SW Michigan Fruit Update

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Southwest Michigan Fruit Update, August 16, 2007

Mark Longstroth, Bill Shane, Greg Vlaming

Weather

The past 10 days have been a break from the hot, dry weather.  Highs were continued in the 80s with lows in the 60s.  Numerous rain showers fell across the region Sunday, August 5 and Tuesday August 7.  Scattered storms on Tuesday (8/7), Thursday (8/9) Saturday (8/11) and Wednesday (8/15) generally dropped less than a tenth of an inch.  Rainfall totals continued to be generally higher in the southern tier of counties and closer to the lake.  Berrien County received about 6 inches of rain in August.  Less rain fell away from the lake and to the north.  Most areas in Van Buren County received 2 to 3 inches.  The topsoil now has moisture but the subsoil is still dry.  The forecast is for thunderstorms and a cool weekend with highs in the 70s and lows near 50. 

Southwest Michigan Growing Degree Days (GDD) Totals March 1 through August 16, 2007				Grapes April 1	August Rain
Location	GDD 42	GDD 45	GDD 50	GDD 50
Scottdale	3431	3017	2370	2263	6.4
SWMREC:	3318	2906	2267	2169	5.7
Bainbridge:	3234	2829	2197	2097	6.1
Hartford:	3115	2711	2084	1989	4.0
Lawton	3421	3009	2359	2256	3.1
South Haven	3075	2674	2054	1961	2.8
Fennville:	3080	2678	2056	1976	1.9

Insects

Japanese beetle adults have increased in areas that were very dry earlier.  Fall webworm are very noticeable.  Growers should be aware of a possible suicide generation for some fruit pests.

Tree fruit

Trees have responded well to the increased moisture and leaves no longer hang limp on the trees.

Peach harvest continues.  The third generation of oriental fruit moth should be emerging at about 2400 GDD base 45.

Cherry trees should enter the winter in good shape.

In Apples, Codling moth trap catches of the second generation have been heavy.  Biofix for high-pressure sites was July 14^th (~1275 GDD) and lower pressure site biofix was approximately July 21^st (1674GDD).  We anticipate that this flight will end 950 GDD after it started.  It is likely that orchards, which had earlier flights and biofixes for second-generation codling moth may see a partial third generation in late August.  If you are catching moths after 2225 and 2524 GDD base 50 you are catching second-generation moths that will lay their eggs in your apples.  With wide spread rain I expect apple maggot to emerge around the edges of fields so border sprays will be useful in some areas.  We are finding feeding damage of second-generation oriental fruit moth in apple fruit.  Scouts are reporting leaf drop due to the second generation spotted tentiform leaf miner.  Dock sawfly larvae are feeding on broadleaf weeds in some orchards.  This pest is often confused with codling moth in apples later in the season as it looks for an overwintering site and attacks the fruit.  With this rain, fungicides should be included in cover sprays to control sooty blotch and fly speck.  Cork spot is showing up on early apple varieties.  Paulared harvest is underway and Gala harvest should begin about August 24^th. 

Pear harvest is underway.

Small fruit

Blueberry harvest is winding down and fresh berries are scarce.  Currently we are finishing Elliot harvest.  Fruit bud formation has begun on early varieties.  With wide spread rain I expect blueberry maggot to emerge around the edges of fields so border sprays will be useful in areas where there is still crop to protect.  Japanese beetles and blueberry aphids are out.  Be sure to check the new Blueberry IPM Newsletter at the MSU Blueberry Site. 

In Grapes veraison is underway in Concord.  Grape berry moth trap catch numbers are up.  The second-generation flight is heavy and egg hatch has begun.  Backyard growers have reported heavy losses to black rot.  Phomopsis berry rot and drop has begun on early ripening varieties.  There is no reason to treat for these diseases now.  These losses are due to infections in the past.  The berries after veraison are resistant to most grape diseases.  Botrytis is the major concern while the berries are ripening.  Botrytis bunch rot sprays are timed for veraison in wine and table varieties and for wet periods during ripening.  Downy mildew has been scarce, due to dry conditions.  Now we are beginning to have heavy dews every morning and the conditions are good for downy mildew to increase.  There is so little downy mildew in the area that I do not expect it to be a problem but growers should be aware that infections can come from wind blown spores that will infect the upper canopy or from the over wintering spores in the soil where you would expect to see the initial ‘oily spot’ lesions low in the canopy.  Phosphorous acid materials would be effective materials to use at this time due to their eradicant and systemic properties.  Check the MSU Grape website for scouting updates.

Strawberry growth is good where irrigation has been used and potato leafhopper controlled, Otherwise strawberries have suffered from the drought. 

In raspberries , fall raspberry harvest is underway.  With heavy morning dews growers should protect against gray mold.