SW Michigan Fruit Update

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Southwest Michigan, August 18, 2008

Mark Longstroth, Bill Shane

Weather

Weather the past two weeks has been seasonal with highs in the mid 80s and lows near 60s, with no significant rainfall.  Soils are dry.  Annual plants such as weeds and field crops are wilting due to water stress.  A few scattered storms have moved through the region and left some much needed rain in a few areas.  Rainfall amounts were between a third and a half-inch.  The forecast for the upcoming weeks is for continued cooler and dryer than normal conditions indicating that the lack of water will continue.  The Growing Degrees below have been corrected for some missing data at sites marked with an asterisk*.

Southwest Michigan Growing Degree Day Totals March 1 through August 17, 2008				Grapes, April 1
Location	GDD 42	GDD 45	GDD 50	GDD 50
Berrien Springs:	2966	2576	1977	1967
Scottdale: *	2963	2573	1973	1965
SWMREC: *	2870	2477	1877	1883
Bainbridge:	2837	2459	1882	1875
Hartford:	2711	2337	1766	1762
Lawton:	2944	2556	1954	1949
Grand Junction:	2981	2594	2004	1998
South Haven:	2716	2346	1774	1767
Fennville: *	2680	2307	1733	1729

Tree fruit

The window for leaf sampling for nutrient analysis in Southern Michigan is ending.  If you plan on nutrient sampling take the samples this week.  Young trees should be irrigated to reduce drought stress.  San Jose scale crawlers are out and can cause fruit damage.  We are seeing this pest in more orchards this year.  Few Japanese beetles have been out recently. 

Peach fruit are 2.5 to 3 inches in diameter.  Dry weather has resulted in firm, relatively sweet fruit.  Harvest of Red Haven and Starfire is ending, harvest of PF 17 is underway.  Brown rot is still a problem, including infections of wood next to infected fruit.  It is usually associated with bacteria spot or insect feeding.  X-disease symptoms are easy to find in the area.  Bacterial spot symptoms on peach leaves and fruit are fairly widespread.  Check the PHI (days to harvest) when applying sprays to reduce bacterial spot.  Stinkbug puncture wounds to fruit are more obvious.  Watch for western flower thrip damage to peach and nectarine fruit with hot dry weather. Delegate offers a new option for thrip control.  Oriental fruit moth trap catch is up indicating the start of the third generation. 

In Cherries, yellowing leaves and leaf drop due to cherry leaf spot and bacterial canker are common in some orchards.  Few orchards have lost most of their leaves.  Be sure to check the leaves for signs and symptoms of these two diseases, as the controls are different.  The scattered rains of the last two weeks resulted in no wide spread cherry leaf spot infection periods in the southwest region.  A few areas had significant infection periods.

Plum varieties being harvested range from Shiro and Ozark Premier.  Stanley fruit and leaves showing a fair amount of bacterial canker symptoms from earlier cool and wet weather.  Growers should scout for apple maggot, white apple and potato leafhoppers. 

Apples are 2.5 to 3 inches in diameter.  Harvest of Paulared, Earlymac, and Zestar are underway.  Gala and Golden Delicious are relatively typee (elongated).  Fire blight infections have stopped as the dry weather halts growth.  Very few sooty blotch and flyspeck symptoms have been found.  Trap catch for codling moth is high indicating the second-generation flight.  There was no gap between generations in some orchards.  Codling moth entries are easy to see, especially on yellow skinned varieties.  It is doubtful that there will be a third generation this year.  Few Apple maggots have been caught for several weeks in SW Michigan.  Apple maggot emerges following rain, about ¼ of an inch is considered the trigger amount.  This means that growers can expect an increased emergence following rain.  Obliquebanded leafroller larvae are easier to find feeding on leaves.  With very little leafroller feeding on apple fruit.  Spotted tentiform leafminer mines can be found.  The new insecticides Delegate and Altacor seem to be doing a good job controlling this insect.  Green apple aphids are common in growing shoot tips.   White apple leafhopper leaf stippling and bronzing due to European red mites are generally scarce.  Growers should inspect calyx ends of apples for mite eggs.  San Jose scale crawlers are out and red spots on apple fruit is showing up.  Young trees should be irrigated and examined for potato leafhopper.

Pears are about 2.5 inches in diameter.  Pear psylla numbers are generally low.  Sooty blotch and flyspeck are a concern; fungicides should be included in cover sprays.  Both codling moth and oriental fruit moth can damage pear fruit at this time. 

Small fruit

Blueberry harvest of the late season varieties, Jersey and Elliot continues with heavy harvest volumes.  Anthracnose ripe rot, small fruit and soft fruit have been a problem.  Leaf spots are a problem is some areas.  Drought stress is revealing other mineral nutrition problems such as iron and potash.  Japanese beetles and blueberry maggot flies are out. 

Grapes are at nearing veraison and Concord has begun to change color.  Grape berry moth trap catches are variable.  They are down in some vineyards but scouts are finding more eggs.  Trap catches late in the season are a poor indicator of berry moth pressure and vineyards that have historically had high Grape Berry Moth pressure should be treated.  Larval stings and split berries are easy to find in vineyards with light crop and minimum sprays.  Grape leafhoppers are scarce.  Wine grapes need to be protected from potato leafhoppers.  Japanese beetles are not abundant.  Fungicides at this time should target downy mildew, and phomopsis.  Berry susceptibility to black rot ends as veraison begins.  Phomopsis lesions in the fruit clusters can be found.  The fruit becomes resistant but the cluster rachis is always susceptible to this disease.  With frequent heavy dews we expect downy mildew to increase.  Botrytis fruit rot has been found in wine grapes

Strawberry regrowth is underway.  Some growers report poor growth.  This seems be due to drought stress, black root rot or insect feeding.  Growers should protect against potato leafhoppers to prevent hopper burn and stunting of new growth.  Irrigation is very important do get good growth during this dry season.

Summer Raspberry and Blackberry harvest has ended.  Growers should be prepared to protect against gray mold in ripening fall brambles. 

Upcoming Meetings

The last evening grape IPM meeting of the season is coming up on Thursday, August 28.  This meeting begins with a free dinner at 6:00 pm at the Lemon Creek Winery and will end with a trip out to the Vignoles vineyard scouted for the weekly scouting report.  We are expecting one RUP credit to be available for this meeting.