East Michigan fruit update – May 26, 2020

With warmer temperatures of the last week, fruit crops have taken on big swell of new growth. Bloom is almost finished for all of our fruit crops.

Weather

With warmer temperatures over the past week, we saw a big jump in degree day accumulations. Our season is still running behind normal, but now by only five to seven days. Last week, we were almost two weeks behind normal.

East Michigan growing degree day (GDD) totals for March 1 to May 25, 2020

Location

GDD42

GDD45

GDD50

Commerce (Oakland County)

522

398

236

Deerfield (Monroe County)

614

472

291

Emmett (St Clair County)

499

376

222

Flint (Genesee County)

597

461

281

Freeland (Saginaw County)

494

371

214

Lapeer (Lapeer County)

542

414

247

Pigeon (Huron County)

436

325

193

Romeo (Macomb County)

526

398

233

Tree fruits

Apples have moved through bloom very rapidly over the past week with warmer temperatures. Most of the region ended up having several good pollinating windows for bees and other pollinators to work. Apples in the south are at petal fall to early fruit set. Further north, apples are at the tail end of bloom. Most of the bloom will be dropping in the next few days. Petal fall sprays will be going on fairly quickly. Fruitlets for most apple varieties are 4 to 5 millimeters in size and with the heat of the last week have 4 to 6 inches of new terminal growth.

While I am still not able to travel as widely as I would like in springtime due to the ongoing situation, in grower visits that I made yesterday, May 25, to assess the state of the apple crop, most growers are surprised to find less frost damage to flowers than they expected to see last week at this time. While damage to apple bloom is all over the board, from very light to very heavy damage, I am pleasantly surprised with the number of young apple fruitlets that I see at this writing that appear to be viable.

Growers are now starting to assess crop load and are beginning to formulate a thinning plan. Consider a cautious approach to thinning this season. Growers might start with a mild thinner application when fruitlets are 7 to 8 millimeters in size, which for many growers may be later this week. Products to use at this timing could include Sevin or NAA at half the rate growers would normally use at this fruit size. Due to the three frost events in apples this season, most growers did not do any blossom thinning.

I have three new insect pests to report in apples this week. The first are low numbers of codling moth in traps. The second is the first sightings of a few rosy apple aphids. The third is the first sightings of tarnished plant bugs, both adults and nymphs, in just a few apple blocks. Last week I reported first trap catch of oriental fruit moth, a few blocks have moderate numbers, but most trap catch numbers are still low. Redbanded leafroller adult trap catch has rebounded some in the last week. Recall that the week before last, many redbanded leafrollers appeared to have been killed off due to frost events. Spotted tentiform leafminer adult trap catch has remained low for the second week in a row. I was not able to find many predators in scouting that I did yesterday.

The fire blight model on Enviroweather had very high EIP (Epiphytic Infection Potential) numbers the last few days. Where growers have even had light amounts of precipitation in the last week, some on Tuesday, some on Sunday and others on Monday, streptomycin applications have been needed to protect for fire blight infections. Some growers have made one application of streptomycin, but most have made two applications. There is still a lot of bloom on younger trees and newly planted trees; growers will need to make more applications on these trees if we receive any rain fall later in the week, even popup showers. There is a good chance of precipitation predicated for Thursday, May 28.

A few apple growers have had enough rain and wetting in the past week for a low to moderate risk of an apple scab infection period. Last week, I found my first few apple scab lesions on leaves and this week I am finding a few more apple blocks with just a few lesions. These lesions were most likely from the May 14 to 16 wetting event. Yesterday, I found a good number of powdery mildew infected terminals at many farms on mildew prone varieties. Protection programs need to be underway soon on mildew prone varieties.

Pears are mostly 4 to 12 millimeters in size. Most trees are loaded with small fruitlets with very little to no frost damage to flower buds or blossoms. Pear psylla adult numbers continue to slowly raise with warmer temperatures.

Peaches are out of the shuck with the largest fruit at 10 millimeters in diameter. Some blocks have seen a good amount of fruit drop as they have emerged from the shuck. Peach frost damage is all over the board this season, depending on the site. Some poorer peach sites have seen a good amount of damage and the best peach sites have a full crop, with a good amount of thinning that will need to be done in June.

Peach leaf curl symptoms started to be found on leaves late last week at several farms. This has been disappointing for peach growers to see this for the second year in a row. Most growers have stepped up their peach leaf curl control programs last fall and early this spring, expecting not to see these symptoms this year. Growers using either chlorothalonil or copper have seen leaf symptoms. Low levels of copper from early spring to early shuck split are useful in suppressing bacterial spot populations. The amount of copper is to be reduced as the season progresses and growers need to monitor for phytotoxicity.

Sweet cherries are around 7 to 10 millimeters for the largest sized fruit. As sweets came out of the shuck in the past week, most growers saw a good amount of fruit drop, especially on larger sized trees. Younger trees have more crop, about 40 to 60% of a crop. But if I average older trees with younger trees, the crop potential is much lower, in the 10 to 20% range. Leaf spot and brown rot control programs need to be maintained at least for the time being.

Tart cherries are at shuck split, with just a few blossoms remaining. As is the case this week in sweet cherries, I am finding a good amount of flower bud damage in tarts in many blocks. While it is too early to tell the crop potential for certain, many blocks only have 10% of a crop remaining. As in sweet cherries, leaf spot and brown rot control programs need to be maintained at least for the time being.

Plums are at shuck split for European varieties, with Japanese varieties being at fruit set to the largest fruit at 5 millimeters in diameter. I continue to find freeze damage in all plum varieties, but the percent of damage varies widely, from 40 to 80%, depending on the site and variety.

Small fruits

Strawberries are at full bloom for many varieties. With the heat of the last week, their growth rate has progressed quickly. Many growers were finding numerous black blossoms on early varieties and early flowers over the past two weeks. Many were concerned that they lost most of their strawberry crop due to frost. But as more flowers opened in the past week, growers are pleasantly surprised to see that the frost damage was not as extensive than they had anticipated.

New leaves are starting to look more normal on fruiting plants, but the growth is still not normal at most farms. A light application of liquid nitrogen through the irrigation system is needed at this time to help improve the vigor and plant health in most fields. Newly planted strawberry leaves continue to slowly emerge from the crown, with the first fully expanded leaves just starting to be seen.

Spittlebug is a new pest to report in strawberries this week, but their numbers are very low at this time. No strawberry clipper has been found yet but look out for adults or feeding injury to flower petals or flower stems. With bloom in strawberries, apply fungicides for gray mold control at this time.

Raspberry growth has picked up in the past week as a result of warmer temperatures. Flower buds have emerged on many early fruiting summer varieties, the canes are 3 to 4 inches. Many new canes have emerged from the soil on fall raspberries, most are 4 to 6 inches in length. I have seen a good number of fall raspberry fields with new leaves that are slightly yellowed caused by herbicide injury. It is most likely from Sinbar; I think they will grow out of this injury nicely in a few weeks.

Blueberries are mostly full bloom for most varieties. Blueberry stem gall wasp adults are emerging as bloom is underway.

Saskatoons are at fruit set with most fruitlets 3 to 5 millimeters in size. New shoots are 8 to 10 inches in length. I started to see the first plum curculio feeding damage yesterday in saskatoons.

Grapes have moving quickly in the last week. Most are at late bud burst to 2 to 4 inches of new cane growth. Wild grapes are starting to see some flower buds emerging.

Haskaps are at small fruitlets, most are at 3 to 4 millimeters in diameter.

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