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Rally® Fungicide Canker Diseases Dow AgroSciences has received registration from U.S. EPA and CA DPR for Rally® fungicide to aid in the control of grapevine canker diseases. Under this Special Local Need (SLN) label, Rally is tractor-applied to pruning wounds immediately after pruning, helping to manage fungal pathogens which infect woody tissue, including various Botrysphaeria species and others. The SLN is for use in California only. “Research conducted by Doug Gubler and Ryan Herche at UC Davis has shown that Rally applied immediately after pruning can help prevent infection by fungi that cause these canker diseases,” says Jim Mueller, Dow AgroSciences field scientist.

Tractor Application “What makes this new label very practical for growers is that Rally can be applied by tractor,” says Mueller. “Growers can apply another fungicide after pruning, but must paint it on by hand or use hand-held spray bottles, which is a time consuming and expensive process. With Rally, standard vineyard sprayers can be used by capping certain nozzles so that the fungicide is directed toward pruning wounds. “The other management option growers have is simply to prune out infected wood,” he says. “But it’s best to also protect the pruning wounds.”

Apply Rally After Pruning Rally should be applied within 24 hours after pruning, as pruning wounds are the primary route of infection. “Depending on conditions, pruning wounds can take several weeks to heal and are susceptible until healed,” says

Mueller. “Rally fungicide will provide at least two weeks of protection. If wounds have not healed by then, growers can apply another Rally treatment. That’s especially important if rain is expected. Just a quarter inch of rain would release additional spores into the air and provide the conditions needed for spore germination and infection.” When possible, final pruning should occur in late winter. At that time, pruning wounds tend to heal faster and disease pressure tends to be lower, as spore sacks become depleted from winter rains. A late winter application of Rally also can reduce overwintering powdery mildew infections. UC Davis researchers found that this application can reduce powdery mildew similar to a lime sulfur Trademark of Dow AgroSciences LLC and oil treatment applied Always read and follow label directions. at that time. ®

December CAPCA Adviser  

December CAPCA Adviser