MSU Extension Fruit & Nuts

Welcome to the 13th 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 two weeks since the last update, many farms have moved further into peach harvest, with farms in warmer areas starting Red Haven. Growers in the region have been carrying early apples like ‘Lodi’ and ‘Yellow Transparent’ for a couple weeks with ‘Paula Red’ fast approaching. Grape growers around the state, including in southeast Michigan, are reporting veraison in their first varieties, including ‘Marquette.’ 

We’ve seen an average of 3 inches of rain in the region over nearly 30 hours of rainfall in the last two weeks while temperatures have hovered below normal. 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. A virtual training is being offered on using Enviroweather on Friday, July 26, and registration can be found here. 

We are expecting scattered showers Tuesday (July 23) into Wednesday followed by clear conditions until early next week when showers and storms again become possible on Monday and Tuesday. Temperatures will climb to the mid-80s over the weekend with lows in the 50s. You can see an overview of disease risks on the RimPro interactive location chart. Make sure to check the models frequently as they change with weather forecasts. 

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. 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 75-80 millimeter (mm) range. Early cultivars like Lodi and Yellow Transparent have been harvested with Paula Red coming up quickly. We expect high infection probability the entirety of the next week. 

Blueberries 

Blueberry harvest continues. 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 

Blackberries and black raspberries are starting to ripen. Most summer bearing raspberry U-picks have closed. SWD has been caught in the region. See our MSU Extension collection of factsheets and videos on SWD. 

Cherries 

Harvest has wrapped up in both tart cherries and sweet cherries. There have been reports of problems with both cherry fruit fly and SWD and some growers have asked about SWD control post harvest. A 2017 MSU bulletin on SWD reports, “At the end of harvest, cherries, especially tart cherries, should not be left on the tree as SWD readily infest them leading to increasing pest densities. Additionally, there is evidence that flailing or otherwise crushing dropped fruit will help reduce post-harvest opportunities for SWD infestation, build-up and movement to adjacent orchards.” 

Grapes 

We have seen veraison in ‘Marquette’ in southeast Michigan as well as other parts of the state. 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 

Red Haven harvest is starting in warmer parts of the region. There may still be time to use fungicidal sprays for brown rot for later cultivars. 

Pears 

Pears observed in Fenton were 60 mm on July 15. Some sooty blotch has been seen, which is a problem exacerbated by pear psylla. 

Plums 

Italian plums were changing color in Romeo as of July 15, with Golden plums and early red skin plums available in markets. 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 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. Some light infestations of green apple aphids have been reported by scouts. 

Borer complex: Lesser peachtree borer numbers are climbing in Fennville while greater peachtree borer and dogwood borer have declined. Dogwood borer counts have been increasing in northwest Ohio, so they may climb in Michigan soon. 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, but recent trap counts have been low and cherry harvest is done. 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 have been climbing, indicating that we have entered into another generation. You can track the codling moth model on Enviroweather. 

Grape berry moth: Grape berry moth catch is down, indicating the end of a generation. 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 stable in Fennville but have remained 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. 

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.   

Spotted wing drosophila: SWD are still be caught in traps and larvae are still being found in fruit. Trap counts don’t necessarily correlate with crop pressure; high pressure can exist with low trap counts. 

Disease conditions 

Apple scab: We are at the end of primary scab season. There is a chance for secondary scab infection on July 30-31. Scab pressure seems light this year. 

Brown rot: This disease affects stone fruit and can proliferate during bloom. There is still time to use control measures for later varieties three weeks before harvest when fruits start to color. 

Cherry leaf spot: We expect risk of infection on July 30-31. 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 30-31 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 24-31. 

Powdery mildew and downy mildew of grape: Scouting should start early for these diseases. There is risk of powdery mildew infection from July 24-31 in the region with downy mildew infection risk peaking the 30-31. 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 two weeks, we saw about 30 hours of rain accumulating to 3.1 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 a dry period from Thursday to Sunday bookended by scattered showers and storms on Wednesday and next Monday. Temperatures will climb into the mid-80s over the weekend with lows in the 50s. 

The medium term outlooks are projecting wetter and warmer than normal conditions through August with long the long lead projecting warmer than normal temperatures to continue beyond then. 

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.