East Michigan fruit update – June 11, 2019

Robert Tritten, Michigan State University Extension - June 11, 2019

Strawberry harvest is expected to begin late this week or over the weekend for many farms, one of the latest harvest starts for many. Apple growers need to lookout for fire blight strikes.

Weather

What seems to be this never-ending precipitation cycle brought another good batch of rain starting on Sunday late afternoon, June 9, and continuing into Monday, June 10. Many fruit farms, mainly and roughly north of the M-59 corridor, saw 1.6 to 3.1 inches of precipitation from this last round of showers. Many for our Michigan State University Enviroweather stations across the region have received measurable precipitation in two to four of the last seven days. This was the fourth to fifth week in a row for growers receiving measurable rainfall over so many days.

Wet soils continue to be a major challenge for fruit growers. Our soil temperatures are still cold for this time of the season. We did have some warm days over the last week, however, most nights saw temperatures still in the lower 50s. While last week was not as warm as the week before, we still saw big additions to our growing degree day (GDD) totals for the week. Many of our MSU Enviroweather stations across the region added over 100 base 50 GDD in the last week alone. Our season is still running between three to four days behind normal when looking at both flowering stages and GDD totals for region, even with warmer daytime temperatures.

Weed growth has been a major problem for all fruit growers this season. Many growers have applied a second herbicide application, as the earlier applications have been moved too deep in the soil profile to be effective any longer. Perennial and vine type weeds are particularly troublesome.

East Michigan GDD totals for March 1 to June 10, 2019
Location	GDD42	GDD45	GDD50
Commerce (Oakland County)	847	674	436
Deerfield (Monroe County)	988	795	530
Emmett (St Clair County)	634	482	279
Flint (Genesee County)	907	729	479
Freeland (Saginaw County)	806	634	413
Lapeer (Lapeer County)	822	655	426
Pigeon (Huron County)	669	518	315
Romeo (Macomb County)	873	698	455

Tree fruits

Apples in the southern parts of the region are mostly between 20 to 28 millimeters and in the midparts of our region (Ann Arbor through Flint) are at 20 to 24 millimeters in size. A good amount of fruit drop has taken place in many apple varieties over the last 10 days. It appears there will a bit more drop yet to come. Some blocks will require some hand thinning beginning in a week or so. Overall, most growers have good fruit set at this time.

Growth of terminal branches and new leaves has continued to be rapid over the past three weeks. Some varieties have very large leaves this season, bigger than I have ever seen. It is also odd to see some apple leaves that appear to have lobes on them.

Insect pest pressure has continued to pick up again this week. Two new apple pests being seen this week are white apple leafhopper adults and the first trap catch of brown marmorated skink bug adults, both being found in low numbers and only in a few blocks. Codling moth trap counts are generally higher this week, even in some mating disrupted blocks. Most growers biofixed in the last week. This is a season that it would be very useful to trap for codling moth on your farm so you can set your own biofix date, as the trap catch numbers are all over the board this season. If I had to set a regional biofix date, it would be May 31.

A few more tarnished plant bug adults and nymphs are being seen, along with some fruit damage. I am seeing more plum curculio adults and damage this week in apples and other tree fruit crops. I continue to see a few green apple aphids and potato leafhopper adults. A few obliquebanded leafroller larvae continue to be found in apple terminals at most farms. I expected to find the first signs of woolly apple aphids this week but have not seen any yet. I found a few blocks of apples yesterday that had spotted tentiform leaf miner larvae in the leaves. A few green lacewing adults are the only beneficials I have found this season.

Late last week, growers reported seeing their first fire blight strikes, mainly a few blossom clusters. Yesterday, I saw just a few terminal strikes in a few apple blocks. More streptomycin leaf yellowing or burn continues to show up on more sensitive varieties. Most apple growers have applied four to six fire blight control sprays this season. Yesterday, I found my first of the season apple scab lesions on fruit; I have been finding lesions on leaves since May 17 and 18.

Last week, I reported being out of primary apple scab season. This has been a tough apple scab season. Powdery mildew-infected terminals continue to be found in a few apple blocks. Over the weekend, I found the first signs of cedar apple rust symptoms on leaves. Oddly, I am not finding any galls on nearby cedar trees.

Pears are 16 to 18 millimeters in size. Pear psylla adult flight continues.

Peaches are mostly 18 to 21 millimeters in diameter for the largest sized fruit. There is some fruit drop in a few varieties of peaches this week. A few green peach aphids continue to be found. Peach leaf curl symptoms are very common this season in many blocks.

Sweet cherries are still mostly 11 to 13 millimeters in size for the largest fruits. Fruit drop is common in sweet cherries this week. Most growers have a good crop of sweets coming along.

Tart cherries also remain 11 to 13 millimeters in size for the largest fruits. Pit hardening is underway in tart cherries. As I am seeing in other stone fruit, some drop is taking place in tart cherries.

Plums are 15 to 17 millimeters in diameter for European varieties and 18 to 21 millimeters in diameter for Japanese varieties. Many Japanese varieties have a light crop this season.

Small fruits

Strawberry bloom has finished up at most farms and fruit is sizing and coloring in many varieties across the region. Harvest of early varieties is expected to begin late this week or over the weekend at many farms. There are a good number of berries in most varieties. Leaf growth has continued to improve.

There are no new pests to report in strawberries this week. A few tarnished plant bugs and spittle bugs are being found. I continue to find a few flower petals that were fed on by strawberry clipper before the flower was open. Most growers have not been able to apply all of the cover sprays this season for gray mold control due to wet soils. Scout closely for slugs due to wet soils this season.

Raspberry canes continue to elongate in both summer and fall raspberries. Most summer raspberries have newly emerging canes that are 20 to 30 inches in length, and in fall raspberries the longest canes are approaching 24 inches in length. Summer raspberries have small fruitlets that are developing.

Fall bearing blackberries have been very slow to emerge from the ground this season. Some of this might be due to winter injury. I had the first of the season trap catch of spotted wing Drosophila adults in traps last week, although it is too early to have fruit damage in raspberries.

Blueberries mostly have fruitlets around 10 millimeters in size with a few late blossoms still present. I had the first of the season trap catch of spotted wing Drosophila adults in traps last week, although it is too early to have fruit damage in blueberries.

Saskatoons are 7 to 8 millimeters in size, with a nice crop coming along this season.

Grapes are at pre-bloom, and most have 15 to 24 inches of new growth. Some mildew signs are starting to show up.

This article was published by Michigan State University Extension. For more information, visit https://extension.msu.edu. To have a digest of information delivered straight to your email inbox, visit https://extension.msu.edu/newsletters. To contact an expert in your area, visit https://extension.msu.edu/experts, or call 888-MSUE4MI (888-678-3464).