East Michigan fruit update – June 9, 2020

Warmer temperatures brought a good amount of new growth in all fruit crops and rapid rise of growing degree day totals. Strawberry harvest will begin later this week at some farms. Soils continue to dry quickly.


With warm temperatures for the second week in a row, we have seen rapid growth in all our fruit crops. As a result of another week of warm temperatures, we saw another big jump in growing degree day (GDD) accumulations. Most of our Michigan State University Enviroweather stations have seen a jump of 120 to 160 GDD base 50 accumulations in the last week.

Our season has now moved back to normal to even a few days ahead of normal for both growth stages and GDD. Our season was 14 days behind normal just three weeks ago.

Precipitation totals have varied greatly over the last week, but at the most a few of our MSU Enviroweather stations have seen close to 0.5 inches of rain last Wednesday, June 3. Our soils have continued to quickly dry out due to high temperatures and generally strong winds. Strawberries and newly planted tree and small fruit crops need supplemental irrigation at this time.

East Michigan growing degree day (GDD) totals for March 1 to June 8, 2020





Commerce (Oakland County)




Deerfield (Monroe County)




Emmett (St Clair County)




Flint (Genesee County)




Freeland (Saginaw County)




Lapeer (Lapeer County)




Pigeon (Huron County)




Romeo (Macomb County)




Tree fruits

Apples have moved quickly over the last week with most fruit doubling in diameter, now at 14 to 20 millimeters in diameter. Most apple varieties have between 12 to 16 inches of new terminal growth.

Most apple growers have applied a second thinner application in the past week. Fruitlets are starting to drop as a result of these thinner applications. June drop is just starting as well in some varieties. It is hard to distinguish between fruit that is dropping as a result of thinners and June drop. Except for apples in the Ann Arbor, Michigan, area, most apple growers appear to have a nice crop. Hand thinning will most likely be needed in many apple varieties. Ann Arbor was hardest hit from the three frost events of this spring, with little to no crop remaining.

There are two new insect pests to report in apples this week: white apple leafhopper adults feeding on leaves and a few twospotted spider mites feeding in newer leaves. Their numbers are low at this time. Woolly apple aphids continue to be seen around old pruning scars and a few potato leafhoppers are on apple leaves. I saw my first of the season codling moth larvae yesterday. Trap counts of adults are generally declining. Rosy apple aphid populations are about the same as last week, predators have been feeding heavily on them. Oriental fruit moth, obliquebanded leafroller, redbanded leafroller and spotted tentiform leafminer trap catch numbers are all down. Beneficials or predators are starting to be seen over the last week, mainly lady beetles and lacewing adults.

Last week I reported finding a few cedar apple rust infected leaves. This week I am seeing it in light amounts in more apple blocks. For the second week in a row, the fire blight model on Enviroweather has had very high EIP numbers, and many growers have sprayed mid-week last week to control it. There are reports of some fire blight shoot strikes in the Grand Rapids area, but I have not seen or heard of any in east Michigan. With no bloom remaining in apples, the risk of fire blight infection is reduced but it is not over yet. Twigs can be infected in trauma events. We are expecting strong winds tomorrow.

I continue to find a few leaves with apple scab lesions. Based on apple scab spore numbers in the Grand Rapids, Michigan, area, we are not at the end of primary apple scab season yet. With rain predicated for tomorrow, I expect that the end of primary apple scab season is very close.

Some apple blocks have high numbers of powdery mildew infected terminals on mildew prone varieties. Protection programs need to be ongoing on mildew prone varieties.

Pears are mostly 15 to 20 millimeters in size. Most pear growers have seen a good amount of fruit drop in the past week. Pear psylla adult numbers continue to slowly raise with warmer temperatures.

Peaches are between 18 and 22 millimeters in diameter. Their size has doubled in the past week. Fruit drop is continuing due to frost damage on poorer peach sites. Some poorer peach sites have seen a good amount of damage with the best peach sites having a full crop. Thinning has begun in some blocks. Green peach aphids continue to be found in many peach blocks. Peach leaf curl symptoms are common across the region.

Sweet cherries remain around 10 to 13 millimeters for the largest sized fruit. A good amount of the remaining fruit is continuing to yellow and drop. I suspect that some of this fruit will drop as well. Most growers have seen a good amount of fruit drop over the last three weeks. Larger sized trees seem to have had lots of fruit drop, with younger trees having more crop. The crop potential is now reduced to the 5 to 10% range. Many growers report they will not be opening for either ready picked or pick your own. Several blocks have plum curculio damage. Leaf spot control programs need to be maintained at least for the time being.

Tart cherries also remain about the same diameter as last week, they are mostly 10 to 11 millimeters in diameter. As is the case in sweet cherries, I am finding a good amount fruit drop this week. Most blocks only have 5 to 10% of a crop remaining. As is the case in sweet cherries, many growers report they don’t have enough crop to open for tarts. Leaf spot control programs need to be maintained at least for the time being.

Plums are 17 millimeters in diameter for European varieties, with Japanese varieties 18 to 20 millimeters in diameter. I continue to find many plum blocks that have a poor crop due to freeze damage.

Small fruits

Strawberry fruit are coloring and sizing well at most farms. Many farms to the south are expecting to begin harvest of a few berries later this week. The new leaves on both newly planted and fruiting plants are looking more normal. Leaves on newly planted strawberries continue to emerge from the crown, with the first flower trusses just starting to emerge from the crown. I have not seen any runners yet.

I have seen a number of strawberry fields that appear to have had feeding injury from thrips earlier this season. The feeding was most likely from western flower thrips. However, I have not been able to find any adult thrips. This is a difficult insect pest to scout for as they do their feeding damage when flowers are opening and early in the flowering process, then they move on to feed on other plants. Western flower thrips do not overwinter in colder climates like Michigan. They come to Michigan with storm fronts from the south. The damage appears as seedy small berries that have a bronze color. Please be on the lookout for this feeding damage (see the “West central Michigan small fruit update – June 9, 2020” for pictures of this damage). Many times, the feeding damage will just be seen a single variety that was at the right stage for thrips to do their damage.

With many soils being dry, keep a close eye on soil moisture levels. Developing strawberries need around 1.5 inches of either rainfall or irrigation a week.

Slugs were found last week at a few farms. Thoroughly scout now to check for the presence of slugs. Low numbers of spittlebugs continue to be found in strawberries. No strawberry clipper adults or damage has been found yet, but be on the lookout for adults or feeding injury to flower petals or flower stems. I have not seen any tarnished plant bug feeding damage yet this season.

Raspberry growth has continued to be rapid again this week as a result of warmer temperatures. Many summer raspberries have fingernail sized berries. Many summer varieties have new canes that are 12 to 15 inches in length. During the last few weeks, new leaves on fall raspberries were slightly yellowed. Many growers that have fertilized are seeing this symptom of yellow leaves turn back to a good, healthy green color. These yellowed leaves might have been caused from herbicide injury, most likely from Sinbar.

Blueberries are mostly at fruit set for most varieties. They are mostly between 5 to 8 millimeters in diameter. Blueberry stem gall wasp adults are continuing to emerge.

Saskatoon fruit are 5 to 7 millimeters in size. Berries are starting to color. New shoots are growing quickly with most being 15 to 18 inches in length.

Grapes have moved quickly again this week, with most having flower clusters fully emerged. I have not seen any bloom yet, but it is very close. Wild grapes are in bloom. Many new canes are 14 to 20 inches in length.

Haskap fruit are mostly 6 to 8 millimeters in diameter.

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