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Last week’s heatwave subsided and cooler weather prevailed in Wisconsin during the week ending July 25. Widely scattered, variable showers brought 0.1-3.0 inches of rain July 20-23, while daytime high temperatures in the mid-60s to upper 80s were well below stressful levels for corn and soybeans advancing through reproductive phases of development. Corn fields reaching the silking stage progressed 23 percentage points to 40% complete at the start of the week, five days ahead of last year and three days ahead of the five-year average (USDA NASS, July 22). In contrast, soybean development continued to lag behind the average, with 47% of the crop now blooming compared to a 57% five-year average.
Despite weekly fluctuations following downpours and severe weather events, crop condition ratings overall have remained consistent this month. Currently, about 61% of the state’s corn acreage is rated in good to excellent condition, the same percentage reported on July 1. Soybeans improved from 57% in good to excellent condition at the start of the month, to 60% as of July 22.
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Western bean cutworm moth counts have peaked across most southern and central Wisconsin trap locations and will begin to decrease in the week ahead. In the northern region (areas north of Wausau), the annual flight is still increasing and should peak July 26-August 8 as degree day accumulations reach 2,704 (modified base 38°F), the point at which 50% emergence is expected.
DATCP’s western bean cutworm monitoring network captured a weekly total of 3,091 moths July 19-25, compared to 2,805 moths the week of July 11-18. The current cumulative state count is 6,644 moths in 69 traps, or an average of 96 per trap. This week’s highest individual trap count of 357 moths was reported from Taylor in Jackson County, while the trap east of New Glarus in Green County captured 318 moths. These two sites and six others each registered 100 or more moths this week, including the trap near Durand in Pepin County, which caught 198 moths, its highest one-week count ever recorded. Based on the recent extremely high catches, larval infestations are probable for these areas in early August.
Although the primary scouting window for egg masses has closed across the south, there is still time to assess northern Wisconsin corn fields. Scouting requires checking 20 consecutive plants in five separate areas of the field for egg masses laid on the upper surface of the top leaves. The treatment threshold has been met if egg masses or small larvae are found on 5% or more of the plants. |
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The summer codling moth flight is underway in southern and central Wisconsin apple orchards. Counts this week ranged as high as 17 moths per trap, with six locations reporting above-threshold catches. High codling moth pressure is indicated by a weekly count of five or more moths per trap for orchards not using mating disruption (non-MD) and two to three or more moths per trap for orchards using mating disruption (MD).
For non-MD orchards with high codling moth counts in the range of 5-17 moths per trap, second generation pressure may be heavy and applying first controls at 250 degree days from the summer biofix is recommended. In contrast, orchards seeing low moth pressure as the second flight begins (less than five moths per trap for non-MD and 0-1 moths per trap for MD) can delay treatment until 350-400 degree days from the summer biofix. Most southern Wisconsin sites observed a second generation biofix around July 15, though some central Wisconsin orchards still have not established the biofix date as of July 25.
Codling moth traps should be checked regularly until the biofix is set and throughout August to determine the need for late-season control. An insecticide application is not necessary if trap counts do not exceed the economic threshold of five moths per trap per week. Growers are reminded to rotate control products between generations and review pre-harvest intervals before making an application. |
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Ash trees infested with the emerald ash borer (EAB) were found in Burnett County on July 13 and officially confirmed by USDA on July 18. Burnett is the third new county this season with an EAB detection (following Taylor and Washburn on April 29) and the last remaining county in Wisconsin to confirm EAB.
First discovered in July 2008 in Ozaukee County, EAB has spread to all 72 Wisconsin counties in just 16 years. DATCP, DNR, Tribal partners, and UW-Extension will continue to track the spread of EAB in the state and provide current distribution information through online maps. To see if EAB has been found in your community or to report a potential new detection in an area not yet infested, please visit the interactive Wisconsin EAB Detections map.
The rapid range expansion of EAB across North America has led to the destruction of millions of ash trees in its path. The DNR Forest Health Program reports that efforts are underway to identify and propagate surviving ash with potential resistance to EAB. Referred to as “lingering” ash, these resistant trees in combination with introduced biological control agents may eventually offer opportunity for ash recovery in Wisconsin and U.S. forests. |
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