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Looking Ahead
Volume 59 Number 10 Date 07/10/2014 EUROPEAN CORN BORER - The treatment window for first generation larvae has closed near Beloit, Madison, La Crosse, Lone Rock and other southern locations where 1,100 degree days (modified base 50°F) were surpassed as of July 9. Third and fourth-instar larvae are entering corn midribs, tassels and stalks where they are protected from insecticide sprays. Chemical control remains an option for growers in the southeastern, central and northern counties for another week. SOYBEAN APHID - Counts remain extremely low in most soybean fields. All of the 87 sites surveyed since the last report had averages below 14 aphids per plant and 78% of the fields had no detectable aphid population. Economic densities of 250 or more aphids per plant have not been observed as of July 9. TRUE ARMYWORM - Larvae are still fairly common in corn and many surveyed fields are showing 1-6% of plants with ragged leaves and defoliation. Continued scouting is recommended throughout July since black light traps are registering locally heavy flights (82 moths at Janesville from July 3-9) and environmental conditions remain very favorable for armyworm problems. WESTERN BEAN CUTWORM - The annual flight is under way in the southern half of the state where black light and pheromone traps registered low counts of 1-8 moths from July 3-9. Twenty-five percent emergence of the moth population is anticipated in the next two weeks as far north as Hancock in Waushara County, as accumulations of 1,320 degree days (modified base 50°F) are reached. Corn in the pretassel stage is preferred for oviposition and should be inspected for eggs and small larvae in the week ahead. APPLE MAGGOT - The first flies of the season appeared on traps in Fond du Lac and Sheboygan County apple orchards last week, marking the start of the adult emergence period. Close inspection of red sphere and yellow sticky traps is suggested, particularly for orchards impacted by recent hail storms. The apple maggot fly is distinguished from similar fruit flies by an F-shaped wing banding pattern and a pronounced white spot on the thorax. CORN ROOTWORM - Beetles are emerging in Dane and Rock counties. These insects will become increasingly abundant this month, with peak emergence anticipated by mid- to late August. Corn that lodges unexpectedly after storms or heavy rain should be examined to determine if corn rootworm larvae are the cause of the damage. Growers of Bt-rootworm hybrids with the Cry3Bb1 trait (YieldGard RW, VT Triple products and Genuity SmartStax) who experience poor root protection this season and suspect resistance are advised to notify their seed company representative. -- Krista Hamilton, DATCP Entomologist |