SW Michigan Fruit Update
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Southwest Michigan Fruit Update, August 3, 2009

Mark Longstroth, Bill Shane, Diane Brown-Rytlewski

Weather

Last week was warm with highs near 80 and lows in the 50s.  A few tenths of an inch of rain fell over the weekend.  Soils are very dry.  We continue to lag a week or two behind normal.  Fruit crop development seems close to normal.

Southwest Michigan Growing Degree Day Totals March 1 through August 2, 2009				Grapes, April 1
Location	GDD 42	GDD 45	GDD 50	GDD 50
SWMREC:	2449	2092	1542	1502
Fennville:	2259	1913	1379	1353

You can find weather and IPM information for Southwest Michigan at the Enviroweather website. 

Insects

Japanese beetle numbers are still low.  Apple maggot and blueberry maggot numbers are generally low, but an increase after this weeks rain showers can be expected.

Tree fruit

Peach harvest continues with the yellow flesh types Red Star, PF11, and Red Haven and the white fleshed Spring Snow and Saturn (a flat peach) are coloring well.  Bacterial spot symptoms continue to increase especially for susceptible varieties growing in sites exposed to wind-blown sand.  Summer dews are conducive to bacterial spot.  Rain is needed to size fruit in sandier sites.  Oriental moth catches are low.  Oblique-banded leafroller larvae are causing shallow feeding damage on peach fruit.  Pheromone lures should be changed in anticipation of the beginning of the third generation flight.  Brown rot can be found sporulating on fruit, in mummies, and blighted twigs.  It is important to remove these after harvest to reduce the inoculum for the beginning of next season.  Fungicide treatments for brown rot are needed as fruit color.  Watch for signs of western flower thrip on peaches.  Thrip damage appears as light brown fuzzless spots up to 1 inch in diameter usually on the blush region.

In Plums, Methly Japanese plum harvest is ending and Shiro and Linedecker harvest is starting.  Apple maggot is a problem in ripening plums.  Scout for leafhopper damage from white apple or potato leafhoppers.

Apple fruit size and quality still look good.  Pristine are being harvested with harvest of Zestar, Chenango and Dandee Red to start soon.  Fire blight is not spreading due to the dry conditions.  The second generation of codling moth is flying, with trap catches generally increasing and should peak in mid August.  Oriental fruit moth trap catches are low.  Apple maggot flies are out and we expect a strong flight with any rain.  Expect to see Obliquebanded leafroller larvae on shoot tips.  Apple aphids are easy to find.  Mite numbers continue to increase.  The treatment threshold for European red mite in July and August is over 7 mites per leaf. 

Pears are over 2 inches in diameter.  Pear Psylla populations are building in some blocks causing sooty appearance and honeydew symptoms on leaves near veins.  European red mites are causing black leaves in some blocks.  Growers should protect against the second generation of codling moth, which emerges in late July through August and attacks pears just before harvest. 

Small fruit

Blueberry harvest continues with hand and machine harvest of Jersey.  Fruit size and quality are good in irrigated fields.  Growers should maintain protection against alternaria fruit rot.  Blueberry maggot flies are out.  Symptoms of phomopsis cane collapse are still appearing.  No treatment is effective at this time.  These should be pruned out and removed from the field.  For more information look at the Michigan Blueberry IPM Newsletter posted by Paul Jenkins at the Berry Entomology Lab. 

Grapes look good.  The crop appears heavy and growers are still thinning to reduce their crop and avoid immature fruit at harvest.  Generally there are few diseases.  Phomopsis lesions are easy to find on stems and clusters in some vineyards.  Botrytis symptoms are showing up in scouted vineyards.  See the most recent copy of Grape IPM Newsletter at the MSU Grape current conditions webpage.  Powdery mildew has been found on a few wine grape varieties.  Morning dews are good for the spread of downy mildew, so fungicides against downy mildew are required during the summer season when there are morning dews.  Grape berry moth eggs are hatching and stings and tunnels can be found on the fruit.  Japanese beetles numbers are low. 

Strawberry growers should control potato leafhoppers to prevent stunting of new growth.

Fall raspberry harvest has begun in early varieties.  Morning dews can cause fruits rot problems such as Botrytis gray mold, so fungicides are needed when there are morning dews.