MSU Extension Fruit & Nuts

Welcome to the 12th in-season fruit article update for southeast Michigan for the 2024 season. Throughout the season, these updates will include information about the weather in the past week and the upcoming week, a fruit-by-fruit guide to current conditions with appropriate pest and disease updates, and other relevant observations.

General observations

In the week since the last update, many farms have moved fully into blueberry harvest, with summer raspberry and cherry harvests slowing down. Growers in the region are starting to carry their early peaches and plums in their markets. Peaches, pears and apples can still be hand-thinned. Fruit set has been good on grapes and the fruit continues to expand.

We’ve seen an average of 0.5 inches of rain in the region over about 4 hours of rainfall in the last week while temperatures have climbed. When using Michigan State University (MSU) Enviroweather and other weather models, keep in mind that the weather station closest to you may have different topography or be in the path of weather events that pass by your location. The legacy version of Enviroweather is currently unavailable, so for the time being it is necessary to use the newer version of the site.

We are expecting rain tomorrow (July 10) coming from the remnants of Hurricane Beryl with continued chance of rain over the weekend. With these events come an increased risk for fungal infections like secondary apple scab and powdery mildew. After a post-storm cooldown, temperatures will gradually climb back up, reaching the low 90s early next week. You can see you an overview of disease risks on the RimPro interactive location chart. Make sure to check the models frequently as they change with weather forecasts. These weather conditions may make finding a suitable spray date tricky. You may need to consider using spreaders and stickers as adjuvants to make sure that you have adequate coverage.

Spotted wing drosophila (SWD) pressure is very high this year across the state in blueberries, cherries and brambles. Low trap counts do not necessarily correlate with low presence in fruit, and once it is seen in traps growers should be monitoring their fruit for SWD. The upcoming rainy conditions may make it difficult to get into fields to reapply protectants for SWD, so the use of adjuvants to enhance the longevity and coverage of sprays may be necessary. You can read about the 2024 outlook for spotted wing drosophila in Michigan cherry orchards.

Local scouts in southeast Michigan have also caught apple maggot and cherry fruit fly in the region. Regional counts for codling moth and oriental fruit moth are down, but the trap line at the Trevor Nichols Research Center in Fennville, Michigan, indicates new generations of each. San Jose scale is at the waxing up stage where they are no longer susceptible to larvicidal treatments. Scab and fire blight pressure remain low and powdery mildew seems to have been kept under control, but the risk of powdery mildew in tree fruit and grapes remains high.

Our southern Michigan virtual grower meetings finished at the end of June. You can see recordings of the latest weekly fruit meetings for southern Michigan on MSU’s Kaltura Media Space (these may take a few days to upload after the Monday meetings).

Fruit-by-fruit conditions

Apples

Apples in the region are generally in the 65-70 millimeter (mm) range. Hand thinning can still be done to improve fruit size and color. Primary scab season is over with all spores being released, but secondary scab risk continues in places that have existing scab infections. Scab and fire blight strikes have been seen in Monroe County and other fire blight strikes have been seen blocks with historic pressure. We expect high infection probability for powdery mildew July 14-18.

Blueberries

Harvest has started in blueberry plantings in Fenton. Anthracnose pressure has been high on the West side of the state, as has SWD. See our collection of factsheets and videos on SWD from Michigan State University Extension.

Brambles

Summer red raspberry U-picks remain open and blackberries and black raspberries are starting to change color. SWD has been caught in the region. See our MSU Extension collection of factsheets and videos on SWD.

Cherries

Harvest has mostly wrapped up in both tart cherries and sweet cherries. There have been reports of problems with both cherry fruit fly and SWD. Read this article on bird management options for fruit growers. See our MSU Extension collection of factsheets and videos on SWD.

Grapes

Berry touch has been seen in Concords, table grapes and cold hardy wine grapes. Diseases of concern include powdery mildew, black rot and Phomopsis.

Strawberries

Harvest has finished. Renovation should begin as soon as you are done harvesting. This is an important step to ensure continued productivity next season. Read this 2023 article on strawberry renovation for additional information.

Peaches and nectarines

Peaches in Fenton and Romeo have passed the pit hardening stage and are moving into the expansion stage. Early peaches like Flaming Fury, Desiree and Rich May have started to be harvested. It is time to think about fungicidal sprays for brown rot for main cultivars.

Pears

Pears observed in Fenton were at 50 mm. Some sooty blotch has been seen, which is a problem exacerbated by pear psylla.

Plums

Golden plum harvest has started. European plums observed in Romeo are at pit hardening but color is not yet changing. The critical period for most fungal control is from petal fall to late June, but for brown rot specifically the critical times are during bloom and later on at fruit coloring.

Insect conditions

Our mid-summer insect conditions remain relatively consistent from week to week. In tree fruit, our insect concerns include codling moth, spotted wing drosophila (for cherries) and apple maggot. In small fruit, spotted wing drosophila remains the biggest concern.

