ELISA test reveals new information about leafroll disease

Abstract

Postharvest defoliation by prune rust did not adversely affect dry yield or fruit quality in the current or following seasons in our experiments. In both orchards, the significant differences among treatments were few, minor and inconsistent. Differences in postharvest defoliation among our treatments were not reflected in dis-similarities in yields the following season. If accelerated postharvest leaf loss was deleterious to the next crop, this effect was overshadowed by other horticultural factors, such as alternate bearing, and was not detected by our experiments. Although we selected orchards whose histories and locations indicated that preharvest defoliation by prune rust was likely, such leaf loss did not occur during the course of these experiments. Consequently we were not able to corroborate the yield losses attributed to preharvest defolia-tion by prune rust in other regions. The history and pattern of prune rust in orchards should be considered in making treatment decision for control of this disease. Orchards with histories of early rust infection, or those situated along rivers or in high rainfall areas, should be treated annually for control of prune rust. Such orchards need protection from severe early preharvest defoliation and the associated yield losses that have been reported elsewhere. However, orchards in which rust infection and leaf loss are late-season events should not require treatment to control prune rust. Such late-season defoliation, even though repeated annually, does not appear to harm crop yield or quality. prunes in California) was superior to sulfur for control of prune rust.