenic fungus, Beauveria bassiana increase fitness costs of Helicoverpa armigera (Lepidoptera: Noctuidae) offspring.

We assessed the effects of exposure of the cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) larvae to the entomopathogenic fungus Beauveria bassiana (isolate DC2) on life history parameters of the subsequent generation. Mortality assays against second instar larvae showed B. bassiana isolates to be significantly virulent, causing high mortality. Life history parameters such as developmental time, fecundity and survivorship were affected in the offspring of survivors of exposure to LC25 and LC50 concentrations of B. bassiana DC2. Pre-adult duration of H. armigera was significantly extended and total longevity and female progeny fecundity were decreased. Oviposition duration was shortened compared to offspring of untreated controls. All population parameters including intrinsic (r) and finite (λ) rates of increase and net (R0) and gross (GRR) reproductive rates were significantly decreased in offspring derived from H. armigera larvae treated with B. bassiana DC2. The intrinsic rate of increase (r) was 0.198 d-1, 0.120 d-1 and 0.111 d-1, respectively, for the F1 generation of controls (untreated), LC25- and LC50-treated cotton bollworm. The morphogenetic effects of B. bassiana observed due to the indirect effect of sub-lethal concentrations included abnormal pupae and adults and mortality resulted from the malformations. Pupal weight was reduced in offspring of treated individuals but sex ratios did not differ. Our results revealed that B. bassiana increased fitness costs of H. armigera in both direct (mortality) and indirect (disruption of normal development) ways. Adverse effects of sub-lethal fungal treatments on the parent generation carried over to the next generation.

Exposure Route Affects the Toxicity Class of Thiamethoxam for the Predatory Bug, Orius albidipennis (Hemiptera: Anthocoridae) by Changing Its Fitness.

In many cases, pesticides' side effects on natural enemies have closely related to their exposure route. We assessed long-term lethal and sublethal effects of thiamethoxam (TMX) on the predatory bug, Orius albidipennis (Reuter), fed on Aphis gossypii Glover (Hemiptera: Aphididae), through three exposure routes. First-instar nymphs were treated with the maximum field recommended concentration (MFRC), ½ MFRC, and » MFRC of TMX for 24 h. Based on the results, the soil-application treatment (bottom-up effect: plant-aphid-predator) led to the lowest survival reduction. In contrast, leaf-dip (residual contact) and aphid-dip (oral exposure route) treatments decreased the survival severely. While the soil-application treatment had no significant effect on adult longevity and egg production, all tested concentrations of TMX in the leaf-dip and aphid-dip treatments negatively affected both traits. The egg hatchability was not affected by the insecticide in all exposure routes. Among all treatments, » MFRC of TMX in the residual contact and oral treatments shortened the egg incubation period compared to control, but others failed to affect it. Finally, based on the criteria provided by the International Organization for Biological and Integrated Control (IOBC) regarding toxicity classification, systemic (soil) application of TMX was harmless for this predator. However, it was moderately harmful and harmful (depending on concentration) to the predator through the residual contact and oral exposures, even at » MFRC. Given our results, the soil-application of TMX is compatible with O. albidipennis, and it can improve conservation approaches of the predator in the integrated management of A. gossypii.

Ontogeny and reproductive biology of Diadegma semiclausum (Hym.: Ichneumonidae), a larval endoparasitoid of Diamondback Moth, Plutella xylostella (Lep.: Plutellidae).

In this article, the ontogeny and reproductive biology of Diadegma semiclausum (Hym.: Ichneumonidae), an important parasitoid of Plutella xylostella (Lep.: Plutellidae) are described in detail. We did dissect parasitized P. xylostella larvae in phosphate-buffered saline and determine the external morphology of its parasitoid at all developmental stages. The developmental duration of its immature stages, adult longevity, total oviposition period and fecundity of the parasitoid are determined at 24 ± 1 °C, 65  ±  5% R.H., and a photoperiod of 16:8 h L:D. The mean duration of egg and larval stages is 9.56 days and the prepupa and pupa stages last for 8.27 days. In average, female longevity is 1.31 times longer than that of males, and females lay 300 eggs in total. The peak of D. semiclausum oviposition is on the eighth day after mating. The egg loading pattern of D. semiclausum was investigated to determine the parasitoid 'ovigeny index' throughout the female's parasitoid lifetime. Initial egg load in immature females (<2 h age) is 1.45 per female and the mean lifetime potential fecundity (total immature and mature oocytes), at four interval ages, is 34. With an ovigeny index value of 0.038, D. semiclausum is considered moderately to strongly synovigenic. In the absence of the host, after 3 days, the number of eggs is decreased in D. semiclausum. Our results demonstrated that there is a negative relation between the ovigeny index and egg resorption in this parasitoid.