East Michigan fruit update – July 31, 2018

Drought conditions persist across the region. We have seen a spike in spotted wing Drosophila infested fruit in the last few days in raspberries and blueberries.

July 31, 2018 - Author: Robert Tritten

Weather

The drought continues for most all fruit growers in the region, with soils remaining very dry. Many growers have not had any significant amount of rain in six to eight weeks. Signs of drought stress are becoming more common, even in well-established tree fruits.

Rainfall over the last week has amounted to under a tenth of an inch for most growers. The range of precipitation over the last week at our MSU Enviroweather stations listed in the following table was on the low end, just at a tenth of an inch for most growers to 0.58 inches on the high side, with total rainfall being extremely variable over short differences.

This being said, a very few fortunate growers have received good amounts of precipitation in a short period of time from localized popup thunderstorms. Last week I was on a farm that received 2.4 inches of rain from one of these events, and then another 0.5 inch the following day. The grass in that orchard was green as green could be.  

We are at a point now where it will take some good long rains over several weeks for soils to come back to normal moisture levels. For growers who were lucky to receive good rain events, this relief may only be temporary.

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 30, 2018

Location

GDD42

GDD45

GDD50

Commerce (Oakland County)

2470

2168

1685

Deerfield (Monroe County)

2673

2357

1860

Emmett (St Clair County)

2335

2039

1571

Flint (Genesee County)

2621

2314

1826

Freeland (Saginaw County)

2413

2111

1633

Lapeer (Lapeer County)

2414

2115

1641

Pigeon (Huron County)

2245

1955

1479

Romeo (Macomb County)

2584

2280

1796

Tree fruits

Apple size is good for this time of the season, but has slowed in the past week, most likely due to dry soils. Most apples are just over 2 inches in diameter, with well-thinned Honeycrisp this week mostly between 2.25 to 2.625 inches in diameter. Lodi and Vista Bella harvest has wrapped up, and a few other early season varieties are getting started with harvest.

European red mite populations have continued to build at most farms. Drought conditions are aiding in their rapid population increases. Most farms have isolated trees with higher than threshold numbers of red mites, and not entire blocks. I am still encouraging growers who are only finding isolated trees with bronzing leaves to hold off on applying a miticide to see if predator numbers can keep them in check. Twospotted spider mite numbers are on the decline in most apple blocks.

Brown marmorated stink bug stinging/feeding injury is being found in a few more apple blocks this week, especially in Gala and Honeycrisp. Adults and nymphs continue to be found in low numbers in traps at most farms. Woolly apple aphid populations are on the raise in blocks where it was a problem last season. Apple maggot trap catch on red sticky balls has been lower at most farms this week. Japanese beetle populations are starting to decline in most apple blocks. Potato leafhopper adults continue to be found, but here again their populations are starting to decline.

As for beneficial insects, good numbers of lady beetles and green lace wings continue to be found and this week I am starting to find red velvet mites.

Black rot fruit symptoms were reported last week at a limited number of farms. Sooty blotch and fly speck symptoms have still not been seen this season.

Pears are mostly at 1.75 to 2.25 inches in diameter this week. I am finding a few more blocks where pear rust mites are starting to be a problem. Pear psylla populations are high in blocks where suckers have not been removed.

Peaches have put on a slight swell in the past week, which is good, but most farms are seeing smaller than normal size this season. They are also starting to color. They are mostly 1.75 to 2.125 inches in diameter. Harvest of early peach varieties continues. Red Haven harvest is expected to begin around August 8th to the 10th, which is later than I have been predicting. We’re seeing more leaf cupping and yellowing this week, even on established trees.

European red mite and twospotted spider mite numbers seemed to have either leveled off or are dropping in the last week. Growers need to be on the lookout for brown marmorated stink bugs in peaches.

Sweet and tart cherry growers who did not apply a post-harvest cherry leaf spot spray are starting to see leaf yellowing and drop.

Plums have sized a bit over the last week, with European varieties just over 1.125 to 1.25 inches in diameter and 1.75 to 2 inches for Japanese varieties. More color is developing in both European and Japanese varieties. Overall, most varieties have a poor crop this season.

Small fruits

Strawberries continue to rebound from renovation. Where berries have been watered well, the rows are starting to fill in. Fields where watering or precipitation has not occurred are struggling to come back from renovation. Many new plantings still need some attention to potato leafhopper feeding damage and weed control. In new plantings where soil moisture has been adequate, a good amount of runnering continues and rows are starting to fill in.

Raspberry harvest in summer red raspberries continues at some farms and varieties where soil moisture has been adequate. However, where soils are dry, berries have been small, miss-shaped and have some drupelets that have a white color to them. Harvest has been tough on these farms. More farms are opening for limited picking of fall red raspberries as they continue to ripen.

Blueberry harvest continues at all farms. Berries have not sized well at farms where soil moisture has not been adequate this season. Spotted wing Drosophila (SWD) trap catch took a sharp rise in blueberries early last week, and this week I am finding infested berries on farms where control measures have not been adequate. SWD control measures need to be continued on a regular basis as long as harvest continues. Trap catch of blueberry maggot continues for the fourth week. Trap catch of its close relative, the apple maggot, has leveled off or declined at most farms in the past week.

Saskatoon leaves on unsprayed plants have high populations of leafminers, with some seeing extensive injury on the leaves.

Grapes continue to put on berry size. Japanese beetle populations are declining this week. Powdery mildew continues to be seen on leaves and twospotted spider mite populations continue to build slowly.

Tags: east michigan, fruit update, msu extension


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