East Michigan fruit update – Aug. 20, 2019

Red haven peach and fall red raspberry harvest is in full swing. Most fruit farms are experiencing dry soils with some growers seeing signs of drought stress in tree and small fruits planted this spring.

Weather

Soils across most of the region remain abnormally dry, with many areas seeing a soil moisture deficit of 2 inches over the last month or so. The sod in many orchards has turned brown and newly planted tree and small fruits are showing signs of drought stress. Many growers are devoting more and more time to irrigating fruit crops.

This being said, a few growers have seen good rainfall in the last week, a few in the range of 2 to 4 inches. These rains have mostly been from quickly forming thunderstorm events that have brought good rainfall totals; however, the rain has come over a short period of time. These rain showers have come in narrow bands or pockets.

Our season remains about five to 10 days ahead of normal when looking at growing degree day (GDD) totals for most of the region. The tip of the Thumb is the only area of east Michigan that remains a few days behind normal.

East Michigan GDD totals for March 1 to Aug. 19, 2019

Location

GDD42

GDD45

GDD50

Commerce (Oakland County)

2,871

2,489

1,900

Deerfield (Monroe/Lenawee County)

3,105

2,701

2,086

Emmett (St Clair County)

2,480

2,125

1,584

Flint (Genesee County)

2,986

2,598

1,998

Freeland (Saginaw County)

2,782

2,409

1,829

Lapeer (Lapeer County)

2,752

2,375

1,798

Pigeon (Huron County)

2,550

2,189

1,636

Romeo (Macomb County)

2,973

2,589

1,996

Tree fruits

Apple harvest of Zestar began in the last few days with a very light first picking, and harvest of other summer varieties continues. Where soil moisture has been adequate, most apple varieties continue to size well; most are in the range of 2.75 to 3.25 inches in diameter. Most apple varieties have set their terminal buds for the season, but as noted in last week’s report, a few varieties (like Honeycrisp) have started to put on a late season flush of growth.

Apple growers are continuing to get ready for harvest that will begin over the next few weeks. Growers are mowing orchards, making Retain applications and setting bins in staging areas. Predicted apple harvest dates for east Michigan will be published in a separate article—watch the Michigan State University Extension Fruit & Nut News page for it.

I have no new apple pests to report this week. Apple rust mite numbers have continued to build in the last three weeks or so, with bronzing in many apple blocks. There is an uptick in codling moth and obliquebanded leafroller trap catches this week. Codling moth larvae feeding injury is visible in a few apple blocks. Overall, I am not finding nearly as many woolly apple aphids as I expected based on very high populations in many blocks last fall. Trap catch of apple maggot has also remained low over the last few weeks, perhaps due to dry soils at most farms. Where rainfall has been seen around the state, I hear many reports of high numbers of apple maggot being caught in traps.

Potato leafhopper and green apple aphid numbers have dropped off as terminal buds have been set in most varieties. Japanese beetle adult populations were lower this week; their numbers have been bouncing around over the last few weeks. Surprisingly, European red mite and twospotted spider mite populations have remained low this season in most apple blocks. Oriental fruit moth and redbanded leafroller trap catches are generally low at this time.

Again this week there are no new beneficials to report; generally their populations have been declining in August. Lady beetles, six spotted thrips and green lacewing adults continue to be found.

Necrotic leaf blotch and black rot were new pests reported last week, and this week symptoms are on the rise for both diseases. I have starting to see some leaf drop from necrotic leaf blotch in the last few days. While cedar apple rust symptoms were first reported the second week of June, many growers are finding leaf symptoms in the last three weeks. Sooty blotch and fly speck symptoms are not showing up yet, but growers need to be covering to control it.

Apple scab symptoms are showing up this month in many apple blocks, and growers are trying to determine the timing of the infection. In looking at fruit symptoms, it appears the infection may have come toward the mid- to late part of primary apple scab season. We had extreme pressure from rain events this spring and early summer, and it is not surprising to see so much apple scab showing up on leaves and fruit this summer. Lastly, concerning the pressure from apple scab this season, keep an eye on crabapples that are defoliating at this time from apple scab infections this spring. Even crabapple species that are moderately resistant to apple scab are losing their leaves due to apple scab infection.

