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Mostly hot, humid weather with periods of light rain prevailed in Wisconsin during the second week of August. Daytime temperatures were a few degrees above normal and ranged from the 70s to upper 80s, while lows were in the 50s and 60s. Accumulated precipitation August 4-10 varied from 0.01 to 1.0 inch in the east-central area near Lake Winnebago.
Despite the modest increase in rainfall this month, crop conditions are still tenuous and an estimated 82% of the state remains under moderate (D1) to exceptional (D4) drought. According to the U.S. Drought Monitor released August 8, exceptional (D4) drought has now been introduced into Wisconsin for the first time since the Drought Monitor started in 2000. The D4 area includes the northernmost part of Bayfield and Douglas counties.
Crop development has been adversely impacted by this summer’s prolonged dryness and heat. Many corn fields are exhibiting poor ear and kernel formation, soybean fields are heavily infested with spider mites and plants are flipping leaves to preserve moisture, and growth of third-crop hay has been significantly reduced, with 55% of the crop now rated in poor to fair condition.
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DATCP’s annual corn rootworm beetle survey began August 1 and is approaching the halfway point. Counts in the 100 grain corn fields sampled so far have been mostly low, with 72 fields averaging low counts of 0.0-0.4 beetles per plant and 11 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 17 of the sites as of August 10, a sharp drop from 33 fields with economic beetle counts in the same counties in 2022. The 2023 running average of 0.5 beetle per plant compares to 1.0 beetle per plant at this time last season.
Although early indications suggest that rootworm pressure may be down from 2022 levels, the survey is only partially complete and beetle emergence has not yet peaked for much of the state. 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 2024. DATCP’s survey includes 230 cornfields and is scheduled to be finished by the end of the month. |
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The 2023 western bean cutworm moth flight currently underway has already been the largest on record for Wisconsin. DATCP’s monitoring network of 42 pheromone traps has captured a cumulative total of 8,854 moths, or an average of 211 moths per trap since the survey began in mid-June. This preliminary count far surpasses the previous record of 4,804 moths in 36 traps (133 moths per trap) collected last season and is the highest in the 19-year history of western bean cutworm monitoring in the state.
Moths are still appearing in moderate numbers in survey traps, but counts across southern sites have decreased markedly since the flight peaked July 21-27. Most of DATCP’s 42 monitoring locations reported lower counts this week, the exceptions being sites in central and far northern Wisconsin and one anomalous Green Lake County trap that captured 270 moths. The network’s total weekly capture of 1,098 moths is a sharp decline from 2,674 moths last week and 3,431 moths the week before.
This season’s large flight is expected to produce localized heavy larval populations in the central areas of the state with a history of higher western bean cutworm pressure. Early-stage larvae have been observed in the last few days during surveys in Adams, Juneau, Monroe, and Trempealeau counties.
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 indicates counts have peaked across most of the monitoring region. |
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