MSU Extension Fruit & Nuts

Welcome to the 15th 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 into early major apple varieties, including Wildfire Gala, Early Macs and Premier Honeycrisp. Some farms have wrapped up peach harvest, with some later cultivars like ‘Cresthaven’ still being picked. Some table grapes have hit markets and ‘Concord’ has moved into veraison.

We’ve seen an average of 1.8 inches of rain in the region over about 31 hours of rainfall in the last two weeks while we’ve experienced a slight temperature drop. When using 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 was offered on using Enviroweather on Friday June 26 and the recording can be found here.

After today’s rain, we are experiencing cooler temperatures and clear conditions for the remainder of the week with showers possible over the weekend. Temperatures will climb back up into the 80s over the weekend and into 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.

It has been a relatively quiet two weeks on the insect front. Brown marmorated stink bug counts are climbing in orchards. BMSB can be challenging to control because of their activity close to harvest. See this linked factsheet on managing BMSB. Spotted wing drosophila pressure is very high this year across the state in blueberries and brambles. Low trap counts do not necessarily correlate with low presence in fruit. Regional counts for codling moth have stabilized after a brief increase while those for oriental fruit moth are down. Low counts of apple maggot continue to be caught in some orchards. Secondary scab pressure remains low and powdery mildew seems to have been kept under control, but the risk of powdery mildew in tree fruit and grapes remains high for the entire week.

Fruit-by-fruit conditions

Apples

Apple harvest in the region has moved into some of the early major cultivars, including Paula Red, Zestar, Early Mac and Premier Honeycrisp. We are only one week away from our predicted McIntosh harvest dates for warmer parts of the region. You can see our predicted harvest dates for Southeast Michigan at this link. We expect high infection probability for powdery mildew the entirety of the next week.

Blueberries

Blueberry harvest continues at some U-pick operations, but it is coming to a close. Anthracnose pressure has been high on the West side of the state, as has spotted wing drosophila. See our MSU Extension collection of factsheets and videos on SWD.

Brambles

Blackberry growers have been picking ripe fruit for a couple weeks already with a report of a good crop. Some raspberry u-picks are open for their fall bearing fruit. Spotted wing drosophila 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 spotted wing drosophila 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 saw veraison in Concord start this week in Romeo. Table grapes including Canidice, Venus, and Reliance were being harvested last week in Britton. Higher value varieties at some vineyards have been put under bird netting. Diseases of concern include powdery mildew, black rot and Phomopsis. Powdery mildew infection risk is moderate to high for the entirety of the week, while downy mildew and black rot infection risks are low.

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

We are close to the end of peach season, with some farms already done harvesting and a few working through Cresthaven.

Pears

Bartlett pear harvest has started in Fenton. Some sooty blotch has been seen, which is a problem exacerbated by pear psylla.

Plums

Italian plums and later prune plums continue to ripen on trees. Like other crops their harvest is likely to be ahead of schedule. Brown rot control is critical around the time of fruit coloring and there may still be time for control in cooler parts of the region.

Insect conditions

Our mid-summer insect conditions remain relatively consistent from week to week and the last few weeks have been pretty quiet. In tree fruit our insect concerns include codling moth, apple maggot, and brown marmorated stink bug. In small fruit spotted wing drosophila and grape berry moth are the biggest concerns.

Aphids: Woolly apple aphid counts are down after a mid-summer spike. While some aphids are best controlled during dormancy, woolly apple aphids are controlled during the season. Woolly apple aphids have moved towards terminals, which is a transition that happens in mid-summer. See linked articles for more information. 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.

Brown marmorated stink bug: Scouts are reporting a few brown marmorated stink bug adults in orchards that have historically had problems. See this factsheet on managing brown marmorated stink bug in Michigan orchards.

Borer complex: Lesser peachtree borer numbers are climbing in Fennville and greater peachtree borer counts are increasing. Dogwood borer counts remain at zero. 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.

Codling moth: Codling moth catches have dropped after a slight uptick in Southeast Michigan, and remain on the low side. You can track the codling moth model on Enviroweather.

Grape berry moth: Grape berry moth catch is down to zero in Fennville, indicating that we are between generations. Control is usually most effective in the second and third generations.

Japanese beetle: These are generalist feeders with a single generation per season. They have been seen in apple orchards in the region but we seem to be past the peak. 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

San Jose scale: Characteristic spots on fruit are starting to appear in some locations. Male SJS counts have dropped over the last couple weeks in Fennville. See the fruit guide. Some growers have asked about mating disruption in SJS. Research indicates that it is an effective tool but there are no commercially available approved products. This survey (linked here) is gauging interest in this method of control.

Spotted wing drosophila (SWD):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: This week has a low probability of secondary scab infection. Scab pressure has been light this year.

Brown rot: This disease affects stone fruit and can proliferate during bloom. There may still be time to control in later varieties starting three weeks before harvest when fruits start to color, but be mindful of pre-harvest intervals.

Cherry leaf spot: We do not expect the risk of infection in the next week. See this 2013 article on cherry leaf spot management. It can be helpful to control cherry leaf spot outside of the season to prevent inoculum buildup in the orchard.

Fire blight: We do not anticipate fire blight risk this week. Strikes have primarily been reported in orchards that have had fire blight in past years, but there do not appear to be many new infections this year. Fire blight is not limited to springtime infection and it can infect orchards with existing infections in the fall. 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. Our current cool and dry conditions should limit rot development.

Grape black rot: There is not much infection risk this week. See this 2014 article for grape black rot management options and consult E-154.

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

Peach leaf curl: Control needed to be done before bud break. The next chance to control it will be with fall sprays in preparation for next season.

Phomopsis: In blueberries the Phomopsis fungus is active from bud swell until after harvest. Phomopsis has been seen in grapes in the region.

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 the entire week.

Powdery mildew and downy mildew of grape: Scouting should start early for these diseases. There is risk of powdery mildew infection 21-29 in the region. Downy mildew infection risk is low this week with a small peak August 26. 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 31 hours of rain accumulating to 1.8 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 cool and dry weather through the end of the week with the possibility of isolated showers over the weekend. Temperatures will climb back into the 80s over the weekend into early next week and there’s potential for lows in the upper 40s Wednesday with lows climbing back to 60s by the weekend.

The medium term outlooks are projecting a transition to warmer than normal conditions with below normal precipitation after the cool temperatures of the next few days. The long lead currently calls for warmer than normal conditions with normal precipitation.

Our regional average growing degree day accumulation for the season are ahead of the 5 year averages. This puts us at 1 to 2 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.