DETECTION OF INFECTION PERIODS AND EVALUATION OF THE PARAMETERS FOR THE EPIDEMIOLOGY OF THE APPLE SCAB DISEASE

The dates of primary and secondary infections of Venturia inaequalis w ere determined by a bioassay with seedlings of cv. 'Golden Delicious'. The infection periods detected by the seedlings were compared to the disease predictions recorded by standard electronic scab warning devic es. The infection parameters obtained with the bioassays were used to evaluate Mills' criteria. The ascospore release was monitored by volum etric sport traps, a jet spore sampler and a waterbath method. The eas y to perform waterbath method was the most sensitive approach at the b eginning of the season. Furthermore, with this method there was a posi tive correlation to the patterns obtained by spore traps. A fungicide program with a delayed onset of the applications indicated that the in cidence of primary infections depended only on the amount of ascospore s even though the trees were heavily infected in the previous year.