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Corn
Volume 54 Number 18 Date 08/28/2009 EUROPEAN CORN BORER - Development of corn borers is variable, depending on area of the state. Near Arlington, Janesville, Lancaster and Mazomanie in the southwest and south-central counties, the peak of summer moth activity has subsided. In the eastern areas, the peak has yet to occur. Black light counts have been extremely light since the flight began in late July and surveys indicate that egg masses and second generation larvae are scarce. Larvae in the 3rd-5th instars were found in Marquette, Monroe and Wood counties. Practically all of the late-instar larvae present by mid-August will enter diapause and will not pupate until next spring WESTERN BEAN CUTWORM - Damaging populations were noted in Adams, Green Lake, Juneau, Marquette, Monroe, Rock and Waushara counties this week, where 5-45% of the ears were infested with intermediate to late-instar larvae. One corn field near Brooks in Adams County had approximately 30% of the ears infested with 2-3 full-grown cutworms. Most were located in the ear tips, although some were observed at the base of the ear near the shank. The heaviest infestations generally can be found in the central counties. CORN ROOTWORM - Below is a table summarizing the PRELIMINARY results of the 2009 corn rootworm beetle survey conducted between August 4 and 27. Populations decreased greatly as compared with the 2008 data, particularly in the southeast and east-central districts. The state average thus far is 0.6 beetle per plant, compared to 1.0 last season. District average populations are 0.5 per plant in the west-central district, 0.4 per plant in the central district, 0.6 per plant in the east-central district, 0.7 per plant in the southwest district, 1.1 per plant in the south-central district, and 0.3 per plant in the southeast district. Economic numbers of beetles (0.75 or more per plant) were found in 43 of 188 (23%) surveyed fields. Please note these results are preliminary and are subject to change as surveys of corn are completed in the northern counties. Final results will be published in the 2009 summary issue. --Krista Hamilton, DATCP Entomologist 
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