SW Michigan Fruit Update
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Southwest Michigan, May 18, 2009

Mark Longstroth, Bill Shane

Weather

Last week was another cool week with highs in the 60s and lows in the 40s.  Scattered frost Monday caused scattered damage in frost pockets.  Warmer weather is forecast for this week with highs near 80 and lows near 60.  Cooler more seasonal weather with highs near 70 and lows in the mid 50s are forecast for the Memorial Day weekend.  The warm dry weather should bring on an increase in insect activity.

Southwest Michigan Growing Degree Day Totals March 1 through May 17, 2009				Grapes, from April 1
Location	GDD 42	GDD 45	GDD 50	GDD 50
SWMREC:	556	431	263	223
Fennville:	487	372	219	193

You can find weather and IPM information for Southwest Michigan at the Enviroweather website.  Here is a link a table of SW Michigan’s Growing Degree-Days from March 1 to May 17, 2009.  Our heat accumulations are lagging behind recent years. 

Tree fruit

Fruit growers should look for plum curculio egg laying when warmer evening temperatures return this week.  Stone fruit that is out of the shuck is accessible to this pest.

Apricot fruit are 12 to 18 mm in diameter.

Peaches are beginning to emerge from the shuck. Peach leaf curl symptoms have appeared.  Oriental fruit moth flight and egg laying continue.  Growers with nectarines should check to see if western flower thrip are present in the shuck where they cause scarring of developing fruit. Protect peach fruit against rusty spot once it emerges from the shuck.  Rusty spot is caused by the apple powdery mildew pathogen and causes fruit blemishes on some peach and nectarine varieties.

Sweet cherries fruit are 8 to 10 mm in diameter.  Bacterial canker symptoms have been found.  Potential crop loads vary greatly by variety. Sweet cherry fruits are always susceptible to brown rot, warm rains are good infection periods.  Growers need to protect against cherry leaf spot and plum curculio.  Plum curculio egg laying occurs when we have warm night temperatures.

Tart cherries are emerging from the shuck.  The crop is very variable.  Growers need to protect against cherry leaf spot and plum curculio as the fruit emerges from the shuck next week.  Tattered looking leaves could be bacterial canker or leafroller larvae feeding in the leaves.

In Plums, European plums are in the shuck.  Oriental plums are emerging from the shuck.  Growers should apply fungicides to reduce black knot.  Growers also need to protect plum curculio as the fruit emerges from the shuck next week.  .

Apple bloom is ending.  Fruit of early blooming varieties is 8 to 10 mm in diameter and late varieties are at petal fall.  Warm weather this week will be favorable for apple thinning.  Sprays applied Tuesday and Wednesday will be more effective than later in the week.  Cooler weather by Friday will close this thinning window.  Apple scab symptoms are becoming abundant.  All the scab symptoms for the late April wetting events should be visible now.  No new symptoms should appear until after Memorial Day.  Virtually all the overwintering spores should be mature by now and another good rain may mark the end of primary scab season.  Cool weather has kept the risk of fire blight low.  But warm weather this week will allow bacterial populations to rise to high levels and rain Wednesday through Friday could result in blossom blight infections.  Use the new model for fireblight on the Enviroweather website to track disease development.  Insect activity should increase with warmer weather.  Leafroller larvae have been found.  Spotted tentiform leafminer adults are flying and laying eggs.  European red mite eggs have hatched.  Oriental fruit moths are still flying in good numbers.  Codling moths have been trapped in several Berrien County orchards but not in numbers high enough to set a Biofix.  We expect a strong flight when warmer nights return. 

Pear fruit are 4 to 8 mm in diameter.  Pear scab is a concern with infection conditions similar to apple scab.  Pear growers can use the apple scab model at the enviroweather site to track pear scab.  Pear Psylla eggs and nymphs are hard to find.

Small fruit

Blueberry bloom is underway.  Cool weather has given many fields a distinct reddish orange coloration that should go away when our soils warm up.  Mummyberry shoot strikes are appearing in good numbers.  Pollinators carry spores from sporulating shoot strikes to the flowers.  Controls should focus on preventing flower infection.  Flowers are most susceptible when they open and become less susceptible to infection as they age and fertilized flowers are resistant to infection.  Cherry fruitworm are being trapped and we expect to see cranberry fruitworm flying during this week’s warm weather.  A model for cranberry fruit worm development in availble under the small fruit section in the Enviroweather website.  The Michigan Blueberry IPM Newsletter is posted at the MSU Blueberry IPM web site .  

Grape shoots are about 2 to 6 inches long with leaves unfolding and flower buds exposed.  Many growers have applied fungicides to suppress disease development, especially phomopsis.  There is a Grape IPM meeting this Thursday evening from 6 to 8 PM, at the Dongvillo’s Vineyard at 4930 M139 south of St Joseph.  A few grape berry moths have been trapped but since bloom is over a week away this is not a concern.  See the most recent copy of Grape IPM Newsletter at the MSU Grape current conditions webpage.  Here is a link a table of SW Michigan’s Grape Growing Degree-Days from April 1 to May 10, 2009.  Low temperatures on Monday killed some shoots in frost pockets in a few areas.  Damage was generally light and scattered.

Strawberry bloom is underway and many growers have made ice with their frost control systems.  Some damage was reported Saturday and Monday mornings.  Growers should be applying fungicides to protect against fruit rots Tarnished Plant Bug are out and may require controls during the warm weather.

Raspberry flower clusters are emerging and bloom in early varieties should begin later this week.  Primocanes are elongating and 8 to 12 inches tall.

Miscellaneous

The Fruit Code-A-Phones in Van Buren County (269) 657-8217 and Berrien County (269) 944-4126 ext 1 are being updated.  There will be no Monday meeting on Memorial Day next Monday (May 25).  The next Monday Fruit IPM Update meeting will be, Monday June 1, at the Fruit Acres Farm in Berrien County.