SW Michigan Fruit Update
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Southwest Michigan, July 27, 2009

Mark Longstroth, Bill Shane, Diane Brown-Rytlewski

Weather

The last two weeks was pleasant with highs generally in the 70s and lows in the 50s and 60s.  Rains have been spotty, light and generally less than a tenth of an inch.  Soils, especially sandy soils are very dry.  Wilting, leaf rolling and leaf drop are becoming common.  We continue to lag a week to ten days behind normal in heat units, but we are close to last year’s totals.  Crop development seems close to normal since the cooler temperature allow most fruit crops to be more efficient at warm, not hot, daytime temperatures and decrease energy lose due to high respiration during warm evening.

Southwest Michigan Growing Degree Day Totals March 1 through July 26, 2009				Grapes, April 1
Location	GDD 42	GDD 45	GDD 50	GDD 50
SWMREC:	2263	1927	1411	1371
Fennville:	2079	1754	1254	1227

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

Insects

Japanese beetle numbers are generally reported to be lower than in recent years.  Apple maggot and blueberry maggot numbers are generally low and will increase after rain or irrigation.

Tree fruit

Peach varieties being harvested include Bright Star, Risingstar, Garnet Beauty, and Summer Serenade.  Bacterial spot symptoms are becoming more obvious on more susceptible varieties especially those on sandy sites lose to roads.  Cooler nighttime temperatures have resulted in dew conducive to bacterial spot.  Dry conditions are slowing growth and producing nitrogen deficiency symptoms (leaves with reddish hue often associated with holes in the leaves).  Rain is needed to size fruit in sandier sites.  Oriental moth catches for the second generation is on the decline.  Larvae from their eggs are generally still focusing on twigs but as growth slows and twigs harden off the larvae will attack fruit. 

Cherry trees have generally been treated for cherry leaf spot.  Unsprayed tart cherries have been almost defoliated from cherry leaf spot and many orchards have severe symptoms in some places.  Japanese beetles are showing a fondness for sweet cherry leaves.  Tart cherry fruit quality was variable this year due to freeze losses and poor pollination in some sites and wind whip damage.  Harvested trees should be treated for cherry leaf spot when rains return.  Recent dry conditions, tree shaker effects, and ethrel treatments have left some orchards looking rough.  Post harvest is a good time to remove some unwanted larger limbs in older trees that have filled their space.

In Plums,Japanese plum harvest is underway.  Apple maggot is a problem in ripening plums.  Scout for leafhopper damage from white apple or potato leafhoppers.

Apples are over two inches in diameter with some early season apple varieties at three inches in size.  Fruit size and quality look excellent due to the cool conditions most of the season, and early season moisture.  Fire blight symptoms are not spreading so quickly since the dry conditions have generally stopped new growth.  Sucking insects such as aphids and leafhoppers can spread fire blight to new trees.  Codling moth trap catch may be increasing, signaling the second generation that usually begins in late July and peaks in early August.  There has been a flush of codling moth flight noticed in traps near wooden bin piles that were placed in orchards. Development of larvae that overwinter in wooden bins is often delayed, and these may emerge later than normal.Oriental fruit moth trap catch is down with the decline of the second generation.  Apple maggot flies are out and we expect a strong flight with any rain.  Expect to see Obliquebanded leafroller larvae on foliage.  Scout shoot tips for signs of feeding.  Apple aphids are easy to find.  Dry conditions are good for mites.  Mite numbers have exploded in some blocks.  The treatment threshold for European red mite in July and August is over 7 mites per leaf.  The SWMREC weather station has recorded 543 hours of leaf wetting conducive to sooty blotch and flyspeck since early June.  In contrast, 2008, 2007, and 2006 had approximately 370 hours of leaf wetting for the same time period.  Frogeye leaf spot can be found in some orchards, but infection levels are generally light. Frogeye is a foliar disease caused by the same organism that causes black rot. 

Pears are 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 August and attacks pears just before harvest.    Growers should be prepared for the second generation of codling moth, which emerges in August and attacks pears just before harvest.

Small fruit

Blueberry harvest continues with hand picking for the fresh market and machine harvest for the process market.  All midseason varieties are being harvested.  Fruit size and quality are good in irrigated fields.  Growers should maintain protection against alternaria fruit rot.  Blueberry maggot flies are out.  Japanese beetle numbers are building.  Symptoms of phomopsis cane blight are being reported, where the whole cane collapses.  These should be pruned out and removed from the field.  Two blueberry viruses, blueberry shock and blueberry scorch; new to Michigan have been detected in a few locations in the region.  Both these viruses cause collapse of new growth early in the spring and could be confused with mummyberry and phomopsis twig blight.  The blueberry shock virus is pollen borne and does not spread after bloom, during the growing season.  Aphids vector blueberry scorch, so aphid control will be important with this disease as it is with blueberry shoestring virus.  Information about how to recognize the new virus diseases can be found in the Fruit CAT Alert of July 14^th.  It is important to test any plants used for cuttings for virus diseases before using them for cuttings for new plants.  For more information look at the Michigan Blueberry IPM Newsletter posted by Paul Jenkins at the Berry Entomology Lab. 

Grape foliage generally lush due to rains in June.   Gramoxone spraying underway to control suckers and open lower canopy.  We are past the 1200 GDD base 50 from April 1.  Generally the crop appears heavy and growers thin and reduce their crop.  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 are in hybrid and vinifera grapes.  Grape leafhopper nymph numbers are low.  See the most recent copy of Grape IPM Newsletter at the MSU Grape current conditions webpage. 

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

Summer raspberry and black raspberry harvests are declining with the dry conditions.  Japanese beetles have been reported in raspberries.  Fall raspberry harvest will start soon.  Morning dews can cause fruits rot problems such as Botrytis gray mold, so fungicides are needed when there are morning dews.