By Becky Wiepz and Dan Kielar
Insect populations continue to be high while current temperatures are pushing crop development and appear to be heading to a slightly early cherry harvest throughout the county.
Scale pests, both San Jose and Oyster Shell, are in some orchards. According the the NEWA model, Door county Orchards have not yet reached the crawler stage of development but Kewaunee county has so apply treatments accordingly. Monitoring for crawlers with double sided sticky tape traps around limbs is a good tool to help time insecticide applications correctly. This article from Christelle Guédot provides information on San Jose Scale and proper monitoring technique.
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.
PARS will be hosting an orchard and vineyard field day on Wednesday June 26, from 9:30am to 12:30pm. Join the UW Fruit Team to get updates on current research, discuss the growing season, and ask any questions you might have. For more information or to register call the station at 920-743-5406.
| Date 6/20 | 2020 | 2021 | 2022 | 2023 | 2024 | 20-year avg. |
| Base 50 | 484 | 674 | 503.5 | 587.5 | 654 | 567 |
GDD50 continues to be approximately 3-5 days ahead of the 20-year average.
Apples
Hormonal thinners are no longer effective as most fruit has surpassed 20mm in diameter. At this time, hand thinning is the only effective option. Removing excess fruit as soon as possible will lead to the greatest improvements in size and quality at harvest.
If using plant growth regulators to encourage return bloom, especially in Honeycrisp, applications should be completed after fruit reaches 30mm in diameter but before mid July. This article from Amaya Atucha provides information on rate and timing of different chemicals.
When choosing to apply foliar calcium to manage Bitter Pit, applications should start early and be applied frequently. However, you can learn more about the factors, other than Calcium, that contribute to Bitter Pit in this article.
Insects
European Red Mite pressure continues to be low throughout the region but Aphids, Stink Bugs, Tarnished Plant Bugs, and Borers (other than Dogwood Borer) continue to be caught in low numbers.
Codling Moth populations are very high this year and after reaching biofix last week, the second pesticide application should go out shortly.
Disease
This week had fewer wetting events for apple scab than previous and now that initial spore maturity is complete, time between sprays can be extended to 10-14 days while continuing to monitor the forecast and NEWA’s Apple Scab Model.
Powdery Mildew pressure continues to be high this year and can require different fungicides than those used to manage Apple Scab. Check the Midwest Fruit Pest Management Guide for chemical recommendations.
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.
Fireblight strikes may be appearing in orchards over the next few weeks, be sure to prune them out promptly to prevent spread within the tree. Additionally, remember that Strep is not an effective tool for managing shoot blight.
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
GDD continues to be ahead of last year and the twenty year average, so harvest appears to be slightly early throughout the region as cherries are currently straw color to blush.
Insects
Spotted Wing Drosophila continues to be prolific throughout the county but most cherries have not yet entered the ‘medium risk’ category. Monitor your nearest weather station at wisconet.wisc.edu to time your SWD insecticide application. In parts of the county, fruit is predicted to reach a vulnerable stage in about a week.
European Red Mite populations are low in all blocks, but avoiding Pyrethroid (IRAC 3A) chemistries can prevent ERM flare ups and will also save that chemical group for SWD management closer to harvest, which will help to prevent resistance development.
Large populations of borers are currently in flight and some leaf and fruit feeding is present. Additionally, some leaf roller larvae continue to be detected during sampling.
No Cherry Fruit Flies have been caught.
Disease
Some blocks are starting to see Sour Cherry Yellows Virus so be sure to check if yellow leaves in your orchard are due to Cherry Leaf Spot or Sour Cherry Yellows to manage properly. Sour Cherry Yellows exhibits green to yellow mottling and interveinal chlorosis of the leaves while Cherry Leaf Spot starts as purple spots on the upper leaf surface that develop white sporulation underneath and eventually turn brown. When sever Cherry Leaf Spot can lead to yellowing and leaf drop.
Powdery Mildew continues to be present in many blocks and may require different products to manage than your Cherry Leaf Spot program. The Midwest Fruit Pest Management Guide is a good resource to check product efficacy. For both Cherry Leaf Spot and Powdery Mildew, cover sprays should until terminal buds are set to protect new growth.
GRAPES
Grapes on the station are at pre-bloom and will reach bloom in the next week or so. We expect bloom to move quickly with the current high temperatures.