West central Michigan tree fruit update – June 6, 2017
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EmailUpdates on growing degree-days, fruit development stages, apple scab, cherry leaf spot, fire blight, plum curculio, oriental fruit moth, codling moth and stone fruit borers.
Warmer, drier weather has moved fruit development along rapidly in west central Michigan during the past several days. A soaking rain over the weekend combined with high afternoon temperatures and a sunny forecast for the rest of the week should continue this trend. New growth has expanded rapidly and tree canopies are now looking full.
Apple fruitlets are about 10-15 millimeters, sweet cherries are about 10 millimeters, tart cherries are 5-10 millimeters and peaches are 5-10 millimeters. The crop is generally looking light in most areas, but fruit set is highly variable across the region. The crop is spotty, even within fields. Fruit set ranges from heavy to almost absent within a single row on some farms.
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Growing degree-days (GDD) for west central Michigan Jan 1. – June 6, 2017 | |||
|---|---|---|---|
|
Enviroweather station |
GDD 42 current |
GDD 45 current |
GDD 50 current |
|
684 |
514 |
297 |
|
|
829 |
651 |
410 |
|
|
918 |
729 |
471 |
|
|
830 |
648 |
406 |
|
|
781 |
606 |
372 |
|
The cold spring, frost, subsequent damage and extensive plant growth regulator applications following the frost have had interesting effects on the apple crop. High variability in fruit set, size, quality and bloom can be observed across the region. In particular, rag-tag bloom has had an exceptionally lengthy in duration this season. Thinning fruits and keeping apple trees covered against fire blight on apple blossoms this season has been challenging as a result.
Primary apple scab is still ongoing, and lesions from apple scab infection events several weeks back are showing up. We are at 100 spore maturity in west central Michigan, but not at 100 percent spore discharge. The discharged rate ranges by site across the region depending on green tip date, but is between about 80 and 95 percent across the region. At this pace, we should be at 100 percent in another seven to 10 days.
Farmers should still be protecting against scab. However, the warm, dry weather forecasted for the next several days means the next applications on most farms will not be applied for a few days.
Cherry leaf spot is appearing in orchards around the area. All but one west central Michigan State University Enviroweather station recorded a full progress towards infection over the weekend; we have had several full progresses towards infection in the past few weeks. MSU Extension suggests monitoring blocks carefully in the coming days for this disease, and staying protected ahead of all rain events.
Plum curculio damage in most areas around west central Michigan has been low this spring due to the cold weather. However, an uptick in egglaying is possible with the warmer weather. Many growers are going with a border spray in blocks with no history of plum curculio damage, while opting for a full cover in blocks with historical issues with this pest.
The first generation of oriental fruit moth has largely ended, so watch for shoot strikes in coming weeks.
Codling moth trap catch numbers have been low overall due to cooler weather in recent weeks, but we expect they will increase with the warmer weather. Using an estimated regional biofix of May 18, 2017, our GDD base 50 since biofix are currently at 165. Materials for early hatch and larval activity should be applied near 250 GDD 50 past biofix in blocks with high pressure.
This is a good week to apply borer sprays in stone fruits.
