Southeast Michigan fruit update - August 22, 2023

Table grapes are starting, apples and peaches continue, and pest scouting is winding down.

Spotted lanternfly trap
Spotted lanternfly trap set up on a tree of heaven at the Tollgate Farm in Novi, Michigan, Aug. 10, 2023. Photo by Derek Plotkowski, MSU Extension.

Welcome to the 19th in-season fruit article update for southeast Michigan for the 2023 season. With apple harvest imminent and most pest and disease intervention finished these updates will be less frequent through the fall. 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

The upcoming week will be a mixture of weather conditions, with showers and storms possible Tuesday, Aug. 22, into Thursday followed by fair and dry conditions into the weekend. While much of our region remains in a state of “abnormally dry” conditions according to the U.S. Drought Monitor, some areas are back in the normal range and the whole region has above normal soil moisture in present conditions.

Growers are moving through peach harvest, with Redhaven mostly wrapped up. Raspberry u-picks remain open, but blueberries would only have a few lingering locations still picking. Paula Reds and Ginger Golds are in season for apples with Premier Honeycrisp being picked in the warmest parts of the region. Here is a recent article from Penn State Extension that serves as a good refresher for apple maturity indices.

Based on the RimPro models at the Romeo station, for which you can see you an overview by following the link, we will see continued risk for apple powdery mildew. The similar weather patterns we’ve seen the last couple weeks and expect to continue will bring about similar disease patterns.

Most pest scouting is winding down for the season as we get close to harvest. Some growers have used some of their final sprays, but it is important not to neglect late season cultivars like Northern Spy and Evercrisp that may need extra protection that can still be applied while respecting pre-harvest intervals. Apple maggot, brown marmorated stink bug, and spotted wing drosophila have been caught in the region. Spotted wing Drosophila counts are rising, so bramble growers should still be treating if possible with their pre-harvest intervals. Here is a collection of spotted wing Drosophila factsheets that MSU Extension has put out. Among the collection of videos and factsheets is this video on insecticides for spotted wing Drosophila control. Brown marmorated stink bug numbers are also climbing. A good way to prepare for it this season is to read this management factsheet for brown marmorated stink bug in Michigan. Apple maggot numbers remain low outside of hot spots.

Our Southern Michigan Fruit IPM weekly meetings wrapped up at the end of June. The back catalog of the weekly fruit meetings for southern Michigan can be seen on MSU’s Kaltura Mediaspace.

Fruit-by-fruit conditions

Apples: McIntosh harvest is expected the week of Sept. 6 in warmer parts of the region. Apple maggot has been caught in the region but counts remain low. Brown marmorated stink bug populations are climbing, with numbers ranging from zero to five adults depending on the site. Paula Reds and Ginger Golds are being picked in most of the region with Premier Honeycrisp being picked in warmer areas.

apples on a tree
Apples on tree in Britton, Michigan, Aug. 10, 2023. Photo by Derek Plotkowski, MSU Extension.

Blueberries: U-pick blueberry harvest is mostly wrapped up  but continues in some spots.

blueberries ready for harvest
Blueberry ready to harvest in Fenton, Michigan, Aug. 14, 2023. Photo by Derek Plotkowski, MSU Extension.

Brambles: Some summer red raspberry patches have ended harvest and been mowed down, though harvest continues in other places. Blackberry harvest also continues. Growers should continue to protect plants from spotted wing Drosophila.

Raspberries on a bush
Raspberries in Fenton, Aug. 14, 2023. Photo by Derek Plotkowski, MSU Extension.

Cherries: Sweet and most tart cherries are harvested.

Grapes: Early table grapes, like Reliance, are being harvested in Lenawee County. We are seeing color change in some varieties, like Marquette and Frontenac. From this point the berries will start to ripen and sugars will increase. This can be measured in the field with a refractometer. Growers interested in protecting their grapes from birds may want to read this recent MSU Extension article on bird damage reduction.

