SW Michigan Fruit Update

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Southwest Michigan Fruit Update, May 21, 2007

Mark Longstroth, Bill Shane, Greg Vlaming

Weather

Last week’s weather was variable.  Monday and Tuesday were hot with highs near 80.  A cold front moved through the region on Wednesday May 16, with thunderstorms and the overnight rain.  Precipitation totals were about a third to a half inch of water. Soils are still dry.  There was a long enough wetting period 17-19 hours at 50F to be a concern for apple scab, cherry leaf spot.  A fire blight infection was possible but unlikely due to cool conditions following the rain.  Cool weather most of the week ended with scattered frost on Friday morning.  Scattered storms crossed the region Saturday and Monday but not all areas received precipitation.  The forecast is for hot weather with lows in the near 50 and highs near 80 for the next 2 days.  Thunderstorms are possible Thursday followed by cooler temperatures with highs in the 60s and 70s.

Southwest Michigan Growing Degree Days (GDD) Totals March 1 through May 20, 2007				Grapes from April 1
Location	GDD 42	GDD 45	GDD 50	GDD 50
SWMREC	778	630	426	328
Lawton	858	709	495	358
Fennville	692	553	362	282

Tree fruit

The May 16 rain was an infection period for apple scab and cherry leaf spot.  Plum curculio egg laying scars have been found in stone fruit.  Plum curculio activity should return with warmer temperatures.  Oriental fruit moth catch in pheromone traps is down.  Oriental Fruit Moth, Biofix was April 21 at 230 GDD at SWMREC.  The end of egg hatch should be about 646 GDD base 45 after biofix so the end of egg hatch will be about 975 GDD base 45.  We are catching American plum borer and lesser peach tree borer. 

Peach fruit are 18 mm in diameter and growers are hand thinning.  We are finding shoot flagging from Oriental fruit moth larvae feeding in the shoot tips.  We are about two thirds of the way through egg hatch.  Peach leaf curl is scarce this year.  Grower should protect susceptible varieties from peach mildew or rusty spot.  This disease needs a wetting period to begin spore release but does not need continuous wetting for infection.  Tarnished plant bug and plum curculio damage can be found on fruit.  Pheromone disruption of lesser peach tree borer also suppresses greater peach tree borer.  This tactic works best in large homogeneous blocks.

Tart cherry fruit are 12 mm in diameter and pit hardening is nearly complete.  The crop is light and very variable.  Fruit set is spotty within the orchard and between orchards.  Plum curculio egg laying should increase with the warm weather.  The May 15 rain was a light infection period for cherry leaf spot.

Sweet cherries are 12 mm in diameter and the pits are hard.  Growers need to protect against plum curculio.  Sweet cherries should be protected from brown rot from bloom until harvest and the possibility of warm wet rains exist this week. 

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

Apple fruits are 12 to 18 mm in diameter.  Growers are spray thinning.  Many blocks do not need thinning.  Blossom blight symptoms of fire blight appeared Monday May 21.  These symptoms are from the May 9 infection.    Apple scab symptoms can also be found from the May 9 infection.  The Enviroweather website is forecasting that all the apple scab spores are mature but growers should maintain fungicide protection through the next good rain.  Plum curculio will be attacking fruit during this warm period.  Oriental fruit moth is still being caught in pheromone traps.  Egg hatch should continue for several more weeks.  Codling moths began flying May 5, and were biofixed on Wednesday, May 9 in some locations, but the flight has been very spotty, light and variable.  It is not necessary to treat orchards without a sustained flight of moths.  Growers should not be applying codling moth controls if they have not recorded a sustained flight of moths.  It is entirely possible that many orchards have not had a sustained flight because of the cool evening temperatures.  We are catching Obilquebanded leafroller moths in pheromone traps.  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 15 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 at petal fall and bees are active.  Both cranberry and cherry fruit worms were reported caught in pheromone traps. Treatment for these pests is focused immediately after bloom after bees have been removed.  Obilquebanded leafroller larvae are feeding on fruit buds.  Many fields have shoots that lack many leaves but have lots of fruit.  Bluecrop and some other varieties are  showing this symptom.  The shoots affected are generally older shoots with short shoots from last year.  In some cases the leaf buds immediately below the flower buds were killed by the Easter freeze.  In other cases it appears the few leaf buds remained after the flower buds formed.  Vigorous shoots with good growth do not show this symptom.  Little can be done to force new leaf growth at this time in severely affected fields growers should remove shoots that have a large number of fruit and very few leaves as the fruit on these shoots will not size.  By removing excess fruit now growers can reduce stress and maintain good fruit size at harvest.  It is likely that severely stressed shoots will not have marketable fruit and will dieback this winter.  See the Blueberry IPM Newsletter at the MSU Blueberry Site.

Grapes: Concord shoots are about 12 to 16 inches long and flower clusters are separating in the bunch.  Vinifera shoots are 6 to 8 inches long.  Wild grapes bloom has begun and bloom could begin later this week depending on the weather.  Growers are applying the last prebloom disease control materials.  Phomopsis lesions were found on grape leaves and shoots.  Grape berry moths are still being trapped.  Treatment 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 at full bloom.  Given the dry conditions growers should be irrigating and applying bloom fungicides.

Raspberries: Summer raspberry bloom has begun.  Fall raspberry shoots are about 12 inches high.  Orange rust has been reported.

Cranberry buds are elongating.  Now is the time for the first fungicide treatment.

Miscellaneous

The Van Buren County MSU Extension Office has moved.  The new phone number for the Paw Paw Extension Office is 657-8213.
The new Code-A-Phone number is 657-8217. 

The next Monday Fruit Update meeting will be Monday June 4, 5 pm, at the Fruit Acres Farm in Berrien County.  There will be no Monday Update meeting on May 28, Memorial Day.  There are RUP credits available for the Monday Fruit Updates meetings.