August 7th, 2025 Weather Outlook

Current Wisconsin weather and climate conditions

• Precip was concentrated in the south last week, with localized areas topping 2”. Overall, the last 30 days in WI have been at or below average for most, with above normal totals in the SW and NE.
• August has gotten off to a cooler-than-normal start for most of WI, with average temperatures for the last 7 days lagging normal by 1-3°F. However, GDD accumulation (since 5/1) is still running well ahead of normal pace.

Impact

• After a relatively quiet week of precip last week, soil moisture is estimated to be at near normal levels for most of WI. Wisconet research farm stations show slight decreases in 4” soil moisture from last week.
• Wisconsin remains drought-free, with isolated pockets of D0 covering <2% of the state.
• Crop progress for the major field crops in WI continue to run at near-normal pace as we head into August, with some corn beginning to hit dough stage. Crop condition reports indicate no major changes from last week (NASS).

Outlook for Wisconsin weather and climate

• Multiple rain chances are forecasted thru early next week, with the best chances for rain in the south/southwest.
• Climate probabilities for Mid-August show a lean towards above-normal temperatures for all of WI (50-70% likelihood).
• The outlook for all of August (updated 7/31) does not indicate strong probabilities of above- or below-normal conditions, but hints at the chance of warmer than average temperatures.

