Selectivity of insecticides to the egg parasitoid Trichogramma galloi Zucchi, 1988, (Hym., Trichogrammatidae)

Trichogramma galloi Zucchi is an efficient biological control agent against the sugarcane borer, Diatraea saccharalis (F.) in sugarcane fields in Brazil. This parasitoid is also a candidate to be used in pest management programmes in corn, as D. saccharalis has become a serious pest of this crop in some areas in Brazil. However, there is no data on the side-effects of chemicals on this species. The side-effects of promising chemicals to control the sugarcane borer in corn were tested by dipping eggs of the factitious host into the insecticidal solutions. Two different treatments were tested. First, dipping parasitized host eggs at different stages of immature development (egg-larva, prepupa and pupa), and second, by offering treated eggs to newly emerged females. The toxicity of the chemicals tested were dependent on the age of the parasitoid, affecting the immature survival. developmental time from egg to adult, parasitization capacity, adult longevity and the development of the filial generation. Spinosad. tebufenozide, triflumuron and lufenuron delayed adult eclosion of T. galloi when used to treat the host egg during the pupal stage. Spinosad was harmful when tested against any immature stage and adults of T. galloi. Lufenuron and triflumuron were harmful only when applied during the egg-larval development of the parasitoid. Although they did not affect the pa rasitization capacity, they caused almost 100% mortality of the immatures when used to treat eggs prior to parasitization. Tebufenozide was harmless to T. galloi causing a very slight immature mortality if used during the prepupal development.