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Vegetables
Volume 63 Number 12 Date 07/19/2018 SQUASH BUG - Counts of 1-4 egg clusters per 20 plants were found on squash in Dane County vegetable gardens, along with adult and nymphs. Handpicking the eggs and all squash bug stages from the undersides of leaves is suggested if only a few plants are infested, or dusting diatomaceous earth over plants may help reduce numbers. Levels that become intolerable can be spot treated with an organic insecticide or a pyrethroid, but insecticides are generally only effective against the small, newly-hatched nymphs, and thorough coverage is critical. The economic threshold for this pest in one egg cluster per plant when vines are flowering. LATE BLIGHT - Disease severity value accumulations in the state's primary potato production regions (i.e., Antigo, Grand Marsh, Hancock and Plover) have exceeded the late blight risk threshold, thus conditions are appropriate for disease development. Home gardeners and farmers, whether conventional or organic, should consider preventive fungicide applications to protect their tomatoes and potatoes. Registered fungicides for potato late blight in Wisconsin are listed at the UW-Madison Vegetable Pathology website: http://www.plantpath.wisc.edu/wivegdis/pdf/2018/2018%20Potato%20Late%20Blight%20Fungicides.pdf. No cases of late blight have been confirmed in Wisconsin as of July 19. COLORADO POTATO BEETLE - Second-generation larvae are appearing on potatoes in the southern and west-central areas. Late-season control of this pest may be warranted if defoliation exceeds 30% during tuber formation. Treatments applied after egg hatch and before the majority of the larval population reaches the destructive fourth-instar stage are most effective. Potato growers who opt to chemically control the larvae should follow CPB resistance management guidelines by avoiding consecutive use of the same insecticide product or products with similar modes of action. STRIPED CUCUMBER BEETLE - Although these insects have been scarce so far this season, growers of cucurbits should continue to monitor plants for beetles and signs of bacterial wilt. Control is warranted for populations of one beetle per plant in cucumbers and young pumpkins, and five beetles per plant in watermelon and squash. -- Krista Hamilton, DATCP Entomologist 
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