Pattern of egg management by Trichogramma cacoeciae and T-dendrolimi (Hymenoptera : Trichogrammatidae)

The effect of temporary host deprivation on parasitization rates of Trichog ramma cacoeciae Marchal and T. dendrolimi Matsumura a was investigated The study was conducted with females that we allowed to engage in 3 days of ovi position after various periods of host deprivation. It seems that the produ ction and management of eggs by the two species is completely different. Du ring the first day of oviposition, parasitization by T. cacoeciae was almos t unaffected after 1 to 5 days of host deprivation. As deprivation time inc reased, however the number of parasitized hosts decreased from an average o f 28.6 +/- 2.0 hosts provided at emergence to an average of 12.5 +/- 2.3 ho sts when the waiting time was 10 days. The number of hosts parasitized on t he first day of parasitization by T. dendrolimi were not affected whatever the waiting test period. During the second ol third days of oviposition, th e lack of suitable hosts for T cacoeciae did not depress egg-laying potenti ality, whereas a strong I eduction in parasitization rates by T. dendrolimi occurred in the next 2 days of oviposition whatever was the waiting period This leads to ca. 50% reduction in total activity of 3 days of oviposition . Only in T. cacoeciae was it possible to distinguish between ageing and ho st deprivation. The data suggest that T. dendrolimi is a typical proovigeni c species, while T. cacoeciae is neither definitely proovigenic nor synovig enic. A slight decrease in rate of emergence of offspring of T. cacoeciae f emales that had waited 8 to 10 days for their hosts was observed As far as biological control is concerned, the efficiency of T. dendrolimi females ma y be more sensitive to host deprivation than T. cacoeciae.