SW Michigan Fruit Update

Check the Index for earlier postings

Southwest Michigan, August 5, 2008

Mark Longstroth, Bill Shane

Weather

Weather the past two weeks has been seasonal with highs in the mid 80s and lows near 60s, with no significant rainfall.  Soils are beginning to dry.  Annual plants such as weeds and field crops are wilting due to water stress.  Storms moved through the region Monday morning and left some much needed rain.  Rainfall amounts were between a third and a half-inch, about enough water for two days.  This wetting period (3 hours) was no long enough to be an infection period for many diseases.  The forecast for the upcoming weeks is for cooler and dryer than normal conditions indicating that the lack of water will continue.  The Growing Degrees below have been corrected for some missing data at sites marked with an asterisk*.

Southwest Michigan Growing Degree Day Totals March 1 through August 3, 2008				Grapes, April 1
Location	GDD 42	GDD 45	GDD 50	GDD 50
Berrien Springs:	2612	2263	1734	1724
Scottdale: *	2602	2254	1724	1716
SWMREC: *	2516	2165	1635	1641
Bainbridge:	2496	2160	1650	1643
Hartford:	2374	2043	1539	1535
Lawton:	2583	2238	1705	1700
Grand Junction:	2617	2273	1747	1741
South Haven:	2373	1995	1542	1535
Fennville: *	2331	2000	1496	1492

Tree fruit

The window for leaf sampling for nutrient analysis in Southern Michigan ends in early August.  If you plan on nutrient sampling take the samples this week.  Young trees should be irrigated to reduce drought stress.  San Jose scale crawlers are out and can cause fruit damage.  We are seeing this pest in more orchards this year.  Japanese beetles are still active. 

Peach fruit are 2.5 to 3 inches in diameter.  Harvest of Red Haven, PF 14 New Jersey, PF 15A and Starfire underway.  There are a fair amount of split pits in some varieties.  Brown rot symptoms are becoming easier to find and are often associated with split pits.  Short rains such as Mondays morning storm are enough to cause brown rot fruit infections.  X-disease symptoms are easy to find in the area.  Bacterial spot symptoms on peach leaves and fruit are fairly widespread.  Check the PHI (days to harvest) when applying sprays to reduce bacterial spot.  Stinkbug puncture wounds to fruit are more obvious.  Watch for western flower thrip damage to peach and nectarine fruit with hot dry weather. Delegate offers a new option for thrip control.  Oriental fruit moth trap catches for the second generation are declining. 

In Cherries, yellowing leaves and leaf drop due to cherry leaf spot and bacterial canker are common.  Several orchards have lost most of their leaves.  Be sure to check the leaves for signs and symptoms of these two diseases, as the controls are different.  The most recent significant cherry leaf spot infection periods in the southwest region were July 2, 13 and 16.  No significant infection periods have occurred since.

Plum varieties being harvested are Shiro and Victory.  Stanley fruit and leaves showing a fair amount of bacterial canker symptoms from earlier cool and wet weather.  Growers should scout for apple maggot, white apple and potato leafhoppers.  

Apples are 2.5 to 3 inches in diameter.  Fire blight infections are still moving and growers report oozing from active infections.  The oozing should stop as the dry weather halts growth.  Very few sooty blotch and flyspeck symptoms have been found.  Trap catch for codling moth is up indicating the beginning of the second-generation flight.  There was no gap between generations in some orchards.  Codling moth entries are easy to see, especially on yellow skinned varieties.  Few codling moth larvae can be found in the fruit.  Small numbers of Apple maggots have been caught for several weeks in SW Michigan.  Apple maggot emerges following rain, about ¼ of an inch is considered the trigger amount.  This means that growers can expect an increased emergence following Monday’s rain.  Obliquebanded leafroller larvae are easier to find feeding on leaves.  With very little leafroller feeding on apple fruit.  Spotted tentiform leafminer mines can be found.  The new insecticides Delegate and Altacor seem to be doing a good job controlling this insect.  Green apple aphids are common in growing shoot tips.   White apple leafhopper leaf stippling and bronzing due to European red mites is scarce.  San Jose scale crawlers are out and red spots on apple fruit is showing up.  Young trees should be irrigated and examined for potato leafhopper.

Pears are about 2.5 inches in diameter.  Pear psylla numbers are generally low.  Sooty blotch and flyspeck are a concern; fungicides should be included in cover sprays.  Both codling moth and oriental fruit moth can damage pear fruit at this time. 

Small fruit

Blueberry harvest of the midseason varieties Bluecrop and Jersey continues with heavy harvest volumes.  Many growers are handpicking large volumes for the fresh market because of low prices for process fruit.  Japanese beetles and blueberry maggot flies are out.  Preharvest sprays primarily target the diseases alternaria and anthracnose, as well as Japanese beetle and blueberry maggot. 

Grapes are at nearing veraison and early varieties have begun to change color.  Grape berry moth trap catches are up indicating the start of the second generation.  Larval stings and split berries are easy to find in vineyards with light crop and minimum sprays.  Grape leafhoppers are scarce.  Wine grapes need to be protected from potato leafhoppers.  Japanese beetles are easy to find but not abundant.  We expect more beetles to emerge following Monday’s rain.  Fungicides at this time should target downy mildew, and phomopsis.  Berry susceptibility to black rot ends as veraison begins.  Phomopsis lesions in the fruit clusters can be found.  The fruit becomes resistant but the cluster rachis is always susceptible to this disease.  With frequent heavy dews we expect downy mildew to increase.  Botrytis Fruit rot has been found in wine grapes

Strawberry regrowth is underway.  Some growers report poor growth.  This seems be due to drought stress, black root rot or insect feeding.  Growers should protect against potato leafhoppers to prevent hopper burn and stunting of new growth.  Irrigation is very important do get good growth during this dry season.

Raspberry and Blackberry harvest is continues.  Growers should be prepared to protect against Japanese beetles. 

Cranberries have small green fruit.

Upcoming Meetings

The final Monday Fruit Update meeting will be on Monday August 18, at the Fruit Acres Farm in Berrien County.