I have seen a number of Zestar blocks that have a good amount of damage from birds pecking the fruit, mostly on fruit in the tops of trees. I have not noted this type of damage in Zestar in previous seasons. It is possible that dry soils have caused birds to look for moisture in fruit, and that Zestar is the variety that is the closest to being ready to harvest at this time. Bird pecking damage from crows feeding in Honeycrisp has been common over the years.

Pears have taken on a good swell this past week where soil moisture has been adequate; fruits are mostly 2.25 to 2.5 inches in diameter. Growers are continuing to remove suckers from pears. Last week I saw my first ever leaf spotting on pears from cedar apple rust, with more symptoms showing up this week. This disease also causes leaf scorching symptoms. Pear psylla continue to be present in all stages.

Peach harvest of Red Haven continues. Split pit was an issue in some early varieties but seems to be much less in main season varieties. Fruit have taken on a good swell in the last week; they are mostly at 2.75 to 3.25 inches in diameter for the largest sized fruit. Many early varieties showed signs of uneven ripening or maturity, resulting in even more pickings than usual. I believe this is the result of the long bloom period in peaches this season.

I am also continuing to see some oriental fruit moth feeding damage on fruit from this second generation larvae, and this week I am even getting a few reports of small larvae being found in fruit. I continue to see terminal flagging or tip feeding damage from the first generation of oriental fruit moth. Trees that were affected by peach leaf curl this spring have recovered well with new leaf growth. However, fruit on these trees is generally much smaller and ripening slower.

Tart cherry leaf drop from cherry leaf spot disease continues at a rapid pace, with some trees being nearly defoliated. Fungicide applications that were made in some tart cherry blocks was not effective in stopping the spread of this disease this season.

Plums have taken on a good swell this past week and Stanley types have colored well. Most European varieties have fruit that is 1.25 to 1.5 inches in diameter. Many Japanese varieties have been harvested in the week to 10 days.

Small fruits

Strawberry regrowth continues in renovated berries where precipitation or irrigation has been adequate. Where soils moisture supplies have been short, regrowth has been slow. This is a critical time of the season when soil moisture is needed for the formation of strong crowns for next year’s crop. Newly planted strawberries continue to runner well, with rows filling in nicely in many fields with good soil moisture. Here again, where soil moisture has been short, rows are struggling to fill in well. In these situations, walk fields or gently cultivate to pull runners back into the row in order to fill the row.

I continue to see several new plantings with severe leaf curling or cupping from potato leafhopper adult feeding. I am also seeing many new plantings where weeds have not been controlled well with herbicides applied a month or so ago and thus where weeds are competing with berries. In these situations, cultivation and hand weeding are needed at this time.

Raspberry harvest has ramped up for fall red raspberries. Blackberries have small fruitlets with a few blooms remaining. Many growers have stopped trapping for spotted wing Drosophila for the season because we know adults will continue to lay eggs in fruit if uncontrolled and cause fruit damage to the end of harvest. I am still maintaining one spotted wing Drosophila trap in fall red raspberries, and adult trap catch remains very high.

Blueberry harvest continues but is winding down at most farms. Berry size is small where soil moisture supplies have been low. High trap catch of spotted wing Drosophila adults continues in blueberries where growers are still trapping for this insect. Control measures should have started over three weeks ago at most farms and will need to continue to the end of harvest. I am continuing to see a few dead canes from Phomopsis canker.

Grape clusters are continuing to tighten; I have not seen the start of veraison or fruit coloring. Grape berry moth larvae continue to be found feeding in grape clusters. Japanese beetles continue to be found, but their numbers are dropping this week. Two spotted spider mite populations continue to build in isolated vines, but not entire vineyards. Black rot symptoms are more common this week. Powdery mildew and downy mildew symptoms continue to be seen on leaves.


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