SW Michigan Fruit Update

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Southwest Michigan Fruit Update, May 28, 2007

Mark Longstroth, Bill Shane, Greg Vlaming

Weather

Last week was hot and windy.  Highs were in the upper 80s until a cold front moved through the region on Friday May 25, with overnight rain and a rainy Saturday.  Precipitation totals were about one to 1.5 inches of water.  A long wetting period of over 24 hours at about 60F was a major infection period for all fruit diseases.  A fire blight trauma infection was possible due to hot windy conditions before the storms.  The forecast is for warmer weather with temps above 80 to return with thunderstorms possible the rest of the week.  Cooler temperatures with lows in the 70s are forecast for the weekend.

Southwest Michigan Growing Degree Days (GDD) Totals March 1 through May 27, 2007				Grapes from April 1
Location	GDD 42	GDD 45	GDD 50	GDD 50
Scottdale	1000	828	583	476
SWMREC	958	789	551	453
Bainbridge	947	783	547	536
Hartford	919	754	524	429
Lawton	1038	868	619	464
Grand Junction	1007	839	590	461
South Haven	881	722	499	406
Fennville	849	688	463	383

Insects

We expect Rose Chafer to emerge soon.  Potato leafhoppers have been reported in the region.  Fresh plum curculio damage is fairly common on edges of some peach, plum, and apple blocks.  We expect peak egg laying for plum curculio this week in Southwest Michigan. 

Tree fruit

Peach fruit are 20 mm in diameter and growers are hand thinning.  We are finding shoot flagging from Oriental fruit moth larvae feeding in the shoot tips.  Oriental Fruit Moth trap catch is down.  We are nearing the end of egg hatch.  Biofix was April 21 at 230 GDD at SWMREC.  The end of egg hatch is about 646 GDD base 45 after biofix so the end of egg hatch will be about 975 GDD base 45.  Growers should protect susceptible varieties from peach mildew or rusty spot. 

Tart cherry fruit are 14 mm in diameter.  With the light crop, growers need to maintain protection for plum curculio and cherry leaf spot.  Cherry leaf spot symptoms are easy to find on unsprayed tart cherries.

Sweet cherries are 16 mm in diameter and some fruit is coloring and being shed.  Growers need to protect against plum curculio and brown rot.  Bacterial canker symptoms are appearing on fruit and leaves.  Black cherry aphids are curling the leaves of terminal shoots.  Cherry leaf spot can be found in the area.

Plumfruit are about 14 mm in diameter.  Growers should be protecting against plum curculio black knot and brown rot. 

Apple fruits are 12 to 20 mm in diameter.  We have not seen a heavy drop and some growers are considering follow up spray thinning.  Many blocks do not need thinning.  Fire blight and apple scab symptoms are becoming common.  The Enviroweather website is forecasting that all the apple scab spores are mature and the weekend rain probably removed almost all the primary spores.  Growers should check their orchards for scab lesions on the leaves and determine if they should maintain fungicide protection.  The fruit will still be susceptible to scab infection for several weeks.  Plum curculio will be attacking fruit during this warm period.  Growers should consider materials that have activity against both plum curculio and codling moth.  Codling moths began flying May 5, and were biofixed on Wednesday, May 9 (325 GDD50 at SWMREC).  We are now catching moths widely and have a sustained flight.  It is now over 250 GDD past biofix and time to spray conventional materials such as Guthion, Danitol or Warrior.  A few Oriental fruit moths are still being caught in pheromone traps but egg hatch of the first generation is ending.  European red mites and rosy apple aphids are out and growers and scouts should be looking for sap feeding spotted tentiform leafminers and the first mines.

Pear fruit are 18 mm in diameter.  Pear psylla nymphs are feeding in the axils of leaves.  Pear blister mite symptoms have appeared.  Pear scab is similar to apple scab and pear scab symptoms should appear this week as with apple scab.  A good scab program usually controls Fabraea leaf spot but the infection period lasts longer than pear scab. 

Small fruit

Blueberries are small green fruit.  Many growers have treated for cranberry and cherry fruit worms.  Growers should apply fungicides to reduce anthracnose fruit rot later.  Be sure to check the new Blueberry IPM Newsletter at the MSU Blueberry Site. 

Grapes: Concords are at first bloom.  Wild grapes are past full bloom.  Vinifera bloom could begin late this week.  Growers have applied the last prebloom disease control materials.  Growers who did not have materials on for the May 26 rain should consider materials with back action.  The rain over the weekend was an infection event for grape diseases.  Phomopsis lesions were found on grape leaves and shoots.  There was some scattered frost injury on Friday May 18.  Treatment for grape berry moth should be timed for the end of bloom.  We expect to see rose chafer soon.  Check the MSU Grape website for scouting updates.

Strawberries are beginning to color and harvest of berries on and under plastic have begun. 

Raspberries: Summer raspberry have green fruit and the crop looks good.  Fall raspberry shoots are about 12 inches high.  Orange rust has been reported.

Cranberry shoots are elongating.  Now is the time for prebloom fungicide treatments.  Upright dieback has been common in the fields I have seen.

Miscellaneous

The next Monday Fruit Update meeting will be Monday June 4, 5 pm, at the Fruit Acres Farm in Berrien County.  There are RUP credits available for the Monday Fruit Update meetings.