Temperatures under glass slides used in monitoring the seasonal release of apple black spot ascospores

Abstract

Temperatures were measured under two glass slides mounted over leaf litter under the canopy of an apple tree, configured as for monitoring Venturia inaequalis ascospore release. They were compared with temperatures on the surface of the adjacent litter, and in air 20 cm above ground. Temperatures under the slides were higher during the day than those on the adjacent surface, which in turn were higher than daytime air temperatures. However, comparison of accumulated temperatures under the slides with accumulated temperatures on the adjacent litter surface suggests that ascospores are unlikely to be released more than one or two days earlier under glass slides than in undisturbed leaf litter.