West central Michigan tree fruit update – April 26, 2022

Emily Lavely<lavelyem@msu.edu>, Michigan State University Extension - April 26, 2022

A warmup over the weekend led to rapid changes in tree phenology, but cooler weather this week will slow growth down again.

Apple, peach, cherry and pear branches. — Figure 1. Stage of tree phenology for apple, peach, cherry and pear in Oceana County on April 25, 2022. Photo by Emily Lavely, MSU Extension.

Weather update

A warmup over the weekend led to rapid changes in tree phenology and bud growth in west central Michigan (Figure 1). At the Michigan State University Hart Enviroweather station for April 23, the overnight low temperature was 46 degrees Fahrenheit and the high was 76 F. This led to an accumulation of 19.2 growing degree days base 42 (GDD₄₂) and 11.8 GDD₅₀. On April 24, the overnight low was 51 F and the high was 72 F with an accumulation of 19.8 GDD₄₂ and 11.8 GDD₅₀. In addition, a storm system brought 0.32 inches of rain, which led to a three-hour period of leaf wetness and pooling water in the area. On Monday, April 25, temperatures gradually decreased and remained cool with a high of 51 F to a low of 40 F.

Based on the Hart Enviroweather station for April 25, current GDD₄₂ is 148.9 and GDD₅₀ is 55.5. Across the region, GDD accumulation is below the five-year average (Table 1).

Table 1. Current and five-year average GDD summary from Jan. 1- April 26. Numerical integration was used for degree day calculations.
Station	2022 GDD base 42 F	5-year average GDD base 42 F	2022 GDD Base 50 F	5-year average GDD base 50 F
Benona/Shelby	120	148.6	43	48
Elbridge/Hart	141	186.5	57	68.6
Fremont	158	212.6	65	80.8
Grant*	173	190.7	74	69.5
Hart	148	184.8	56	68.0
Ludington	136	175.5	54	62.2
Mears**	147	186.6	58	65.3
New Era**	138	179.0	54	58.1

*Averages were calculated using data from 2020-2021.
**Averages were calculated using data from 2018-2021.

Below average temperatures are predicted for the week through May 2, and low temperatures may be below freezing on Wednesday and Thursday this week with lows near 27 F. Rain and snow showers are also expected on Tuesday, and dry conditions are expected through the end of the week.

Bud damage from low temperatures is not expected at the current stage of tree bud phenology. See table of critical spring temperatures for tree fruit bud development stages from Michigan State University Extension. Cooler temperatures will slow further changes in bud development stage this week (Figure 2).

GDD graph — Figure 2. Cumulative and forecasted degree days for base 42 F and base 50 F for the Hart Enviroweather station.

More information and reports on normal weather conditions and departures from normal can be found on the NOAA Climate Prediction Center website, NOAA U.S. Climate Normals website, NOAA Climate Normals Quick Access Page (which may be searched by region) and Midwest Regional Climate Center website.

Crop update

Over the past week, growers have been able to get out into the field to finish tree trimming, clean up brush, plant trees and install trellis systems where needed. For some growers, protective copper sprays were also applied to protect new green tissue that emerged over the weekend from scab and fire blight.

With cooler temperatures this week, further growth is expected to be slow over the next week.

Apple varieties in Oceana County range from first green to half-inch green. Early varieties such as Zestar and Idared are at half-inch green, and later varieties such as Gala and Honeycrisp are at green tip. As a reminder, half-inch green in apple is 205 GDD₄₂ for McIntosh based on over 30 years of observation from Sparta, Michigan; other apple varieties will be ahead or behind McIntosh. Hart, Michigan, is at 148 GDD₄₂.

Tart and sweet cherry buds range from bud swell to green tip. If you have not been able to get out in the field yet, there is still time to apply delayed dormant applications of oil or copper sprays to manage bacterial canker and early pests such as mites or scale insects.

Peaches are showing signs of swelling and green tip. If you have not already applied a spray for peach leaf curl, an application for final spring sprays using copper products for management of peach leaf curl and bacterial canker is warranted in the next week.

Pear varieties are showing signs of bud scales separating and some blossom buds are exposed. Dormant applications of oil can still be applied to help suppress pear psylla and San Jose scale populations.

Pest and disease update

With cooler temperatures and slow bud development, emerging tissue in apple is at low risk for apple scab infection. Spores were first observed during the rain event on April 24. We have had three or four wetting events, but lower temperatures require longer wetting periods for infection. Generally, our wetting periods have not been long enough to result in infection; however, it will now be important to protect new green tissue and maintain adequate fungicide coverage. Through the rest of the week, risk of scab infection will remain low due to cool and dry conditions.

Some insect activity has been observed in pear in west central Michigan. Pear psylla eggs were identified on Bartlett pear on Friday, April 22. Similarly to last week, the Trevor Nichols Research Center trapped a few adult green fruitworm this week, but green fruitworm is not a major pest in our area. Red banded leafroller and spotted tentiform leafminer were also trapped on April 25 at the Trevor Nichols Research Center. In west central Michigan area orchards, we expect that continued cool conditions this coming week will suppress additional insect pest activity.

If you have still not applied delayed dormant sprays such as oil or copper, be sure to do so shortly.

Pests to start thinking about:

Black stem borer
Green fruitworm
Pear psylla
Redbanded leafroller
Spotted tentiform leafminer
Oblique banded leafroller
Climbing cutworms
San Jose scale
European red mite
Rosy apple aphid

For more information about regional reports, please visit the Michigan State University Extension website.

This article was published by Michigan State University Extension. For more information, visit https://extension.msu.edu. To have a digest of information delivered straight to your email inbox, visit https://extension.msu.edu/newsletters. To contact an expert in your area, visit https://extension.msu.edu/experts, or call 888-MSUE4MI (888-678-3464).