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Vegetables
Volume 58 Number 14 Date 08/08/2013 CABBAGE CATERPILLARS - Populations of diamondback moths, cabbage loopers and imported cabbageworms are reportedly high in a few southern Wisconsin cabbage plantings. The larvae of these cabbage pests initially feed on leaves, causing large ragged holes, and eventually move to the center of the plant to infest the developing heads of broccoli, cabbage and cauliflower. Treatment thresholds are reached when 10% of cabbage in the early heading to mature head stages are infested, or 10% of broccoli and cauliflower in the first flower or curd to maturity phase are affected. Bacillus thuringiensis (Bt) and chemical insecticides are the most effective forms of control. LATE BLIGHT - Conditions in recent weeks have been favorable for late blight development. Potato fields infected with this disease have to date been confirmed in Adams, Brown, Dunn, Juneau, Langlade and Portage counties. Two cases of the disease on tomato have also been verified in Brown and Sauk counties. Continued scouting of potatoes and tomatoes for symptomatic leaves and stems is advised. Organic growers should maintain preventative copper-containing fungicide treatments (approved for organic use) on a 5- to 7-day schedule. CORN EARWORM - Moth collections increased sharply at Dane, Fond du Lac and Green Lake County trap locations. A surge from 26-178 moths was registered near Ripon, and the weekly count at Green Lake increased from 21-150 moths. Another 145 migrants were collected in the pheromone trap north of Sun Prairie. These counts are indicative of a large and potentially destructive flight of corn earworm migrants capable of laying eggs in silking sweet corn. All susceptible fields should be checked at this time. Counts in the past week were as follows: Chippewa Falls 0, Coon Valley 1, Cottage Grove N 38, Green Lake 150, Janesville 2, Marshfield 17, Mazomanie 5, Manitowoc 0, McFarland 96, Ripon 178, Sun Prairie N 145, Sun Prairie W 39, and Watertown 60. ONION MAGGOT - The third generation of flies is expected to begin emerging in the southwest, south-central and west-central areas in the week ahead following the accumulation of 3,230 degree days (base 40°F). Since this final generation will produce larvae that overwinter in cull onions and old bulbs left behind in fields, thorough sanitation or rotating to a non-crop host is recommended for growers who experienced onion maggot problems earlier this season. -- Krista Hamiton, DATCP Entomologist 
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