Grand Rapids area tree fruit update – June 14, 2022

Tree fruit is continuing fruit sizing, with most apples between 20-25 millimeters. Hot weather expected this week.

Tree fruit.
Tree fruit in Sparta, Michigan, on June 13. Photo by Anna Wallis, MSU Extension.

Weather and phenology update

Over the past week in the Grand Rapids area, conditions were cooler than normal and dry. High temperatures for most of the week were in the low 70s (F) and overnight lows in the 40-50s. As of June 13, the Michigan State University Sparta Enviroweather station has accumulated 1040.5 degree days base 42 F (DD42). This is slightly above average, which is 986.4 DD42, and approximately two to three days ahead of normal.

It was a very dry week. On Wednesday, approximately 0.25-0.35 inches of accumulation was recorded in most locations, followed by no precipitation for the remainder of the week through the weekend. Overnight Monday, most weather stations received nearly an inch of rainfall.

Tree fruit is continuing to size. A very good potential crop is setting well in most locations. Most varieties of apples are between 20-25mm. Earlier blocks and varieties such as Ginger Gold and Zestar are beyond 30mm. Peaches and cherries are continuing to size as well.

A heatwave is being experienced across the Midwest this week, and excessive heat is forecasted for most of Michigan for the next two days. Expect hot and humid conditions, with highs in the upper 80s to low 90s. Scattered showers and thunderstorms are possible overnight Wednesday. This will be followed by slightly cooler, dry conditions through the weekend with highs in the mid to upper 70s, and then a return to very hot conditions. Dry weather will continue through the weekend, with the next chance of precipitation at the beginning of next week. Hot, dry weather will be coupled with high potential evapotranspiration (PET) this week and next, leading to an unusually high water demand across the region.

Degree day accumulation at Enviroweather stations in the Grand Rapids area
Weather Station Degree Days Base 32 from Jan. 1 Degree Days Base 42 from Jan. 1 Degree Days Base 50 from Jan. 1
Aetna - Fremont 1767.5 996.6 563.2
Alpine 1887.6 1077.4 620.3
Belding 1849.8 1057.2 615.8
Clarksville (CRC) 1902.7 1083 626.8
Conklin 1869.7 1062.9 603.2
Fremont 1807 1023.6 588.4
Grant 1815.6 1024.6 586.2
Kent City 1818.3 1031.5 591.1
Reeman-Fremont 1803.6 1014.1 574.1
Sparta 1836.5 1040.8 595.2
Sparta 20m Tower 1849.2 1047.4 598.1
Sparta - North 1857.1 1056.9 605.9
Standale 1947.2 1115.4 651.9
Average DD from Sparta historical data for Jan. 1 to date 1826.7 986.4 541.7
Comparative Date of Averages @ Sparta 14-Jun 16-Jun 17-Jun
Days +/- Average @ Sparta + 1 day + 3 days + 4 days

For these updates, we used averages for 1997-2021 from the Michigan Automated Weather Network (MAWN) to represent normal conditions. Weather data was gathered from MSU Enviroweather.

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.

Tree fruit diseases

Primary apple scab continues to be an issue. I did catch an average of one spore per rod with the June 13 rain event, so this is still a primary scab infection event. There is a bit of apple scab showing up in managed McIntosh blocks, but many other varieties are clean. Macs are just so susceptible. Careful spouting is needed from now until the end of June to be sure no primary scab got through.

Warm and humid weather this week is the ideal environmental conditions for powdery mildew to again be an issue. In many tree fruit crops, there is an abundance of lush, tender leaves and small, fuzzy fruits – all very susceptible to fungal pathogens for the next few weeks. If you have blocks with powdery mildew established, fungicides are definitely needed to keep that infection at bay.

Fire blight risk is lower now that bloom is over and in the general Grand Rapids area, most blocks look really clean of blight. If you do have blight showing up, remove it as soon as possible and continue a strong management program to keep it from spreading further.

Tree fruit insects

Some insects to be thinking about now as you plan for monitoring and management.

Plum curculio activity should be over for the 2022 growing season. Apples are now over the 20 mm stage and plum curculio adult females should be done with egg laying. Overall, damage from PC was low this year.

Codling moth adult flight has been variable with the ups and downs in the evening temperatures. A Grand Rapids regional biofix was set for May 15, 2022 (254 DD50). In general, this area should be at 20 percent egg hatch and management programs should be in place to prevent fruit damage.

Obliquebanded leafroller are mostly in the pupae stage. A few adult moths were trapped in the past few days, but not in all traps, so a biofix has not been set yet.

Adult flight is declining for first generation oriental fruit moth. A Grand Rapids regional biofix was set for May 12, 2022 (312 DD45). We are likely past the peak egg hatch stage and cover sprays are still important to maintain. Flagging of shoots in stone fruits should begin to be apparent this week.

Rosy apple aphids are curled up in apple terminals. Green apple aphids are also now starting to be found on apples terminals. Woolly apple aphids are also present, having overwintered in some blocks well this year. Various predators present in aphid populations – monitor for them too and consider their effectiveness in your general IPM program.

Very few male San Jose scale continue to be caught in pheromone traps – they seem to be very late or very low in number this year.

European red mite eggs and nymphs are present. Adults are likely to appear soon with the push of the hot weather this week. Predatory mites found in European red mite populations. There are a few two-spotted spider mites in some areas. The recent heavy rains should have helped to wash some mites off leaves. Continue to monitor for all mites.

I continue to find a few White apple leafhopper nymphs and now a few adults. There are also adult potato leafhopper present.

Beneficials witnessed on orchard visits include: Ladybug beetles – adults and larvae, syrphid flies – adults and larvae, and beneficial mites and chiggers, ground beetles, earwigs, and robber flies.

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