Current Wisconsin weather and climate conditions

• Most of WI received 0.5” or more of rainfall over the last week. Higher totals of 2-4+” were observed near Eau Claire. Over the last month, spottier showers in south and north central WI have created below normal rain amounts in those regions.
• Warmer-than-average temperatures were seen across the state last week, with some days exceeding 90°F. This was a switch back to early July conditions after a slight cool-down in the middle of the month.

Impact

• Abnormally wet soil moisture conditions are common across the state with the continued shots of precip. Most Wisconet research farm sites experienced gains in 4” and 8” soil moisture from last week.
• Drought has been eliminated in the state, with the lowest drought coverage/severity in the state since July 2024
• Corn and soybean development are running at a pace near to the 5-year normal, with winter wheat and oat harvest both well underway. Condition for corn, soybeans, and wheat showed notable gains from last week (NASS).

Outlook for Wisconsin weather and climate

• Turning drier for much of the state over the next week, except for the southern region.
• Climate probabilities for early August show a lean towards above-normal temperatures for all of WI (40-50% likelihood).
• The outlook for all of August 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 and western bean cutworm. Corn earworm is likely to produce earlier than normal larval infestations this year. 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. Check out the latest disease update.
  • Be vigilant for white mold in soybean as plants begin to flower. See risk forecast here. Check out the new White Mold ROI calculator.
• Forage Management ​ 
  • Alfalfa stands are at or nearing second harvest with some starting a third cut in southern WI. Scout for potato leafhopper. Also scout for pea aphid.
  • Consider annual forage options for late season forage supply.
  • Recording when silage tassels can help predict harvest date. Consider in-field management strategies to reduce mycotoxins in silage.
• 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.
• 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
    • ​Western bean cutworms damage risk is high across central WI and will be moving into northern WI within the week. This resource can help distinguish between WBC and other sweet corn pests.
    • The second generation of true armyworms is now active in WI. Check the True Armyworm Trap Network data from DATCP for trap catches in your area. While they primarily feed on grasses like sweet corn, they can also be a pest of many other vegetables including cabbage, carrot, onion, and pepper.
    • Onion thrips can infest your plants throughout the season, but the risk increases when nearby alfalfa or small grains are harvested. Be on the lookout for white spots or streaking on leaves
    • Begin scouting for European corn borer egg masses in southern WI in the next week. 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.
      • There are confirmed cases of late blight of potato in Dufferin County Ontario and tomato in Cattaraugus County, NY. All regions of WI have surpassed the degree day threshold and should spray preventative fungicide treatments if they have no done so already.
      • The risk is high for botrytis leaf blight of onions. Symptoms are small, white, oval-shaped lesions that are surrounded by a light green or silver halo. As the disease progresses, leaf tips will wither and yield can be negatively impacted. Scouting tips to distinguish botrytis lesions from other damage can be found here.

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