Development of strategies for fire blight control in organic fruit growing
2011
Kunz, S. | Schmitt, A. | Haug, P.
In organic fruit growing, effective control strategies are needed to prevent blossom infections by the fire blight pathogen Erwinia amylovora. In Germany, many potential control agents have been considered and more than 40 different preparations have been tested systematically in laboratory trials in vitro and on detached blossoms to select the products with highest efficacy. In eleven field trials conducted since 2004 according to EPPO guideline PP1/166(3) BlossomProtectTM and Myco-Sin had the highest efficiencies (79 and 65%, respectively). In 2010 LX4630 was tested the first time and showed comparable efficiency to BlossomProtect. BlossomProtect contains blastospores of the yeast Aureobasidium pullulans. The blastospores are sensitive to fungicides including sulphur and lime sulphur that are used for apple scab control. In some cases, A. pullulans enhanced fruit russet depending on the number of applications and of the apple cultivar treated. Spray strategies in which BlossomProtect was used alternating with sulphur fungicides did not hamper the efficacy of BlossomProtect against fire blight. However, up to 8 applications had to be made during bloom to achieve fire blight and scab control. Applying BlossomProtect and wettable sulphur in a tank mixture reduced the total number of applications to four without reducing significantly the efficiency against fire blight. With a strategy to alternate BlossomProtect applications with sprays of a mixture of wettable sulphur and Myco-Sin, the total number of applications during bloom could be reduced to four, with only a slight decline in fire blight control. In addition in this strategy the reduction of the number of applications of BlossomProtect from four to two reduced the risk of fruit russet.
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