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Looking Ahead
Volume 65 Number 3 Date 05/14/2020 BLACK CUTWORM - Development of black cutworm larvae has been slowed by abnormally low May temperatures. Very few growing degree days (modified base 50F) have accumulated in the five weeks since the earliest moths were captured, and the peak corn-cutting window is unlikely to open until June 3 for south-central and southwestern Wisconsin. An early start to the corn planting season and the relatively small moth migration documented since mid-April indicate a low threat of damage to vegetative corn this spring. ALFALFA WEEVIL - Larvae should begin emerging in advanced alfalfa fields in the week ahead. Regular scouting is advised starting at 300 degree days (sine base 48°F), or by May 21 in the southern counties. Scouting can begin around May 27 in the central counties. CODLING MOTH - Apple growers in the DATCP trapping network are reminded to begin daily pheromone trap checks to determine the date of the first sustained capture of moths on consecutive nights, referred to as the biofix. This event could occur during the week of May 17-23 in southern Wisconsin. PLUM CURCULIO - Degree day accumulations in the warmest southern areas of the state will soon be favorable for weevil activity. A mean daily temperature of 60°F or more for 3-4 days prompts the spring emergence and migration of overwintered weevils into apple orchard perimeter trees. VIBURNUM LEAF BEETLE - Gardeners, landscapers, nursery stock growers and retailers in southeastern Wisconsin should be on alert for the distinctive skeletonization of viburnum leaves caused by this insect. Newly-hatched larvae usually appear at this time of year, particularly on arrowwood viburnum, American cranberrybush viburnum, and European cranberrybush viburnum. Viburnum leaf beetle was first detected in the state in 2009 and populations have been confirmed in Dane, Iron, Kenosha, Milwaukee, Ozaukee, Racine, Walworth, Washington, Waukesha and Winnebago counties. GYPSY MOTH - The first aerial treatments of the season are tentatively planned for May 20 in southwestern Wisconsin. Approximately 14,657 acres are scheduled to receive applications of Bacillus thuringiensis var. kurstaki, or Btk. Aerial spraying is weather-dependent. Conditions such as high winds, rain predicted within four hours, fog, or high humidity can delay or cause cancellation of spray plans. -- Krista Hamilton, DATCP Entomologist 
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