Therefore, fungicide application may be applied one hour before an expected rain with good results. The fungicides have excellent post-infection activity. They may be applied up to 72 hours after an infection period has started with good results. The recommended fungicides will protect buds from infection for about four to ten days after application, depending on the infection conditions. If conditions favor infection, then a shorter spray interval is needed to get protection.
Research indicates that rain or fog is necessary to initiate an infection period.
Moisture from dew usually is not enough to initiate infection. Field frost for even one hour dramatically increases the susceptibility of buds to Monilinia . The increased bud susceptibility lasts for approximately four days after the frost. Infections do occur without frost, but levels are much lower, and longer wetness durations and higher temperatures are required. If the answer is NO, then a spray is not necessary.