East Michigan fruit update – Sept. 4, 2019

Brown marmorated stink bug populations are on the rise at some farms. Gala and McIntosh apple varieties are nearing maturity. There is a wide range of soil moisture levels across the region.

Weather

Most soils across the region remain abnormally dry, with many areas seeing a soil moisture deficit of 3 inches over the last few months. The sod in many orchards remains brown and newly planted tree and small fruits are showing signs of drought stress. This being said, a few growers have seen good rainfall over the last month. In a long day with many miles on the road on Monday, Sept. 2, I saw many small pockets where the sod was lush green and corn was not rolled from drought stress. These rains have mostly been from quickly forming thunderstorms that have brought good rainfall totals.

Most of the region remains 5 to 10 days ahead of normal when looking at growing degree day totals. The tip of the Thumb is the only area of east Michigan that remains a few days behind normal.

Tree fruits

Apple harvest for summer varieties continues. Gala and McIntosh harvested and tested on Monday, Sept. 2, are still immature and at least a week away from beginning harvest. Where soil moisture has been adequate, most apple varieties have great size this season. Apple growers are continuing to get ready for harvest, mowing orchards, making Retain applications and setting bins in staging areas.

About half of the brown marmorated stink bug traps I checked on Monday had a good spike in numbers. At these same fruit farms, I could easily find good numbers of adults and young nymphs feeding in apples. While we have been catching a few of the overwintering generation of brown marmorated stink bugs in traps over the last few months, the stink bugs I am seeing this week are emerging this season. You need to do a good job of scouting at this time. If you’re finding them in your area, an insecticide application will be needed to control them in apples. Watch out for them in all varieties—they seem to like green apple varieties, like Crispin and Golden Delicious.

I found my first stings or marks on apples this week from San Jose scale. I am not finding nearly as many woolly apple aphids as I had expected based on very high populations in many blocks last fall. Trap catch of apple maggot has also remained low over the last few weeks, perhaps due to dry soils at most farms. Where rainfall has been seen around the state, I hear many reports of high numbers of apple maggot being caught in traps.

Necrotic leaf blotch and black rot symptoms are on the rise for both diseases. I am finding some leaf drop from necrotic leaf blotch. Sooty blotch and fly speck symptoms are not showing up yet, but you need to be covering to control it.

Apple scab symptoms are showing up in many apple blocks, and growers are trying to determine the timing of the infection. In looking at fruit symptoms, it appears the infection may have come toward the mid to late part of primary apple scab season. Remember, we had extreme pressure from rain events this spring and early summer, and it is not surprising to see so much apple scab on leaves and fruit this summer.

Lastly, concerning the pressure from apple scab this season, keep an eye on crabapples that are defoliating now from apple scab infections this spring. Even crabapple species that are moderately resistant to apple scab are losing their leaves due to apple scab infection.

Pears have continued to size well where soil moisture has been adequate. Fruits are mostly 2.5 to 3 inches in diameter.

Peach harvest has wrapped up at most farms.

Tart cherry leaf drop from cherry leaf spot disease continues at a rapid pace, with many trees being nearly defoliated.

Plums have colored well in the past week. Stanley plums are nearing harvest. Most Japanese varieties have been harvested.

Small fruits

Strawberry regrowth continues in renovated berries where precipitation or irrigation has been adequate. Where soils moisture supplies have been short, regrowth has been slow. This is a critical time of the season when soil moisture is needed for the formation of strong crowns for next year’s crop.

Newly planted strawberries continue to runner well, with rows filling in nicely in many fields where soil moisture has been adequate. Here again where soil moisture has been short, rows are struggling to fill in well. In these situations, walk fields or gently cultivate to pull runners back into the row in order to fill the row.

Several new plantings have severe leaf curling or cupping from potato leafhopper adult feeding. I am also seeing many new plantings where weeds have not been controlled well with herbicides applied a month or so ago and thus where weeds are competing with berries. In these situations, cultivation and hand weeding are needed. Labor Day time is a good one to consider an herbicide application to control weeds through fall.

Raspberry harvest continues for fall red raspberries. Blackberries have large fruitlets with a few blooms remaining. Many growers have stopped trapping for spotted wing Drosophila for the season because adults will continue to lay eggs in fruit if uncontrolled and cause fruit damage to the end of harvest. I am still maintaining one spotted wing Drosophila trap in fall red raspberries, and adult trap catch remains very high.

Blueberry harvest has wrapped up at most farms, except those will late season varieties like Elliott.

Grape clusters are continuing to tighten, veraison or fruit coloring has begun. Some early season wine grapes are ready for harvest. Powdery mildew and downy mildew symptoms continue to be seen on leaves.


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