Botrytis cinerea is a fungus that infects strawberry flowers and later develops into Botrytis fruit rot on the mature fruit. Cornell University has patented a fungal biological control agent, Trichoderma harzianum strain 1295-22, that prevents infection by Botrytis on the flowers. This strain has been registered with the Environmental Protection Agency and various formulations are being manufactured by TGT Inc. of Geneva, NY. Strawberries are expected to be on their label in 1996.
Studies conducted at the New York State Agricultural Experiment Station in 1994 and 1995 showed that both honey bees and bumble bees can effectively deliver Trichoderma spores to strawberry flowers to prevent Botrytis fruit rot. In their experiments, about 20% of the untreated berries were infected with Botrytis, whereas only 5% of the fruit was infected when Trichoderma was disseminated to the flowers by honey bees (compared with 4-5% fruit rot for plots treated with one bloom spray of the standard fungicide Ronilan). Bumble bees were not quite as efficient as honey bees (about 7% diseased berries), but both significantly reduced fruit rot. Bee delivery was even better at reducing Botrytis infection than spraying a single bloom spray of Trichoderma directly on the plants, possibly because the bees concentrated more spores on the flowers.
Not only can bees assist with disease protection, they can increase yields. Even though strawberries are primarily gravity or wind pollinated, studies have shown that fruit weight can be increased 18-26% by adding hives to strawberry fields.
Although more research is needed on strawberries in other states and on other varieties, bees show considerable promise as effective disseminators of biological control agents.
- Joe Kovach, Cornell University, Geneva, NY
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