The effect of temperature on infection and a warning system for pear blossom blast caused by Pseudomonas syringae pv. syringae

Abstract

Blossom blast caused by Pseudomonas syringae pv. syringae van Hall, is a major disease of pears (Pyrus spp.) in Chile. Freezing temperatures may predispose pears to infection, however, our results demonstrated that blossom blast infection might occur in the absence of frosts, at temperature higher than 5degreesC, provided that the appropriate inoculum concentration, moisture levels and the susceptible bloom stages were available. Regardless of the flower bud stage development, blossom blast was lowest at 5degreesC and highest at 20degreesC. The first symptoms appeared after 2-3 days at 20degreesC, and were delayed 2 days at 5 C. A significant and positive linear regression best explained the relationship between disease incidence and temperature. A warning system, based on temperature and free moisture conditions, was developed and found to be useful for prediction of blossom blast infection in the field. Antibiotic treatments applied after each warning significantly (p<0.05) reduced blossom blast on Packham's Triumph pears. (C) 2002 Elsevier Science Ltd. All rights reserved.