June 7, 2024


    By Becky Wiepz and Dan Kielar

    With continuing rain events in the forecast every few days it is critical to get fungicide coverage on when possible. Rotating modes of action in all crops is essential for minimizing resistance development, especially in high pressure years like this, so be sure to check the FRAC numbers of each chemistry before application. Using a compatible spreader-sticker in your tank mix can also help treatments to be effecting for longer.

    Powdery Mildew (PM) pressure, in particular, is high in all crops. Remember that PM is a different organism family than Cherry Leaf Spot or Apple Scab and requires unique products for management. Visit the Midwest Fruit Pest Management Guide to check efficacy for different fungicides in your crop.

    Spotted Wing Drosophila has been caught throughout the county! Cherries are not vulnerable yet but monitor your closest Wisconet Station to know when your orchard needs protection.


    Date 6/72020202120222023202420-year avg.
    Base 50312420313439.5455373

    GDD50 is approximately 4-6 days ahead of the 20-year average.

    Apples

    Hormonal thinners like NAA and MaxCell are most effective while fruit is less than 20mm in diameter. The Carbohydrate Thinning Model on NEWA can help determine your tree’s responsiveness to chemical thinners. Read more about your thinning options in this article from Amaya Atucha at UW Madison.

    As fruitlets exceed 20mm in diameter, hand thinning becomes your only effective tool, so be sure to get as close to your ideal cropload as possible before then to minimize your labor inputs.

    Insects

    European Red Mite pressure is low in all blocks scouted but some leafhopper nymphs and Green and Rosy Apple Aphid adults were found in a few orchards.

    Codling moth has been caught and more blocks are at or beyond biofix. Stink Bug and Tarnished Plant Bug are present in some blocks; those with a history of damage should consider treatment using an effective insecticide as referenced in the Midwest Fruit Pest Management Guide.

    Leafrollers flight has started and Spotted Tentiform Leafminer and Green Fruit Worm Flight are ending or over.

    Disease

    Another two Apple Scab infection periods occurred in the last week in Sturgeon Bay. Pressure continues to be high and full cover sprays are needed to protect new growth. Initial spore dispersal is complete for the year and blocks with no initial pressure can consider stretching out their time between sprays to 10-14 days while continuing to monitor the forecast and NEWA’s Apple Scab Model.

    As I mentioned in the introduction, Powdery Mildew pressure is high this year and requires special management if found in your orchard. Check the Midwest Fruit Pest Management Guide for efficacy ratings of different chemicals.

    Remember that fungicides are almost exclusively protective, so it’s important to treat as soon as symptoms are present to prevent infection from moving onto new growth.

    Some Honeycrisp blocks are experiencing ‘Rat Tail Bloom’ an uncommon second bloom that can emerge from the bourse or vegetative shoot located adjacent to each initial blossom cluster. If your block is experiencing extensive rat tail bloom, you may consider a streptomycin application to prevent fireblight infection. The current wet weather and warmer temperatures are ideal conditions for fireblight infection and late blooms are a perfect entry point for the bacteria.

    To learn more about the apple scab and fireblight models from NEWA, visit the ‘Newsletters’ section of the Cornell Tree and Small Fruit Extension Resource Blog.

    Cherries

    Spotted Wing Drosophila continues to be caught throughout the county but cherries are not vulnerable yet, monitor your nearest weather station at wisconet.wisc.edu to time your SWD insecticide application.

    Insects

    Fruit is vulnerable to Plum Curculio damage now that is is out of the shuck but no scars have been found during station scouting. Be sure to use a non Pyrethroid (IRAC 3A) chemistry in order to save that chemical group for SWD management closer to harvest. Additionally, Pyrethroid use can cause flare ups in the European Red Mite population.

    Light Black Cherry Aphid feeding on some terminal shoots was found throughout the county along with minor damage from Lepidoptera species on fruit.

    Disease

    Cherry Leaf Spot pressure continues to be high. With the added challenge of finding times when wind and rain are absent, early season control has been very difficult to achieve. Active lesions are present in many orchards throughout the county and full cover sprays with rotating of modes of action are needed to limit continued spread of infection.

    Powdery Mildew is also present in many blocks and may require different products to manage than your CLS program. Check the Midwest Fruit Pest Management Guide to product efficacy.

    Do not use chlorothalonil based fungicides now that cherries are out of the shuck.

    GRAPES

    Grapes on the station are at 6-12 inches of growth and will approach pre-bloom in the next couple of weeks. Pre-bloom through berry touch is a critical time for fungicide application to protect the rachis of each cluster and prevent cluster rots after veraison.

    Now is an ideal time to shoot thin your canopy if needed.