EFFECTS OF TEMPORARY HOST DEPRIVATION ON THE REPRODUCTIVE POTENTIAL OF TRICHOGRAMMA-BRASSICAE

The effect of host deprivation on the reproductive potential and paras itization behaviour of Trichogramma brassicae Bezdenko (Hymenoptera: T richogrammatidae) was investigated. Upon emergence, females were depri ved of hosts for one to four days, and were subsequently provided with an unlimited number of hosts. Regardless of its duration, deprivation did not affect female longevity, overall rate of progeny emergence, o r progeny sex-ratio. As deprivation time increased, however, the total number of parasitized hosts decreased from an average of 81.2 when ho sts were provided at emergence, to an average of 34.0 when the waiting time was 4 days. This reduction was mainly due to the reduction in th e parasitizations following the first laying peak, which was not affec ted when deprivation lasted fewer than 4 days. Trichogramma females ar e able to store ripe eggs (about 35) for 3 days without damage, but re sorption occurs after four days of deprivation. Our results suggest th at imaginal vitellogenesis occurs in this proovigenic wasp but that it is affected by host deprivation. The behaviour of females, as measure d by the average distance between all parasitized hosts, was also modi fied by host deprivation. When deprivation exceeded one day, parasitiz ations were more scattered over the host patch. Moreover, increased de privation times also appeared to delay the initiation of parasitizatio n by a few hours. Host shortage is likely to occur in nature, reducing the efficiency of Trichogramma as a biocontrol agent. The individual history of females must be taken into account in any study of the repr oductive strategies of parasitoid females.