The control of apple scab using METOS-D equipment for predicting disease infection

The accuracy of METOS-D equipment in predicting apple scab infection and its use in disease control were investigated from 1992 to 1996. In investigating its accuracy, the position of leaves on young apple shoots and their susceptibility t9o pathogenic fungi were examined, in order to estimate the actual infection period and infection volume in the field. The susceptibility of leaves to fungi at inoculation was high for the four leaves from folded leaf position 1 to unfolded leaf position 3, but especially so in unfolded leaves of positioning 1 and 2. The day and the amount of infection in the apple leaves were estimated, and on checking the estimate against the disease development, it was found that the number of diseased leaves increased 2 to 3 weeks after the estimated infection days. Since the incubation period of the disease is approximately 2 to 3 weeks, the estimate was considered fairly accurate. The days of ascospore dispersal more or less coincided with the estimated infection days. On comparing estimated infection days and warnings provided by the METOS-D models developed by Mills and McHardy respectively, it was found that both models produced virtually identical results, although Mills's model tended to be more accurate on estimated infection days. Also,a comparison of the danger indication signs with estimated infection volume using Mills's model showed that the indication of M or higher coincided more or less with the estimated infection volume. In an apple scab control experiment using METOS-D, the number of fungicide sprayings was decreased to a maximum of 5 times compared to regular preventive sprayings at 10-day intervals. When the number of sprayings was the same, control efforts using METOS-D were more effective than tranditional methods