SW Michigan Fruit Update
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Southwest Michigan, June 2, 2009

Mark Longstroth, Bill Shane, Diane Brown-Rytlewski

Weather

Last week was warm with highs near 80 and lows in the upper 50s.  Significant rain fell last Tuesday and Wednesday (May 26-27) and yesterday (June 1) as well.  The warm weather increased insect activity and plant growth.  Cooler temperatures with thunderstorms are forecast for early this week.  Warmer weather is forecast for the weekend.

Southwest Michigan Growing Degree Day Totals March 1 through May 31, 2009				Grapes, from April 1
Location	GDD 42	GDD 45	GDD 50	GDD 50
SWMREC:	852	686	451	411
Fennville:	756	601	382	356

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 through May 31, 2009.  Our heat accumulations are now close to normal. 

Insects

Tree fruit should be protected from plum curculio.  Curculio egg laying scars have been found in many abandoned fruit plantings.  Oriental fruit moth and codling moth are flying.  We expect to see the first Japanese beetle this week.  The main surge of Japanese beetles comes out in early July.  Rose chafer usually emerges in large numbers during grape bloom (next week).  San Jose scale flight began about May 13. 

Tree fruit

Apricot fruit are 18 to 24 mm in diameter.

Peach fruits are 14 to 18 mm in diameter.  Generally the crop looks good.  We are seeing some symptoms of winter injury.  In trees that were damaged by the cold, we are seeing the oldest leaves on the shoot yellow and fall off.  Peach leaf curl symptoms remain scarce.  The window for copper sprays to suppress bacterial spot is over.  Green peach aphids are curling the leaves.  After the leaves curl contact materials are ineffective against this pest, and systemic materials such as Provado or Actara should be used.  The first generation of Oriental fruit moth (Biofixed on 4/26) is past peak egg laying and the flight is tapering off.  Peach fruit are large enough that we should be seeing injury to peach fruit soon.  Lesser peach tree borer will emerge soon.  Non-bearing trees can be sprayed with Lorsban, providing control for greater peach tree borer as well.  Pheromone disruption does not work well for these pests in young orchards because the open nature of the planting allows the pheromone plumes to dissipate.  Pheromone disruption is very effective for protecting larger peach trees in plantings more than two acres in size.  Growers need to 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 cherry fruits are 16 to 18 mm in diameter, and beginning to color.  Birds are already a problem feeding on early cherry varieties.  Harvest of cherries in high tunnels may start this weekend.  Plum curculio egg laying scars can be found in cherry. Sweet cherry fruits are especially susceptible to brown rot as they ripen, warm rains are good infection periods.  Growers also need to protect against cherry leaf spot.

Tart cherries are 12 to 14 mm in diameter.  The cherry crop appears light and spotty.  Some growers report a good crop.  Spurs are collapsing in ‘Montmorency’ orchards.  The wet season and bacterial canker leaf lesions hint that this may be bacterial canker.  ‘Danube’ is also very susceptible to European brown rot (Monilinia laxa); spur collapse and spur gumming are common symptoms of European brown rot.  Growers need to protect against cherry leaf spot and plum curculio.

In Plums, European plums are 10 to 12 mm in diameter.  Oriental plums are 16 to 20 mm.  Shoot growth continues in many plums and growers should apply fungicides to reduce black knot.  Growers also need to protect against plum curculio.  Shoot holing symptoms similar to bacterial canker or prunus necrotic leaf spot have been found in Japanese plums.

