West central Michigan tree fruit update – April 18, 2023

Emily Lavely<lavelyem@msu.edu>, Michigan State University Extension - April 18, 2023

Summer-like weather rapidly advanced bud developed last week, but winter returned bringing snow and wind early this week in the west central region.

Stage of tree phenology for apple, peach, cherry, plum and pear — Figure 1. Stage of tree phenology for apple, peach, cherry, apricot and pear in Oceana County on April 17, 2023. Photo by Emily Lavely, MSU Extension.

Weather update

In west central Michigan, last week was hot and bud development advanced rapidly. For apple, buds of many varieties went from dormancy to tight cluster with some buds showing a little pink. With highs in the 70s degrees Fahrenheit and 80s F and lows in the 40s F and 50s F, growing degree days (GDD) also accumulated rapidly. For the Hart Enviroweather station on April 17, GGD₄₂ are currently at 206.4 and GGD₅₀ are at 102.9. Over the past week, 124 GGD₄₂were accumulated and 80.1 GGD₅₀ were accumulated. This warmup was unprecedented with record highs and lows measured in the Grand Rapids, Michigan, area for this time of year.

Cooler weather has slowed bud development since Saturday, April 15. Growing degree days are predicted to increase by about 25 for base 42 and about 8 base 50 over the coming week with highs predicted in the mid to upper 40s F with a slight warm up to 62 F on Thursday.

However, lows this week may be a concern. Sites in Mason, Oceana and Newaygo counties are predicted to have low temperatures down to low 30s F and upper 20s F on Tuesday and Wednesday nights. There may also be another dip in nighttime temperatures on Sunday and Monday next week. Growers can monitor hourly overnight temperatures and windspeed using the Enviroweather overnight temperatures model and the meteogram. Rain showers are also expected later in the week and through the weekend with possible rain and snow mix.

Weather data was gathered from Enviroweather. You can watch a full weather update from Jeff Andresen, MSU climatologist.

More information and reports on current 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.

Thinking ahead, there may be some frost risk over the next few weeks. Michigan State University Extension has an article with helpful tips and recommendations for managing frost: What can fruit growers do if a freeze is coming?

Rapid changes in bud development occurred over the past week (Figure 1), but phenology is expected to move slowly with cooler temperatures this week. Growers continuing to prune should watch nighttime temperatures. Pruning can make some trees more sensitive to low-temperature injury for a short time. However, if temperatures do not fall well below 32 F, trees should remain undamaged.

Crop update

Apple varieties in Oceana County range from 0.5-inch green to showing a touch of pink. Early varieties such as Zestar and Idared are showing signs of pink with early spur leaf development. Most buds remain at 0.5-inch green or tight cluster across the region for varieties like Gala, Jonagold and Golden Delicious. As a reminder, tight cluster in apple is 242 GDD base 42 F for McIntosh based on over 30 years of observation from Sparta, MI. Other apple varieties will be ahead or behind McIntosh. Hart, MI, is at 206.4 GDD base 42 F.

Tart and sweet cherry buds range from green tip to open cluster. If you have not done so yet, there is still time to apply dormant or delayed dormant applications of oil or copper sprays to manage bacterial canker and early pests such as mites or scale.

Early peach bud phenology ranges from side green to calyx red. Venture peach buds are at calyx green at the West Central Michigan Research and Extension Center in Hart.

Some apricots are in full bloom and had a few days of good pollination weather last week.

Pear varieties are between blossom bud exposure and tight cluster.

Pest and disease update

With warmer conditions last week, there was some pest activity throughout the state. The trapline at Trevor Nichols Research Center in Fennville, MI, trapped an average of six adult green fruitworm this week. Increased numbers of red banded leafroller (74) and spotted tentiform leafminer (734) were also trapped. In Oceana County, only three green fruitworm adults were trapped this week. Pest activity will slow for a few days because of the cooler weather in west central area orchards.

Be prepared to protect apple and pear trees from upcoming scab infections. A release of apple scab spores (Venturia inaequalis) was detected in Oceana County from a wetting event on April 16–18, and there was a light infection period. Only 2.5 spores per rod were found at a monitoring site in Oceana County. The risk of scab infection is currently low with cool temperatures in the early part of the week, but risk will be higher later in the week with forecasted high temperatures in the 60s F and rain on Thursday.

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).