East Michigan fruit update – Aug. 18, 2020

Brown marmorated stink bugs are being found in apples and peaches over the past week, with some feeding damage seen in apples.

Brown marmorated stink bug late instar on apple
Brown marmorated stink bug late instar on a Golden Delicious fruit on Aug. 17, 2020. Photo by Bob Tritten, MSU Extension.

Weather

Again, this week most growers received only a few tenths of an inch of rain in several short precipitation events, mostly on Sunday morning, Aug. 16. However, precipitation totals varied greatly over short distances. The Thumb received heavy rains Sunday morning, some in the range of 4 to 7 inches.

Soils continued to dry in the past week, and signs of drought stress returned in young trees and newly planted small fruits. Drought conditions remain for many growers across the region. Many growers paused irrigating fruit crops for a few days last week but have resumed irrigating in the last few days.

For most of our region, our season has moved ahead again this week to being seven to 11 days ahead of normal for growing degree days (GDD) and four to five days ahead of fruit crop growth stages and beginning of harvest.

East Michigan growing degree day (GDD) totals for March 1 to Aug. 17, 2020

Location

GDD42

GDD45

GDD50

Commerce (Oakland County)

2932

2557

1982

Deerfield (Monroe County)

3149

2755

2157

Emmett (St Clair County)

2835

2461

1896

Flint (Genesee County)

3107

2720

2127

Freeland (Saginaw County)

2908

2535

1966

Lapeer (Lapeer County)

2866

2489

1914

Pigeon (Huron County)

2808

2447

1901

Romeo (Macomb County)

2982

2603

2022

Tree fruits

Apples have continued to size well this season, especially for growers that have been irrigating on a regular basis over the summer. For these growers, most fruit are 2.75 to 3 inches in diameter. For other growers, apple sizing seems to have picked up again this week, with most apple fruit 2.25 to 2.5 inches in diameter. Many apple varieties are coloring well for this time of the season.

Harvest of a few summer apple varieties continues. Jersey Mac harvest is wrapping up, Ginger Gold harvest will start in the next four to five days, and Paul Red harvest is about 10 days from beginning. Bird feeding damage continues to be seen, especially from crows in Honeycrisp.

Brown marmorated stink bug (BMSB) feeding damage has been seen in the last few days in apples in a few blocks, mainly on Golden Delicious and other green or light skinned apple varieties. I am also finding late BMSB instar nymphs and adults in apple and peach blocks. Most of the apple feeding damage is being found on orchard edges and along fence rows and woodlots. The drought conditions we have been experiencing may be creating conditions conducive to stink bug movement from field crops and woodlots into orchards. BMSB damage can occur between now and the end of harvest. Movement into apple blocks is unpredictable, so scout for these pests every few days. This is a hard insect to scout for and prevent damage.

Codling moth trap catch has continued to be on the rise in some blocks over the last three weeks. Keep covered for them as we close out insect control programs for the season. There is some fruit damage. Oriental fruit moth trap catch has been high this week in most apple blocks. Apple maggot trap catch has dropped off this week. Woolly apple aphid numbers have continued to climb in many apple blocks; growers are finding clumps of woolly apple aphids on terminal branches. More growers are finding increasing amounts of San Jose scale damage in many apple blocks again this week. Now is the time to keep good records of where this damage is being found to target oil applications next spring. Beneficial numbers continue to slowly build, this week I am finding good numbers of red velvet mites.

Black rot fruit infections are being seen in more and more apple blocks. Bitter rot symptoms are being seen for the second week in light amounts in many apple blocks. More apple blocks are finding pinhead apple scab on fruit and sheet scab on leaves. Sooty blotch and fly speck symptoms are being seen by more growers this week.

Pears have put on a nice swell of growth in the past week, they are mostly 2.25 to 2.5 inches in diameter. Bartlet harvest is about two weeks away. Some blocks are finding a good amount of sooty mold growth from pear psylla feeding and secretion.

Peach harvest continues for Red Haven and other main season varieties. Fruit size is surprisingly good in most blocks, despite the drought conditions most farms have seen this season. There has been some fruit cracking as fruit has taken on this final swell in size. Early varieties saw uneven ripening, but as Red Haven have ripened this problem seems to have diminished.

There continues to be a few peach blocks with a few BMSB nymphs and adults. I have not found any feeding damage. We have been catching just a few BMSB in traps for the last several weeks. Rusty spot was seen in some early peach varieties, however I have not seen any in Red Haven or later season varieties.

Sweet cherry leaves are yellowing and leaf drop is common this week where growers received rainfall a few weeks ago. Fungicide applications need to be made to slow this leaf infection and drop.

Tart cherry leaves are yellowing and leaf drop is common this week where growers received rainfall a few weeks ago. Fungicide applications need to be made to slow this leaf infection and drop.

Plums have taken on another swell and colored well in the past week; European varieties are mostly at 1.375 inches in diameter. I expected harvest to begin soon, but they are still very green to eat and are very firm. Japanese varieties are continuing with harvest. Most plum blocks have a poor crop due to freeze/frost damage.

Small fruits

Strawberry regrowth has continued to rebound well in most renovated fields that have either received good amounts of precipitation or irrigation since renovation. Growers with dry soils are continuing to irrigate both renovated fields and new plantings. Newly planted strawberry rows continue to fill out well. Potato leafhopper leaf cupping damage is common in newly planted strawberries, but I am no longer finding the actual insects. Most of the leaf cupping damage is old.

Raspberry harvest for fall red raspberries started over the weekend for some growers. This first picking was light. Growth has responded well to recent rain events of the past few weeks for fall raspberries. Blackberry harvest is underway.

Spotted wing Drosophila (SWD) trap catch has taken another nice jump this week. Trap catch started across the region nine weeks ago but has been low up until the week before last. SWD protection programs need to be ongoing in fall red raspberries.

Blueberry harvest continues on mid and late season varieties. Berry size is diminishing on most varieties. SWD trap catch started across the region nine weeks ago, and until two weeks ago trap catch has remained low. However, for the second week in a row I am finding a jump in SWD trap catch. SWD protection programs need to be ongoing in blueberries. Blueberry maggot trap catch has dropped off this week.

Grapes are at berry touch for all varieties and clusters are filling out. I started seeing veraison in Freedonia late last week, but none in other varieties yet. Japanese beetle populations have declined again this week. Third generation grape berry moth trap catch is starting to wind down, control measures need to be underway. Downy mildew symptoms continue to be found this week.

Saskatoon leaf yellowing and some drop continues on leaves that were fed on by Japanese beetle earlier in the season. It is too late for control measures at this time, as the damage has already occurred.

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