Southwest Michigan fruit regional report – August 30, 2016

Peach and pear harvest continues. Apple harvest is beginning. Rains have impeded blueberry harvest and wet, humid conditions are good for diseases and insect pests.

A single night’s oriental fruit moth catch. Moth numbers this high pose a real threat to apples and peaches. Photo: Bill Shane, MSU Extension.

A single night’s oriental fruit moth catch. Moth numbers this high pose a real threat to apples and peaches. Photo: Bill Shane, MSU Extension.

Weather

Last week was similar to the previous week, but with less rainfall. High temperatures were in the mid-80s and lows in the mid-60s. Rainfall for the week ranged from 0.7 to 1.2 inches. The air is still humid and we have heavy dews in the mornings. Rainfall for the month of August totaled 6.5 to 7 inches, helping to size peaches and apples, but heavy rains have led to some flooding.

Potential evapotranspiration rates are 0.10 to 0.16 inches per day. We are slightly more than a week ahead of normal for heat accumulation.

Southwest Michigan GDD summary from Jan. 1 - Aug. 28, 2016

Station

GDD 42 F

GDD 45 F

GDD 50 F

Benton Harbor (SWMRC)

3,805

3,346

2,641

Lawton (Lawton)

3,821

3,356

2,644

Fennville (TNRC)

3,380

2,941

2,268

Average for the SW region

3,571

3,119

2,430

Accumulation last week

206

185

150

Tree fruit

Trap catch numbers for oriental fruit moth and codling moth remain high in many orchards. This is the fifth week of the second generation codling moth flight. Obliquebanded leafroller trap catch dropped to zero at the Trevor Nichols Research Center, signaling the possible end of the summer generation flight after five weeks. San Jose scale trap catches over the past week dropped for the seventh week of the second generation flight. Using insecticides such as pyrethroids with activity against scale crawlers may flare mite populations. A third generation of this San Jose scale usually appears in early September.

Brown marmorated stink bug numbers have increased slightly. Last year, brown marmorated stink bug numbers increased sharply in mid-August in southern Berrien County. Damage to fruit from brown marmorated stink bug feeding can be confused with several disease or nutrient deficiencies, depending on the particular fruit that is affected.

Spotted wing Drosophila (SWD) numbers continue rising across southwest Michigan and we are catching flies in most traps. Fruit left on the tree to soften are very attractive to SWD infestation.

Peach harvest of mid- to late-season varieties continues in central Berrien County. Miscellaneous fruit diseases such as brown rot, rhizopus rot and anthracnose rot are becoming more common. Rainy, moist conditions only make these diseases harder to control. Oriental fruit moth flight is still strong in some orchards with considerable damage in some locations. Trapping is necessary so growers can judge which blocks are experiencing high moth pressure (more than approximately 20 moths per trap per week). High trap counts can be caused by insecticide resistance problems.

Constriction canker (phomopsis) is causing gumming of branches and terminal decline. Brown rot control programs should rotate among the different classes of fungicides to stave off resistance problems. Save the most effective fungicides for when ripening fruit are coloring and most susceptible to infection.

Cherry leaves need to be protected from cherry leaf spot all season, ideally to keep the foliage in good shape through September. Cherry leaf spot disease pressure has been relatively light in most tart cherry orchards due to relatively dry conditions up to now. Growers can do modest pruning in cherries after harvest through August.

Plum harvest of NY9, Bluebyrd and Stanley is underway in central Berrien County orchards. Bacterial spot and brown rot are the primary fruit disease disorders as well as some obliquebanded leafroller feeding damage. Growers should tighten up brown rot spray programs as fruit start to color and ripen. Brown rot infected fruit should be knocked off the tree to reduce future disease problems.

Apple harvest dates estimates are available from Michigan State University Enviro-weather for weather stations across Michigan. Retain applications for reducing fruit drop and delaying harvest are targeted for 30 days before expected harvest. SweetTango and Jonamac harvest has started in some orchards. Main season McIntosh are testing 17-to-18-pound pressure with starch removal indices of 3. Gala fruit are testing very firm flesh pressures of 22 pounds and starch removal indices of 3.2 to 3.6, compared to 1 to 1.8 for last week. This fruit can be harvested successfully for storage.

Red Gala apple

This red sport of Gala will be ready to harvest soon. Photo: Mark Longstroth, MSU Extension.

Fruit entry holes from codling moth or oriental fruit moth larvae are easy to find in unprotected fruit. Obliquebanded leafroller trap catch for the summer generation numbers are up for the fourth week and larvae from this generation are webbing leaves and feeding on fruit. Apple maggot trap catch numbers continue to be significant in the Trevor Nichols Research Center trap line for the ninth straight week. See “Managing apple maggots with insecticides” by MSU Extension for more information.

Sooty blotch and flyspeck disease symptoms are common in unsprayed apples. A general rule of thumb is to reapply fungicides for these diseases after an additional 220 hours of leaf wetness, or 2 inches of rain has occurred following application. The recent rains will increase problems from these diseases.

Pear fruit are generally 2.25 inches or more in diameter. Bartlett harvest is continuing for the second week in area farms. Some fruit has fire blight damage. Harrow Sweet pears will be ready for harvest soon. Harvesting pears is determined by pressure testing the flesh. European pears testing 19 to 23 pounds are hard ripe, 17 to 18 pounds are firm, and 15 to 16 pounds are firm ripe.

Small fruit

Spotted wing Drosophila (SWD) numbers continue to increase in southwest Michigan (see “Michigan spotted wing Drosophila report for Aug. 26, 2016”). Growers with ripe berries should be protecting against this pest. Japanese beetles are scarce.

Grape veraison has occurred in many varieties. Growers continue with vineyard canopy (leaf pulling) and crop load management practices. The crop looks good, perhaps too heavy in some vineyards. Pressure from grape leafhoppers, potato leafhoppers and Japanese beetles remains low in most vineyards. Third generation flight of grape berry moth continues and fruit damage is increasing. There will very likely be a fourth generation of berry moth this year. Where pressure is heavy from the third generation, a spray at 2,430 growing degree-days from wild grape bloom may be needed. This window for this application is currently open, or is opening soon: Aug. 28 in Benton Harbor, Aug. 31 in Lawton and Sept. 2 in Berrien Springs. Wait four to five days after the beginning of the window for broad-spectrum materials. Use short pre-harvest interval materials for this application to avoid affecting harvest.

Disease pressure remains low. Downy mildew and powdery mildew leaf infections are beginning to show up from recent rains. Wet conditions are also conducive to botrytis and sour rot infection on clusters of susceptible varieties.

Blueberry harvest is winding down. Elliott harvest continues. Wet, soggy fields have impeded harvest. Growers scrambled to reapply insecticides washed off by the heavy rains. We still see high SWD numbers in our traps (see “Michigan spotted wing Drosophila report for Aug. 26, 2016”). See the current recommendation for SWD control in blueberries.

Strawberries are growing vigorously with recent rains. Growers should protect leaves from potato leafhoppers, leaf diseases and leaf feeding insect pests. Day-neutral strawberry growers need to protect their fruit against SWD.

Bramble harvest continues with fall red raspberries and blackberries. Ripening raspberry fruit is very attractive to SWD. Growers should pick every two days to avoid SWD. See the current recommendations for SWD control in raspberries and blackberries.

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