Southeast Michigan fruit regional report – June 4, 2013

The thinning window is beginning to close for apple growers, and strawberry harvest is approaching.

Weather

Widely varying amounts of rain swept across the region in the past week, with most of our Enviro-weather stations reporting rain in five of the last seven days. Many of these fast-moving thunderstorms have brought large amounts of precipitation in a short period of time. Most of our Enviro-weather stations recorded around 2.5 inches of rain over the last seven days, with much lesser amounts in counties to the south. Michigan State University Extension has received several reports of precipitation totals in the 4- to 5-inch range over this same seven-day period.

Many of these storms have had pea-sized hail and strong winds. Tornados were also sighted on Tuesday evening (May 28) around Flint, Mich. I received a few reports of light scattered, roof-top frost on the morning of June 3. No damage to fruit crops was reported.

In last week’s regional report, I stated that many of our soils had become very dry. With good amounts of precipitation across the region, many of our soils have quickly become waterlogged. It has been a difficult season for most fruit growers in that soils have gone from too much, to too little, and back again to too much soil moisture in four weeks.

Our season is back to normal for growth stages and growing degree day (GDD) totals.

East Michigan GDD totals for March 1 to June

Location

GDD42

GDD45

GDD50

Commerce (Oakland)

775

637

444

Emmett (St Clair)

760

625

436

Flint (Genesee)

883

736

530

Lapeer (Lapeer)

796

659

469

Petersburg (Monroe)

897

746

528

Pigeon (Huron)

717

590

414

Romeo (Macomb)

788

651

452

Tree fruits

Apples are mostly 14 to 16 millimeters around Flint, Mich. Most apple fruit have grown 7 millimeters in the last week, which is average – 1 millimeter per day at this time of the season. Most apple growers are not seeing any fruit drop or even a reduction of fruit sizing as a result of thinners that were applied early to mid-last week. Many growers are considering applying a final thinning application today (June 4) or tomorrow, as this may be the last chance to hope to get some fruit to drop. The carbohydrate model is predicting that apples will not be under any stress over the next several days, so growers are considering kicking their thinner rates up and moving to a more aggressive material. This year’s thinning decision is tougher than normal due to weather conditions and crop load at most farms where there was no May 13 freeze damage. For more information, see the MSU Extension article “Apple thinning pointers for 2013.”

With the exception of codling moth trap catches, insect activity seems to have stalled a bit this past week. Codling moth trap catches have remained high over this past week. I set a regional biofix date for codling moth of May 22. Based on the current weather forecast, the window for insecticide applications for codling moth control will begin to open over the weekend and early next week, depending on your choice of insecticides. Consult the codling moth model on the Enviro-weather website for more details.

I am finding a few plum curculio in trees and seeing just a few egglaying scars. Rosy apple aphids have been curling leaves at several orchards and may need to be controlled. Oriental fruit moth trap catch leveled off this week; I would expect to see a decline in trap catches over the next few weeks. I have not seen any terminal flagging due to oriental fruit moth. Recall that I set a regional biofix date of May 16 for oriental fruit moth.

Oystershell scale crawlers continue to be found and may be starting to wax over, so the control window is starting to close. I continue to see a few green apple aphids and apple grain aphids; however, the abundance of predators this season is doing a good job of keeping them in check. European red mite numbers remain low at most farms; here again predators are doing a great job controlling them. Mullein bugs continue to be found in apples, but I believe they are now predators. There are record-setting numbers of predators being seen this season.

Apple scab spore discharge continues, although spore numbers have declined in the last rain event. According to the apple scab maturity model, all of the spores have matured for the season, and almost all have been released. We are not at the end of primary apple season yet.

I continue to see twig infections of powdery mildew mainly on susceptible varieties. I have not seen any signs of fire blight infection. I saw a few apples yesterday (June 3) that were infected with cedar apple rust.

Pears are 12 millimeters for growers that have a crop. Frost ring scars are more visible on pears in the last week. Pear psylla adults continue to fly and egg hatch continues.

Peaches are 14 to 15 millimeters in size. Some blocks are being abandoned due to the lack of a crop. The foliage in these blocks appears to be yellowing and stunted. There may be more damage in these blocks that is yet to be revealed. Tarnished plant bugs have been found in peaches in the last week. Peach leaf curl-infected leaves continue to be seen in light amounts. I continue to see very low to no oriental fruit moth trap catch in peaches. Bacterial spot infection on the leaves continues to be found at many farms.

Sweet cherries are 15 to 16 millimeters in size. Just a few plum curculio scars have been seen. Cherry leaf spot disease symptoms are starting to be seen.

Tart cherries are 11 to 12 millimeters in size. Cherry leaf spot disease symptoms are appearing.

Plums are 17 millimeters in size where growers have a crop this season. Growers need to be on the lookout for black knot infections.

Small fruits

Strawberries have sized well in the last week with many being at thimble-sized fruit. Harvest is expected to begin in the southern parts of the region in seven to 10 days and in more northern parts of the region in 14 to 18 days. I have not seen any tarnished plant bugs in strawberries, but I am finding them in peaches. Usually when I find them in one of these fruit crops, I find them in the other in a few days, so be on the lookout for it.

Raspberries are at 9 to 12 inches of new growth for summer-bearing types, with full bloom in most varieties. Canes of fall-bearing types are about 15 to 21 inches tall where they were not killed back to the ground from the May 13 freeze event. New canes continue to emerge from the soil in these freeze-damaged plantings.

Blueberries are at petal fall for most varieties. It appears that there is quite a difference in the amount of foliage growth between varieties. In the two farms I visited yesterday that grow blueberries, I noted at both farms that Jersey and other varieties had considerable more leaf growth than Bluecrop or Blueray.

Grape cane growth continues at a rapid pace with new canes at 24 inches of new growth; however, flower growth seems to have stalled in the past week. Blossoms are ready to open in a few days. Wild grapes are now in bloom.

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