Effects of conventional and transgenicBacillus thuringiensisgalleriaetoxin onExorista larvarum(Diptera: Tachinidae), a parasitoid of forest defoliating Lepidoptera

Abstract

The Cry9Aa entomocidal toxin from Bacillus thuringiensis ssp. galleriae (Btg) and an epiphytic Pseudomonas sp. derivative carrying the cloned cry9Aa gene from Btg are active against the pine processionary moth Thaumetopoea pityocampa and the laboratory model species Galleria mellonella. A laboratory study was conducted to investigate the side effects of the Cry9Aa toxin and the engineered bacterium on the post-embryonic development of Exorista larvarum, a larval parasitoid of forest lepidopterous defoliators, cultured in the factitious host G. mellonella. In a first experiment, the purified toxin and the commercial Bt preparation Foray 48B induced a mortality of G. mellonella sixth-instar larvae significantly higher than that of the distilled water control. In parallel, the development of E. larvarum in this host was assessed, but no significant difference was found for any of the parasitoid parameters examined (i.e., eggs oviposited, percentage of puparia and adults and puparial weights). In subsequent experiments, cry9Aa-Pseudomonas suspension significantly increased the mortality of sixth instar G. mellonella larvae compared to untransformed Pseudomonas sp. suspension and distilled water. As to the parasitoid parameters, the cry9Aa-Pseudomonas did not significantly affect the number of oviposited eggs, percentage of puparia and puparial weights. It can be concluded that the postembryonic development of E. larvarum was not affected by host treatment with either Cry9Aa toxin or cry9Aa-Pseudomonas under the laboratory conditions tested. Although direct effects on parasitoid performance have not been shown, indirect effects could still occur and need to be considered in future studies concerning the effects of genetically modified Bt-derivatives.

Production of Dipteran Parasitoids

“…The availability of efficient rearing techniques for tachinids or other dipterans may also be helpful in studies concerning pesticide effects on nontarget species (Marchetti et al, 2009(Marchetti et al, , 2012. Aspects concerning dipteran parasitoid rearing are therefore important for biological control from different points of view, and all deserve to be exploited.…”

Low‐temperature storage of Exorista larvarum puparia as a tool for assisting parasitoid production

“…In the view of possible utilization of low‐temperature storage protocols for mass rearing of tachinid flies, our study on E. larvarum is motivated by the potential usefulness of this species against several insect pests. Moreover, E. larvarum is a non‐target species during insecticide spraying in agricultural ecosystems, therefore its production may prove useful for investigations on the side effects of chemical control on non‐target insects that are commonly present in the environment (Marchetti et al., ; Francati & Gualandi, ). On the basis of preliminary experiments, we focused on the use of 15 °C as a storing temperature, investigating the effects of storage for 28 days in a first experiment, and the effects of storage for 7, 14, or 21 days in a second experiment.…”

Insect-resistant biotech crops and their impacts on beneficial arthropods

“…Marchetti et al [57] Bt (Cry1Ab) Sisterson et al [92] Bt (Cry3Aa) potato (S. tuberosum) L. decemlineata several heteropteran predators and spiders no effect of predator densities in the field Reed et al [93] Bt (Cry3Aa) potato (S. tuberosum)…”