By Becky Wiepz and Dan Kielar
Warm temperatures and continuing rain events mean that fungal pressure is high in all crops and should be diligently scouted and managed.
Spotted Wing Drosophila has been caught in Southern Door, Egg Harbor, and Sister Bay! Cherries are not vulnerable yet but monitor your closest Wisconet Station to know when to protect your orchard.
| Date 5/30 | 2020 | 2021 | 2022 | 2023 | 2024 | 20-year avg. |
| Base 50 | 211.5 | 289.5 | 245 | 315 | 368.5 | 293 |
GDD50 continues to be approximately 7-10 days ahead of the 20-year average.
Apples
Hormonal thinners like NAA and MaxCell are most effective while fruit is still small. The Carbohydrate Thinning Model on NEWA can help determine your tree’s responsiveness to chemical thinners.
As fruitlets approach 20mm in diameter, read more about your thinning options in this article from Amaya Atucha at UW Madison.
Insects
Codling moth has been caught but most orchards have not reached biofix yet. 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 reference in the Midwest Fruit Pest Management Guide.
Leafrollers and Spotted Tentiform Leafminers are a continued presence in many orchards and Scale species should be close to their crawler stage when they are vulnerable to insecticides and biological enemies.
Disease
Two Apple Scab infection periods occurred in the last week at the Station. Pressure continues to be high and full cover sprays are needed on tight windows to protect new growth.
Powdery Mildew pressure is high this year and occurring earlier than usual. If your block has a history of Powdery Mildew, scout your orchard and apply effective treatments in a timely manner. Check the Midwest Fruit Pest Management Guide for efficacy ratings of different chemicals.
Fireblight blossom infection risk has passed, and while there was low risk for potential infection, growers should scout for strikes in the next couple of weeks and remove them promptly with a cut twelve inches past the end of the canker.
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
Most orchards are out of the shuck.
Insects
Spotted Wing Drosophila has been caught throughout the county. Cherries are not yet vulnerable but be sure to monitor the SWD model on Wisconet at your local station to time your sprays when they reach that stage.
Fruit is vulnerable to Plum Curculio damage now that is is out of the shuck but no scars have been found during station scouting yet. 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.
Disease
Cherry Leaf Spot pressure is high based on the predictive models and the scouting results. Active lesions are present in many orchards throughout the county. Full cover sprays on a tight schedule are critical to protect new growth until constant rain events subside.
Powdery Mildew is 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 inches of growth. Scout your vineyard for Downy and Powdery Mildews and apply fungicide as needed.