Current Wisconsin weather and climate conditions

• Last week was quite dry across most of WI, with only the far north receiving near-normal precip totals. Elsewhere, totals were a tenth of an inch or less. The past 30 days remain wetter-than-normal in the south from storms earlier in August.
• Cooler-than-normal temps were common last week, with lows dipping into the upper 30s and low 40s on August 25-26. This is a switch from what has been a warmer-than-normal past 30 days.

Impact

• After a relatively dry week, soil moisture is estimated to be near normal for most of the state, with some dry pockets in the N and E. Wisconet research farm stations show decreases in 4” soil moisture from last week at most sites.
• Drought remains non-existent in WI, with some D0 removal in the far northwest following the rains last week.
• Nearly all the corn and soybean crops are in the reproductive phase of their growth cycle, with winter wheat harvest nearly complete. Crop condition reports indicate 83% of corn and soybean rated good to excellent (NASS).

Outlook for Wisconsin weather and climate

• Precip for the next 7 days is once again predicted to be highest in the north, with chances statewide for measurable precip.
• Climate probabilities for early September show a strong lean towards below-normal temperatures for most of WI (50-60% chance).
• 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.
  • 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).
  • An increase in corn earworm moth activity in the last 2 weeks signals a high risk of egg laying in sweet corn with green silks. Monitor pest activity through mid-September.
  • 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.
  • 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 southwestern region of the state. 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
    • 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 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.
  • Apples​
    • Oblique banded leafroller larvae were observed in Southern WI. Monitor traps and scout for “catfacing” injury in apples and pears to help identify any large populations.
    • 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.
  • Grapes​
    • Many grape varieties have hit veraison in the last week or so. This may translate to increased bird and disease pressure (sour/bunch rot).
    • 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.
• Specialty Crops- Vegetables​
  • Pests
    • Green peach aphids continue to be observed in central and northern WI. These aphids can transmit many viruses including Potato Virus Y and cucumber mosaic virus. Make sure you are scouting frequently to determine if aphids are present and if populations are increasing or decreasing. Thresholds for several crops can be found here.
    • 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 and northern 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.
• Diseases​
  • Phytophthora crown and fruit rot can infect a large range of fruiting crops including cucurbits and solanaceous crops (tomato, pepper, eggplant). Crown rot will cause the entire plant to collapse and die in a short period of time. Vines will turn brown and appear water soaked before collapsing. Symptoms on fruit often appear on the underside of fruit where it is contact with the ground, but they can also start around stem if the infection is systemic. Lesions appear water soaked and under humid conditions, sporangia may form that are similar in appearance to yeast. Water management is one of the best cultural controls for this disease. Other management options can be found here.
  • 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.
  • Continue monitoring for septoria leaf spot. Common sources of infection include diseased plant debris in the soil and contaminated equipment. 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.

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