East Michigan fruit regional report – May 31, 2016

Unusually warm weather this past week has rapidly pushed fruit growth and degree-day totals. Apple growers have been very actively thinning apples to drop some fruit.

Weather

Hot and dry conditions have dominated the weather scene over the last week. Most of our Michigan State University Enviro-weather stations have accumulated an average of 170 degree-days base 50 in the last week alone, which is an amazingly high number for late springtime.

Most growers have missed the fast-moving narrow bands of thunderstorms that have developed over east Michigan this past week. Most of our region had little to no rain over the past two weeks. Fruit growers that did receive rain only had a few tenths of an inch. Our soils generally are very dry, and growers are working hard to get irrigation systems fired up for the season, especially on newly planted tree and small fruits.

Due to the heat of the last week, our season has jumped ahead of normal in terms of fruit crop growth stages and degree-day totals. Based on the 10-day forecast, growth should drop back to a more normal rate.

East Michigan growing degree-day totals for March 1 to May 30, 2016

Location

GDD42

GDD45

GDD50

Commerce (Oakland County)

777

619

410

Deerfield (Monroe County)

925

742

488

Emmett (St Clair County)

736

590

396

Flint (Genesee County)

852

691

471

Freeland (Saginaw County)

731

590

401

Lapeer (Lapeer County)

783

635

436

Pigeon (Huron County)

627

500

337

Romeo (Macomb County)

801

644

435

Tree fruits

Apples are mostly 10 to 22 millimeters for growers south of the I-69 corridor and 6 to 10 millimeters to the north, with the exception of growers close to Lakes Erie or Huron, where fruit growth is delayed. Bloom has ended for most growers. Apple fruitlets have been sizing very quickly over the past week, some days almost doubling the rule of thumb of 1 millimeter per day of average new growth. Growers have been doing a lot of thinning in most apple varieties in the past week, as it appears we have a tremendous crop of apples this season. With cooler temperatures predicted this week, it appears there will be no stress on the tree and therefore thinner rates may need to be bumped up a bit in order to be effective. Many growers are looking to go back to thin specific varieties in the next few days one last time as the thinning window is closing quickly.

The four new insect pests to report this week in apples are a few white apple leafhopper adults, plum curculio egglaying scars on fruit, European red mite adults and San Jose scale adult trap catch. Codling moth trap catch continues to be on the rise. Many growers have biofixed for codling moth and with all of the heat of the last week have blown by the early window of control. Brown stinkbug continues to be found. Oriental fruit moth trap catch continues to rise, with some farms having high trap catches in the range of 100 to 150 moths per trap. Tarnished plant bugs are being seen in several tree fruits. I am still finding small larvae of obliquebanded leafroller, redbanded leafroller and fruittree leafroller, especially where no pink spray was used. A few apple blocks have rosy apple aphids and green apple aphids. Spotted tentiform leafminer adult trap catch has declined again this past week. Beneficials continue to be found in greater numbers, including lady beetle larvae, minute pirate bugs, lacewings and syrphid flies.

We did have an apple scab wetting event Sunday afternoon, May 29, at my apple scab spore trapping location; I caught 39 spores in the brief shower that brought only 0.15 inch of rain. The number of spores are declining as primary apple scab season is working its way to the end, but more rainfall is needed to release the remaining spores. Thus, we are not at the end of primary apple scab season. Powdery mildew continues to be found in more apple blocks. There is a slight curl or upwards roll in the expanding leaves as well as a few spots on the upper leaf surface. Many terminals are completely infected now.

With the end of bloom at most farms, the threat of fire blight infection of flowers is ending. Keep an eye on the Michigan State University Enviro-weather MaryBlyt model if any ragtag bloom remains. However, growers need to be alert for trauma blight infections to new shoots. Just yesterday I saw a few fire blight overwintering cankers from last year where the blight seems to be moving again further down the tree. Growers need to watch blocks and varieties where fire blight was a problem last season, as well as be on the lookout for oozing fire blight cankers where it was a problem last season. Lastly, we now have around 8 to 10 inches of new growth in apples, so now is the time for the second application of Apogee.

Pears are mostly 12 to 15 millimeters in diameter. The pear crop is variable in most blocks this season. Pear psylla adults continue flying, with nymphs and eggs present as well.

Peaches are 10 to 15 millimeters in size for most growers. Oriental fruit moth trap catch continues to be seen at many farms, with most conventional blocks well-beyond biofix. I have not seen any terminal flagging from oriental fruit moth feeding.

Sweet cherries are 12 to 14 millimeters in diameter for the largest fruit. They are starting to turn a straw color and pit hardening has taken place in the last few days. I am seeing a better crop of sweet cherries the past few weeks. Some smaller fruit are also turning brown and may be ready to drop soon. Brown rot control sprays continue being made.

Tart cherries are mostly 8 to 10 millimeters in diameter. Tart cherry crop load is more variable in the last few weeks with a fair amount of the smaller fruit dropping off. It is a shrinking crop.

Plums are 11 to 14 millimeters in diameter for European types and Japanese types are mostly 14 to 16 millimeters in diameter. However, some Japanese varieties have little to no crop this season.

Small fruits

Grapes took on another good spurt of growth this past week; canes have 8 inches of new growth for Concord types and 12 to 16 inches of shoot growth for European varieties. Flower buds are now elongating for both types.

Strawberries are at mostly at red fruit for farms in the south to thimble-sized fruit for farms further north. Most farms are done with bloom. Farms in the very southern parts of our region report they will be opening for the first picking this coming Sunday or Monday, June 5-6. It is amazing how quickly berries have ripened with all of the heat we have gotten in the past week.

Strawberry clipper or clipped buds continue being found at several farms where controls have not been applied. Angular leaf spot continues to be found on leaves at a few farms. Fields look spectacular at a few farms, however at others berry plants continue looking weak and off-colored. I have recommended light nitrogen applications of urea at many farms this season.

Lastly, I am concerned about small berry size where rainfall has been short and on farms where no or limited irrigation occurred just after blossom. These farms may have decent berry size for the first picking, but then will rapidly decline for later harvests.

Raspberry shoots, leaves and flowers continue emerging for summer fruiting types, with 12 inches of new shoot growth. Flower buds continue expanding on summer raspberries with a few early blooms open on early fruit varieties. New canes continue emerging from the ground in fall raspberries; the longest canes are 12 to 15 inches in length.

Blueberries are at small green fruit for early varieties and Jersey are at late bloom to small green fruit. Blueberry stem gall wasps continue emerging from overwintering galls and are looking to lay eggs on new shoots. As soon as bees are out of the planting, control sprays need be made for this pest. I have not found any signs of mummy berry mummies on the ground this season.

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