Urban Pest News

Parasitic Wasps For Control of Cockroaches

Small and inconspicuous, tiny parasitic wasps have potential as biological control agents of cockroaches, although none are commercially available yet. Eighteen species have been investigated as possible candidates, but only two are particularly promising for cockroach control in indoor urban settings. The wasps alone will not provide satisfactory control; they will have to be used in conjuntion with baits, traps, and other cultural controls. At this time neither wasp is available commercially, although mass rearing techniques have been developed.

The encrytid wasp Comperia merceti is very host specific for egg cases of the brownbanded cockroach, a common species in homes, laboratories and animal-rearing rooms. Five to 25 individuals develop in each parasitized cockroach egg case and emerge through a hole drilled in the egg case. This wasp is used successfully as part of an integrated managment program for the brownbanded cockroach at University of California Berkeley. Innundative releases (along with trapping, exclusion and santitation) can provide excellent control. Unfortunately, this wasp does not attack other types of cockroaches.

The eulophid wasp Aprostocetus hagenowii has a broader host range than C. merceti, although it prefers egg cases of the American cockroach and related cockroaches. Adults of this wasp also feed on egg cases in addition to parasitizing them. Up to 260 individuals may emerge from an egg case. Over 90% parasitism can be achieved (based on experimental releases in test kitchens), and parasitism is not adversely affected by baits that can further reduce the cockroach population. Residues of chemical sprays will kill the wasps, but boric acid doesn't affect the adult wasps.

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