dispersed to flowers by wind or splashing rain. 

 Most fungicides are not particularly effective in 

 reducing spore production on the leaves; how- 

 ever, we found that chlorothalonil (Bravo™) 

 applied to green and dead leaves before flower- 

 ing suppressed fruit rot as effectively as captan 

 applied in the conventional way during flower- 

 ing and fruiting. Could we achieve the same 

 kind of result with biocontrol fungi? 



We found that the Gliocladium, Trichoderma, 

 and Penicillium fungi each suppressed Botrytis 

 in the leaves markedly and sometimes com- 

 pletely. The tests were done in the field in the 

 spring, late summer, and fall. Again, Gliocladium 

 was overall the most effective fungus, in part 

 because it was highly suppressive under cool ( 50 

 to 59°F) as well as warm (68 to 77°F) conditions. 

 Effectiveness of the other fungi was reduced 

 below 59°F. Gliocladium roseum is now being 

 developed further as a biocontrol agent. 



Spray applications of biocontrol agents to 

 protect flowers and fruits are horrendously waste- 

 ful. Only a tiny fraction of the spray is deposited 

 on the intended target, the flowers. Moreover, 

 flowers that open after spraying likely remain 

 unprotected until the next spray is applied, 

 during which time Botrytis may attack the flow- 

 ers. Is there a more efficient method? Why not 

 use honey bees? 



Our studies have shown that honey bees are 

 effective vehicles for delivering spores of 

 Gliocladium to strawberry flowers. With the 

 help of Dr. Peter Kevan, a pollination biologist 

 at the University of Guelph, a special spore 

 dispenser was designed to fit inside bee hives. 

 Spores of Gliocladium were blended with talc 

 (500 million spores per g) and the formulation 

 was placed in the dispenser, which, in turn, was 



inserted into the hive. As bees left the hive, 

 spores and talc adhered especially to the hairs 

 on their legs and bodies. Payloads on take-off 

 were around 200,000 to 400,000 spores per bee. 

 Many missions of the "bee-52s" each day main- 

 tained about 50,000 spores on each flower, which 

 suppressed fruit rot as effectively as spray appli- 

 cations. A bit of blanket bombing of leaves by 

 overflying bees also was evident. Formulation 

 was replaced in the dispensers every second or 

 third evening after the bees settled in for the 

 night. 



From our studies we conclude that biological 

 control is a feasible alternative to fungicides for 

 managing Botrytis in strawberries, at least in 

 Ontario. Gliocladium roseum is the most effec- 

 tive biocontrol agent we have been able to find, 

 and isolates of this fungus are consistently as 

 effective or better than captan; however, some of 

 the other fungi examined also may have a place 

 in a biocontrol program. Several strategies are 

 open to us for using Gliocladium. We could 

 apply it to leaves to suppress Botrytis at the 

 source, or to the flowers to protect them against 

 spores of the fungus, or we could use both ap- 

 proaches. In all instances we simply would be 

 increasing the amount of a fungus that occurs 

 naturally and frequently, but harmlessly on 

 strawberries in commercial fields. It would not 

 be difficult to develop honey bees as a low input 

 approach to applying fungi to the flowers, but 

 this may require use of bee attractants on the 

 strawberries in some instances. Technical 

 aspects of developing Gliocladium roseum for 

 large scale use appear entirely feasible. Satisfy- 

 ing the requirements for registration agencies 

 are forthcoming hurdles that are not entirely 

 clear at this time. 



This article was reprinted with permission from Northeast LISA Small Fruits Newsletter 2(2):1 -3. 

 For information about Northeast LISA Small Fruits Newsletter, contact David Marchant, Depart- 

 ment of Plant Pathology, Fernald Hall, University of Massachusetts, Amherst, MA 01003 (tele- 

 phone: 413-545-0179). 



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Fruit Notes, Winter, 1992 



