Current Wisconsin weather and climate conditions

• Precip was statewide last week, but especially concentrated in the south and southeast, topping 5-10”. Overall, the last 30 days in WI have been above average for those in the south and west-central, with below normal totals for most of central and northern WI.
• August has gotten off to a warmer-than-normal start by 2-6°F, and GDD accumulation (since 5/1) is still running well ahead of normal.

Impact

• After a relatively active week of precip, soil moisture is estimated to be above normal for most of SE, SW, and west-central WI. Wisconet research farm stations show increases in 4” soil moisture from last week.
• Wisconsin remains drought-free, with some minor increase in D0 coverage up north after a dry last 30 days.
• Crop progress for the major field crops in WI continue to run at a near-normal pace, with a third of the corn crop at 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 northern half of WI.
• Climate probabilities for Late August show a lean towards below-normal temperatures for all of WI (40-50% 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, especially those in the Eastern part of the state that experienced historic floods.
  • Assess flood damage to soybean and corn. ​
• 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.
  • 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 late-planted sweet corn and grain corn with remaining green silks.
  • 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).
  • 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.
  • Southern Rust has been reported in southern and central regions.
• Forage Management ​ 
  • Alfalfa stands are varying between third 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. Those affected by flooding can review flooded forage options.
  • 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. Read corn silage harvest management considerations.
• Small Grains​ 
  • Winter wheat harvest is mostly complete. 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
    • Sun scald and southwest injury to trunks and branches has been observed across many orchards and vineyards this summer, likely due to wide variations in winter temperatures that can cause trunk and branch damage.
    • Fruit sunburn has been observed across many fruit crops in southern WI. Consider removing this fruit while out picking to prevent other pests attracted to the volatiles released from impacting fruit.
    • 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 pheromone traps and degree-day (base 50℉) accumulation for Codling moth.
    • 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).
    • Grape berry moth has been observed in southern WI. Continue monitoring traps and using NEWA models.
    • 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.
    • 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
    • ​The second generation of adult crucifer flea beetles are active in central WI. Yellow sticky cards can be used to help determine their population. Treatment is recommended when 10-20% of a stand shows damage. Populations can be spotty across a field so spot treatment can be very effective.
    • Imported cabbageworm moths are expected to complete a third generation through the month of August. Be on the lookout for small yellow to orang colored eggs on the underside of leaves. Management strategies are most effective when based on crop growth stage and caterpillar count to determine the level of infestation.
    • Continue to be vigilant for squash bug adults. The predicted damage risk is high across the state. While younger plants are more susceptible to damage, large populations can cause wilting and feeding on fruit which can prevent development and lead to rot.
  • Diseases​
    • The first symptoms of brassica alternaria are pin sized black specks on the leaves or stem. As the lesions expand, they will form concentric rings and black, sooty spores form during periods of high humidity. Sources of inoculum include infected plant debris and brassica weeds. It is spread by wind, rain, and insects like flea beetles.
    • 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.
    • Anthracnose of cucurbits can infect all above ground plant tissue. Symptoms vary based on which cucurbit is infected. On melons and cucumber lesions are brown, irregularly shaped, and often have a yellow halo. On watermelons, the lesions are darker and smaller. Stem infections on melon will often secrete a red colored gum. Fruit lesions are black and sunken and salmon colored spores will form during high humidity. Winter squash and pumpkins are not often infected.
    • The last confirmed cases of cucurbit downy mildew in Michigan were detected over a week ago. Luckily, there are still no confirmed cases in WI. Downy mildew can be confused with many other stresses including angular leaf spot, heat stress and herbicide damage. Check out this resource from Michigan State to help with diagnosis. ​
    • 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. If early blight is problem on your farm, consider planting a resistant variety. While not immune, these varieties will not be as severely impacted.
    • 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.
    • Bacterial spot in peppers was recently diagnosed in Iowa county. Fruit lesions are often slightly raised, brown, and often occur on the stem ends of peppers.
    • Purple blotch in onions is caused by a fungus that leads to water-soaked lesions with concentric rings and red or purple borders. Leaves injured by thrips are more susceptible to infection. It can overwinter in crop residue so make sure to remove or till in infected residue to prevent carry over to the next year.

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