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Vegetables
Volume 63 Number 7 Date 06/14/2018 POTATO LEAFHOPPER - Counts in snap beans and potatoes could increase markedly before the end of the month as leafhopper reproduction and harvesting of second-crop alfalfa begin. Commercial vegetable growers may use an insect sweep net to monitor fields, taking 25 sweeps per sample site and sampling from at least five sites per 30 acres. Counting nymphs and adults by turning over 25 leaves from the middle of the plant is the protocol for gardens or smaller-acreage farms. Recommended treatment thresholds for potatoes are one adult per net sweep or an average of 2.5 nymphs and adults on the undersides of 25 potato leaves. In snap beans, the threshold is 0.5 adults and nymphs per sweep for seedlings, and one leafhopper per sweep for larger plants in the third trifoliate to bud stages. SQUASH VINE BORER - Moth emergence is beginning in warm southern Wisconsin locations. Close inspection of pumpkins, squash, gourds, and other vine crops for eggs and evidence of larval boring should start once 900 degree days (simple base 50°F) have been reached around the third week of June. If insecticide use is warranted for SVB control, materials must be applied before the larvae bore into vines and become protected by vine tissue. Applying treatments while runners are shorter than two feet long is most critical. IMPORTED CABBAGEWORM - Adult butterflies have become more common this month and larvae of varying sizes can be found on cabbage, cauliflower and broccoli in most vegetable plantings. Manual removal of the caterpillars is suggested for smaller gardens, while treatment with a product containing the bacterial insecticide Bacillus thuringiensis (Bt) subspecies aizawi (Agree, Xentari) or subspecies kurstaki (Biobit, Cutlass, DiPel, Javelin, Lepinox, MVP, Thuricide) can be considered for larger production fields. Bt is most effective against small larvae and may not control larger, full-grown caterpillars. Most Bt products persist on plants only a few days and must be reapplied if small larvae are actively feeding. LATE BLIGHT - Disease severity value accumulations near Grand Marsh in Adams County have exceeded the late blight risk threshold, indicating that the conditions required for disease development have been met. Considering inoculum is likely present in various areas of the state following last year's confirmed late blight detections in 13 counties, gardeners and farmers, whether conventional or organic, may want to use preventative fungicide applications to protect their tomatoes and potatoes. No cases of late blight have been confirmed in Wisconsin as of June 14. -- Krista Hamilton, DATCP Entomologist 
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