Current Wisconsin weather and climate conditions

• An active July 10-11 brought 2-4” or more across SW WI, bringing 30-day totals up to 130% or more of normal. Most of the state had 30-day precip totals that were 110% or more of normal, with areas in the east and far north running slightly below normal (less than 5”).
• The extreme heat took a break last week with no days topping 90°F. Temps were seasonal last week with most in the state within a degree of normal. 30-day temps were at least 2°F above normal for most, helping push GDD accumulation (since 5/1) to above-normal levels.

Impact

• Abnormally wet soil moisture conditions are common across the north-central and west where precip totals have been higher over the past month. However, most Wisconet research farm sites have 4” soil moisture that is still below beginning-of-season (May 1st) levels.
• Corn and soybean development are running at a pace near to the 5-year normal, with silking underway in corn and blooming approaching halfway done in soybeans. Pod setting has begun in some soybean fields. Condition for corn, soybeans, and wheat showed minimal change from last week (NASS).

Outlook for Wisconsin weather and climate

• Late July climate probabilities show a lean towards above normal temperatures and precip. The lean towards warmer-than-normal conditions is stronger in the south (50-60% likelihood).

Agronomic considerations

• Field Work and Conditions
  • Avoid trafficking fields in moist conditions to prevent compaction. ​
  • Corn and soybean are well into reproductive stages throughout the state.
• 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. ​
  • While slug issues have not been as severe this year, UW recently concluded monitoring populations weekly across the state with SlugNet. ​
  • 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: true armyworm, stalk borer, and European corn borer. ​
  • Use the VDIFN model to see risk in your region for several economically important pests. ​
  • 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.
  • Be vigilant for white mold in soybean as plants begin to flower and 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.
  • Consider annual forage options for later season forage supply.
  • Consider in-field management strategies to reduce mycotoxins in silage.
• Small Grains​ 
  • Winter wheat and oats are being harvested in select areas. As you harvest, remember the importance of combine cleaning to prevent weed seed spread from field to field.
• Specialty crops- Fruit​
  • General
    • Wisconsin fruit growers can reference the Midwest Fruit Pest Management Guide (MFPMG) for a list of registered products and recommended best practices. View the MFPMG Online or order a hard copy here: MFPMG Hard Copy.
    • Make sure newly planted fruit crops are getting enough water in this heat. Without irrigation, growth can stall during establishment. Irrigation frequency depends on soil type—sandy soils need water daily or every two days, while heavier soils like silt or clay can be watered less often by applying several days’ worth of water at once.
    • Japanese beetle has been observed in Southern WI. Review best monitoring and management practices here: Japanese beetle.
    • Apples​
      • Apple growers should continue monitoring degree-day (base 50℉) accumulation for Codling moth. Second generation larvae will typically emerge at ~1250 degree-days (base 50℉) from the biofix date. Ensure to refresh traps/lures and continue monitoring weekly.​
      • Apple maggot was captured in southern WI. Growers can use red sphere traps to monitor populations and establish a biofix date.
      • 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).
      • Woolly apple aphid has been observed in southern WI. Check for white “cottony” appearing tufts where leaf petioles meet branches.
      • Check out the WI DATCP Orchard Insect Pest Bulletin for more information on current insect trap captures across the state.
    • Grapes​
      • 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).
• Specialty Crops- Vegetables​
  • Pests​
    • 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
    • Tomato hornworms often do not warrant chemical control because their damage is often minimal, but if you have a large infestation of over 2 hornworm per plant consider spot treating the bad areas. Make sure to treat when the larva are small and more susceptible to an insecticide.
    • Regularly scout stems and the underside of leaves of squash and pumpkins for squash bugs and eggs. Depending on your scale either crush egg clusters or if chemical control in necessary, make sure to target the young nymphs that are most susceptible to chemical control. Visit the commercial vegetable production guide for control options. Organic options can be found here. 
    • Continue scouting for cabbage loopers, diamondback moths, and imported cabbage worms. Imported cabbageworm activity is high across the state and the second generation of cabbage loopers will be moving into the state in the week.
  • Diseases​
    • The recent hot and wet weather are prime conditions for many diseases to develop.
    • Stemphylium leaf blight is often spread by infected residue or alternative hosts including purslane, pigweed, and bull thistle. Control methods include removing or destroying infected residue, reducing damage from other diseases and insects, reducing periods of leaf wetness when possible and fungicides.
    • No new confirmed cases of late blight in tomato or potato in the past week in the US. The last confirmed case this year was over a month ago in Florida.
    • Early blight risk is high across the state. Early blight infects tomatoes, potatoes, eggplants, and peppers. Prevention is key and includes limiting periods of leaf wetness (when possible!) and increasing air flow through pruning. One way to distinguish this from other diseases is the larger lesions will have concentric rings.
    • Another disease of peppers and tomatoes that likes hot and humid conditions is bacterial spot. Both fruits and leaves can be affected. To prevent the spread of disease, only work in these crops when leaves are dry and sanitize pruners often.
    • Downy mildew has now been confirmed on cucumbers in 6 Michigan counties.
    • Alternaria leaf spot, also known as black spot, can infect leaves as well as broccoli and cauliflower heads. Leaf symptoms are black lesions with concentric rings and often a yellow halo. On heads, symptoms first appear as brown spots on otherwise healthy beads/curds. Weeds in the brassica family such as sheperd’s purse and field mustard can be alternative hosts. 
    • Continue scouting brassicas for black rot. Symptoms begin as yellow blotches along the leaf edge and then progress into V shaped lesions. Control methods include proper fertilization as N deficiency can make plants more susceptible, avoiding working in plants when wet, and maintaining good airflow through plant spacing. For conventional chemical control visit the Commercial Vegetable Production Guide. Organic options can be found here, but please check the label for usage in WI as this resource is provided by Cornell.

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