Predatory and parasitic activity of Aphelinus asychis (Hymenoptera: Aphelinidae) following exposure to the entomopathogenic fungus Paecilomyces fumosoroseus (Deuteromycotina: Hyphomycetes) under different humidity regimes

Abstract

The effect of the hyphomycete Paecilomyces fumosoroseus (Wise) Brown & Smith on the predatory and parasitic activity of Aphelinus asychis Walker, a common parasitoid of the Russian wheat aphid, Diuraphis noxia (Mordvilko), was investigated under three different humidities. Three cohorts of 20 female A. asychis were treated with 5.2 x 10(4) spores/cm² (twice the LD95 for D. noxia). Each female was then individually maintained in a ventilated Petri dish in which were placed three barley leaves and 20 third-instar D. noxia. Cohorts of 20 treated females were each held at one of the following relative humidities along with an equal number of untreated control insects: 67-73%, 85-89%, and 94-98%. Every 24 hours over a period of one week, the surviving parasitoids were transferred into a new Petri dish provided with fresh leaves and 20 aphids. After each 24-hour period of exposure and for each parasitoid, dead aphids were counted and the leaves with live aphids were transferred to barley plants to permit the re-establishment of the aphids. Nine days after the transfer of aphids, the mummies were counted. The total number of aphids consumed and mummies originated from the treated parasitoids incubated at 94-98% RH was significantly lower than in the control group. There was a significant decline in predation and parasitism per treated female per day and a progressive reduction in the number of treated parasitoids surviving each day. The death of all treated parasitoids incubated for 7 days at 94-98% RH after treatment and the high level of mycosis in cadavers demonstrate the susceptibility of adult A. asychis to P. fumosoroseus at high relative humidity. However, the reduced suceptibility of parasitoids at lower humidities means that may still be possible to construct an integrated program of pest management using parasitoids and pathogens.

Seletividade de Beauveria bassiana e Metarhizium anisopliae a Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae)

“…Parasitóides também são suscetíveis aos fungos entomopatogênicos, como observado para adultos de Aphelinus asychis Walker, parasitóide do pulgão-russodo-trigo, suscetíveis ao fungo Paecilomyces fumosoroseus em condições de alta umidade relativa (Mesquita et al 1999). Observações semelhantes foram feitas por Tounou et al (2003) Dados originais apresentados, para análise estatística os dados foram transformados em x + 0,5.…”

“…Poucos estudos foram conduzidos para determinar o efeito de microrganismos entomopatogênicos sobre Trichogramma ou outros parasitóides (Mesquita et al 1999, De La Rosa et al 2000, Tounou et al 2003, Santos Jr et al 2006.…”

Is Isaria fumosorosea selective to Trichogramma pretiosum (Hymenoptera: Trichogrammatidae)?

“…However, the isolates of I. fumosorosea may not have resulted in the death of the females that came in contact with sprayed eggs as the fungus may have infected the body of T. pretiosum after death. Death due to infection with entomopathogenic fungi is reported for adults of the parasitoid, Aphelinus asychis Walker (Hymenoptera: Aphelinidae), treated with I. fumosorosea isolate ARSEF 4501 (Mesquita et al, 1999). Dalvi et al (2007) also do not report a statistical difference in the longevity of T. atopovirilia females that come in contact with L. lecanii and those in the control.…”

Entomopathogenic Fungi for Control of Bemisia tabaci Biotype B: Foreign Exploration, Research and Implementation

“…This suggests the existence of a high humidity boundary layer surrounding the nymphs. Research on the fungus with other insects has revealed a need for high humidity to promote germination and infection (Poprawski et al 1985;Mohamed and Varma 1992;Mesquita et al 1999). Conidia of P. fumosoroseus are rapidly killed by solar radiation, particularly UV-B Smits et al 1996Smits et al , 1997.…”