SW Michigan Fruit Update

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Southwest Michigan, May 13, 2008

Mark Longstroth, Bill Shane

Weather

Last Monday and Tuesday were very warm with temperatures close to 80.  Wednesday (May 7) and Sunday (May 11) were cold and rainy.  Cool conditions between the two rain events made for poor pollinating weather.  We have had several good days for pollination followed the April 30 freeze.  Rainfall over the region varied from an inch to almost two inches.  These rains represented infection events for some diseases.  Soil moisture levels are good and some soils are still very wet.  We expect continued cool weather this week.  The forecast is for highs in the 60s and lows near 40.  Rain showers are forecast for Tuesday and another wet weekend.  The forecast is for cooler than normal temperatures for the next several weeks.  This means we need to be aware of the danger of frosts when we get clear calm conditions.  We still have about a ten percent chance of cold down to 28F.

Southwest Michigan Growing Degree Day Totals March 1 through May 11, 2008				Grapes, from April 1
Location	GDD 42	GDD 45	GDD 50	GDD 50
Berrien Springs:	524	417	274	264
Scottdale:	514	408	266	258
SWMREC:	481	381	248	242
Bainbridge:	495	395	260	253
Hartford:	460	365	239	235
Lawton:	514	411	271	266
Grand Junction:	525	421	283	277
South Haven:	442	351	229	222
Fennville:	431	337	217	213

Tree fruit

Insect activity increased early last week and then dropped to low levels.  Oriental Fruit Moth were caught and biofixed last week on Sunday May 4 at 310 GDD45 at SWMREC.  Trap catch was generally low but continuous. Redbanded leafroller and spotted tentiform leafminer are flying.  Plum curculio is out.  This pest feeds on developing fruit.  Curculio egg laying should not be a problem until warm temperatures return.

Apricots are out of the shuck for most varieties. 

Peaches are in the shuck.  Oriental Fruit Moth were caught and biofixed last week on Sunday May 4 at about 310 GDD45 at SWMREC.  Treatment is timed for 200 GDD after biofix and we are now at about 70.  With this cool weather we will need to apply controls early next week.

Sweet Cherries are at the end of shuck split.  The largest fruit are about 10 mm in diameter.  Sweet cherries are always susceptible to brown rot.  This disease requires wet and warm conditions, 5 to 6 hours of wetness at 70F.  We are unlikely to see conditions that warm this week.  Since the leaves are out and developed they are susceptible to cherry leaf spot.  The rain Wednesday May 7 was a cherry leaf spot infection in some areas, but Sunday’s rain was not quite long enough for the cold.

Tart Cherries are in the shuck.  The leaves have emerged enough to be susceptible to cherry leaf spot.  Recent rains have been marginal infection periods due to cool average temperatures, but growers should apply shuck sprays to provide protection in upcoming rains.

Plums are in the shuck.  Japanese plums are at shuck split.  Growers need to protect against black knot.

Apples are at full bloom.  Rain on Mother’s Day May 11, was an apple scab infection for most sites.  Symptoms from the April 19 and May 2, infections should be visible.  We are about half way through primary scab season so scab protection will be necessary for about another month.  The rain last Wednesday following 2 very warm days caused the enviroweather fireblight prediction program to call for a fire blight infection and some growers applied antibiotics to some of their plantings.  Wednesdays rain was too cold for the fire blight bacteria and by the end of the day no infection periods were recorded.  Generally a cold rain following a cold front has not resulted in fire blight especially when the temperatures remain cool for several days afterwards inhibiting bacterial growth.  Southern Berrien County came closest to an infection.  Fireblight should not be a problem for the next few days.  The cool weather has kept bacterial populations low and there will not be enough heat this week to raise the level to dangerous levels.  It seems likely that we will not have good conditions for infection until the end of bloom.  Now is the time to apply Apogee sprays to reduce the spread of fire blight.  A single application at petal fall for king bloom is most effective is reducing the spread of fireblight after an infection.  To control vegetative growth longer into the season, applications are spread out over the next 6 to 8 weeks.  The cool weather forecast means that we will not have any good apple thinning windows soon.  Generally thinning sprays work best if applied at the beginning of a warming trend when temperatures will be above 70 for several days.  Growers can use the next week to begin to think about which blocks will need significant thinning.  There are wide differences in frost injury between varieties and sites. 

Pears are at petal fall.  Pear psylla eggs are hatching.  Growers should protect against pear scab.

Small fruit

Blueberry bloom has begun.  Mummyberry shoot strike symptoms have been found.  Symptoms from an infection following the April 30 freeze should be visible. 

Grapes have two to four inch long shoots, with two to three leaves out.  Vinifera grapes are a little behind in development and late varieties are noticeably behind.  There is no apparent movement of secondary buds yet in vineyards damaged by the freeze and shot growth makes severely affected vineyards very noticeable from the road.  In the past it has taken four to six weeks for new growth to become apparent.  Cool temperatures will slow all grape growth.  The conditions generally have been too cool for powdery mildew and, downy mildew, and marginal for black rot but phomopsis does well in cool damp weather. 

Strawberries are at full bloom.  Avoid using insecticides during bloom. These cool wet conditions favor angular leaf spot a bacterial disease.  Applications of copper can reduce this disease (see notes on control in E154).  Fungicides are applied at bloom to reduce gray mold, anthracnose, leaf spot diseases and leather rot. 

Raspberry and Blackberry shoot growth has slowed.  Flower bud clusters are visible on early varieties

Cranberry beds are greening up and tip buds have burst.

Miscellaneous

Last week growers were planting trees and applying fungicide sprays.

There is a Blueberry IPM meeting this Wednesday May 14 at Cornerstone Ag. 01240 57th Street, north of Phoenix Road, west of Grand Junction. 

The next Monday Fruit Update meeting will be, Monday May 19, at the Fruit Acres Farm in Berrien County.

There is a pair of Grape IPM meetings are Wednesday May 21.  The morning meeting will be from 10 AM to noon at the Cronenwett Farm Shop at 70123 28th Street, east of Lawton. The afternoon meeting will be at 2 PM in the Berrien County MSU Extension Office at the Southwest Michigan Research & Extension Center.  These meeting are co-sponsored by National Grape Cooperative and MSU Extension and are open to all grape growers.