under bio-intensive "third-level IPM" would be as 

 colorful, sweet, large, firm, and as plentiful as fruit 

 produced with more chemically based IPM practices, 

 and this is what we found. We were surprised, how- 

 ever, that there were no differences due to planting 

 density, because other studies have shown high den- 



sity apple blocks produced larger, more colorful and 

 more plentiful (yield per acre) fruit than blocks with 

 larger less densely planted trees. For 1999, we plan to 

 study these factors more comprehensively. We will 

 increase the number of apples, branches, and trees that 

 are examined. 



•s!^ *^ •st* •st^ •J^ 



•^ •^ ¥^ •^ ^^ 



Evaluation of Flint and Sorvran,Two New 

 Strobilurine Fungicides, Against Apple 

 Diseases 



Daniel Cooley and Arthur 1\ittle 



Department of Microbiology, University of Massachusetts 



Joe Sincuk 



Department of Plant & Soil Sciences, University of Massachusetts 



Heather Faubert 



Department of Plant Sciences, University of Rhode Island 



For the first time in many years, the agricultural 

 chemical industry is releasing new types of fungicides 

 for control of apple diseases. One new class of fungi- 

 cides, the strobilurines, is particularly interesting. The 

 first registered versions of these on apples are Flint® 

 (trifloxystrobin) and Sovran® (kresoxim-methyl). The 

 original discovery of this class of chemistry was in a 

 forest mushroom, Strobilurus tenacelius. In a natural 

 setting, the mushroom produces a chemical called 

 strobilurine to fight off other fungi that may be trying 

 to feed off the forest debris, or off the mushroom it- 

 self. Strobilurine A is a natural fungicide. Several com- 

 panies have synthesized versions of chemicals similar 

 to Strobilurine A, collectively called strobilurines, and 

 are completing evaluation and registration of them. 



These fungicides offer some interesting opportu- 

 nities for apple growers. They are very effective against 

 scab and fly speck, the two key fungal diseases of apple 



in New England. In addition, they have a very clean 

 bill of health on the environmental front, with low tox- 

 icity to mammals, bees, birds, and earthworms. While 

 toxic to fish and other aquatic organisms, strobilurines 

 are broken down very quickly, and tests show that un- 

 der normal use patterns, they will not reach water be- 

 fore they break down. 



It will also be important to use them wisely, since 

 it will be relatively easy for pathogens to develop re- 

 sistance to them. Indications are that the resistance 

 that develops will be "all or nothing." That is, if resis- 

 tance develops, it will come on with little warning, 

 probably leaving significant disease in the wake. 



The manufacturers recognize the potential for re- 

 sistance and attempted to address the problem by lim- 

 iting the total number of applications that can be made 

 in a year, the amount of material that may be applied 

 in a year, and the number of consecutive sprays of 



Fruit Notes, Volume 64 (Number 2), Spring, 1999 