Grapes on the vine
Reliance grapes in Britton, Aug. 17, 2023. Photo by Derek Plotkowski, MSU Extension.

Strawberries: Most growers have wrapped up harvest. Renovation should start as soon as harvest is finished.

Peaches and nectarines: Red Haven harvest has mostly wrapped up and growers have started to pick late season cultivars.

Pictured: Peach in Romeo, MI, August 14, 2023. Photo by Derek Plotkowski, MSU Extension.

Pears: Both Asian and European pear fruits continue to size up.

Asian pears in Macomb Township, MI, August 14, 2023. Photo by Derek Plotkowski, MSU Extension.

Plums:In southwest Michigan, early European plums are being harvested with Stanleys starting in about a week. Much of southeast Michigan (depending on where) is roughly a week behind southwest Michigan, so expect early European plums in about a week and Stanleys in about two weeks. Continue to pay attention to brown rot, codling moth and spotted wing drosophila.

Disease conditions

Apple black rot has been seen in the region. Fruits with this condition will often ripen well ahead of healthy fruit and can be a source of spores to infect other fruit. These fruits should be removed from the orchard.

Apple powdery mildew has been seen in the region, and the RimPro model indicates that we are entering another period of high infection risk. Here is a link for a 2010 article on what to do with current apple powdery mildew infection. As always with older articles cross check the recommendations for chemicals with the current E-154 guide.

Apple scab has been reported in the region in susceptible cultivars and locations. We are past the primary scab infection window. If scab is present in your orchard, you may need to spray to prevent secondary infections.

Fire blight strikes have been seen in the region, especially in areas with recurring infections and areas that experienced physical damage. For shoot blight, strikes should be pruned out with cuts 12-18 inches below visible damage and instruments should be sanitized between cuts. Here is some practical management information from Washington State Extension. Some unique fire blight symptoms have been showing up in cider apples like Dabinett, where leaf margins also get a burnt look.

We have the potential for some grape powdery mildew infections this week.

Pear rust is primarily controlled by separation of juniper species from pear plantings (much like cedar apple rust). Symptoms appear on pears in summer, but most control needs to happen early in the season when galls appear on junipers (around May).

Peach rusty spot has been seen in the region.

Scouts are seeing sooty blotch in the centers of trees with large canopies, but not in high-density orchards with good spray penetration.

Insect conditions

samba wasps
Samba wasps (Ganaspis brasiliensis) ready for release in Leelanau County for biocontrol of spotted wing drosophila, Aug. 15, 2023. Photo by Derek Plotkowski, MSU Extension.

In tree fruit, we are at the point of controlling summer pests like spotted wing Drosophila, brown marmorated stink bug and apple maggot. The E-154 guide can be purchased here:

Apple maggot: Scouts have seen these around the region. Areas that usually have high pressure are seeing high counts, but numbers are lower than last week with zero to two maggots being found on most traps.

Brown marmorated stink bug: We are seeing small, though rising, numbers of brown marmorated stink bug (zero to five per trap), which is expected to climb as we get closer to harvest. Early control is key here because they will continue to be a pest up until harvest when sprays are not possible because of pre-harvest intervals.

Codling moth: Numbers are mostly down with catches in the teens. Many people of put their final covers on for this pest.

Grape berry moth: We should be a little past the start of the third generation. Second and third generation control are most effective at reducing infestations during harvest.

Oriental fruit moth: Catches are down.

Spotted lanternfly: We haven't had new reports yet this year of spotted lanternfly in the state outside of the last year's infestation site. I set up some traps this week and last week and I have been monitoring orchard sites all summer.

Spotted wing Drosophila: Scouts in southeast Michigan caught some spotted wing Drosophila in grapes and raspberries. Numbers are climbing, with catches in traps as high as 9 each week. spotted wing Drosophila infestations can still be present when catches are low and the damage from spotted wing Drosophila can be extensive enough that for many growers it makes sense to treat susceptible crops even if there are low counts in traps. Familiarize yourself with information on our spotted wing Drosophila factsheets page. Among the collection of videos and factsheets is this video on insecticides for spotted wing Drosophila control.

