Fruit Crop Pest Report- May 14, 2019

2019 Fruit Pest Update

May 14, 2019

Click for link to

2019 – 2020 Midwest Fruit Pest Management Guide


*** Be prepared for a potential apple scab infection period this weekend with the predicted rain. With temperatures in the 40s, if leaves are wet for over 14 hours, they can be infected. Make sure that susceptible varieties are protected***


There was an apple scab infection period at all weather stations in Door and Kewaunee counties except Egg Harbor with the rain last Thursday. Symptoms from any infections that may have occurred would be apparent in about 7-10 days.

Apples at the station are at tight cluster in most blocks. Apple scab sprays should be ongoing on a 7-10 day schedule for susceptible varieties (see disease section below).

Cherries are primarily at tight cluster. There is a bit of green fruitworm feeding on the buds at the station, but no action is needed.  Grapes are at bud swell and there are also no concerns at this time.

There was a light frost recorded Saturday night in some parts of the county. Currently, critical temperatures for 90% flower bud kill have risen to between 24ºF & 21ºF for cherry and apple at their current stage of development. Grape buds continue to be slightly more tolerant of cold temperatures at this time, but will be less so when buds begin to swell. Click a link below for more information on tree fruit crop bud cold temperature injury.

Tree Fruit – Critical Temperatures


Below is a degree day comparison of the last five years. We are at about half the degree day accumulations from average.

Date 5/13 2015 2016 2017 2018 2019 5 yr avg
Base 50 117 84 71 98 34 81

Delayed dormant applications for control of early season disease and insect pests can still be made, but depending on location, limited time remains to make these type of applications.

Continuing scouting for overwintering mite eggs. Options for mite control are listed in the most recent issue of the WI Fruit News, linked below. If red eggs are present, overwintering mite eggs can be controlled now through tight cluster on apple with a 1-2% oil application (1-2 gal dormant oil per 100 gal water). Be aware that the later you make this type of application that you might consider the lower 1% application rate as phytotoxicity can be a risk, especially if you combine a copper fungicide for the control of early scab. Do not apply oil 48 hours before or after a frost. Captan should be avoided when making early season oil applications.




Disease Pressure – Apple scab spray programs should be ongoing to protect apple scab susceptible varieties (e.g. McIntosh and Cortland), as the 1/2 inch green through first cover time period is the most critical time for primary scab infections to occur. Keep these varieties covered with fungicide treatments through the end of primary scab season; typically mid to end of June in Northeast WI. Applications of copper can still be made to reduce fire blight inoculum. These copper sprays will also provided protection from apple scab infection.


Insect Pressure – Green fruit worm adults continue to fly and lay eggs. Scout for presence of their hatching larva as well as overwintering oblique-banded leafroller larva starting at the ½ inch  green stage of development through petal fall.



Disease Pressure – Little to worry about because of plant stage. Fungicide applications targeting cherry leaf spot will need to begin after bract leaves begin to unfold,  so probably not for another few weeks.

Insect Pressure – Green fruit worm adults continue to fly and lay eggs. Once significant leaf tissue begins to develop, scout for presence of their hatching larva as well as overwintering oblique-banded leafroller larva


**Mark your calendar for July 18, 3-5pm, for the 2019 Vineyard Walk at the Peninsular Ag Research Station!**

Disease Pressure – Little to worry about because of plant stage

Insect Pressure – As buds begin to swell, keep an eye out for grape flea beetle damage (see WI Fruit News article in Issue 2 at the link below).


Wisconsin Fruit News:  *New issue this week*

WFN–Vol 4, Issue 3 (May 10, 2019)

  • NEWA new weather monitoring partnership
  • Malusim app released
  • Insect diagnostic lab update
  • Controlling mites in berries
  • Impact of rain on fungicides
  • Blossom thinning


WFN — Vol 4, Issue 2 (April 26, 2019)

  • New fact sheets
  • Insect diagnostic lab update
  • Stocking densities of bees for berry
  • Cranberry degree day
  • Grape developmental stages
  • Flea beetles are here
  • Impact of last winter on apple diseases
  • Managing San Jose scale in apple
  • Pollen tube growth model


WFN — Vol 4, Issue 1 (April 12, 2019)

  • NEWA weather stations
  • Insect Diagnostic Lab update
  • Berry Spring insects
  • Cranberry degree day insecticide trials
  • Grape Flea Beetle
  • Promoting branching apple trees
  • Prebloom fertility apple trees
  • Dog wood borer mating disruption


Links to individual Enviro-Weather stations:

Kewaunee/Stangelville    Kewaunee/Casco 

Southern Door/Nasewaupee   Southern Door/Sturgeon Bay

Sturgeon Bay   Egg Harbor

W Jacksonport   Sister Bay