Evolution of a Weather-Based Peanut Leaf Spot Spray Advisory in North Carolina. J. E. BAILEY, Department of Plant Pathology, North Carolina State University, Raleigh, 27695-7616. G. L. JOHNSON, Department of Horticulture Science, North Carolina State University, Raleigh 27695-7609; S. J. TOTH, JR., Department of Entomology, Box 7613, North Carolina State University, Raleigh, NC 27695-7613. Plant Dis. 78:530-535. Accepted tor publication 29 September 1993. Copyright 1994 The American Phytopalhological Society. DOI: 10.1094/PD-78-0530.

A weather-based leaf spot spray “advisory” was deployed in North Carolina beginning in 1983 to help growers time fungicide applications to improve the management of early leaf spot (Cercospora (arachidicola). Volunteer growers collected weather data that county extension staff used to compute spray advisories. In spite of the logistical difficulties in spraying according to a daily advisory, over 80% of peanut growers surveyed used these advisories in making spray decisions some, most, or all of the time. In an effort to give growers more time to respond to leaf spot spray recommendations, a method was developed lo predict advisories 2 days in advance. These “forecast advisories” were relayed to county offices through an electronic mail system. Real time advisories fell within the estimated range of 2-day predicted advisories 71% of the time. It was concluded that these leaf spot spray advisories play an important role in the decision-making process for North Carolina farmers and that forecast advisories can be a useful tool in extending the time farmers have to respond to spray advisories.