Volume 64 Number 10 Date 07/04/2019
EUROPEAN CORN BORER - Early whorl feeding was first noted in V7 corn in Dane County on June 26. Larvae were in the first and second instars last week and have now begun boring into the midribs of corn leaves. Chemical and biological insecticides targeting first-generation ECB are only effective for about a week after egg hatch, and must be applied soon in fields where small larvae are emerging. The treatment window is expected to close by July 7 near Madison and July 14 near Hancock. Scouting and management decisions should be made in the week ahead.
WESTERN BEAN CUTWORM - The first moths of the season were captured in pheromone traps between June 27 and July 3. One was collected near Bangor in La Crosse County and another was caught near Sparta in Monroe County. The appearance of western bean cutworm adults indicates that the annual flight is beginning in the southern half of the state. Close inspection of corn plants for egg masses and small larvae should start once fields enter the late-whorl and pre-tassel stages. The eggs are deposited on the upper surface of the top 3-4 leaves, often on the flag leaf, and the larvae can be found in developing tassels.
TRUE ARMYWORM - Conditions remain very favorable for armyworms after the recent rains. Continued scouting of corn and small grains is recommended. Light larval infestations involving 1-4% of perimeter row plants have been noted in about 16% (21 of 133) of cornfields surveyed by DATCP since mid-June. Localized problems were reported last week in the east-central area.
-- Krista Hamilton, DATCP Entomologist