Volume 63 Number 15 Date 08/16/2018
SQUASH BUG - Growers of melons, pumpkins and squash should continue to inspect plants for squash bug adults, nymphs and eggs as fruits ripen. Most crops have matured beyond the critical period of control (seedling and flowering stages), but squash bug feeding is expected to persist throughout fall, causing aesthetic damage and, in extreme cases, killing plants. Late-season control consists of disposing of cucurbit foliage and plant debris around the garden to eliminate overwintering sites and help reduce next year's squash bug population.
LATE BLIGHT - UW-Extension Vegetable Pathologist Dr. Amanda Gevens reports that late blight has been confirmed in potato fields in Adams and Marquette counties. This disease could begin to spread rapidly if weather conditions turn cool and damp in coming weeks, causing entire plants to decline and die in as few as 7-10 days. Gardeners are advised to increase monitoring of potato and tomato plants for signs of infection, including brownish-black water soaked leaf lesions, dark stem lesions or sunken golden- to dark brown spots with distinct rings on the fruit surface. Removal and destruction of infected plants is required if lesions are noticed. Composting will not generate sufficient heat to kill the pathogen and is discouraged for infected materials.
ONION MAGGOT - Late-summer flies are emerging across southern Wisconsin. Emergence is expected to begin next week in the central areas, following the accumulation of 3,230 degree days (base 40°F). Larvae from this third and final generation will overwinter in cull onions or bulbs left behind in fields. Proper sanitation and rotating to a non-crop host are recommended for growers who experienced onion maggot problems earlier this season.
CABBAGE LOOPER - Migrants are expected to continue arriving this month, and increased scouting is advised beginning now and through early September. A 10% infestation threshold is suggested from early heading until harvest to protect the market quality of cabbage. The same threshold applies to broccoli and cauliflower once flowers or curds begin to develop.
-- Krista Hamilton, DATCP Entomologist