The Reemergence and Management of Currant Cane Dieback in the Northeastern United States.

Abstract

Currant cane dieback, caused by the fungus Botryosphaeria ribis (syn. Neofusicoccum ribis), devastated currant production in the northeastern United States approximately a century ago. Later epidemics of this disease were halted by bans on the planting of Ribes spp. to control white pine blister rust, but since regulations restricting the planting of currants were removed in the 1980s and 1990s, currant cane dieback has reemerged in the northeastern United States. In this study, we obtained fungal isolates from diseased canes at four production operations in New York and Connecticut. We confirmed the isolates as N. ribis on the basis of morphology and ribosomal DNA sequence analysis, and verified pathogenicity through inoculation of healthy currant bushes. Furthermore, field trials to study the effects of cultivar, pruning of symptomatic canes, and fungicide applications were conducted over 2 years. Differences in Ribes cultivar susceptibility to N. ribis were demonstrated, with a pink fruiting cultivar (Pink Champagne) having lower levels of dieback compared to two red cultivars (Rovada and Jonkheer van Tets) and one white cultivar (Blanka) evaluated. While there were no consistent reductions in cane dieback incidence over both years and for all cultivars when pruning or fungicide treatments (copper hydroxide and sulfur applications) were used alone, fungicide treatment combined with pruning resulted in significant (P < 0.05) reductions (>80%) in the incidence of dieback compared to bushes not treated with fungicide or pruned.