East Michigan fruit update – June 16, 2020

Strawberry harvest has begun with strong consumer demand for ready picked and pick your own berries. Even with some rain over the last week, many areas have slipped into drought conditions.

Blueberries
Blueberries. Photo by Bob Tritten, MSU Extension.

Weather

Most of the region received an inch of precipitation in the last week. Even with this rainfall, soils over much of the region have continued to dry out. With another week of strong winds, soils have lost a good amount of moisture. Signs of drought stress are starting to be seen in newly planted tree and small fruit crops, as well as in shallow rooted fruit crops such as strawberries. Sod in some orchards is starting to dry up. It looks more like the dry conditions that we would normally see in mid- to late July.

With moderating to even cold temperatures of last week, the rapid growth that we had been seeing in all our fruit crops has slowed down. Even with cooler temperatures, we saw another good jump in growing degree day (GDD) accumulations. Most of our Michigan State University Enviroweather stations have seen a jump of nearly 100 GDD base 50 accumulations in the last week.

Last week, our season moved back to normal for both growth stages and GDD. We are at about the same point this week as last week. Our season was 14 days behind normal just four weeks ago.

East Michigan growing degree day (GDD) totals for March 1 to June 15, 2020

Location

GDD42

GDD45

GDD50

Commerce (Oakland County)

1019

833

572

Deerfield (Monroe County)

1155

950

667

Emmett (St Clair County)

975

791

539

Flint (Genesee County)

1114

916

637

Freeland (Saginaw County)

972

787

533

Lapeer (Lapeer County)

1016

829

567

Pigeon (Huron County)

901

728

497

Romeo (Macomb County)

1026

836

571

Tree fruits

Apples have continued to size well over the last week, with most fruit now 25 to 29 millimeters in diameter. Most apple varieties have between 16 to 18 inches of new terminal growth.

June drop is under way in most varieties. Fruitlets continue to drop, although it is hard to distinguish between fruit that is dropping as a result of thinner applications or June drop. Where growers have left check trees, it appears that about the same amount of fruit is dropping where thinners were not applied. Most apple growers appear to have a nice apple crop. Hand thinning will be needed in many apple varieties.

I have three new insect pests to report in apples this week and two new beneficial insects. The first new insect pest is low numbers of San Jose scale adult males in traps. The second is obliquebanded leafroller adults in traps and the third is European red mite adults. A few white apple leafhopper adults continue to feed on leaves, as well as a few twospotted spider mites, woolly apple aphids and potato leafhoppers. I continue to see a few codling moth larvae. Trap counts of adults are generally low at this time. The two new beneficials or predators that I am starting to see this week are minute pirate bugs and red velvet mites. Lady beetles and lacewing adults continue to be found.

I have just two reports of growers finding fire blight strikes, one of these reports was on a highly susceptible cider variety. So, these are the first reports for fire blight strikes. A few more growers are finding cedar apple rust.

I have been relying on my colleague Amy Irish-Brown’s apple scab spore trapping data from the Ridge this season after my trapping equipment was destroyed in a strong wind storm this spring. With the rainfall over the state last Wednesday and Thursday, she caught no apple scab spores. So, based on years of experience of both of us trapping apple scab spores to help determine the end to primary apple season, I feel comfortable in calling an end to primary apple season. Yesterday I found my first apple scab lesions of fruit.

Some apple blocks continue to have high numbers of powdery mildew infected terminals on mildew prone varieties. Protection programs need to be ongoing on mildew prone varieties.

Pears are mostly 22 to 24 millimeters in size. Most pear growers saw a good amount of fruit drop in the past week, resulting in a nicely thinned crop with a good crop remaining. Pear psylla adult numbers continue to slowly raise as suckers continue to elongate.

Peaches are between 23 and 34 millimeters in diameter. Thinning continues in some blocks; others will not require thinning due to frost damage. Green peach aphids continue to be found in many peach blocks. Peach leaf curl symptoms are common across the region.

