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Corn
Volume 57 Number 15 Date 07/26/2012 CORN ROOTWORM - Surveys in the past week yielded economic populations of 0.75 or more beetle per plant in 6 of 36 (17%) fields sampled in the south-central and central areas. This represents a decrease from the 33% that had economic counts when the same sites were examined last season. Beetle counts in Columbia and Dodge counties varied from 0.1-9.3 per plant and averaged 1.3 per plant. In the central counties of Adams, Juneau, Green Lake, Marquette, Portage, Waupaca and Waushara, counts were lower and ranged from 0.2-4.5 per plant, with an average of 0.5 per plant. The high count of 9.3 beetles per plant was noted in the Cambria area of Columbia County. The annual survey is now in progress and the final results should be available in August. CORN EARWORM - The significant migration that began three weeks ago has accelerated. Large flights of 45-157 moths have been registered in Dane, Jefferson, Fond du Lac and Waushara counties and treatments are under way. Trap counts for the period of July 19-25 were: Aztalan 157, Bloomington 0, Chippewa Falls 2, Columbus 18, Hancock 70, Janesville 9, Manitowoc 0, Marshfield 4, Oregon 45, Ripona 47, Riponb 59, Sun Prairie 56, Wausau 0, and Westport 22. A pheromone trap count of 10 or more moths for two consecutive nights indicates the need for protective treatment of sweet corn fields with green silks. WESTERN BEAN CUTWORM - Moth collections have declined to low levels at most sites as the annual flight subsides, although a few locations in Clark, Calumet, Marinette and Outagamie counties registered higher numbers this week. Early results of the trapping survey show a decrease in the state moth count, from 3,466 last year to 3,078 as of July 25. However, this figure is preliminary and subject to revision. Cumulative totals for the 129 pheromone traps distributed throughout Wisconsin are illustrated in the map below. Sites that registered 101 or more moths are represented by the orange symbols. JAPANESE BEETLE - Light to moderate beetle infestations were observed this week in scattered corn fields in the south-central area. In Columbia County, approximately 2-3% of the plants in one field had silks pruned to the ear tip and as many as six beetles per plant were feeding on the silks, thus impairing pollination. Control is warranted if populations exceed three beetles per ear and pollination is incomplete. --Krista Hamilton, DATCP Entomologist 
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