SW Michigan Fruit Update

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May 29, 2006

Mark Longstroth, Bill Shane, Al Gaus

Weather

Last week began cool.  Frosts Monday and Tuesday (May 22-23) mornings caused scattered damage to apples, blueberries and new growth on grapes.  It quickly became hot with temperatures into the 80s and 90s by the end of the week.  Growing Degree Day accumulations increased rapidly this week.  We picked up 150 GDD base 45 and 100 GDD base 50.  Scattered rain fell Thursday with some areas reporting no rain but most received 0.1 to 0.3 inches of rain.  These hot conditions are quickly drying the topsoil.  Soil temps are in the mid 60s.  This week’s forecast is for warm weather with highs into the 80s and chance of thunderstorms, with a cooler weekend.  The GDD below are from the Enviroweather site.

Southwest Michigan Growing Degree Day Totals March 1 through May 28, 2006				Grapes, from April 1
Location	GDD 42	GDD 45	GDD 50	GDD 50
Scottdale:	824	660	434	404
SWMREC:	810	637	405	372
Bainbridge:	851	674	436	402
Hartford:	741	581	367	340
Lawton	854	681	444	419
South Haven (April 1)	605	480	310	310
Grand Junction:	851	678	447	410
Fennville:	729	566	354	326

Tree fruit

Plum curculio egg laying scars have been found.  Expect lots of renewed insect activity.

Apricot fruit are about 1.5 inches in diameter.

Peach fruit are about an inch.  Oriental fruit moth trap catches are high.  We are past peak adult emergence.  Biofix for Oriental fruit moth was April 16 with a GDD of 180 Base 45 at SWMREC.  Chemical controls are focused on egg hatch, which continues to about 650 GDD after biofix.  We are about 457 GDD past Biofix.  Tarnished plant bugs have been found in peach orchards and growers are mowing orchards.  This can drive the bugs into the tree canopy to feed on the fruit.  We are catching lesser peach tree borer.

Sweet cherries are 15 mm fruit and past pit hardening.  Fruit drop has reduced the crop in areas that were not damaged by frost.  Plum curculio egg laying has begun.  Leaf spotting due to bacterial canker can be found in some orchards.

Tart cherries are at 12 mm fruit and past pit hardening.  Growers need to protect against plum curculio and cherry leaf spot.  No cherry leaf spot symptoms have been found yet.  There is some shot holing of the leaves from bacterial canker but not other symptoms (yellowing leaves or fruit lesions) have been found.

Plumsare at 14 mm fruit and smaller fruit is falling.  The crop looks good.  Growers need to protect against plum curculio and to maintain protection for black knot. 

Apple fruit are 16 to 20 mm in diameter and there is a wide variation in size between varieties.  Apple growers applied thinners last week and the hot temperatures may cause over thinning.  There has been little fruit drop from apple trees that were not stressed before now.  Growers need to protect against plum curculio.  Scab symptoms from infection periods in early May are appearing.  We should be at the end of primary scab but growers need to maintain scab protection through the next rain.  Growers should protect against powdery mildew.  Fire blight symptoms began to appear over the weekend.  Blossom blight, canker margin symptoms (wilting shoots near cankers) and bacterial ooze can be found.  Trauma blight could be a problem if we get severe weather in orchards with oozing shoots.  Oriental fruit moth and codling moths trap counts are up.  A regional biofix for codling moth occurred on Thursday May 25.  Codling moth Biofix at SWMREC was at 328 GDD base 50.  You can monitor the GDD model for these pests at the Enviroweather site.  See the article on pesticides for codling moth in the Fruit CAT Alert.  Obliquebanded leafroller traps should be out.  Other regions are report high numbers of European red mites in some areas so growers should scout their hot spots.

Pear fruit are at 16 mm. Growers need to protect against pear scab.  Pear psylla nymphs are common in some orchards.  Pear sawfly exit holes from pear fruit were found Monday near Paw Paw.

Small fruit

Blueberries are still blooming.  Growers should be protecting against mummy berry and anthracnose fruit rots.  Cherry fruitworm and cranberry fruitworm are being caught in pheromone traps.  See the article on these fruitworms in the Fruit CAT Alert.  Growers should be ready to treat for these pests at the end of bloom.  Post bloom sprays also control blueberry gall midge and blueberry tip borer.

In Grapes, flower clusters on primary shoots are elongating and separating. Bloom will start this week. New growth has been off-color and weak due to the cool weather.  But now secondary and tertiary buds are opening and an accurate estimate can made of flower clusters on new replacement shoots are visible.  At least 75% of the juice grape acreage is showing enough growth for growers to decide that harvest on a ton or less per acre is not worthwhile and this acreage will receive reduced maintenance sprays to maintain the vigor of the plantings for next year. Probably less than 10% of the acreage will have a full crop, having suffered little loss in the April 26 freeze.  Growers should continue their disease control programs in areas that show fair growth and may have a marketable crop.  Grape flea beetle larvae have been found feeding on the leaves.

Strawberry fields have thimble-sized fruit.  In early fields and in fields under plastic harvest has begun. 

Raspberry and blackberry bloom is underway.  Growers should be scouting for leafrollers.

Cranberry buds are beginning to burst.

Miscellaneous

The next Monday Fruit Update meeting will be, Monday June 5, at the Fruit Acres Farm in Berrien County, at 5 PM.