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Corn
Volume 60 Number 15 Date 07/30/2015 WESTERN BEAN CUTWORM - The western bean cutworm degree day model indicates that 75% or more of the moth population has emerged near Beloit, La Crosse, Spring Green and other advanced locations. Emergence is about 50% complete in the south-central and central counties where activity appears to have peaked this week. The high count for the period of July 23-29 was 49 moths in the pheromone trap near Fall River in Columbia County and 32 in the Pardeeville black light trap. The cumulative state count to date is only 275 moths in 97 pheromone traps, the lowest total since surveys for this pest began in 2005. EUROPEAN CORN BORER - Moths of the second flight continue to appear in very low numbers in black light traps, signaling that eggs are being deposited on corn and other hosts. The peak of summer moth activity can be expected by August 14 across the southern two-thirds of Wisconsin. Sweet corn and non-Bt field corn should be inspected for egg masses and larvae before 2,100 degree days (modified base 50°F) are surpassed and the treatment window for second generation corn borers closes. JAPANESE BEETLE - Minor infestations of 1-14 beetles per 100 plants have been observed since early July in scattered fields in the southern and west-central counties. The greatest threat to corn at this time of year is when large numbers of beetles converge on corn silks, potentially impairing pollination. Control is warranted for populations that exceed three beetles per ear when pollination is occurring. CORN EARWORM - Moth counts remained low from July 23-29, with pheromone traps in Green Lake, Pardeeville, and Ripon registering very small flights of 2-3 migrants. A pheromone trap capture of 5-10 moths for three consecutive nights indicates the need for protective treatment of sweet corn fields with green silks. Counts this week were as follows: Arlington 0, Beaver Dam 0, Green Lake 2, Hancock 0, Janesville 0, Manitowoc 0, Marshfield 0, Pardeeville 2, Prairie du Chien 0, Ripon 3, and Wausau 0. CORN LEAF APHID - Light populations of 15-40 aphids per plant were noted on a few corn plants in Dane, Grant and Green County fields on July 23. Pressure of 50 or more aphids per plant on 50% of the plants can interfere with pollination and may require treatment. -- Krista Hamilton, DATCP Entomologist 
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