East Michigan fruit update – July 28, 2020

With another week of hot temperatures and not much precipitation, drought conditions returned. Blueberry harvest continues, early peach harvest begins and summer red and black raspberry harvest is ending.

Photo by Bob Tritten, MSU Extension


A few growers received nearly a half-inch of rain in the last week, but for most growers the rain events have not been enough to “settle the dust.” Most soils have slipped back to drought conditions this week after a brief respite when modest rains came the week before last. Most growers resumed irrigation. Signs of drought stress on newly planted, young fruit crops and shallow rooted fruit crops, like raspberries, were once again becoming apparent yesterday, July 27.

While precipitation totals for east Michigan since June 1 vary greatly over short distances, the average for the eight Michigan State University Enviroweather stations that I track growing degree day totals (GDD) is just 3.6 inches. The range of precipitation totals is a low 2 to 5 inches. We had only two good widespread good rains during this timeframe, one on June 10 and the other on July 10. The driest portions of the region are the far southeast corner of the region and over most of the Thumb.

With another week of warm to hot temperatures last week, we saw another good jump in growing degree day (GDD) accumulations. Most of our MSU Enviroweather stations have seen a rise of another nearly 175 GDD base 50 accumulations again this past week.

Our season is still five to seven days ahead of normal for GDD and three to five days ahead of fruit crop growth stages.

East Michigan growing degree day (GDD) totals for March 1 to July 27, 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 continued to size this week, but their growth rate has slowed over the past three weeks. This reduced growth rate is most likely the result of dry soils/drought. Lodi harvest is underway at most farms. More fruit color is being seen on several varieties this week.

Most apple fruit are 1.75 to 2.25 inches in diameter, with Honeycrisp 2.125 to 2.5 inches and a few of the largest, well-thinned Honeycrisp blocks having fruit at 2.75 inches. Hand-thinning continues for many apple varieties. Some Honeycrisp growers are finding they will need to go back through some blocks to do a second round of thinning, as they did not drop enough fruit the first time. Proper thinning is key on Honeycrisp to promote good return bloom next season.

Again this week there are no new insect pests to report in apples, but there are several developments on insects we have already seen this season. Apple maggot trap catch has remained strong over the last week, mostly on red ball traps. Codling moth trap catch continues to be high; I believe this is the beginning of the second generation adult flight. However, codling moth trap catch numbers didn’t seem to drop off after the first generation adult flight. Keep covered for apple maggot and codling moth. More growers are finding light amounts of San Jose scale damage on fruit this week. Woolly apple aphids have been moving to terminal branches, and a few growers are finding clumps of woolly’s on terminal branches.

This week, twospotted spider mite populations seemed to surge to much higher numbers. Apple rust mite and European red mite populations are continuing to slowly build. Some limited bronzing of leaves from all three of these insects is being seen. Most blocks are still below threshold numbers, and predators are building in numbers to help control them. I am finding a few spotted tentiform leafminer second generation larva in leaves. Japanese beetle populations have declined over the past week. Beneficial or predator numbers continue to build. I am finding good numbers of lacewing eggs and adults, lady beetle adults and minute pirate bugs.

Sooty blotch and fly speck symptoms were first reported last week, and more growers are finding light symptoms this week. Black rot fruit infections are more common this week. Limb collapse, wilting and browning from black rot infections in the wood tissue have been seen over the last month. Three weeks ago, the first black rot leaf infections started to be seen, and two weeks ago I started to see fruit infections.

Pears are mostly 1.75 to 2 inches in diameter. Pear blister mite feeding symptoms on leaves is being seen this week.

Peach harvest is underway for early varieties. Red Haven harvest is expected to begin in under two weeks. Fruit coloring is continuing this week. Most mid-season peach varieties are between 1.875 and 2.25 inches in diameter. I am concerned peach size development has stalled for many growers; the result may be too many small sized peaches this season. Peach size in the Romeo, Michigan, area is better than other regions.

I have found a few peach blocks with just a few late stage brown marmorated stink bug (BMSB) nymphs or very young adults. This is a new pest to report this week. I have been catching a few BMSB in traps this summer, but this is the first week to find them on a fruit crop. I did not find any feeding damage. Some limited amount of flagging in terminals from oriental fruit moth continues to be found in peaches this week. Japanese beetle populations have declined over the past week. Rusty spot continues to show up on some early peach varieties, however it is being seen in very light amounts.

Sweet cherry leaf spot disease symptoms and leaf drop are slowing where post-harvest fungicide applications have been made.

Tart cherry leaf spot disease symptoms and leaf drop is less common than on sweets. Where post-harvest fungicide applications have been made, symptoms have been reduced.

Plums have sized over the past week to 1.125 inches in diameter for European varieties, with coloring continuing to develop. Japanese varieties are continuing with harvest. Most plum blocks have a poor crop due to freeze/frost damage.

Small fruits

Strawberry leaf regrowth is well along in renovated fields. Growers with dry soils are irrigating both renovated fields and new plantings. Leaves on newly planted strawberries continue to emerge from the crown, along with runners that are rooting. Rows are filling out well in some fields where soil moisture has been adequate. Potato leafhopper leaf cupping damage is common in newly planted strawberries.

Raspberry harvest is winding down for summer red raspberries and black raspberries. Berry size remains small where soils have been dry this summer. Where irrigation has not been applied, fruiting canes are already drying down. These canes need to be removed soon. New growth in both summer and fall raspberries has slowed due to dry soils. Fall red raspberries are in bloom to flower trusses and young fruitlets forming. Growth in fall raspberry plantings have canes the are shorter than normal this season. A few berries are continuing to be harvested on the bud berry canes or shorter fall red raspberry canes. Blackberry flowering is just beginning.

Spotted wing Drosophila (SWD) trap catch started across the region six weeks ago, and again this week’s trap catches remains low. Regardless of this low trap catch, I have more reports of growers finding small SWD larva in fruit. So, even though pressure from SWD is low, protection programs need to be ongoing as long as harvest continues.

Some light amounts of gray mold continue to be found in summer red raspberries.

Blueberry harvest continues on many varieties. Berry size continues to be good on Jersey and other mid-season varieties, but berry size is starting to diminish on early season varieties. The largest berries are 15 to 18 millimeters in diameter. Remaining berries are coloring well.

SWD trap catch started across the region six weeks ago, and again this week trap catches remain low in blueberries. Regardless of this low trap catch, SWD protection programs need to be ongoing in blueberries. Blueberry maggot trap catch has been on the rise for the second week in a row.

Grape growth continues to be rapid again this week, with Concord being at berry touch and Vinifera varies are nearly at berry touch. Growers are doing some cane removal this week. Japanese beetle populations have declined over the past week. Grape berry moth larva feeding was seen in more grape varieties this week.

Saskatoon growth continues. Japanese beetle populations have declined over the past week.

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