Sweet cherries have put on a big swell of growth and have colored well in this last week. Most remaining fruit are between 15 millimeters 18 mm in diameter. As I have been reporting over the last month, there has been a slow but steady amount of fruit drop in sweet cherries. In some varieties it is hard to find any fruit at all. A good amount of bird damage is being found in remaining fruit, mostly from cedar waxwings and robins. The new growth has leaves at the tip of the branch that have an off or reddish color, I believe that this reddish color was caused by cold temperatures of the last week. Leaf spot control programs need to be maintained at least for the time being.

Tart cherries also remain about the same diameter as last week, they are mostly 11 to 12 millimeters in diameter. The remaining fruit is starting to turn a straw color. As is the case in sweet cherries, I have seen a good amount fruit drop in tarts. Most blocks only have 5 to 10% of a crop remaining. As is the case in sweet cherries, many growers report that they don’t have enough crop to open for tarts. Leaf spot control programs need to be maintained at least for the time being.

Plums are 18 to 20 millimeters in diameter for European varieties, with Japanese varieties 25 to 29 millimeters in diameter. As is the case for both sweet and tart cherries, most plum blocks have a poor crop due to freeze/frost damage.

Small fruits

Saskatoons
Saskatoons. Photo by Bob Tritten, MSU Extension.

Strawberry harvest is underway at most farms from the Flint, Michigan, area and southward. Most others will be opening in the next few days. Demand for both ready picked and pick your own has been very strong, and many farms have needed to close for a day or two to allow more fruit to ripen. Cooler weather has also slowed to ripening process. Some growers have needed to close off picking in order to irrigate due to dry soils. With hot weather predicted for later this week, growers may need to water in the afternoon for evaporative cooling of berries.

The new leaves on both newly planted and fruiting plants are looking more normal over the past two weeks. Leaves on newly planted strawberries continue to emerge from the crown, with the flower trusses continuing to emerge from the crown, deflowering will need to be done fairly quickly. Some varieties are starting to runner.

With evapotranspiration rates being so high from hot, windy and low relative humidity conditions over the last few weeks, many soils continue to be dry to very dry. Keep a close eye on soil moisture levels. Developing strawberries need around 1.5 inches of either rainfall or irrigation a week, and with many days of having high evapotranspiration rates of as much of a quarter of an inch a day, strawberries need a good amount of water. I am concerned that with low soil moisture supplies that the second and subsequent pickings may have many small berries, due to dry soils.

I have seen or heard of a number of strawberry fields that appear to have had feeding injury for thrips earlier this season. The feeding was most likely from western flower thrips. However, I have not been able to find any adult thrips to aid in the identification of this pest. This is a difficult insect pest to scout for, as they do their feeding damage when flowers are opening and early in the flowering process, then they move on to feed on other plants. Western flower thrips do not overwinter in colder climates, like Michigan. They come to Michigan with storm fronts from the south. The damage appears as seedy small berries that have a bronze color. Be on the lookout for this feeding damage. Many times, the feeding damage will just be seen a single variety that was at the right stage for thrips to do their damage.

Slugs were found last week at a few more farms. Thoroughly scout now to check for the presence of slugs. No strawberry clipper adults or damage has been found yet but be on the lookout for adults or feeding injury to flower petals or flower stems. I have not seen any tarnished plant bug feeding damage yet this season.

Raspberry growth has continued to be good; many summer raspberries have fingernail or larger sized berries. Summer varieties have new canes that are 15 to 18 inches in length. Fall red raspberry canes are in the range of 16 to 18 inches in length.

Blueberries are mostly between 5 to 10 millimeters in diameter, fruit are starting to color. Blueberry stem gall wasp adults are continuing to emerge.

Saskatoon fruit are 6 to 8 millimeters in size. Berries have colored well in the past week. Harvest is expected to begin in two weeks. New shoots are growing quickly with most 18 inches in length. A good amount of bird feeding is being seen, mostly from cedar waxwings and robins.

Grapes have moving quickly again week with Concords at 10% bloom. Wild grapes are in bloom. Many new canes are 24 to 36 inches in length.

Haskap fruit are mostly 6 to 8 millimeters in diameter. A good amount of bird feeding is being seen, mostly from cedar waxwings and robins.

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