Grand Rapids area tree fruit update – June 28, 2022

Warm, dry conditions expected across the region. Fruit sizing continues. Cherry harvest underway.

Tree fruit.
Tree fruit in Sparta, Michigan, on June 27. Photo by Anna Wallis, MSU Extension.

Weather and phenology update

Over the past week, the Grand Rapids, Michigan, area continued to be hot, with high temperatures in the 80s (degrees Fahrenheit) and overnight lows in the 50s and 60s. A cooler trend over Sunday and Monday included high temperatures in the low 70s and low temperatures in the upper 40s in the Sparta area. As of June 27, the Michigan State University Sparta Enviroweather station has accumulated 1443.0 degree days base 42 F (DD42). This is slightly above average, which is 1352.2 DD42, and approximately three days ahead of normal.

It continues to be very dry. There has been no significant rainfall across the area for the past ten days. Scattered showers resulted in an accumulation of less than 0.05 inch recorded at weather stations across the region. There continues to be a high water demand, as indicated by potential evapotranspiration (ET) of approximately 0.2 inch per day and 1.5 inches over the course of the week and declining soil moisture. While this is fairly normal for the region at this time of year, supplemental irrigation is recommended. The low humidity, sunny skies, and windy conditions that are expected will increase evapotranspiration and water demands.

Tree fruit is continuing to size. A very good potential crop is setting well in most locations. Most varieties of apples are between 30-40 mm. Earlier blocks and varieties such as Ginger Gold and Zestar are beyond 40 mm. Peaches and cherries are continuing to size as well. Sweet cherry harvest began over the weekend.  

Hot and dry conditions are expected to continue this week, with highs in the 80s and overnight lows in the 60s. Temperatures continue to be above average in our area over the next week. A chance of rain is forecasted overnight tonight (Tuesday, June 28), but will likely be scattered and variable across the region. The next chance for rainfall is most likely to be early next week, with possible accumulation and thunderstorms on Tuesday.

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 2298.8 1388 843.7
Alpine 2437.3 1487.1 918.3
Belding 2399.3 1466.7 913.9
Clarksville (CRC) 2460.7 1501 933.1
Conklin 2423.9 1477.1 905.6
Fremont 2344.4 1413.4 864.7
Grant 2344.4 1413.4 864.7
Kent City 2357.6 1430.8 879.5
Reeman-Fremont 2347.9 1420.2 869.1
Sparta 2378.7 1443 886.4
Sparta 20m Tower 2390.5 1448.7 888.1
Sparta - North 2399.5 1459.3 896.4
Standale 2490.2 1518.4 944.7
Average DD from Sparta historical data for Jan. 1 to date 2342.1 1352.2 791.5
Comparative Date of Averages @ Sparta 29-Jun 1-Jul 3-Jul
Days +/- Average @ Sparta + 1 day + 3 days + 5 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 is over for 2022. There were zero spores with the light, daylight rains on June 25. With the last scab infections being in mid-June across the region, all primary scab should now be visible. Do a thorough scouting for apple scab before reducing primary scab fungicide rates.

Overall fire blight risk is lower now that bloom is over and in the general Grand Rapids area, and most blocks look really clean of blight. If you do have blight showing up, remove it ASAP and continue a strong management program to keep it from spreading further. There are a few reports of blight in blocks with a history of this disease.

Powdery mildew is more common this year and cover sprays should continue until shoot growth declines. Peach leaf curl is more prevalent as well, likely due to the ideal cool and wet conditions at bud break that favor this pathogen.

Summer disease management in apples should be considered in areas where the MSU Enviroweather model indicates adequate wetting hours for disease expression. This is not everywhere as rainfall and wetting have been quite variable this year. Be sure to check the summer disease model for the weather station nearest you for guidance.

Tree fruit insects

Codling moth: Grand Rapids regional biofix set for May 15 (254 DD50) with 631 degree days accumulated since. This week, we are past peak egg hatch. Management is needed in blocks over threshold. The next week to 10 days remains critical for good cover spray maintenance in blocks over threshold.

Obliquebanded leafroller: Grand Rapids regional biofix set for June 14 (1076 DD42) with 388 degree days accumulated since. Adult numbers down a bit from last week. Early egg hatch should be starting, but small larvae are very hard to see. First visible larvae predicted for July 8 or 9. Hard to control populations should start apps now to stay ahead developing larvae.

Oriental fruit moth: Grand Rapids regional biofix was set for May 12 (312 DD45) with 903 degree days base 45 accumulated since. Adult flight is still low, but second generation is starting to fly. Monitor for shoot flagging. Early egg hatch for second generation anticipated around July 6.

Aphids: Green apple aphids are enjoying the warm weather and lush green growing shoots. Woolly apple aphids are moving up from roots. Various predators present in aphid populations.      

Continue to monitor. Consider beneficials if present. Don’t forget to monitor non-bearing trees for aphid populations that might curb desired shoot growth.

San Jose scale: A regional biofix for the general Grand Rapids area was set for May 20 (288 DD51) with 594 degree days accumulated since the regional biofix. Crawlers are present. Contact insecticide apps should be applied this week in blocks with a history of San Jose scale injury to fruit. All apps need to be maintained until the end of Gen 1 or mid-July.

All stages of European red mite are present. Predatory mites continue to be found in European red mite populations. There are a few twospotted spider mites in some areas. Summer miticides should be considered in blocks over the threshold of 2.5 mites per leaf. Threshold jumps to five mites per leaf for July.

Various borers species are active in orchards now. American plum borer first generation flight is nearly over. Dogwood borer is in its third week of flight. Peach tree borers (both species) are also flying. All borer sprays need to be considered earlier than when using chlorpyrifos and two applications will be needed in high pressure blocks.

Lacewing larvae.
Lacewing larva. Photo by Amy Irish-Brown, MSU Extension.

A few adult Japanese beetles began to emerge this week. Monitor for their emergence and cover as needed.

Beneficial insects witnessed this week include ladybugs (all life stages), syrphid flies (adults and larva), beneficial mites, ground beetles and earwigs. Continue to monitor and take note of their presence and activity.

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