Woolly apple aphid: Many growers have got these under control this season, though they remain heavy in hot spots.

Seasonal weather update

Through the rest of the week, we expect warm, humid and cloudy conditions with scattered showers and storms, with temperatures rising to the low 90s on Thursday. Friday through the weekend should be dry and cooler. Lows will mostly be in the 50s and 60s, but over the weekend we may see high 40s.

Despite more consistent precipitation, much of the region remains in a state of “abnormally dry” conditions according to the U.S. Drought Monitor. MSU Extension has a collection of articles related to drought on its drought resources page.

Liquid Precipitation Accumulation Mar. 1 - August 22, 2023, issued August 22, 2023
Station (County) Rainfall Total (in.) Current Hours with Rainfall Current Rainfall Total Average (5 Yr.) Hours with Rainfall  Average (5 Yr.)
Commerce (Oakland) 19.2 313 17.0 268
Deerfield (Monroe) 16.2 256 16.7 269
East Lansing MSU Hort (Ingham) 18.0 276 15.9 254
Emmett (St. Clair) 23.4 334 13.9 283
Flint (Genesee) 19.6 289 15.8 260
Freeland (Saginaw) . . . .
Hudson (Lenawee) 16.9 252 17.8 294
Ithaca (Gratiot) 17.3 248 15.5 244
Lapeer (Lapeer) 18.3 246 15.0 262
Linwood (Bay) 17.6 261 14.9 252
Pigeon (Huron) 18.2 280 13.9 243
Richville/Frankenmuth (Tuscola) 18.1 260 14.8 232
Sandusky (Sanilac) 16.0 . 13.9 226
Romeo (Macomb) 20.2 306 15.9 246
Average of stations in this region: 18.4 276.8 15.5 256.4
Difference in Liquid Precipitation Accumulation from Mar. 1 observed August 15 and August 22, 2023; issued August 22, 2023
Station (County) Rainfall Total (in.) August 15 Rainfall Total (in.) August 22 Difference from August 15-22 Hours with Rainfall August 15 Hours with Rainfall August 22 Difference from August 15-22
Commerce (Oakland) 18.7 19.2 0.5 308 313 5.0
Deerfield (Monroe) 15.8 16.2 0.4 252 256 4.0
East Lansing MSU Hort (Ingham) 17.4 18.0 0.6 273 276 3.0
Emmett (St. Clair) 22.7 23.4 0.7 329 334 5.0
Flint (Genesee) 18.6 19.6 0.9 282 289 7.0
Freeland (Saginaw) . . . . . .
Hudson (Lenawee) 16.5 16.9 0.4 248 252 4.0
Ithaca (Gratiot) 16.7 17.3 0.6 244 248 4.0
Lapeer (Lapeer) 17.7 18.3 0.7 240 246 6.0
Linwood (Bay) 16.8 17.6 0.8 254 261 7.0
Pigeon (Huron) 17.5 18.2 0.8 274 280 6.0
Richville/Frankenmuth (Tuscola) 17.2 18.1 0.9 254 260 6.0
Sandusky (Sanilac) 15.6 16.0 0.4 318 . .
Romeo (Macomb) 19.6 20.2 0.7 302 306 4.0
Average of stations in this region: 17.7 18.4 0.6 275.2 276.8 5.1

The medium range guidance calls for near to cooler than normal temperatures with below normal precipitation in the next couple weeks.

The current long lead outlooks for the fall have mean temperatures from normal to above normal and precipitation from normal to below normal.

Our regional average growing degree day accumulation has fallen behind the five-year average.

Read this Michigan State University Extension article to learn more about degree days: Understanding growing degree-days.

GDD totals for southeast Michigan.

