DISPERSAL OF TRICHOGRAMMA-PLATNERI NAGARKATTI (HYM., TRICHOGRAMMATIDAE) FROM POINT-SOURCE RELEASES IN AN APPLE ORCHARD IN CALIFORNIA

Egg parasitoids of the genus Trichogramma are commonly released in inu ndative biological control programmes for lepidopteran pests in a rang e of cropping systems. In this study we evaluated the dispersal of Tri chogramma platneri from a central release point in an apple orchard in relation to time and the number of parasitoids released. Dispersal wa s monitored by parasitism of codling moth eggs from an insectary cultu re-used as sentinel eggs. Higher release rates of T. platneri resulted in greater parasitism of sentinel eggs during the first 3 days, incre asing from about 18% for a release rate of 5 400 to about 36% for a re lease rate of 32 400. T. platneri parasitized a greater percentage of sentinel eggs on the north side of the tree. Parasitism of sentinel eg gs declined by 50% during the second 3 day period following release fr om a point source release in comparison to the first 3 day period. Par asitism of sentinel eggs declined from a mean of 62% at the point-sour ce to less than 10% 14 m away during the first 3 days after release.