Bees deliver fungicide more effectively than sprays, study finds

September 20, 2000

COLUMBUS, Ohio - Researchers from Ohio State and Cornell universities have found that bees can deliver a biological fungicide to strawberry blooms more effectively than can mechanical sprayers.

The study involved placing a tray filled with the fungicide - composed of an anti-fungal microorganism - in front of bee hives. The bees walk through this "foot bath" while exiting the hive and deposit the fungicide on strawberry flowers.

Using the procedure to dispense a natural fungicide that prevents gray mold - a common rotting disease in strawberries - researchers were able to reduce infected strawberries by 72 percent as compared to 40 percent when the same fungicide was sprayed on plants.

The bee-delivered natural fungicide was also as effective at preventing gray mold as a commercially available chemical fungicide that was sprayed on plants. "Since bees carry the fungicide specifically to the flowers, they are more effective than sprays," said

Joseph Kovach, associate professor of entomology at Ohio State's Ohio Agricultural Research and Development Center in Wooster, Ohio. "Sprays cover both leaves and flowers, though the target is only the flowers."

The study appeared in a recent issue of the journal Biological Control.

Kovach did the study while he was working at Cornell University. He and his Cornell colleagues tested the procedure on 12 strawberry fields in New York under the state's Integrated Pest Management (IPM) Program. The fungicide they used for preventing gray mold, which is caused by the fungus Botrytis cineria, was a commercially available strain of a microorganism called Trichoderma harzarium 1295-22.

The study was conducted from 1994 to 1997, using commercial bumblebee colonies and honeybee hives. Although flowers collected from the plants that received bee-delivered treatment had only half the density of the natural fungicide as compared to those that were sprayed, they showed better fungus control.

Strawberries from the plants that received the bee-delivered treatment averaged 22 percent more seeds and weighed between 26 and 40 percent more than berries that were given no treatment.

"Since strawberries are primarily wind- and gravity-pollinated, most growers don't add hives to their fields. However, previous studies have shown that adding hives does increase strawberry yield," said Kovach. "Our results show that adding hives could help growers increase yield and also achieve disease control."

Kovach said growers would prefer the bee-delivery technique to spraying, which is a labor-intensive process involving the mixing and measuring of pesticides and wearing personal protection clothing. "Let the bees do the work," Kovach said.

It was also significant that the bee-delivered natural fungicide was as effective as chemical sprays, because it allows farmers to use less chemicals in their fields, Kovach said. He feels the bee-delivery technique may help growers get into new markets that favor organic farming.

The experiments were conducted in two strawberry fields at the New York State Agricultural Experiment Station in Geneva, New York, and 10 other farm fields spread over eight counties in New York state.

As part of their experiments, the researchers looked at the effect of Trichoderma on individual honey bees and hive health. They found no adverse impact.

The bee-delivery technique needs approval from the Environmental Protection Agency (EPA) before it can be put on the label of commercially available Trichoderma.
The research was supported by grants from the New York State IPM Program, the United States Department of Agriculture and the National Biological Control Institute.

Contact: Jeff Grabmeier, Ohio State Research Communications (614) 292-8457,

Written by Yudhijit Bhattacharjee, a graduate student and Kiplinger Fellow in Journalism at Ohio State University.

Ohio State University

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