Current Wisconsin weather and climate conditions

• Multiple days of precip last week brought 2” or more across most of southern and west-central WI, with pockets of 5+”. Precip in the south and west-central was well above normal over the past 30 days, while the north has been abnormally dry.
• Temperatures were warmer than normal last week by 2-4°F for most of WI, with 3-5°F above normal further to the south.

Impact

• After a relatively active week of precip, soil moisture is estimated to be above normal for most of SE, SC, and WC WI. Wisconet research farm stations show increases in 4” soil moisture from last week at most sites.
• Drought remains non-existent in WI with no change in coverage from last week.
• Corn silking and winter wheat harvest are nearly complete, with pod setting complete in 81% of soybean fields. Crop condition reports indicate 82% of corn and soybean rated good to excellent (NASS).

Outlook for Wisconsin weather and climate

• Rain is most likely in the north over the next few days, but the beginning of next week is looking dry.
• Climate probabilities for the August-to-September transition show a lean towards below-normal temperatures and precipitation.
• The outlooks for the month of September and for fall (Sep-Nov) (updated 8/21) show a lean towards above normal 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 ​ 
  • 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).
  • Southern Rust has been reported in southern and central regions.
  • DATCP fall armyworm traps picked up large flights this week in southern Wisconsin. Egg-laying may be occurring in late-planted corn fields. Also be vigilant of activity in alfalfa fields. Pay attention to trap catches through mid-September. 
• 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.
  • Foliar disease presence can make silage harvest timing critical. Read these considerations for managing disease at chopping.
• 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 peak of the second generation of adult Colorado potato beetles is occurring across the state. Be on the lookout for eggs on eggplants, potatoes, peppers. Chemical treatments should be timed to coincide with egg hatch as the very early instars are most susceptible for chemical control. Detailed management info can be found here.
    • The second generation of European corn borer adults are very active across central WI. Scout for egg masses in beans, eggplant, peppers, potato, and sweet corn. Economic thresholds and management options for these crops can be found here.
    • Corn earworm moth catches are up in WI. The risk to late planted sweet corn is high as egg laying activity is now increasing. Sweet corn is vulnerable from row-tassel to 100% silk. Insecticides must be present on vulnerable silks when eggs hatch. Organic control options can be found here, and conventional insecticide options can be found in the commercial vegetable production guide.
    • 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.
    • Squash bug populations are high across the state. Older plants are less susceptible to damage. However, large populations can cause wilting and feeding on fruit can prevent development and lead to rot. Remember chemical controls are most effective on young nymphs rather than older, larger nymphs or adults. View the commercial vegetable production guide for conventional options and ATTRA for organic control options.
  • 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.
    • 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.  
    • 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. Copper can be used as preventative or very early on in disease development. Other control options can be found here. Be sure to remove or bury diseased tissue at the end of the season to the reduce the chances of the pathogen surviving the winter.
    • Conditions are right for the development of septoria leaf spot. Lesions are tan to grey with dark margins and often contain very small black specks called pycnidia which are the fungal structures that produce spores. Symptoms often appear on the lowest leaves first. Like early blight, copper and chlorothalonil can be useful as preventative treatments.
    • 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.