Southeast Michigan fruit regional report – Aug. 27, 2013

European plum harvest is starting at a few farms; fall red raspberry and blackberry harvest continues as does summer apple varieties; and peach and blueberry harvest is winding down.

Weather

Cooler temperatures have generally persisted over the region for the last three weeks. Our season is running four to seven days behind normal in terms of growing degree day (GDD) totals, however close to normal to a few days behind normal when I look at growth stages and the start of harvest of our fruit crops.

Soil moisture conditions are all over the board this season, but most areas of east Michigan are trending toward soils becoming dry and are at a point where they need to replenish with rain or irrigation. Tree and small fruits are wilting at a few farms.

East Michigan growing degree day totals for March 1 to August 26

Location

GDD42

GDD45

GDD50

Commerce (Oakland)

2942

2553

1940

Emmett (St Clair)

2943

2557

1948

Flint (Genesee)

3237

2839

2212

Lapeer (Lapeer)

2954

2565

1960

Petersburg (Monroe)

3147

2744

2108

Pigeon (Huron)

2866

2486

1889

Romeo (Macomb)

2963

2583

1978

Tree fruits

Apple size has stalled for many growers where soil moisture supplies have been in short supply. Most apples are 2.625 to 2.75 inches in diameter. Harvest of Paula Red has wrapped up for most growers and Gingergolds are being harvested. Galas are the first major fall variety that are nearing maturity, with the earliest strains at least a week away from maturity or the beginning of harvest. Summer pruning continues. Retain applications continue to be made in several varieties.

Bitter pit is being seen more commonly in the past week, especially where fruit is large in areas where soil moisture has been plentiful this season. Growers need to consider additional applications of calcium in cover sprays.

Codling moth trap catch numbers from the second generation flight have dropped back in most blocks. The second generation regional biofix date was set for Aug. 2 and there have been enough GDD base 50 accumulated since then that we are around 40 percent egg hatch and the need to keep good cover sprays on in blocks over threshold. It is crucial right now and for the next several weeks. A third generation of codling moth is not expected for 2013.

As we are nearing the beginning of harvest for many apple varieties, Michigan State University Extension encourages growers to take time to double-check the pre-harvest intervals for any late season pesticide applications that might be needed for various insect pests. I continue to catch a few apple maggots, but their numbers are down these past two weeks, most likely due to the lack of rainfall. I continue to catch apple maggots only on yellow sticky cards.

There are a few isolated hotspots of European red mites and two-spotted spider mites in a few apple blocks, but generally their numbers are well below threshold levels. No brown marmorated stink bugs have been trapped or reported in the region this season. A few have been trapped in known non-fruit sites in south central and southwest Michigan. There continues to be high numbers of predators this season.

Necrotic leaf blotch symptoms continue to be seen, although most of the symptoms are a few weeks old now. This physiological disorder mainly effects Golden Delicious and its related bud sports. Leaves first begin to show irregular-shaped spots and then yellow and drop to the orchard floor. Sooty blotch and fly speck symptoms continue to be seen in apples. Growers need to keep an eye on abandoned apple and crabapple trees for signs of leaf drop caused by apple scab. In some areas, I am seeing extensive leaf drop from this disease. Knowing the pressure in your area may help you next year as you begin assessing apple scab pressure.

Pears have continued to size this past week, with most being 2.5 inches in diameter. I expect to see harvest begin over the next week or so. Fruit damage from spring frosts is becoming very apparent in the last few weeks.

Peach harvest is winding down. Size is less of a challenge as we move through harvest. On varieties harvested earlier in the season, the first picking had good size and finish; however, the size dropped down dramatically for the rest of harvest for that variety. No brown marmorated stink bugs have been trapped or reported in peaches in the region this season.

Plum harvest for Stanley and other European varieties is just getting started and Japanese plum harvest continues.

Small fruits

Strawberries continue to rebound from renovation, with most farms filling in the row and a good amount of runnering taking place. Newly planted berries are continuing to runner well. Potato leafhopper feeding and leaf curling is being seen in most new and renovated plantings.

Raspberry harvest of fall red raspberry and blackberry continues. Spotted wing Drosophila (SWD) are being caught in traps in increasing numbers. Growers keep asking why they are continuing to get SWD trap catch even though they are spraying on a regular basis. The quick answer is trap catch is unlikely to get to zero, particularly now as we head into September when numbers continue to climb.  Rufus Isaacs’s lab at MSU is also still catching SWD in fields across the state where there is a weekly rotation of high toxicity insecticides, and no fruit quality or wormy fruit problems have been observed. So, catches don’t necessarily mean that the sprays aren’t working to get the job done of protecting fruit.

Two-spotted spider mite populations are high in a few bramble patches in the past two weeks. Most of the farms that are affected need to be treated with a miticide. Japanese beetle populations have continued to drop. Potato leafhoppers are being seen in both new and established raspberry plantings.

A disorder known as crumbly berry has been seen at several raspberry farms across the state. While this disorder can be caused by a variety of factors, this year it appears that the lack of pollination and cooler temperatures at bloom time are the main causes. Berries at harvest are small, misshapen and fall apart when harvested. While most farms only have a few varieties impacted by this disorder, the combined list of varieties impacted at all farms across the region is long.

Blueberry harvest continues, however it is winding down as berry size and quality is getting poor. Spotted wing Drosophila have been trapped in blueberries at most farms in the last week. Trap catch numbers are continuing to rise. Blueberry maggot trap catch on yellow sticky traps continues, with most plantings having declining numbers. Birds (mostly robins, starlings and red wing black birds) continue to feed heavily in most blueberry plantings.

Grapes are at veraison for Concord types. Downy mildew continues to be seen in many grape plantings, most from infection earlier this season when conditions were warm and moist. Powdery mildew, favored by cooler temperatures and moist conditions, is present in many vineyards in lesser amounts later this season.

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