2019 Fruit Pest Update
August 13, 2019
A few large storms blew through this past week, with minor reports of hail. Otherwise, it has been warm and humid. Tart cherry harvest is finishing up in the southern part of the county and ongoing farther north. Grapes are at bunch closure and are mostly hard and green, but some are starting to soften. Valiant, the earliest variety at PARS is just starting to color.
For all tree fruit crops, if you plan to take leaf samples for tissue testing, late July to early August is the best time. Take 50-100 leaves from several trees that are representative of that block and put them in a paper bag before sending them to a tissue analysis lab. Grape petiole analysis should take place at veraison. Soil samples are recommended every two year to complement this information, but those can be taken any time before the soil freezes.
Below is a degree day comparison of the last five years.
|Date 8/12||2015||2016||2017||2018||2019||5 yr avg|
INSECT & DISEASE CONTROL
Disease Pressure – Disease pressure is remaining low if there was good apple scab and powdery mildew control early season. Sooty blotch and flyspeck pressure will also remain low, if only sporadic rain events continue.
Insect Pressure – Second generation codling moths have begun their flight. Trap counts will determine the proper spray timing. When using any insecticide, check that it will control apple maggot as well. Many orchards had apple maggots in traps last week, and the adult females are now transitioning to the egg-laying phase. There were zero oblique banded leafrollers caught and there is a light spotted tentiform leafminer flight. No brown marmorated stink bugs have been caught. San Jose scale is in the crawler stage, so it is susceptible to insecticides. If your orchard has a history of scale damage, now is the time to control it.
In general, apple harvest is looking to be about 8-10 days later than average. With that in mind, Stop Drop, or other fruit retention applications might need to be considered. Most products need to be applied once or twice, 2 to 4 weeks before harvest. Read product labels carefully regarding pre-harvest intervals. This is also the time to carry out any summer pruning to allow extra light into the tree canopy and to help add color to the fruit.
Disease Pressure – Continue to monitor cherry leaf spot, even after harvest to determine whether any post-harvest fungicide applications are needed. Any spray should be applied within two weeks of harvest, if possible.
Insect Pressure – Spotted wing drosophila controls should continue in blocks that have not been harvested, as flies are still being caught in traps around the county. After harvest, there is no advantage to continuing to make control applications for SWD. Continuing to spray insecticides after harvest could actually speed up the development of insecticide resistance.
NOTE: Please be aware of re-entry intervals (REI), especially for pick-your-own harvesting and Pre-Harvest Intervals (PHI). Mustang Maxx is still under a Section 24(c) Special Local Need label through the end of 2020, allowing for a 3 day PHI, FOR TART CHERRY ONLY (more info here).
European red mite populations have been low, however, it is important to scout especially sweet cherries for European red mites at this time.
Disease Pressure – Secondary black rot, powdery mildew, downy mildew, anthracnose, and Phomopsis are showing up in the PARS vineyard. Downy mildew, in particular, was extremely prevalent this week. Continue to scout for diseases and use a fungicide spray every 7-10 days as needed.
When scouting for diseases, former UW graduate student, Dave Jones, made an excellent photo disease guide per variety that can be found here: https://fruit.wisc.edu/wp-content/uploads/sites/36/2017/04/Photo-guide-diseases-cold-climate-grape.pdf.
Insect Pressure – Japanese beetle are present in the vineyard, but at PARS are in very low numbers (I found 3). Phylloxera galls are covering leaves on more susceptible varieties, especially Frontenac. Phylloxera needs to be controlled in the early summer, so there is nothing that needs to be done at this time. Leafhoppers are also showing up in the PARS vineyard. Scout your vineyard for small yellow/white stippling on the surface of leaves. If applying an insecticide, consider using a product that controls leafhoppers as well. For more information, click here.
Wisconsin Fruit News:
Wisconsin Fruit News Vol. 4 Issue 7
- Plant Disease Diagnostic Update
Insect Diagnostic Lab Update
Apple Sooty Blotch and Flyspeck
Black Stem Borer
Strawberries Post-Harvest: Renovation or Rotation?
Grape Variety Developmental Stages
Grape Scouting Report: Grape Phylloxera or Grape Scale?
Door County Report
WFN- Vol. 4, Issue 6 (June 21, 2019) We are updating our website, so please click on the links to read these articles.
- Governor Evers Declares Wisconsin Vineyard Week, July 14-20
- Grape Scouting Report: Low Insect Pressure
- Grapevine Phenology for Mid-June
- Promoting Return Bloom in Apples
- Some Cold, Hard Facts about Winter Injury on the First Day of Summer
- Door County Report
WFN-Vol. 4, Issue 5 (June 7, 2019)
- Strawberry angular leaf spot
- Grape downy mildew
- Chlorpyrifos update
- Apple thinning update
- Door County Report
Links to individual Enviro-Weather stations: