Southeast Michigan fruit regional report – June 18, 2013

Strawberry harvest is in full swing; however, cooler temperatures have slowed ripening, resulting in gaps in harvest at most farms


Cool temperatures have slowed fruit growth and development a bit, pushing our season back to behind normal again for both growth stages and growing degree day (GDD) totals. These cooler temperatures have caused a delay in ripening of strawberries at most farms.

Reports of hail were widespread at farms north of Detroit in a series of strong thunderstorms that quickly rolled through the region on Monday afternoon and evening (June 17). Straight line winds also caused some tree tipping in higher density apple blocks.

Most of our east Michigan region received around 1.25 inches of rain in the last week over three to four days. Rainfall totals varied a great deal, however. Soil moisture is more than adequate at most farms.

East Michigan growing degree day totals for March 1 to June 17





Commerce (Oakland)




Emmett (St Clair)




Flint (Genesee)




Lapeer (Lapeer)




Petersburg (Monroe)




Pigeon (Huron)




Romeo (Macomb)




Tree fruits

Apples are approaching 1.5 inches in the south and most are greater than 1 inch in the Flint, Mich., area. More apples are showing up as time goes on, even in freeze-damaged blocks. Honeycrisp leaves are starting to show their typical leaf modeling symptoms.

Many apple growers continue to see fruit drop as a result of thinner applications. I am seeing any June drop yet. Almost all apple growers will need to do a fair amount of hand thinning this season, as thinners did not do the entire thinning job in most apple blocks.

Green apple aphid populations have risen sharply in the past week, with some blocks starting to see some honeydew. In the blocks where honeydew is being found, predators do not seem to be keeping up, so growers need to consider controlling them. Rosy apple aphid leaf curling remains, however the pest has been controlled well this season by predators in most apple blocks. Wooly apple aphids are starting to move from the tree trunks to the terminal branches. A few spotted tentiform leafminer leaf mines are starting to be found. San Jose scale crawlers continue to be seen. I am finding first sightings of potato leafhopper adults at more farms this week. Overall their numbers are low.

Codling moth trap catches remain low. Where trap catches have been high, growers are considering a second insecticide application toward the end of this week. Consult the codling moth model on Enviro-weather for more details. Oriental fruit moth trap catches have remained low again this week. Plum curculio populations have remained very low this season in most of the region, with little fruit “stinging” on any tree fruit this season. Mullein bugs continue to be found in apples; they are now predators. There continues to be high numbers of predators being seen this season.

I have seen a few more scattered fire blight shoot strikes over the last week. Apple scab spore discharge has slowed to a trickle at one of the two spore trapping stations in the region. I expect that it will be the same at the other site when checked later in the day. I will notify growers of the possible end of primary apple scab season later today or first thing in the morning. All of our Enviro-weather stations recorded two to three heavy infection periods in the past week, so growers need to remain covered for those events. I can find just a touch of apple scab leaf infection at most apple farms, and I’ve had a report in the last day of a grower seeing scab lesions on fruit. I continue to see a few twig infections of powdery mildew, mainly on susceptible varieties.

Pears are 22 to 24 millimeters for growers who have a crop.

Peaches are 1 to 1.25 inches size. Peaches fall into two groups this season. Most have an abundant crop on them, in fact so much so that it is taking thinning crews a great deal of time to accomplish hand-thinning. Other blocks have no crop at all and are being abandoned due to the lack of a crop. The foliage in these blocks that have been yellowing and stunted thus far this season continues to look much more like normal in the last two weeks. Tarnished plant bugs continue to be seen in peach blocks. Bacterial spot infection on the leaves continues to be found at many farms.

Sweet cherries are 18 to 21 millimeters in size. Cherries are quickly coloring. These cherries should have been larger prior to coloring. A good number of these cherries are misshaped from cold injury; there is a chance that they will drop early. Birds are starting to feed in sweet cherry blocks. Cherry leaf spot disease symptoms are being seen in many blocks. According to Michigan State University Extension, spotted wing Drosophila traps need to be set in sweet cherries at this time in order to detect first catch of adults.

Tart cherries are 12 to 14 millimeters in size. Tarts are starting to color as well, and I have some of the same concerns for tarts that I do for sweet cherries. Cherry leaf spot disease symptoms are being seen in most tart cherry blocks. Spotted wing Drosophila traps need to be set in tart cherries at this time in order to detect first catch of adults.

Plums are 23 millimeters in size for European types and 20 millimeters for Japanese types where growers have a crop this season. Aphid populations are quickly building in many plum blocks. Growers need to continue to be on the lookout for black knot infections as I am finding much more of it in the last three weeks.

Small fruits

Strawberry harvest is in full swing. Varieties are slow to ripen in these cooler than normal temperatures, causing gaps in harvest. While this cool weather can be a plus for holding berry firmness and quality, the downside to this season’s slow ripening is that many farms need to stop sales for a day or two in order to supply the excellent demand for strawberries. Wet field conditions have also been a problem.

Several weeks ago I reported seeing the bacterial disease angular leaf spot in a few strawberry fields. Last week I had many reports of recent angular leaf spot infections. Growers need to carefully scout for this disease at this time. I have no new pests to report in strawberries this week. Growers need to be on the lookout for tarnished plant bugs, potato leafhopper adults, spittle bugs, strawberry leafrollers and slugs. I continue to see bird feeding damage to mature to over-mature fruit.

Newly planted berries are runnering well. Lastly, growers need to be sure to keep newly planted berries de-blossomed flowered, as this will greatly encourage runner development.

Raspberries are at 24 inches of new growth for summer-bearing types, with green fruit in most varieties. Canes of fall-bearing types are about 24 to 30 inches tall where they were not killed back to the ground from the May 13 freeze event. Spotted wing Drosophila traps need to be set in summer raspberries at this time in order to detect first catch of adults.

Blueberries are 14 to 16 millimeters for Blueray and Bluecrop and 10 millimeters for Jersey and most other varieties. Spotted wing Drosophila traps need to be set in blueberries at this time in order to detect first catch of adults.

Grape cane growth continues at a rapid pace, with new canes at 36 inches of growth. Concord types are in bloom and French hybrid types are nearly ready to begin bloom. Bloom has been very slow to develop in grapes this season due to cooler temperatures. Grape berry moths have been very active in wild grape vines.

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