Volume 58 Number 6 Date 06/06/2013
STRIPED CUCUMBER BEETLE - Seedling and transplanted cucurbits such as cucumbers and melons will be at risk of direct feeding injury and bacterial wilt transmission as beetles emerge this month. Cucumber beetles are such an effective carrier of the bacterial wilt pathogen that serious crop damage can occur if only 10% of the population is infected. Scouting field edges and interiors 2-3 times per week is advised. Beetle counts should not exceed 4-5 per 50 plants.
ONION MAGGOT - First generation flies are active near Cumberland, Medford and Wausau in northern Wisconsin. Flies of the spring generation are often the most abundant and damaging, especially at sites where onions are grown in succession. Rotating this year's plantings as far away as possible from last year's onions is perhaps the most basic approach to onion maggot control. Preventative soil insecticides may be considered if maggot damage to the previous year's crop exceeded 5-10%.
COLORADO POTATO BEETLE - Adults continue to colonize potato fields and egg laying has begun. The presence of widely distributed, in-field populations of adults and early larvae suggests at-plant systemic neonicotinoids are not adequately controlling populations and a foliar spray may be warranted. The first of two foliar applications of an insect growth regulator or the biological insecticide Bt can be made at egg hatch and again 7-10 days later.
IMPORTED CABBAGEWORM - Larvae have emerged statewide. Home gardens and larger cabbage plantings should be checked weekly for the yellow eggs (laid singly on plants) and velvety green caterpillars with a yellow, longitudinal stripe. The economic threshold for this pest in cabbage is 30% infestation at the transplant to cupping stages and 20% infestation at cupping to early head stage.
-- Krista Hamilton, DATCP Entomologist