Broad Based Organic Control of Cranberry Fruit Worm

Note to readers, attached is the complete final report for FNE96-143

The cranberry fruitworm (Acrobasis vacinii Riley) is a serious and chronic pest on cranberry bogs. Mr. Macfarlane, who grows cranberries organically, used his SARE grant to explore various non-chemical means of controlling this insect. He tried 1) establishing habitats for creatures such as bats, toads, and salamanders, that prey upon A. vacinii, 2) catching these insects in moth traps, 3) releasing wasps that parasitize the eggs of A. vacinii, 4) applying Bacillus thuringiensis, 5) planting dill, cilantro, and garlic as natural repellents, 6) emplacing bug "zappers" baited with cranberry vine, and screened to exclude birds, and 7) covering sections of the bog with plastic, thereby raising temperatures to induce early emergence from the pupal stage. Sticky traps were placed under the plastic to catch the adults as they emerged.

Mr. Macfarlane's results are both surprising and instructive. The most effective treatment was the last, but not for the reason postulated. While emerging adults evaded the sticky traps and escaped easily through vents in the plastic, they did not readily return through these vents to lay their eggs. Mr. Macfarlane lost only 2% of the berries under the plastic to cranberry fruitworm, while outside the covering loss was on the order of 12%. His efforts at habitat establishment were successful in the case of frogs and toads, but he was not able to draw bats or salamanders. Of the insect-repellent plants he was able to establish only garlic, but crop loss remained high in this area anyway. The other treatments were either ineffective or, in the case of the bug zappers and moth traps, which caught only beneficial insects, actually detrimental.

• FNE96-143 Final Report