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Another week of mild, mostly dry weather favored fieldwork and benefited late summer crop development throughout Wisconsin. Average temperatures were within 1-2 degrees of normal for the week ending August 22, with daily highs in the upper 60s to mid-80s and overnight lows in the upper 30s to lower 60s. Much of the state received less than 0.5 inch of rain, though a few scattered pockets of heavier rain (up to 2.0 inches) occurred in central and northern areas August 16-17. The rainfall caused only brief delays in harvesting of hay, oats, potatoes, and sweet corn before a drier weather pattern settled in for the remainder of the week.
Condition ratings for the state’s corn improved by one percentage point and 64% of the crop is now categorized in good to excellent condition, while ratings for hay, pastures, and ranges all declined by 1-7 points. The apple picking season has arrived and opening weekend is expected to see heat index values in the mid-90s and temperatures reaching the triple digits early next week.
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Pest Survey summer interns continued counting beetles in corn fields this week as part of DATCP’s annual corn rootworm beetle survey. The survey has been conducted each August since 1971 and provides an estimate of this year’s corn rootworm beetle pressure and a risk forecast to help corn producers make management decisions for the next planting season. Rootworm populations are determined by counting the number of northern, southern, and western corn rootworm beetles on 10 plants per field and calculating the average number of beetles per plant. An average count of 0.75 beetle per plant (all species) in a field indicates high beetle pressure and the potential for larval damage to corn roots the following year.
Preliminary results suggest that overall rootworm pressure may be similar to the levels recorded in 2023, although the survey is incomplete. Beetle counts in the 171 grain corn fields surveyed so far have been mostly low, with 133 fields averaging low counts of 0.0-0.4 beetles per plant and 10 sites having moderate beetle counts in the range of 0.5-0.7 per plant. Above-threshold averages of 0.75 or more beetles per plant have been observed at 28 of the sites (orange circles in the map below). |
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The usual hotspots for beetle pressure are primarily across the southern three tiers of Wisconsin counties, which is normal and expected, while scattered high-count fields have also been documented in the northwest and eastern counties. The 2024 running average of 0.6 beetle per plant compares to 0.5 beetle per plant at this time last season. As the preliminary results map illustrates, there are still several counties in the central and northern parts of the state, and approximately 60 more fields left to sample, before the survey is finalized in the week ahead. |
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A new fall armyworm trapping network has been established to provide advanced warning of potential late-season larval infestations in alfalfa, field corn, sweet corn, and pasture grasses. Although fall armyworm (FAW) migrations generally occur too late in fall to cause much damage and FAW historically has not been a major pest in Wisconsin and the upper Midwest, the changing climate and a recent outbreak across the eastern and southern U.S. in 2021 have brought new interest in tracking flights of this migratory insect.
As of August 22, the 37 pheromone traps in 18 counties have captured 1,594 fall armyworm moths, or an average of 43 moths per trap. A total of 146 moths were collected this week (August 16-22), a sharp decrease from 770 moths the week before (August 9-15). This month's moth activity suggests that egg laying is occurring in late-planted corn fields and is likely to continue into September.
For regional fall armyworm flight data extending across the northeastern U.S. and adjacent Canadian provinces, please see the Great Lakes and Maritimes Pest Monitoring Network (select FAW tab). |
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Late-season corn earworm moth migrations into Wisconsin increased markedly this week with the capture of 670 moths in 14 pheromone traps, up from 217 moths the previous week. Locally, heavy flights were reported from the Beaver Dam (237 moths), Burlington (168 moths), Fitchburg (92 moths), and Mayville (127 moths) monitoring locations, while 10 other sites from Dane to Marathon counties collected fewer than 50 moths per trap.
A cumulative total of 1,148 moths have been captured as of August 22. The recent escalation in corn earworm activity signals that egg laying is intensifying and management programs should be underway for fresh market and processing sweet corn. Treatment schedules based on nightly corn earworm moth trap catches are available at: Commercial Vegetable Production in Wisconsin—2024 (A3422 pg. 278). |
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DATCP has a long history of conducting fall surveys for the European corn borer (ECB). The survey evaluates the extent of damage caused by the second-generation of ECB larvae and forecasts the potential size of the overwintering population. Recent confirmation of field-evolved resistance to Cry Bt proteins identified in ECB populations in Canada and the eastern U.S. have given this historic survey renewed importance.
For the 2024 ECB survey, our program is looking for non-Bt corn fields to scout for larvae and damage. The goal of surveying both Bt and non-Bt fields is to gain a more accurate understanding of ECB pressure (particularly in non-Bt fields where populations are likely higher) and to determine areas of the state where ECB populations may be recovering. Non-Bt corn sites are most needed in Columbia, Dane, Dodge, Grant, Lafayette, and Rock counties.
Corn growers, crop advisors, and Extension educators who have or know of non-Bt corn fields that could be assessed for ECB are asked to email krista.hamilton@wisconsin.gov with:
- Your name
- Phone number
- Field location (county, GPS coordinates, and description of field)
We are hoping to sample 40-50 non-Bt fields between September 3 and October 25. The survey is not destructive and involves examining 25 consecutive corn stalks for signs of ECB infestation and dissecting two stalks to count larvae. Fields that are relatively accessible from a roadside are preferred. Growers will be notified of the ECB population in their fields once the survey is complete.
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