By Becky Wiepz and Dan Kielar
While it’s still hot and humid, we seem to finally be getting a minor break in the rain. This is the window to get ahead of diseases and pests in all crops.
Spotted Wing Drosophila populations are very high throughout the region. Almost all small fruits and cherries are vulnerable once they start to change color and should be protected with insecticide and harvested quickly to limit the chance of infection.
| Date 7/10 | 2020 | 2021 | 2022 | 2023 | 2024 | 20-year avg. |
| Base 50 | 909 | 977.5 | 847 | 959 | 971 | 915 |
GDD50 continues to be approximately 3-5 days ahead of the 20-year average.
Apples
Thinning will no longer impact fruit size at harvest but will still open the canopy to reduce disease pressure and improve fruit color.
Some growers are experiencing russet on certain varieties. A number of physical and biological factors can cause russet including frost, rain or high humidity, and some pathogens such as powdery mildew. Once present, russet can’t be cured, but plans can be made mitigate contributing factors in future seasons. To learn more about russet, and other apple skin disorders, see this article from Penn State Extension.
Insects
Codling Moth flight continues to be very large this year. After a slight dip last week it’s possible we’re moving into the second generation of the season, although it’s difficult to be sure. Treatments should be applied as adults continue to be caught in scouted orchards. For more information on Codling Moth and it’s life cycle see this article from the UW Fruit Team.
Stink Bug, Tarnished Plant Bug, and Borer numbers seem to be decreasing but Potato Leaf Hoppers are present in some blocks causing terminal leaf curling.
Wooly Apple Aphids (WAA) have been found during scouting. The wet conditions are ideal for WAA development and we will likely see continued pressure from this pest.
No Apple Maggots have been caught in scouted blocks.
Disease
Blocks with good initial control are experiencing very low Apple Scab pressure but growers should continue to monitor the forecast and NEWA’s Apple Scab Model to time your fungicide applications.
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 efficacy ratings.
Remember that fungicides are almost exclusively protective, so it’s important to protect new growth when active infection is present in the block.
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. This article from Leslie Holland has more information on the latest recommendations for removing Fireblight strikes. Remember that Strep is not an effective tool for managing shoot blight.
Cherries
Harvest has started throughout the county!
GDD continues to be ahead of last year and the twenty year average, although the long bloom and heavy crop have resulted in uneven ripening in many spots.
Many pick-your-own orchards have started their harvest throughout the county for both sweet and tart cherries.
Machine-harvested orchards should remember that Ethephon applications need to go on at least 7 days before harvest. This article from Michigan State provides information on timing your application and how to adjust for temperature and cropload but be sure to check your label.
Insects
Spotted Wing Drosophila continues to be prolific throughout the county. All cherries are at risk and should be protected through harvest. Most insecticides that are effective against SWD are not rain-fast and require reapplication promptly after wetting events.
Borers populations seems to be decreasing slightly along with leaf and fruit feeding. Pupating Leafrollers are present in some blocks as well.
Cherry Fruit Flies have been caught throughout the county. Most insecticides that are effective against SWD are also effective against CFF but be sure to check the Midwest fruit pest management guide for efficacy ratings.
Disease
Control is going will for Cherry Leaf Spot throughout the county but Powdery Mildew pressure remains strong. Powdery Mildew management may require different products Cherry Leaf Spot. For both Cherry Leaf Spot and Powdery Mildew, cover sprays should continue until terminal buds are set.
Some blocks have 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 before making your management decisions. 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 severe, Cherry Leaf Spot can lead to yellowing and leaf drop.
Zero American Brown Rot Lesions have been detected in scouted blocks so far. Light wind whip bruising is starting to show in fruit which can lead to ABR later.
GRAPES
Grapes on the station are approaching berry touch. Fungicides applied now will help protect the vines from bunch rot through harvest.
Insect pressure continues to be high, and the first Japanese Beetles have been detected in the county. Monitor your vineyards to assess activity and plan management.