2019 Fruit Pest Update
August 19, 2019
Cherry harvest is past us and attention is turning to apples which are starting to color. Grapes are starting to soften and early varieties are at veraison.
For all tree fruit crops, if you plan to take leaf samples for tissue testing, this is the last week for optimal timing. 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 (see article in the most recent Fruit News below). 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 8/19||2015||2016||2017||2018||2019||5 yr avg|
INSECT & DISEASE CONTROL
Disease Pressure – Disease pressure is very low in scouted blocks that were sprayed earlier this year. Apple scab lesions on fruit or leaves, powdery mildew, and fireblight strikes are nearly impossible to find. Drier conditions the last couple weeks resulted in little pressure from late season diseases including sooty blotch and fly speck, except in poorly ventilated orchards with excessive foliage from poor pruning and/or over fertilizing.
Insect Pressure – Second generation codling moths are nearing threshold levels and an insecticide application may be needed this coming week. A few leaf roller larvae have been observed in some orchards on the undersides of leaves. Apple maggot flies are also active and females are going into the egg-laying stage. When spraying for coding moth, it is recommended to make sure that the product you use will work against these pests as well. There have not been any European red mites populations above threshold found in scouted orchards.
Summer pruning can continue through this week to improve apple coloring. ReTain or other plant growth regulators can be applied at this time to aid in fruit coloring and reduce fruit drop before harvest. Next week we will post expected harvest dates for several varieties. This is also a good time for late-season weed control. When using any product, make sure to carefully read the label for the preharvest intervals, to avoid issues at harvest.
Disease Pressure – A final cherry leaf spot post-harvest spray can go out now if cherry leaf spot lesions are present. With cooler temperatures this week, copper products or captan should be safe to use. The goal is to keep leaves on until at least the first week of September or later so the trees are as healthy as possible going into the winter. Conditions were ideal in the last two weeks for American brown rot to explode. Shaking fruit to the ground is strongly recommended in unharvested blocks to decrease the chance that mummified American brown rot-infected cherries will infect next year’s fruit.
Insect Pressure – Unless harvest is still on-going, insecticide applications should stop. Even though trap catches for spotted wing drosophila continue to be high, 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. Check orchards for European red mites because some scouted orchards are currently over-threshold (often due to the frequent use of pyrethroids killing natural enemies of mites). If over threshold, a miticide is recommended to prevent a decrease the leaves’ photosynthetic ability.
This week or next week are the best time to hedge in cherry orchards. You can also mark limbs that you plan to remove during dormant pruning to open up canopies and increase airflow to make the environment less favorable for spotted wing drosophila next year.
Disease Pressure – Untreated vines in the PARS vineyard are showing heavy black rot, powdery mildew, downy mildew, and phomopsis pressure.
Insect Pressure – Japanese beetle are present in the vineyard, but at PARS are in very low numbers. 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.
Leaf pulling to allow for more light penetration to the fruit should be ongoing.
Wisconsin Fruit News:
Wisconsin Fruit News Volume 4, Issue 10
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
Links to individual Enviro-Weather stations: