Current Wisconsin weather and climate conditions

• Wisconsin was unseasonably cold last week, with some folks experiencing temps 10°F or more below average. Overnight lows dipped into the 30s on a few nights, even in central and southern WI.
• Rainfall was concentrated in the north last week, with the southern half of WI experiencing 0.5” or less. Conditions in the southern part of WI have been quite dry (50% or less of normal) over the past 2 weeks.

Impact

• After a relatively dry week, Wisconet research farm stations show decreases in 4” soil moisture from last week at most sites. The exception are northern stations, which showed a gain in topsoil moisture from the rainfall. Overall, soil moisture is rated >80% adequate.
• Drought remains non-existent in the state despite a drier-than-normal last 2 weeks for the southern half of WI.
• Corn and soybean progress are running 3-4 days behind normal pace, but reports indicate that 83-84% of corn and soybean fields are rated good to excellent (NASS). Potato harvest, winter wheat seeding, and 3rd/4th cutting of alfalfa are all underway.

Outlook for Wisconsin weather and climate

• Precip for the next 7 days is once again most likely to occur in the north, namely in the NW.
• Climate probabilities for mid-to-late September indicate a strong lean (50-60% chance) towards warmer-than-normal conditions.
• The outlooks for the month of September (updated 8/31) are uncertain for temps and precip with equal chances.

Agronomic considerations

• Field Work and Conditions
  • With a warmup this week, frost chances are negligible .
  • Recent cooler weather may be impacting corn grain and silage maturity.
• 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.
  • Scout for evidence of soybean gall midge (SGM not presently in Wisconsin; however, the pest has been located in nearby states) which can indicated with dead/wilted plants along field edges. This can indicate maggot infestation. Active feeding is over; however damage can be apparent in the fall. ​
  • Monitor for corn earworm through mid-September. 
  • Southern Rust has been reported across the state. Heavy disease pressure can cause premature dry down, reduced kernel weight, and lower yield potential.  
  • Fall armyworm 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 ​ 
  • Use the alfalfa cutting tool to plan remaining alfalfa harvests for stand persistence.
  • Consider in-field management strategies to reduce mycotoxins in silage. Begin sampling and estimating moisture as silage matures. Read corn silage harvest management considerations.
  • Silage chopping has begun in the southern region of the state. Foliar disease presence can make silage harvest timing critical. Read these considerations for managing disease at chopping.
  • Explore the new Corn Silage Dry Down Monitoring Tool to see what samples are measuring at in your region.
  • Consider planting a cover crop after silage. This will aid in reducing soil erosion going into winter.
• Small Grains​ 
  • The window to plant winter wheat is approaching (September 20-October 10). Review planting and management guidelines as well as Top 9 suggestions for 2025 establishment.
• Specialty crops- Fruit​
  • General
    • Reminder: Always read and follow directions on the label and keep in mind pre-harvest intervals (PHI) as we move through harvest!
    • Growers who experienced heavy rainfall and flooding in the past month should review best practices for identifying and preventing root rots: Rainfall and root rots in commercial fruit operations (University of Connecticut)
    • 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 to prevent other pests attracted to the volatiles (scent).
    • 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.
    • 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.
  • 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).
    • Sooty blotch and flyspeck continues to be 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​
    • Table grape harvest has begun, with wine grapes soon to follow at West Madison Ag. Research Station. Check out last weeks WI Fruit Crop Scouting Report for updates on grape maturity testing.
    • Black rot and fruit rot 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 through harvest.
• Specialty Crops- Vegetables​
  • Pests
    • Be on the lookout for cabbage aphids which are white to grey in color. The aphids themselves may be difficult to see so look for yellowing and wilting leaves, deformed heads, and drops of honeydew aka aphid waste which is a thick, sticky liquid. Their populations can explode quickly in the fall as reproduction rates actually increase in cool temperatures (50-68°F).
    • Tarnished plant bug also known as lygus bug risk is high in northern WI. While tarnished plant bugs prefer plants that are budding or flowering, they will move into nearby vegetable crops if flowering weeds are terminated or dry down. The adults are extremely mobile so it is best to use a sweep net to scout for adults and nymphs either in the early morning or late afternoon/early evening.
    • The recent dry weather means that the risk of damage from western flower thrips is high across much of the state. Thrips can be difficult to control as of result of their small size and their tendency to hide. Control options can be found here.
    • While the peak of the second generation of adult Colorado potato beetles is occurring in central and northern WI, larva populations are decreasing. Remember that the impact of insecticides on adults is minimal. Detailed management info can be found here.
    • The second generation of adult crucifer flea beetles are active in northern 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.
  • Diseases​
    • Potato yield and tuber size can be negatively affected by silver scurf and black dot. These diseases can both occur on the same plant and are difficult to distinguish. An important management strategy for both diseases include limiting the amount of time between vine kill and harvesting as tubers are at greater risk the longer they remain in warm, moist soil. Read Dr. Amanda Gevens’ newsletter for more information on the life cycle and management of both diseases.
    • When possible, harvest mature winter squash rather than let it sit in the field. During rain events, fruits can become infected by the soil dwelling pathogens fusarium and phytophthora. Additionally, as vines die back, squash bugs will be more attracted to the fruit. The damage caused by their feeding can provide entry points for diseases.
    • Scout for symptoms of alternaria and cercospora on carrot leaves. These diseases can be difficult to tell apart as both cause brown lesions often surrounded by a yellow halo. One distinguishing factor can be the timing of infection. Cercospora often occurs on young, rapidly growing plants while alternaria often occurs on older plants although can occur on young plants as well. Both can cause yield loss due to petioles breaking off during mechanical harvest is disease pressure is high.
    • Angular leaf spot has been commonly diagnosed on cucurbits in recent weeks. Symptoms may be confused with downy mildew as lesions are angular and bound by leaf veins. A few ways to help distinguish them is that angular leaf spot often starts as small water soaked lesions on the underside of leaves, the lesions will turn white and papery as they age, and under humid conditions milky colored ooze may form on the spots. The bacteria can survive on plant debris for up to two years. Either remove and destroy or till in infected plant tissue at the end of the season.
    • 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.

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