Southeast Michigan fruit regional report – May 28, 2013

Two more frost events over the weekend thinned off a bit more fruit for a few southeast Michigan tree fruit growers.

Weather

Frost on both Saturday and Sunday morning (May 25-26) did a bit more damage to young fruitlets for a few tree fruit growers. Low temperatures recorded in these orchards were generally in the range of 28 to 30 degrees Fahrenheit in low lying areas. Thinning decisions are now going to be tougher in these blocks because fruitlets exposed to cold tend to thin easier.

Even with cooler temperatures late last week and over the weekend, our season is back to normal timing in terms of growth stages and now growing degree day (GDD) totals. The cooler weather of late has not slowed insect activity with several tree fruits seeing very high numbers of plum curculio, codling moth and oriental fruit moth.

Dry soils remains in many parts of the region with most farms receiving less than a half inch of rain over the last week. Soils have now become very dry at most fruit farms. It is amazing to see how quickly our soils have moved from overly wet to extremely dry; many growers are irrigating newly planted tree and small fruits because soils have dried so much in the past three weeks.

East Michigan growing degree day totals for March 1 to May 27

Location

GDD42

GDD45

GDD50

Commerce (Oakland)

619

503

339

Emmett (St Clair)

595

481

322

Flint (Genesee)

712

586

411

Lapeer (Lapeer)

634

518

357

Petersburg (Monroe)

719

589

403

Pigeon (Huron)

559

451

305

Romeo (Macomb)

624

508

340

Tree fruits

Apples are mostly 12 to 14 millimeters in the south and 7 to 9 millimeters around Flint, Mich. Most apple growers are looking to begin thinning in the next few days as a string of warm days is predicted. The carbohydrate model is predicting that apples will be under some stress over this time as well, thus Michigan State University Extension advises apple growers to consider backing off on their thinner rates a bit. The thinning decision is always a difficult one for growers, and this season is tougher than normal.

Flower bud damage from the two frost events of the weekend is still being evaluated, but there does appear to be some additional fruit loss. It is hard to separate this latest damage from the May 13 freeze event. This latest freeze damage was more localized than the May 13 freeze. Again, freeze damage is extremely variable across east Michigan.

Insect activity has picked up a great deal in the past week. I am finding a good number of plum curculio in trees, but no egglaying scars have been found. The cold weather over the weekend may have delayed the ovipositioning damage by a few days, but growers need to be covering soon to prevent damage to apples. Codling moth trap catches have been very high over this past week; these unusually high numbers were not expected as most growers did not have an apple crop last year. Time will tell more of this story over the next several weeks. I set a regional biofix date for codling moth of May 22.

Oriental fruit moth trap catch continued to be very high as well over the last week. Recall that I set a regional biofix date of May 16 for oriental fruit moth. Oystershell scale crawlers are just starting to be found. Rosy apple aphids are now curling leaves and may need to be controlled. A few mullein bugs are being found in apples. I continue to see a few white apple leafhopper nymphs, green apple aphids and apple grain aphids; however, the abundance of predators this season is doing a good job of keeping them in check. Low numbers of European red mites continue to hatch; here again predators are doing a great job controlling them. There are record setting numbers of predators being seen this season.

Apple scab spore discharge continues with good numbers still being trapped. According to the apple scab maturity model, almost all of the spores have matured for the season, and about 85 percent 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. My concern continues that apple growers may be forgetting about controlling powdery mildew this season. I have not seen any signs of fire blight infection, and with the end of bloom the risk of infection is reduced. Keep an eye on ragtag bloom, however.

Pears are 6 to 9 millimeters for growers that have a crop this year. Frost ring scars are starting to be visible on pears in the last few days. Pear psylla adults continue to fly and egg hatch continues.

Peaches are 7 to 9 millimeters in size. There has been extensive fruit drop in some peach blocks that were frosted on May 13. Some blocks are being abandoned due to the lack of a crop. 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 this season, only in apples. Bacterial spot infection on leaves is just now starting to be seen.

Sweet cherries are 12 to 14 millimeters in size with very heavy fruit drop in blocks hit hard by the May 13 freeze event. No plum curculio scars have been seen.

Tart cherries are 9 to 11 millimeters in size. As is the case of sweet cherries, there is heavy fruit drop in a few blocks. Freeze damage to tarts was also variable, with less damage than in sweet cherry blocks.

Plums are 9 to 10 millimeters in size where growers have a crop this season. Growers need to be on top of black knot sprays at this time.

Small fruits

Strawberries are at full bloom to small fruit at most farms. Several strawberry growers reported heavy ice from frost protection on Saturday and Sunday morning (May 25-26). Leaf growth has begun to take off where nitrogen applications have been made in the last week. Leaf and flower bud development are a bit out of sync this year with the lack of leaf development. I can see more evidence of strawberry clipper feeding injury on the flower petals in the last week or so. Growers need to keep an eye out for tarnished plant bug. Fungicide applications for gray mold control are being made as bloom continues.

Raspberries are at 5 to 8 inches of new growth for summer-bearing types with bloom just starting in early flowering varieties. Canes of fall-bearing types are about 13 to 18 inches tall where they were not killed back to the ground from the May 13 freeze event. New canes are emerging from the soil in these freeze-damaged plantings.

Blueberries remain at full bloom for most varieties. It appears that there was little freeze damage from the May 13 freeze event. At this time we are set for an excellent blueberry crop this season.

Grape cane growth continues at a rapid pace, with new canes being at 16 inches of new growth and flowers ready to bloom later in the week. In plantings that had freeze damage from the May 13 freeze event, new growth is coming along nicely.

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