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A cooler weather pattern with crisp nights and mild days replaced last week’s heat and humidity. Temperatures across Wisconsin were seasonable for early August, with highs in the 70s and 80s and overnight lows ranging from the 40s to mid-60s. Aside from rain showers and storms August 5-6 following the passage of a cold front, conditions were mostly dry and favorable for fieldwork. According to the latest USDA NASS Crop Report, winter wheat was 86% harvested at the start of the week, eight days ahead of last year and nine days ahead of the five-year average. The third cutting of hay was 48% complete, two days behind last year but one day ahead of the average. Reports from apple orchards in the state indicate that this season’s apple crop is 10 days to two weeks ahead of the usual development pace and growers are preparing for an early harvest.
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DATCP’s annual corn rootworm beetle survey is now in progress. Crop scouts have so far sampled approximately one-quarter of the 230 survey sites, and it is still too early to speculate on this year’s corn rootworm pressure. Beetle counts in the 63 grain corn fields sampled as of August 8 have been mostly below the economic threshold of 0.75 or more beetles per plant, with 47 fields (75%) averaging low counts of 0.0-0.4 beetles per plant and five sites (8%) having moderate beetle counts in the range of 0.5-0.7 per plant. Above-threshold averages have been observed at 11 (17%) of the sites so far, including very high counts of 2.6-7.1 beetles per plant recorded in individual corn fields in Dane, Grant, Iowa, Lafayette, and Pierce counties.
Corn producers should be aware of the potential for corn rootworm adults to redistribute from earlier silking fields to later-planted fields as beetle emergence continues. Now is the time to scout to determine this season’s beetle pressure and forecast the risk of larval root injury to continuous corn in 2025. DATCP’s survey is expected to be finalized by the end of the month. |
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The western bean cutworm moth flight has been underway since mid-June and is currently the second largest on record for Wisconsin. DATCP’s network of 69 pheromone traps has captured a cumulative total of 14,654 moths, or an average of 212 moths per trap since emergence began eight weeks ago. This preliminary count is approaching the all-time record of 9,351 moths in 42 traps (223 moths per trap) set last season and is the second highest in the 20-year history of western bean cutworm monitoring in the state.
Moths are still appearing in high numbers in northern survey traps, but counts across southern sites have decreased markedly since the flight peaked July 19-25. Most of DATCP’s 69 monitoring locations reported lower counts this week, the exceptions being sites in northeastern Wisconsin, including one anomalous Marinette County trap that captured a remarkable 1,095 moths. The network’s total weekly capture of 2,678 moths is a sharp decline from 4,765 moths last week and 3,658 moths the week before.
As was the case in 2023, this season’s large moth emergence is expected to produce localized heavy larval populations in the central and southern areas of the state with a history of higher western bean cutworm pressure. The survey map also shows an expanded area of high trap counts in the northwestern and northeastern regions, which is uncharacteristic for this pest and may be attributed to low overwintering mortality during the mild 2023-2024 winter.
For regional western bean flight data extending across the northeastern U.S. and adjacent Canadian provinces, please see the Great Lakes and Maritimes Pest Monitoring Network (select WBC tab). The Great Lakes map also indicates counts have peaked and are declining across most monitoring areas. |
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Annual surveys for the European corn borer (ECB) began in Wisconsin in 1942 and have been conducted each fall for the last 81 years. The survey determines the extent of damage caused by the second-generation of larvae and forecasts the potential size of the overwintering population. For roughly 55 years between 1942 and 2000, ECB was the one of the most costly and damaging corn insects in the state, but the commercialization of Bt corn in the late 1990s was a turning point and Bt corn has effectively controlled ECB for a quarter of a century.
Although Bt corn remains the standard for ECB management, cases of Bt trait failure are increasing and have given the historic ECB survey renewed importance. Since 2018, ECB resistance to Cry Bt toxins (e.g., Cry1Ab, Cry2Ab2, Cry1A.105, and Cry1F) has been documented in parts of Canada (Quebec, Nova Scotia, Manitoba) and in 2023, ECB resistance to Cry1A.105 and Cry2Ab2 Bt traits was confirmed in Connecticut, the first case in the U.S. If this trend continues, corn producers may lose their most effective ECB management tool.
For the 2024 ECB survey, DATCP’s Pest Survey Program is looking for non-Bt corn fields to scout for ECB larvae and damage. The goal of sampling 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 populations may be recovering. Corn growers, crop advisors, and Extension educators who have or know of non-Bt corn fields that could be potential survey sites 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 September 3 to 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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