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Vegetables
Volume 60 Number 3 Date 05/07/2015 COLORADO POTATO BEETLE - Overwintered adults are emerging from hibernation and dispersing to plants near field edges. The early colonizing population is rarely damaging to young potatoes protected with a systemic neonicotinoid, but beetle abundance should be monitored to ensure effectiveness of insecticide products. Egg deposition and larval hatch can be expected by mid-May. The orange-yellow eggs are deposited in clusters of 15-30 on the undersides of leaves. CABBAGE MAGGOT - Peak emergence of flies theoretically has occurred near Beloit, La Crosse, Lone Rock and Madison following the accumulation of 300 degree days (simple base 43°F) as of May 6. Emergence should peak next week across the southeastern and central counties. Damage by this pest can be avoided by planting or transplanting cole crops two weeks from now, after most of the population has pupated. IMPORTED CABBAGEWORM - Adults are appearing in greater numbers and depositing eggs on cruciferous weeds and available early-planted cole crops. Close examination of transplants for eggs and small larvae is most critical during the oviposition period. Infestation levels in cabbage should not exceed 30% at the transplant to cupping development stages. ONION MAGGOT - Emergence of the first and most damaging generation of flies is likely to begin by May 15 in parts of southern Wisconsin. Basic cultural controls such as removing onion cull piles and rotating new seedings away from previous crops (at least ½ mile for commercial fields) have become even more critical now that the onion maggot has developed resistance to many of the insecticides used as granular furrow treatments at seeding. Proper sanitation and planting onion sets one week before fly emergence are the best preventative measures. LATE BLIGHT - Potato growers are reminded that Wisconsin Administrative Code (ATCP 21.15(2)) requires potato cull piles to be fed, disked in or otherwise removed by May 20, to prevent late blight from developing on volunteer plants. Although no cases have been confirmed in Wisconsin so far this season, risk of this disease occurring again in 2015 is elevated given the presence of the late blight pathogen in the state in 2014. -- Krista Hamilton, DATCP Entomologist 
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