West Michigan tree fruit update – May 1, 2018
Tree fruits will respond nicely to warmer weather.
Weather and tree development stage
The warmer weather this week will help move tree development in a nice even pace with no explosion of growth for the most part. Michigan State University Extension Educator, Amy Irish-Brown reports apple varieties seem to be all in the same growth stage right now – green tip to ¼-inch green. With warmth, apples will move to the ½-inch stage by the end of the week and perhaps pink by early next week. Early developing sweet cherry varieties should have a few open blooms this week as well. Peaches are right behind the sweets. There is some winter injury to stone fruits from the extreme cold in December 2017, so check buds closely for healthy pistils and adjust pruning accordingly for potential crop load.
Tree fruit diseases
Apple scab – There have been no significant rain events since my first captured ascospore back on April 12. It is quite dry so far this spring. That will change with rain predicted for much of the latter part of this week and I suspect we will have our first primary apple scab infection. With warm temperature, it will likely take the minimal number of wetting hours to get an infection started. The Mills Table modified by Jones, require only 9 hours of wetting when average temperatures are between 60 and 75 degrees Fahrenheit. With the warmer weather and potentially rapid leaf expansion, try to time your fungicides close to the rain event to make sure expanded leaves are covered. Using an AP (Vangard or Scala) should help as they are systemic and always add a good protectant to the tank. Various forecasts are calling for rainfall totals near an inch, so being well covered ahead of the rain is a really good idea and be ready to come back in and recover if necessary.
Powdery mildew – It is a bit too early to be concerned about mildew in apples. For most blocks, you can wait to add mildewcides closer to the bloom stage. For any blocks with a history of powdery mildew, you might want to begin adding mildewcides a bit earlier at the pink stage or even tight cluster stage.
Nothing much to be concerned about at this time – spotted tentiform leafminer are flying in very low numbers; a few redbanded leafrollers are present, but of little concern; and green fruitworm adults are flying.
If you had high levels of San Jose scale on fruit at harvest in 2017, please consider tightening up your management program for this pest. There are several chemistries that can be used in the pre-bloom apple period to help reduce the eventual numbers of crawlers. Every year for the past 5 or 6 years, I see more and more scale on fruits in the bins.
Black stem borer is likely to become active this week with warmer temperatures. Now is the time to apply trunk sprays in susceptible blocks. Start planning now for placement of oriental fruit moth traps in apples and stone fruits. Lures should be in place prior to flight which could begin later this week.
Pink sprays are right around the corner – maybe some will need to go on early developing apple varieties after the rain predicted for later this week moves out. Normal temperatures are in the forecast, so pink might be around the beginning of next week.