Ascospore maturity assessments provide growers with one predictor for differentiating high versus low risk for early season scab infections. Ascospore maturity counts have been conducted continuously in eastern New York for many years, but maturity counts in other regions were discontinued several years ago when the technician who performed the counts at the Geneva Experiment station retired. Conducting ascospore maturity assessments is a tedious process. Skilled and experienced observers produce more consistent results than novices. Pseudothecia usually contain anywhere from 80 to 150 asci.
Asci are transparent cylindrical sacs that each contain eight ascospores .
The ascospores are clear when immature, but turn an olive-green color as they mature. In microscopic assessments, squashed pseudothecia appear as a jumble of overlapping asci. The technician conducting the counts must visually scan the field of view in the microscope while clicking off on a counter the maturity category for each ascus that is observed. The process is somewhat analogous to trying to count the number of branches in a small brush pile without touching any of the branches. In the tower shoot test, leaves are wetted and placed on a screen about 16 inches above a plenum through which air is drawn by a vacuum pump.