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Timing is everything when it comes to fungicide application. Beating Early Blight Diggin' In Diggin' In FUNGICIDES | Industry Report Every growing season, there are a number of factors that can work against the survival of a potato crop, including disease. One particularly detrimental disease is early blight. Research completed in 2013 by the University of Idaho showed that crop losses due to early blight can exceed 20 percent if left uncontrolled. The same research showed that in potato-growing regions, the use of fungicides can help decrease these crop losses to less than 5 percent. (Results of that research can be found at www.cals.uidaho.edu/edcomm/pdf/CIS/CIS1196.pdf.) When determining how to control early blight, growers should take a proactive approach by planning early and considering fungicides as a part of their disease management plan. "To best prepare for any diseases that may affect their crop, potato growers should develop a fungicide plan prior to the start of the season, so that they are prepared to make timely applications when necessary," says Curtis Rainbolt, a BASF technical service representative based in Idaho. "We recommend Endura fungicide as a solution that's been proven to control early blight as well as white mold, which is another common disease growers in Idaho might face." When such a high risk is associated with uncontrolled early blight, growers should carefully monitor their crop for signs of this and other diseases. The Right Time for Fungicides With a name like early blight, you might think this disease appears early on in the growing season. However, it rarely does and often appears on mature foliage. With this in mind, growers need to time applications of fungicides to their crop carefully. During the vegetative stage, application of foliar fungicides for early blight control is typically not necessary, as plants are still relatively resistant. Fungicide application that occurs too early could have minimal to no effect on the spread of early blight. Instead, growers should begin their early blight management program at or just before row closure. While growers should frequently monitor their fields for signs of disease, fungicides should be applied preventively to avoid disease development. Rainbolt recommends applying fungicides on a tight spray schedule of five to 14 days in accordance with the approved label directions for use and depending on the location and disease pressure. This is especially important in weather conditions that can be breeding grounds for disease-causing fungi. In the case of early blight, alternating wet and dry periods favor disease production. "A potato crop can face a variety of issues each year that threaten its health and yield potential, including diseases brought on by adverse weather conditions and other factors," says Rainbolt. "Growers should control what they can and protect against what they cannot. They can help manage these issues by protecting the crop against yield-robbing diseases through the use of fungicides." Keeping Resistance at Bay While using fungicides to control early blight in a potato crop, growers should be mindful of the products they choose and the management techniques they implement to fight fungicide resistance. "A practice we recommend growers follow to fight resistance is using the most effective fungicides first in their spray programs," says Rainbolt. "Growers should also use tank mixes of protectants like chlorothalonil or mancozeb-based fungicides with Endura fungicide." Endura fungicide has a single mode of action that allows for tank-mixing flexibility to further manage the development of fungicide resistance. Other practices Rainbolt recommends growers follow to manage fungicide resistance include limiting the number of sprays with the same mode of action and rotating different modes of action in spray programs. The Best Plan for Your Crop The use of fungicides to control early blight should exist within a comprehensive integrated disease management plan. Practices such as rotation with non-host crops for early blight, avoiding irrigation in cool, cloudy weather, and the removal of infected plant debris all help reduce the risk of early blight inflicting a potato crop. "Growers can work with their local BASF representative to determine how fungicides can work within their integrated disease control plan," said Rainbolt. "Our representatives recommend Endura fungicide to be included in a grower's disease management plan so they can get ahead of early blight and other diseases to help preserve their crop's yield." For more information on Endura and other BASF crop protection tools, visit www.GrowSmartPotatoes.com. Endura is a registered trademark and GrowSmart a trademark of BASF. 26 POTATO GROWER | APRIL 2019