East Michigan fruit update – July 24, 2018

Brown marmorated stink bug feeding injury on apples has been found at a few farms in the last few days, and spotted wing Drosophila trap catch has taken another big jump in raspberries and blueberries.

Weather

Rainfall over the weekend and continuing through this morning, July 24, has brought some temporary relief to drought conditions for a few growers. However, most fruit growers were disappointed to have only received a few tenths of an inch of precipitation from this long rain event. The range of precipitation from this most recent event was on the low end, just over a tenth of an inch for most growers, to 1.1 inches on the high side with total rainfall being extremely variable over short differences.

Our soils remain dry over most of the region and drought conditions continue for most fruit growers. Many growers have not had any significant amount of rain in five or seven weeks.

Wilting of younger tree and small fruit crops is common this week and even older bearing trees are showing the classic sighs of drought stress. Sandy sites are very dry and showing more severe signs of drought stress. Most growers are spending more time focusing on irrigation. For growers who were lucky to receive good amounts of precipitation from recent rains, this relief may only be temporary.

I am sounding like a broken record, but our season is still running 10 to 14 days ahead of normal in degree-day totals and about five days ahead of normal in terms of the start of harvest of our fruit crops. Degree-day totals have continued to build quickly with hot days and much above normal morning lows.

East Michigan growing degree day totals for March 1 to July 23, 2018

Location

GDD42

GDD45

GDD50

Commerce (Oakland County)

2,289

2,008

1,560

Deerfield (Monroe County)

2,483

2,188

1,725

Emmett (St Clair County)

2,170

1,895

1,462

Flint (Genesee County)

2,429

2,143

1,690

Freeland (Saginaw County)

2,243

1,962

1,520

Lapeer (Lapeer County)

2,239

1,961

1,522

Pigeon (Huron County)

2,096

1,827

1,404

Romeo (Macomb County)

2,386

2,103

1,653

Tree fruits

Apples have continued to size despite drought conditions for most apple growers. Most apples are just over 2 inches in diameter, with well-thinned Honeycrisp between 2.25 to 2.625 inches in diameter. Lodi harvest continues this week, and in the last few days Vista Bella and a few other early-season varieties are getting started with harvest.

Brown marmorated stink bug stinging/feeding injury was visible in a few Gala and Honeycrisp blocks late last week and yesterday, July 23. Adults and nymphs continue to be found in low numbers in traps at most farms. A few growers have seen another week with high apple maggot trap catch on red sticky balls, but most farms have seen lower numbers in traps this week. With rain over the weekend at a few farms, more trap catches are expected for later in the week.

European red mite populations have continued to build at most farms. Hold off on applying a miticide to see if predator numbers can keep them in check. Twospotted spider mite numbers seemed to have leveled off in the last week at most farms. Japanese beetle populations also seemed to peaked and are starting to decline in most apple blocks. Potato leafhopper adults continue to be found, but again their populations seemed to have leveled off or are starting to decline. Good numbers of lady beetles and green lace wings continue to be found this week.

Black rot fruit symptoms are a new pest to report this week, but is found only at a limited number of farms. Sooty blotch and fly speck symptoms have yet to be seen this season.

Pears remain mostly 1.625 to 2 inches in diameter this week. A few more pear blocks are starting to see pear rust mites. Pear psylla populations have continued to build in blocks where suckers have not been removed.

Peaches also remain about the same size this week, which concerns me. They are mostly 1.5 to 1.625 inches in diameter. Harvest of early peach varieties continues. Red Haven harvest is expected to begin in eight to 10 days, however many trees are not sizing fruit, most likely due to dry soils. Some leaf cupping and yellowing is apparent, mostly due to dry soils.

European red mite and twospotted spider mite numbers seemed to have leveled off in the past week. Growers continue to report light amounts of brown marmorated stink bug stinging/feeding injury on fruit. Look out for brown marmorated stink bugs in peaches.

Sweet cherry harvest wrapped up. Many growers are applying a post-harvest cherry leaf spot spray.

Tart cherry harvest wrapped up in the past week. Many growers have applied a post-harvest cherry leaf spot spray.

Plums are about the same size as last week, with European varieties just over 1 inch in diameter and 1.5 to 2 inches for Japanese varieties. Some European and Japanese varieties have some fruit partially color and then drop.

Small fruits

Strawberries are rebounding from renovation. Watering berries following renovation is critical. Many new plantings still need some attention to potato leafhopper feeding damage and weed control. Good runnering continues where soil moisture has been adequate.

Raspberry harvest continues in summer red raspberries, however where soils are dry, berries have been small, miss-shaped and have some drupelets that have a white color to them. A few more farms are opening for limited picking of fall red raspberries as they begin to ripen over a week earlier than normal.

Spotted wing Drosophila (SWD) trap catch has continued to sharply climb this past week at many farms. SWD trap catch has started at most farms, so control measures are underway. Some potato leafhopper feeding damage is visible in new canes or primocanes in summer raspberries and in fall raspberries as well.

Blueberry harvest is underway at all farms. Berries have not sized well over the past week, most likely due to drought conditions.

SWD trap catch has climbed quickly this past week at several blueberry farms. Most farms have some trap catch, so control measures are underway. Trap catch of blueberry maggot continues for the third week. Look out for trap catch at farms. Trap catch of its close relative, the apple maggot, was very high at several farms again this week.

Saskatoon leaves on unsprayed plants have leafminer injury.

Grapes continue to put on a good growth, with concord and vinifera at berry touch. Japanese beetle populations are starting to decline in the last week. Powdery mildew continues to be seen on leaves and twospotted spider mite populations continue to build slowly.

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