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Factors Contributing to Seasonal Fluctuations in Rust Severity on Ribes missouriense Caused by Cronartium ribicola

October 2010 , Volume 100 , Number  10
Pages  986 - 996

Maria Newcomb, Christen D. Upper, and Douglas I. Rouse

Department of Plant Pathology, 1630 Linden Dr., University of Wisconsin-Madison, Madison 53706.

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Accepted for publication 21 May 2010.

Cronartium ribicola, causal agent of white pine blister rust, is a macrocyclic heteroecious rust that cycles between white pines and members of the genus Ribes, which are typically wild plants in North America. To improve predictability of inoculum available for infection of ecologically and commercially important white pines, this research was conducted to identify the factors that influence the development and persistence of uredinia and telia on Ribes in their natural habitats. Numbers of infectious C. ribicola rust lesions (with potentially sporulating rust sori) on tagged Ribes missouriense plants in the woods fluctuated during the season. Changes in numbers of infectious rust lesions were related to rain that occurred 13 days earlier. In field experiments, supplemental leaf wetness provided for 2 days on Ribes shoots resulted in the development of rust lesions more frequently than on control shoots. Viable inoculum and susceptible hosts were present, and the environment was the limiting factor for disease development. Lesion necrosis and leaf abscission contributed to decreases in numbers of infectious rust lesions. Higher lesion density was significantly related to earlier leaf abscission. Telial fruiting bodies occurred in low numbers from early June throughout the remainder of the season.

© 2010 The American Phytopathological Society