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Vegetables
Volume 65 Number 13 Date 07/30/2020 LATE BLIGHT - No cases of late blight have been detected in any Wisconsin potato field or home garden as of July 29. However, the UW is reporting that all potato growing areas in the state have reached the threshold for late blight development, therefore gardeners are advised to continue inspecting tomato and potato plants for leaf lesions and fruit spots. Growers who suspect late blight are encouraged to send symptomatic plant material to the UW Plant Disease Diagnostic Clinic: https://pddc.wisc.edu/sample-collection-and-submission/. Late blight testing is free of charge. SQUASH VINE BORER - Damage to the stems of pumpkins and squash has become more pronounced as larvae approach maturity. Squash vine borer (SVB) larvae in the La Crosse area of western Wisconsin are full grown and will likely pupate by early August. Cultural control advised for SVB includes destroying vines after harvest to prevent borers still in the larval stage from completing development. Fields that have been attacked in the past are more likely to have SVB problems in the future. COLORADO POTATO BEETLE - Late summer control of this pest may be warranted if defoliation exceeds 30% during tuber formation. Treatments should be applied when most of the population reaches the intermediate third instar stage, presuming this does not conflict with label recommendations or resistance management. Proper timing permits most eggs to hatch, but kills the larvae before they reach the destructive fourth instar. Potato growers are reminded to avoid the consecutive use of the same insecticide product or the use of different products with similar modes of action. JAPANESE BEETLE - Beetles are still common in gardens and on farms, and are likely to remain so into September. Physical removal is the recommended control option for small gardens. The best time to hand-pick beetles is either in the early morning or the evening, when the insects are less active. Pheromone traps should be used with caution since they may attract additional beetles from other areas or worsen damage if placed incorrectly. The traps should be set at least 30 feet away from ornamental plants, near a non-flowering tree or shrub such as a pine tree or boxwood. The recommended height for traps is four feet above ground. CABBAGE LOOPER - Surveys indicate that populations of this cole crop pest are lower than last year, although growers should be aware that the second larval generation that will appear in August is usually more damaging than the first generation. The predominant development stages noted in gardens and on CSA farms in the past two weeks were full-grown larvae and adult moths. From early heading until harvest, the UW recommends control to maintain marketability if 10% of plants are infested. SQUASH BUG - Adult and nymphs are very active in pumpkin and winter squash plantings across the state. Vegetable growers should continue to inspect the undersides of leaves for the metallic bronze eggs, deposited in groups of 15-40 between leaf veins or on stems, as long as small nymphs are present. Squash bugs are capable of damaging mature fruit, thus control may be needed as the crop nears harvest. OMRI-listed materials include PyGanic, insecticidal soaps and certain oils. -- Krista Hamilton, DATCP Entomologist .jpg)
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