Aspects of the laboratory production of mushroom phorid flies (Megaselia halterata) parasitised by the nematode Howardula husseyi

Abstract

parasitised by Howardula husseyi is essential if the release of parasitised Megaselia halterata on farms is to become a practicable alternative to insecticidal control of the pest. The effects on parasite incidence in the succeeding fly generation of two methods of spawning mushroom compost, and of three initial levels of parasitism (numbers of parasitised parental flies), were studied in the laboratory. In emerging flies percentage parasitism, and mean number of adult parasites per fly, were significantly affected by the original number of parasitised females. Estimates showed that for every 10 additional parasitised parental flies there was an increase of 0.166 adult parasites per fly in the next generation. 'Top spawning' resulted in a significantly higher percentage parasitism than 'through spawning'. Emerging female progeny were significantly more highly parasitised than males. Statistical models, used to assess the ability of H . husseyi infectives to parasitise M. halterata larvae in compost, indicated that even at very high host densities (20% of the potential parasites successfully invaded a phorid larva. The results suggest that unless an in vitro method of rearing H. husseyi can be developed the nematode will not be of practical use in phorid control.

Susceptibility of mushroom pests to the insect‐parasitic nematodes Steinernema feltiae and Heterorhabditis heliothidis

“…Fifty newly-emerged phorid flies (Megaselia halterata), collected from laboratory cultures, were released into each of four phorid rearing chambers (Richardson & Hesling, 1978). Each chamber contained 1 kg of compost freshly inoculated with Agaricus bisporus grain spawn (Darlington's strain 649) and the flies were allowed 1 wk to oviposit in it.…”

“…Each chamber contained 1 kg of compost freshly inoculated with Agaricus bisporus grain spawn (Darlington's strain 649) and the flies were allowed 1 wk to oviposit in it. The contents of all four chambers were then emptied and the 4 kg compost thoroughly mixed, and used to fill 36 beakers at a rate of 70 g compost/beaker (Richardson & Hesling, 1978). Aqueous suspensions of nematodes were added to the surface of the compost with a pipette.…”

“…Current dependence on insecticides for the control of adult flies, and improved hygiene for protection against cecid larvae, reflects the lack of manipulable natural enemies of Diptera associated with mushrooms. Howardula husseyi (Richardson, Hesling & Riding, 1977), a common nematode parasite of phorids, is unlikely to be exploited for biological control purposes (Richardson & Chanter, 1981). It is a highly specialised obligate parasite and has a unique anatomy (Riding, 1970).…”