Agronomic considerations

• Field Work and Conditions
  • Avoid trafficking fields in moist conditions to prevent compaction. ​
• Manure Applications
  • Reminder of Wisconsin’s NR 151 Runoff Rules with the timing of manure spreading and current runoff levels. Check DATCP Runoff Risk Advisory Forecast.
• Pest Management ​ 
  • Scout fields to note which weed species escaped herbicide application.
  • As corn and soybean crops grow, note growth stages to time future applications and sampling.
  • Check moth trap catches in your region with the DATCP Pest Survey. Sign up for insect pest alerts specific to your region.
  • Routine scouting in corn to watch for corn earworm. Pay close attention to sweet corn.
  • Second generation true armyworm populations are present with several heavy infestations reported. Be actively scouting for this pest!
  • Note Japanese beetle populations in soybean fields.
  • Use the VDIFN model to see risk in your region for several economically important pests.
  • Scout for soybean aphid and soybean gall midge (SGM not presently in Wisconsin; however, the pest has been located in nearby states).
  • Scout for tar spot as it has been reported in Wisconsin. Have a plan in place to deal with tar spot if it becomes an issue. Northern regions of the state still have fungicide application opportunity. Check out the latest disease update.
  • Be vigilant for white mold in soybean as plants flower in northern regions. See risk forecast here. Check out the new White Mold ROI calculator.
• Forage Management ​ 
  • Alfalfa stands are varying between second and fourth cuts depending on location in the state. Scout for potato leafhopper. Also scout for pea aphid.
  • Use the alfalfa cutting tool to plan remaining alfalfa harvests for persistence.
  • Recording when silage tassels can help predict harvest date. Consider in-field management strategies to reduce mycotoxins in silage. Begin sampling and estimating moisture as silage matures.
• Small Grains​ 
  • Winter wheat and oat harvest is underway. As you harvest, remember the importance of combine cleaning to prevent weed seed spread from field to field.
  • Consider planting a cover crop after small grain harvest. Review Cover Crops 101 for a list of viable species and seeding recommendations. Cover crops can also be an opportunity for grazing.
• Specialty crops- Fruit​
  • General
    • Sanitation: remove and destroy (chop/compost) fallen fruit ~weekly to prevent any internally developing larvae from reaching maturity, and to limit the spread of disease.
    • Japanese beetle pressure has lessened in Southern WI, though emergence may continue through September. Review best monitoring and management practices here.
  • Apples​
    • Apple and grape growers can reference the NEWA weather station network to monitor for disease infection periods in their area. Check out your nearest weather station: NEWA Weather Station Network (Cornell).
    • Warm and rainy weather conditions are ideal for bitter rot in apple orchards; see the article on bitter rot management from the July 4 WI Fruit newsletter.
    • Sooty blotch and flyspeck has been observed in Southern WI, pushed along by warm, humid conditions. Continue monitoring NEWA models.
    • Apple growers should continue monitoring degree-day (base 50℉) accumulation for Codling moth. Several locations in Southern WI have hit 300 degree-days base 50F from second generation biofix.
    • Apple maggot pressure is variable across the state. Growers should continue to use red sphere traps to monitor populations.
    • Check out the WI DATCP Orchard Insect Pest Bulletin for more information on current insect trap captures across the state.
  • Grapes​
    • Several grape varieties (Frontenac, Marquette) have hit veraison in the last week or so. This may translate to increased bird and disease pressure (sour/bunch rot).
    • Black rot fruit symptoms have been reported in vineyards around WI. Review this 2022 article by Dr. Leslie Holland on Fruit and Cluster Rots for more information on black rot and fruit rot management.
    • Downy mildew foliar symptoms (“oil-stains”) have been observed in West Madison. Scout for pale-yellow lesions on the tops of leaves and white downy growth on the underside of leaves.
    • Overview of grape insect/mite monitoring and management: Grape Insects and Mite Pests, 2024 Field Season (Cornell, 2024).
  • Berries
    • Grape and berry growers monitoring spotted wing drosophila should continue checking and refreshing traps weekly.
• Specialty Crops- Vegetables​
  • Pests
    • ​Adults from the second generation of imported cabbageworm are emerging in southern WI and large larva are present in central and northern WI. Be on the lookout for eggs through August as they complete a third generation. Management strategies are most effective when based on crop growth stage and caterpillar count to determine the level of infestation.
    • Reports of squash bug adults have increased in the last week. The predicted damage risk is high across the state.
    • Western bean cutworm damage risk is high across northern WI. This resource can help distinguish between WBC and other sweet corn pests.
    • While overall true armyworm activity is decreasing, the risk for crop damage remains high. They primarily feed on grasses like sweet corn, but they can also be a pest of many other vegetables including cabbage, carrot, onion, and pepper.
    • Continue scouting for European corn borer egg masses. Second generation larva will be starting to hatch and can cause heavy damage to mid and late planted corn. In addition to sweet corn, European corn borer can also cause damage to snap beans, peppers and potatoes.
  • Diseases​
    • Basil downy mildew has been detected in Dane and Columbia counties. Sweet green-leafed varieties are more susceptible than purple-leafed or Thai basil. Initially, symptoms may resemble nitrogen deficiency because of general leaf yellowing of lower leaves. As it progresses, leaves will turn brown, may curl and wilt, and grey velvety fuzz may develop on the underside of leaves. Check out this resource for other problems that can be confused with downy mildew.
    • Cucurbit downy mildew has now been confirmed on cucumbers in 11 Michigan counties. There are currently no confirmed cases in WI, but early detection is key so be on the lookout for angular lesions that are initially contained within leaf veins. Downy mildew can be confused with many other disease including angular leaf spot, heat stress and herbicide damage. Check out this resource from Michigan State to help ensure you are correctly diagnosing the symptoms.
    • While scouting your cucurbits also keep an eye out for powdery mildew. Symptoms are pale yellow leaf spots that progress into white powdery spots on both the upper and lower leaf surfaces. Powdery mildew reduces yield and fruit quality because of sunscald, uneven ripening and reduced storability.
    • Septoria leaf spot was confirmed on tomato plants in Walworth county. Disease can survive on infected debris and then is spread by water splashing as well as equipment, people and insects moving through wet leaves. Lesions are tan to grey with dark margins and often a yellow halo.
    • Early blight risk is high across the state. Lesions can occur on both fruit and stems. One way to distinguish this from other diseases is the larger lesions will have concentric rings. This pathogen can overwinter on infected plant debris so make sure to either till in or remove any infected plant tissue at the end of the season. If early blight is problem on your farm, consider planting a resistant variety. While not immune, these varieties will not be as severely impacted if infected.
    • Late blight of potato and tomato has been confirmed in Pennsylvania and New York. All plantings of potatoes should have preventative fungicide treatments applied.
    • Nicotianae blight, a late blight look alike, was identified this past week on potato plants in central WI. The causal pathogen often infects roots and tubers causing pink rot, but occasionally lesions form on leaves. While foliar lesions look very similar to late blight, one way to distinguish between the two is that these lesions do not have the spores that are a symptom of late blight. Photos comparing the lesions can be found here.

If you would like to obtain a PowerPoint copy of this report, please email anastasia.kurth@wisc.edu.