Apple fruitlets are 15 to 20 mm in diameter with a few varieties such as ‘Zestar!’ over 25 mm.  Generally the crop looks good, but some orchards may require more thinning.  The window for applying apple thinners is ending and cooler weather this week will not be favorable for apple thinning.  Growers should carefully assess the fruit set in their apple orchards and determine which orchards still need thinning.  Growers need to apply thinners during a warming trend and one is expected by the weekend.  Optimal thinning can be expected when average temperature rises above 70F.  Growers should use full rates and combination sprays and not expect much response.  Most of the apple cut on Monday had a full complement of seeds indicating that they will stick.  High rates applied to the tops of the trees with the lower nozzles shut off to reduce sprays to the lower half of the tree are recommended to Golden Delicous trees with small fruit in the cluster.  New apple scab symptoms have appeared.  These are probably due to rains May 8 or May 13.  All the primary scab spores are mature and should have been discharged by recent rains.  Grower should inspect their orchards for leaf scab and determine if they need to continue using protectant sprays.  Growers with scab in their orchards will want to continue protecting the fruit until it is about one inch in diameter and waxy.  These fruit are relatively resistant to scab infection.  The bright orange cedar apple rust symptoms are showing on apple leaves.  Growers report numerous blossom blight symptoms mainly in Jonathan apples.  It appears this infection may have occurred on May 8, Warm conditions and rain were apparently sufficient for blossom infection even though the EIP (epiphytic infection potential) index of the Maryblyt model was not high enough build bacterial populations within flowers.  Our hypothesis is that ooze from local cankers could have allowed bacterial populations in some flowers to be high enough to cause an infection, bypassing the need for high EIP values for infection.  Insect activity was variable last week.  Plum curculio egg laying scars have been found in apples.  Codling moth trap catches are variable. Codling moth Biofix was May 19 or 20 for most of the region.  We are just over 180 GDD base 50 since Biofix and the 250 GDD window will be in the middle of next week (~June 8).  Green fruitworm feeding is apparent in abandoned orchards.  White apple leafhopper feeding can be seen.  Spotted tentiform leafminer mines are visible.  European red mites are out but numbers are low.  Oriental fruit moths are still flying in good numbers and we expect to see oriental fruit moth larvae entry holes in apple fruit within the next week. 

Pear fruit are 12 to 14 mm in diameter.  Pear Psylla are hard to find.

Small fruit

Blueberries fruit are pea sized and bloom is finished.  Mummyberry shoot strikes are severe in some fields where more than half the shoots have been killed.  Many growers have mistaken these severe symptoms for frost injury, phomopsis or herbicide injury.  Where there is still bloom in the field growers should apply fungicides to protect against mummyberry in the fruit.  Now is also the timing of anthracnose fruit infection, so fungicides should be included in cover sprays after bloom.  Growers should apply insecticides to protect against cherry fruitworm and cranberry fruitworm where they are a problem.  Cranberry fruitworm was biofixed for May 20 in some areas.  Virus symptoms of shoestring and mosaic are easy to find.  There is an upcoming Blueberry IPM meeting on June 11 at 6 to 8 PM, at Carini Farms, 15039 Port Sheldon Rd., near West Olive.  There is a Blueberry weed control demonstration tour at the Getzoff Farm, 7093 116th St. near Fennville.  The Michigan Blueberry IPM Newsletter is posted at the Dr Rufus Isaac’s Berry Entomology Lab. 

Grape shoots are 12 to 16 inches long; flower buds are separating in the cluster.  Bloom should begin late this week of early next.  Wild grape bloom began last Thursday in southern Berrien County.  Wild grape bloom is used to start the grape berry moth model on the Enviroweather website.  We expect grape growth to move slowly during this cool weather.  This week is the time for growers to apply their prebloom fungicides to suppress grape disease development, especially phomopsis.  An SI material such as Rally or Elite should be included to control powdery mildew.  Downy mildew lesions are on wild grape.  A few grape berry moths have been trapped but sprays should wait until the end of bloom.  Grape Leafhopper adults can be found and we expect to see rose chafer soon.  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 25, 2009. 

Strawberry bloom is winding down and the largest fruit are coloring.  Early harvest has begun and general harvest is expected this weekend.

Raspberry bloom is underway. Avoid using insecticides during bloom.  We expect to see the first Japanese beetle this week.  Large numbers of this pest generally emerge during raspberry harvest.  Primocanes are 12 to 24 inches tall.

Miscellaneous

We are seeing trees collapsing for various reasons.  Young trees did not leaf out that were killed by winter, or phytophthora infections that may have taken place last fall. 

The Fruit Code-A-Phones in Van Buren County (269) 657-8217 and Berrien County (269) 944-4126 ext 1 are being updated.  The next Monday Fruit IPM Update meeting will be, Monday June 8, at the Fruit Acres Farm in Berrien County. 

There is a Blueberry IPM meeting on June 11 at 6 to 8 PM, at Carini Farms, 15039 Port Sheldon Rd., near West Olive.  There is a Blueberry weed control demonstration tour on June 18, at the Getzoff Farm, 7093 116th St. near Fennville.