East Michigan fruit update – July 14, 2020

Much needed precipitation brought some relief to some growers. For others less fortunate, drought conditions continue. Summer red and black raspberry harvest continues and blueberry harvest is starting for a few farms.

Weather

Rain has finally come for most growers late last week and over the weekend. However, precipitation totals vary greatly over short distances. For some growers, rainfall totals for the last week were as high as nearly 2 inches. For others, however, precipitation totals for up to three rain events only totaled 0.33 inches. For some growers, the drought continues, and a good amount of time is still being devoted to irrigation. For others that did receive a good amount of rain, they have a temporary relief.

Overall, soils across the region remain dry. Most fruit farms saw their last rain on June 10. Signs of drought stress in fruit crops have eased up where growers received 1.5 to nearly 2 inches of rain. For others, signs of drought stress are common, especially in newly planted and younger fruit crops and in shallow rooted fruit crops. Sod in most orchards is still brown, looking more like some Augusts.

With another week of hot temperature last week, we saw another good jump in growing degree day (GDD) accumulations. Most of our Michigan State University Enviroweather stations have seen a rise of 200 GDD base 50 accumulations again this past week. Our season moved ahead to being a three to seven days ahead normal for both growth stages and GDD.

East Michigan growing degree day (GDD) totals for March 1 to July 13, 2020

Location

GDD42

GDD45

GDD50

Commerce (Oakland County)

1894

1624

1223

Deerfield (Monroe County)

2062

1773

1349

Emmett (St. Clair County)

1857

1589

1197

Flint (Genesee County)

2036

1754

1335

Freeland (Saginaw County)

1866

1597

1203

Lapeer (Lapeer County)

1871

1599

1198

Pigeon (Huron County)

1787

1530

1159

Romeo (Macomb County)

1920

1646

1241

Tree fruits

Apples that are well established have continued to size well over the past week. Apple size on younger trees has slowed over the last few weeks due to dry soils. Most apple fruit are now 1.625 to 2 inches in diameter. Hand-thinning continues for many apple varieties, especially Honeycrisp. Lodi harvest is expected soon.

Some fruit color is starting to be seen on a few varieties. This coloring may be the result of some mild sun scald injury. Time will tell.

There are no new insect pests to report in apples this week. Apple maggot trap catch has been low on both yellow sticky traps and red ball traps over the last two weeks. For farms that received a good amount of rainfall late last week, I expect to see some adult emergence over the next few days. Where soils remain dry, emergence will continue to be delayed. Early this week, some apple blocks saw high numbers of green apple aphids. The aphids are moving from leaves to fruit as leaves are hardening off. Up until this week, predators have been doing a good job of keeping aphid numbers low. If these aphids remain on fruit, they will need to be controlled fairly quickly. Woolly apple aphids are starting to move from pruning scares to terminal branches.

Apple rust mite populations are continuing to build quickly with the hot weather of last week. While numbers are still below threshold, they will bear watching as this hot weather continues. Potato leafhopper numbers have dropped off this week in most apple blocks, however the curled leaves remain. European red mite and twospotted spider mite numbers continue to slowly build, but neither are at threshold levels yet. Beneficial or predator numbers continue to build, this week I am finding good numbers of lady beetle adults and larvae and lacewing adults.

Silver leaf is a new disease to report this week, leaf symptoms started to be seen on infected trees last week. More apple scab fruit lesions continue to be found as apples continue to size. I continue to have isolated reports of new fire blight strikes. Look out for new strikes. Limb collapse, wilting and browning from black rot infections in the wood tissue have been seen over the last month. Last week, the first black rot leaf infections started to be seen, and this week I am just starting to see some fruit infections beginning. More growers are finding cedar apple rust symptoms on fruit, it is common this season. Some apple blocks continue to have high numbers of powdery mildew infected terminals.

Leaf mottling is more common on Honeycrisp leaves this week. The mottling is caused by the accumulation of large starch granules in the leaves that reduce photosynthesis.

Pears are mostly 1.5 to 1.875 inches in diameter. Sucker removal is continuing in pear blocks.

Peaches are between 1.5 and 1.875 inches in diameter. Pit hardening has taken place. Some growers are finding that they still have too much fruit left on the tree after the first round of thinning, so they are going back to do more hand thinning on some varieties. A few green peach aphids continue to be found in many peach blocks. I have not seen any flagging from oriental fruit moth in peaches yet but I expect to find some soon. While peach leaf curl symptoms are common across the region. As new leaves develop, the symptoms appear to be diminished.

Sweet cherry leaf spot disease symptoms and leaf drop are common this week.

Tart cherry leaf spot disease symptoms and leaf drop are less common than on sweets, but are being found.

Plums remain at an inch in diameter for European varieties, with Japanese varieties at 1.5 to 2 inches and some good color development being seen. Harvest of early Japanese varieties is expected to begin in a week to 10 days. Most plum blocks have a poor crop due to freeze/frost damage.

Small fruits

Strawberry renovation has wrapped up for some growers and is continuing for others. Growers with dry soils will need to get their irrigation systems back into strawberry fields quickly to begin irrigation when renovation is wrapped up.

Leaves on newly planted strawberries continue to emerge from the crown, along with runners that are starting to root down. Drought stress is still common in newly planted strawberries where growers did not get good rains late last week.

Potato leafhopper leaf cupping damage is starting to be seen commonly in newly planted strawberries.

Raspberry harvest continues for summer red raspberries and black raspberries. Berry size is small where soils have been dry over the last month. Where irrigation has not been applied in black raspberries, the berry size is so small that they are not marketable. Growth in both summer and fall raspberries has slowed due to dry soils. Many fall red raspberry plantings have canes that are shorter than normal this season. A few berries are continuing to be harvested on the bud berry canes or shorter fall red raspberry canes.

Light amounts of raspberry cane borer and raspberry sawfly larva feeding damage is being found at just a few farms.

Spotted wing Drosophila (SWD) trap catch started across the region four weeks ago, but this week’s trap catch remains low, most likely due to hot temperatures of last week. Regardless of trap catch, I have a few reports of growers finding small SWD larva in fruit. So, even though pressure from SWD is low, protection programs need to be ongoing.

Blueberry harvest has started on early varieties at a few farms, others will begin harvest over the next week. Berry size took on a nice swell over the last week, with the largest harvestable berries being 15 to 18 millimeters in diameter. Remaining berries are coloring well.

SWD trap catch started across the region four weeks ago in several fruit crops, but this week’s trap catch in blueberries remains low, most likely due to hot temperatures of last week. Regardless of trap catch, SWD protection programs need to be underway in blueberries. Blueberry maggot trap catch has been seen in southwest Michigan, but again this week there has been no trap catch in east Michigan. I expect to see trap catch soon when soils moisten for those growers who received rain late last week.

Grape growth has moved quickly again this week, with concord and vinifera varieties being between buckshot and berry touch. Growers are doing some cane removal this week. Japanese beetle adults are being found in low numbers in many vineyards. Grape berry moth larva feeding was seen in more grape varieties this week. Populations are very high in southwest Michigan.

Saskatoon harvest wrapped up over the weekend for most growers.

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