PARASITISM OF CRANBERRY FRUITWORM (ACROBASIS-VACCINII, LEPIDOPTERA, PYRALIDAE) BY ENDEMIC OR RELEASED TRICHOGRAMMA-PRETIOSUM (HYMENOPTERA, TRICHOGRAMMATIDAE)

Two levels of commercially-reared Trichogramma pretiosum were released during the oviposition period of the cranberry fruitworm (Acrobasis v accinii) in eight Massachusetts (U.S.A.) cranberry bog sites. Release levels of 4.8 X 10(5) T. pretiosum per ha or 1.9 X 10(6) T. pretiosum per ha were made at 3-5 day intervals, with a total of nine releases. Parasitism was estimated by collecting cranberry fruits and examining them for the presence eggs T. pretiosum. Eggs were classified as unhat ched, hatched, parasitized or emergent gent parasite. Collections of c ranberries from four 'neglected' bog sites (not currently under cultiv ation) were examined and classified similarly, but T. pretiosum were n ot released, to determine the level of parasitism from endemic populat ions. Cumulative parasitism from the neglected sites was consistently higher than levels recorded from the release sites throughout the seas on. Parasitism in the neglected sites was determined to be from natura l populations of T. pretiosum. Comparisons of cranberries damaged by A . vaccinii showed that damage was greatest in the neglected sites, but was not significantly different from fruit damage within either the l ow release or high release level. Collections of cranberries were also made within bog sites managed under current Massachusetts Cooperative Extension IPM guidelines. Damage to cranberries was lowest in the IPM -managed sites; although this value was less than the other bog sites, it did not differ significantly.