By Becky Wiepz and Dan Kielar
Fruit-set looks good in apple and cherry blocks throughout the county thanks to good pollination and warm temperatures mean many crops are quickly progressing through growth stages.
| Date 5/22 | 2020 | 2021 | 2022 | 2023 | 2024 | 20-year avg. |
| Base 50 | 113 | 230.5 | 188.5 | 230 | 292.5 | 212 |
GDD50 continues to be approximately 7-10 days ahead of the 20-year average.
Apples
The window for bloom thinning is complete soon and the window for use of hormonal thinners like NAA and MaxCell is here while fruitlets are still small.
To review or learn more about options for thinning, visit any of the following articles from the UW Fruit Program:
- Precision Chemical Thinning Recommendations
- Petal Fall Thinning Options
- Updates To Carbohydrate Thinning Model (Malusim)
- Short Videos: How To Use the Apple Thinning Models On NEWA
Insects
Codling moth has been caught, so first flight is beginning in the county. Blossom feeders including Pug Moths and other Lepidoptera species have been found in some blocks, and a heavy Green Fruit Worm and Spotted Tentiform Leafminer flight continues.
Oblique- and Red-Banded Leafrollers are a continuing presence in many orchards while European Red Mite populations are starting to rise.
Disease
Apple Scab pressure continues to be high as spore release is ongoing and wetting events are regularly occuring. Full cover sprays are needed on tight windows to protect new growth.
Fireblight risk has been listed as ‘low’ to ‘moderate’ for the next few days.
Fireblight risk is ‘High’ when the following conditions are met:
- A certain number of heat units must accumulate during bloom for a threshold level of inoculum to be reached;
- a wetting event is necessary after this point to wash the bacteria to their infection sites; and
- the average temperature is above 60F
You can gauge fireblight risk at your orchard using the NEWA Fireblight Model.
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 at petal fall.
Insects
There is no concern for insect pests in cherries right now. Scout for Plum Curculio after the cherries are out of the shuck.
Disease
Cherry leaf spot pressure is low based on the predictive models due to cool temperatures but continued wet weather means protective cover sprays should go out ahead of rains. Monitor your local Cherry Leaf Spot risk by visiting the ‘Wisconet Crop Models’ link from your nearest weather station at www.wisconet.wisc.edu.
Chlorothalonil based fungicides cannot be applied after shuck split.
GRAPES
Grapes on the station are at 6 inches of growth. The first fungicide application of the season should have been applied.