Aphids: While some aphids are best controlled during dormancy, woolly apple aphids are controlled during the season. Woolly apple aphids are moving towards terminals, which is a transition that happens in mid-summer. Aphids can stunt shoot growth and pave the way for secondary fungal infections like sooty mold. Many growers have gotten woolly apple aphids under control and infestations seem light this year.

Borer complex: Lesser Peachtree Borer numbers are climbing in Fennville while greater peachtree borer and dogwood borer have declined. You can read about the current status of Lorsban in this 2024 update. See the 2024 Fruit Management Guide and the article “Timing trunk sprays for the borer complex in cherries.” While chlorpyrifos is available for use this season, alternatives materials may be used to manage borers as well. Assail is a recommended material for a trunk spray once adult borers are active. 

Cherry fruit fly: Scouts in the region have caught cherry fruit fly and some growers are reporting infestations in fruit. The Michigan Department of Agriculture and Rural Development has been scouting for the related European cherry fruit fly, which has been seen in Ontario.

Codling moth: Codling moth catches remain moderate but are dropping, indicating that we may be between generations. You can track the codling moth model on Enviroweather.

Cranberry fruitworm: Scouts in the state have caught cranberry fruitworm.

Grape berry moth: Grape berry moth has been caught, but control is usually most effective in the second and third generations. See this early season grape berry moth management article.

Japanese beetle: These are generalist feeders with a single generation per season. They have been seen in apple orchards in the region and numbers are climbing. If needed, insecticides can be used to control populations.

Oriental fruit moth: Counts are climbing in Fennville, which indicates we could have an emerging second generation. Counts remain low in southeast Michigan. If control for the first generation wasn’t effective, sprays may be needed to control egg laying and larvae in the subsequent generation.

Pear psylla: This may need control throughout the season

Potato leafhopper: Populations can build quickly in June and peak in July. These can cause leaf margins to brown and are a bigger issue in young plantings. Many growers have successfully implemented controls this season.

Raspberry sawfly: Adults emerge in the spring and lay eggs on leaves before bloom. Larvae feed on the leaves.

San Jose scale: San Jose scale is at the “waxing up” stage where larvae are protected from sprays. Characteristic spots on fruit are starting to appear in some locations. Male San Jose scale flight has been observed in Fennville. See the 2024 Fruit Management Guide.  

Disease conditions

Apple scab: We are at the end of primary scab season. There is a chance for secondary scab infection on July 10-11. Scab pressure seems light this year.

Black knot: There is still time to prune out and burn black knot in plums and sour cherries. Fungicides may be used for limited control to supplement pruning and sanitation efforts.

Brown rot: This disease affects stone fruit and can proliferate during bloom. We are at the control point about three weeks before harvest when fruits start to color.

Cherry leaf spot: We expect risk of infection on July 9-11 and 16-17. See this 2013 article on cherry leaf spot management.

Fire blight: Some fire blight strikes have been reported in orchards that have had fire blight in past years, but there do not appear to be many new infections this year. Read this 2020 article from George Sundin for fire blight management options.

Fruit rots: Rots like bitter rot and black rot can be controlled as early as first cover in apples. Humid, warm nights like the ones we have been experiencing activate infections

Grape black rot: There is potential conidi infection on July 10-11 and 16-17 in the region. See this 2014 article for grape black rot management options and consult the 2024 Fruit Management Guide.

Orange rust: Orange rust continues to be a potential problem in brambles. Read the linked article for control options.  

Peach leaf curl: Symptoms are starting to appear, control needed to be done before bud break. The next chance to control it will be with fall sprays.

Phomopsis: In blueberries, the Phomopsis fungus is active from bud swell until after harvest.

Powdery mildew of apple and pear: You can start to include products labeled for powdery mildew in sprays starting at tight cluster. There is a high risk of infection from July 14-18.

Powdery mildew and downy mildew of grape: Scouting should start early for these diseases. There is risk of powdery mildew infection from July 14-15 in the region with downy mildew infection risk peaking the 9-11 and 15-17. Read the linked article for control options.  

While not a disease, nutrient deficiencies can leave plants more susceptible to disease. Now that the plants have leafed out you can start to see some symptoms. They can be hard to definitively diagnose without nutrient testing, but this article from Eric Hanson is a handy guide to what nutrient deficiency symptoms look like.

Seasonal weather update

In the last week, southeast Michigan’s weather warmed back up and we saw about 4 hours of rain accumulating to 0.5 inches of precipitation. We are ahead of the five-year average in both time and amount of rainfall.

In the short term, we are expecting rain from the remnants of Hurricane Beryl on Wednesday, July 10, with more showers possible over the weekend. Temperatures will drop following the storm, but they will climb back up over the weekend, potentially reaching the low 90s.

The long lead outlooks are still calling for warmer than normal conditions for the late spring and summer seasons with normal precipitation levels.

Our regional average growing degree day accumulation for the season are ahead of the five-year averages. This puts us at one to two weeks ahead of normal in most of the region. Read this Michigan State University Extension article to learn more about degree days: Understanding growing degree-days.

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.