West central Michigan tree fruit regional report – May 19, 2015

The roller coaster ride of weather continues in west central Michigan.

Crop stage and growing degree days (GDD)

Apples are nearing petal fall. At this time it appears fruit are setting, but you are wise to be a bit cautious with your apple thinning this year. Extended cold and rainy weather during the peak bloom period on the Ridge could lead to poor pollination and fertilization.

Growth stages from the MSU Clarksville Research Center as of May 18, 2015, as examined by Dan Platte, assistant farm manager:


  • Empire - Kings up to 5 millimeters
  • Honeycrisp - Very late bloom (rag tag) kings up to 5 millimeters
  • Jonagold - Very late bloom (rag tag) kings up to 7 millimeters
  • Red Delicious - Very late bloom (rag tag) kings up to 5 millimeters
  • Gala - Very late bloom (rag tag) kings up to 5 millimeters

Tart cherries

  • Montmorency and Balaton - Petal fall/very early shuck split

Apricot - 0.25-0.5 inch green fruit

Pluots - Pea-sized fruit

Benton sweet cherries

  • In “protected culture” - Green fruit 0.5 inches or better
  • In “unprotected culture” - 0.25-0.5 inch green fruit

Peaches - Petal fall

Apple scab

Lesions from the very first apple scab infection on April 19 began showing up on minimally managed trees Saturday, May 9. Michigan State University Extension advises growers to look on spur leaves or the first or second true leaf on early developing varieties. A very light rain event moved across the Ridge areas this morning, May 19, and single digit spore numbers were found. This will most likely not turn into an infection as dry weather is supposed to move in for several days.

Fire blight

On May 16 and 17, very warm temperatures and rainy conditions, along with bloom still present, created another infection risk for blossom blight for susceptible apple cultivars. This included all mid- and late-season varieties. Cooler conditions are expected to move in for the remainder of the week and bloom will finish, which will be the end of blossom blight risk for 2015. Symptoms from the first blossom blight infections on May 7, 8 and 9 could begin expression as early as Friday, May 22.

Apogee use for shoot growth and blossom blight management

Now is the time on the Ridge to add Apogee in the tank to help with shoot growth management and maybe more importantly this year, with fire blight. Here are a few reminders about Apogee use:

  • Surfactants. With Apogee, it is recommended that a surfactant (Regulaid, LI-700, etc.) be used at a rate of 1 pint per 100 gallons to assure good wetting and coverage.
  • Water conditioning. If your water is hard and contains 500 ppm or greater calcium, the effect of Apogee will be reduced. Adding ammonium sulfate with Apogee is recommended for our hard well water.
  • Foliar nutrient spray interactions. The Apogee label recommends that foliar nutrient sprays should not be tank-mixed with Apogee. This warning is especially true for calcium chloride and other calcium-containing products. In the presence of calcium, Apogee will precipitate in the tank, clog nozzles and screens and reduce tree response. If you are using calcium chloride sprays, residues left on the leaves may reduce the effectiveness of later Apogee applications.

Powdery mildew

Powdery mildew is just beginning to be seen in unmanaged apples. The warmer periods this spring will favor mildew establishment. Scouts should be looking carefully for mildew.

Tree fruit insects

With apples nearing the end of bloom, it’s time to start thinking about your petal fall insecticide cover spray. Be sure your neighbors’ bees are removed before you apply any insecticides. There have been initial reports of rosy apple aphid egg hatch. Obliquebanded leafroller larvae can be found in various sizes, but overall numbers appear to be very low across the region.

Oriental fruit moth began flying a bit earlier than usual this year and a regional biofix was set for May 6. At the end of Monday, May 18, we have accumulated 200 GDD 45, indicating the need for first cover sprays in stone fruits for oriental fruit moth to prevent flagging of shoot tips. Mating disruption should be set for this pest and traps should be up with lures in them.

Codling moth flight began over the weekend as expected. Problem blocks are reporting very high flight numbers. Mating disruption needs to be up if you are using it.

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