Current Wisconsin weather and climate conditions

• Summertime warmth returned to WI last week, with daily highs topping 80°F and weekly averages several degrees above normal. This is following what had been a very fall-like beginning to September.
• Precip totals were light for most last week, with totals of less than 0.5” common. However, some localized areas in the north, northwest, and south-central regions received over 2”. The last 30 days have been drier than normal for most.

Impact

• Most Wisconet research farm stations saw a decline in soil moisture in the top 4” last week following a relatively dry week, with the latest NASS report indicating increases in the percentage of topsoil that is dry to very dry.
• Despite the dryness in recent weeks, WI is still drought free. However, D0 has been added along the WI-IL border.
• Corn and soybean progress are running 2-3 days behind normal pace, but reports indicate that 81% of corn and soybean fields are rated good to excellent (NASS). Corn is reported to be hitting maturity in 17% of WI fields.

Outlook for Wisconsin weather and climate

• The next 7 days are looking more active for precip statewide, with multiple rain chances through early next week.
• Climate probabilities for late September indicate an increased likelihood (70-80% chance) for warmer-than-normal conditions.
• The outlooks for the month of October (updated 9/18) do not show any strong indications of above or below normal conditions.

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 ​ 
  • Silo gas has been present around a variety of silage storage structures this year. Be aware of the dangers of silo gas and stay away from recently filled structures, particularly when the weather is calm with no wind.
  • 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!
    • 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.
    • Brown marmorated stink bug has been observed at West Madison. Keep an eye out for large populations. Hosts include apple, cherry, peach, pear, raspberry, and cranberry.
  • 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 and wine grape harvest is just about wrapped up at West Madison Ag. Research Station. Check out last week’s 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 can be difficult to see so look for yellowing and wilting leaves, deformed heads, and drops of honeydew aka aphid poop which is a thick, sticky liquid. Their populations can explode quickly in the fall as reproduction rates actually increase in cool temps (50-68°F).
    • The recent dry weather means that the risk of damage from western flower thrips is high. Thrips can be difficult to control as of result of their small size and their tendency to hide. However, there are many tactics that can be combined for better management. Options include promoting more beneficial insects such as minute pirate bugs, using reflective mulch, and chemical control. More details on control options 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​
    • This year’s moisture stress combined with high temperatures can increase the risk of potato tuber diseases this time of year. Test dig potatoes to look for pink eye, enlarged lenticels, and other physiological conditions. If you notice any of these abnormalities, make sure you are carefully monitoring for disease in storage. Diseases to be monitoring for include pink rot, late blight, pythium leak, and bacterial soft rot. More information on symptoms and management options can be found here.
    • 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. 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. Additionally, during rain events, fruits can become infected by the soil dwelling pathogens fusarium and phytophthora.
    • 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.
    • Despite the relatively dry weather, recent conditions with warm days, cool nights, and heavy dew in the morning are right for the formation of alternaria in brassicas. Leaf spots are grey or black in color and have concentric rings as they enlarge. It can be spread by rain, wind, and insects like flea beetles. Although due to their larger size, spores cannot travel as far on the wind as downy or powdery mildew spores. Management options include planting resistant varieties, removing alternative hosts such as sheperd’s purse and field mustard, and fungicides. 
    • Powdery mildew is common after this year’s wet and humid conditions. Remember that fungicides are preventative in nature and while they can help slow the disease when first detected, they will not provide any benefit once the disease has progressed. Powdery mildew is an obligate parasite meaning that it needs a living host to survive. Once there is a killing frost in your area, the pathogen will die along with the plant tissue. Keep in mind that winter squash from infected plants will likely have a reduced storage life. 

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