Degree Day Accumulation Mar. 1 -August 22, 2023, Forecast from August 22-27, 2023; issued August 22, 2023
Station (County) Degree Days Base 42°F Current Degree Days Base 42°F  Average (5 Yr.) Degree Days Base 42°F Forecast Degree Days Base 45°F Current Degree Days Base 45°F Average (5 Yr.) Degree Days Base 45°F Forecast Degree Days Base 50°F Current Degree Days Base 50°F Average (5 Yr.) Degree Days Base 50°F Forecast
Commerce (Oakland) 2833 3072 3012 2444 2683 2605 1848 2076 1979
Deerfield (Monroe) 3060 3300 3247 2656 2892 2824 2037 2262 2175
East Lansing MSU Hort (Ingham) 2941 3116 3117 2548 2722 2705 1946 2109 2073
Emmett (St. Clair) 2646 2919 2804 2260 2536 2401 1673 1944 1784
Flint (Genesee) 3035 3249 3209 2635 2852 2791 2022 2232 2148
Freeland (Saginaw) 2847 3029 3009 2457 3644 2601 1863 2044 1977
Hudson (Lenawee) 2936 3127 3121 2542 2732 2709 1940 2119 2076
Ithaca (Gratiot) 3027 3119 3196 2631 2730 2782 2018 2121 2139
Lapeer (Lapeer) 2790 3008 2955 2402 2621 2549 1813 2021 1930
Linwood (Bay) 2680 2895 2840 2297 2515 2439 1714 1927 1826
Pigeon (Huron) 2758 2865 2915 2377 2491 2516 1793 1911 1902
Richville/Frankenmuth (Tuscola) 2962 3106 3126 2565 2717 2711 1956 2109 2072
Sandusky (Sanilac) 2775 2915 2933 2391 2539 2531 1800 1954 1910
Romeo (Macomb) 2895 3156 3064 2501 2763 2653 1893 2153 2014
Average of stations in this region: 2870 3063 3039 2479 2746 2630 1880 2070 2000
Difference in Degree Day Accumulation from Mar. 1 observed August 15, and August 22, 2023; issued August 22, 2023
Station (County) Degree Days Base 42°F  August 15 Degree Days Base 42°F  August 22 Degree Days Base 42°F Difference Degree Days Base 45°F August 15 Degree Days Base 45°F August 22 Degree Days Base 45°F Difference Degree Days Base 50°F August 15 Degree Days Base 50°F August 22 Degree Days Base 50°F Difference
Commerce (Oakland) 2671 2833 162.0 2303 2444 141.0 1742 1848 106.0
Deerfield (Monroe) 2889 3060 171.0 2506 2656 150.0 1921 2037 116.0
East Lansing MSU Hort (Ingham) 2777 2941 164.0 2404 2548 144.0 1837 1946 109.0
Emmett (St. Clair) 2502 2646 144.0 2137 2260 123.0 1585 1673 88.0
Flint (Genesee) 2863 3035 172.0 2484 2635 151.0 1906 2022 116.0
Freeland (Saginaw) 2686 2847 161.0 2318 2457 139.0 1758 1863 105.0
Hudson (Lenawee) 2774 2936 162.0 2401 2542 141.0 1833 1940 107.0
Ithaca (Gratiot) 2859 3027 168.0 2484 2631 147.0 1906 2018 112.0
Lapeer (Lapeer) 2634 2790 156.0 2267 2402 135.0 1712 1813 101.0
Linwood (Bay) 2527 2680 153.0 2165 2297 132.0 1616 1714 98.0
Pigeon (Huron) 2602 2758 156.0 2242 2377 135.0 1692 1793 101.0
Richville/Frankenmuth (Tuscola) 2801 2962 161.0 2425 2565 140.0 1852 1956 104.0
Sandusky (Sanilac) 2617 2775 158.0 2254 2391 137.0 1698 1800 102.0
Romeo (Macomb) 2726 2895 169.0 2354 2501 147.0 1781 1893 112.0
Average of stations in this region: 2709 2870 161 2339 2479 140 1774 1880 106

Watch Jeff Andresen's biweekly agricultural weather forecast reports.

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.

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