Use of honey bees and bumble bees to disseminate Trichoderma harzianum 1295-22 to strawberries for Botrytis control

The effectiveness of using honey bees and bumble bees to vector a commercia l formulation of Trichoderma harzianum 1295-22 for the control of Botrytis cinerea on strawberries was evaluated from 1994 to 1997 in 2 strawberry fie lds at the New York State Agricultural Experiment Station in Geneva, New Yo rk and in 10 grower fields in eight counties of New York. Commercial bumble bee colonies mere used to deliver the biocontrol agent in 1994 and 1995 an d five-frame nuclear honey bee hives mere used in 1995-1997. Each honey bee exiting the hive carried about 1 x 10(5) colony-forming units of T, harzia num, with the majority found on the bees' legs (58%). Flowers collected fro m the bee-delivered treatment generally had half the density of T. harzianu m as those from the sprayed treatment. However, during the 4 years of this study, T. harzianum delivered by bumble bees or honey bees provided better Botrytis control than that applied as a spray. In addition, the bee-deliver ed T. harzianum provided the same or a better level of control of Botlytis as commercial funscides applied at bloom. Strawberries collected from the b ee-visited treatments averaged 22% more seeds and weighed between 26 and 40 % more than berries in nonvisited treatments. The number of seeds per berry and berry weight were reduced by 7-12% in plots treated with funscides and visited by bees, indicating that the use of some commercial fungicides at bloom may impact pollination and yield. Bee delivery of T. harzianum 1295-2 2 is a viable option for strawberry growers interested in controlling Botry tis with minimal fungicide use. (C) 2000 Academic Press.