SW Michigan Fruit Update
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Southwest Michigan, July 13, 2009

Mark Longstroth, Bill Shane, Diane Brown-Rytlewski

Weather

Last week was pleasant with High temperatures were in the 70s and lows were in the upper 50s.  Warmer temperatures came late in the week, with highs in the 80s and lows near 60.  Storms passed early on Saturday with spotty rains, especially at the south end of the region where rainfall totals were near half an inch.  Other areas received less than a tenth of an inch.  High winds also caused damage to grapes and tree fruits in northern Allegan County.  Cooler temperatures are forecast for this week, with highs in the 70s and lows below 60.  There is a chance of showers mid week, with cooler temperatures during the weekend.  Soils are generally very dry and corn leaves are rolling up due to water stress.  We continue to lag behind average in heat units.

Southwest Michigan Growing Degree Day Totals March 1 through July 12, 2009				Grapes, from April 1
Location	GDD 42	GDD 45	GDD 50	GDD 50
SWMREC:	1885	1593	1150	1110
Fennville:	1725	1447	1021	995

You can find weather and IPM information for Southwest Michigan at the Enviroweather website. 

Insects

Japanese beetle numbers are increasing.  All picture wing fruit flies; cherry fruit flies, apple maggot and blueberry maggot have been reported.  San Jose scale crawlers are out. 

Tree fruit

Apricots harvest is winding down.  Most early season varieties have been harvest while the late season varieties are just beginning to color.

Peach fruits are about 2 inches in diameter.  Harvest of Earlystar has begun in sandy sites in southern Berrien County but is generally expected in about 1 week elsewhere.  Rusty spot can be found.  Second generation of Oriental fruit moth is flying and laying eggs.  We expect egg laying for the second generation to end about 2200 GDD base 42.  This could be about two weeks away.

Sweet cherry harvest is ending.  Eastern cherry fruit flies have been caught in the region this season.  Harvested trees should receive treatment for cherry leaf spot with long lasting protectant materials such as Bravo.  Post harvest is a good time to do modest pruning of older trees with less risk of bacterial canker.

Tart cherry harvest is over for a few farms but still underway, especially on sites with heavier crops and heavier soils.  The extended cool bloom and cherry leaf spot are being blamed for a subset of poorly colored cherries and clinging stems in some orchard blocks.  Harvest should end this week and harvested trees should be treated for cherry leaf spot.  Unsprayed tart cherries have been almost defoliated from cherry leaf spot and many orchards have severe symptoms in some places. 

In Plums, European plums are about an inch in diameter.  Early Japanese plums are coloring and some harvest has begun.  Apple maggot can be a problem in ripening plums.  Treatments for San Jose scale crawlers should be applied where this pest has been a problem.  Scout for leafhopper damage from white apple or potato leafhoppers.

Apples are 1.75 to 2 inches in diameter and the crop is easily visible from the road.  Lodi apples are appearing in local markets and Earligold are about 10 days off.  Fireblight symptoms continue to increase in susceptible varieties and orchards with succulent growth.  Some orchards are becoming quite severe.  Sucking insects such as aphids and leafhoppers can spread fire blight to new trees.  Codling moth trap catches are generally down.  Codling moth Biofix was May 20 for most of the region and we have accumulated about 850 GDD base 50 since codling moth Biofix.  We are close to the end of the first flight (1000 GDD post biofix).  Obliquebanded leafroller egg hatch began last week at 400 to 450 GDD base 42 after biofix (June 8).  We are now at 875 GDD.  Scout shoot tips for signs of feeding.  Leaf feeding pest such as white apple leafhoppers, potato leafhoppers and apple aphids are easy to find.  Hopper burn from potato leafhopper is severe in some low spray blocks.  Mite numbers are building.  The treatment threshold for European red mite in late June and early July is 5 mites per leaf.  Oriental fruit moth trap catch is up signaling the emergence of the second generation.  Apple maggot flies are out and we expect a strong flight after this Saturday’s rain.  Apple mosaic leaf symptoms are disappearing as warmer temperatures inhibit virus multiplication.

Pear fruit are 1.75 inches in diameter.  Pear Psylla is the only pest of interest at this time.  Growers should be prepared for the second generation of codling moth, which emerges in August and attacks pears just before harvest.

Small fruit

Blueberry harvest is well underway.  Large picking crews are hand picking for the fresh market and some growers have begun machine harvest for the process market.  Fruit size and quality are excellent.  Many different varieties are being harvested as fruit maturity in fields with a light crop is advanced.  Reasons for the light crop include winter injury and severe shoot infection by mummyberry early in the season.  Growers should maintain protection against anthracnose fruit rot.  Shriveled berries due to mummyberry are common in some fields.  Blueberry maggot flies are out.  Japanese beetle numbers are building.  Symptoms of phomopsis shoot blight are becoming common.  These are small shoots in the bush not the whole cane canker collapse we were expecting after the severe winter cold.  The collapse of canes due to basal cankers is relatively rare.  Look at the Michigan Blueberry IPM Newsletter posted by Paul Jenkins at the Berry Entomology Lab.

Grapes are at cluster tightening.  We are nearing the 1200 GDD base 50 from April 1.  This point is used to estimate the time when grape berries are at 50% of their size at harvest.  Growers should estimate what their potential crop is at this point.  It appears that we have a very heavy crop and we may not have the late summer heat to ripen a very heavy crop.  The earliest areas in SW Michigan will reach the 1200 GDD point this week.  There is a model on the Enviroweather website to predict the 1200 GDD date.  Phomopsis leaf and shoot lesions are easy to find, and black rot fruit infections have been in some vineyards.  Few Japanese beetles are out.  Grape leafhopper nymph numbers are low.  See the most recent copy of Grape IPM Newsletter at the MSU Grape current conditions webpage.  Here is a link a table of SW Michigan’s Grape Growing Degree-Days from April 1 to July 13, 2009. 

Strawberry growers are finishing renovation, applying residual herbicides and fertilizers.

Summer raspberry and black raspberry harvests are peaking.  Japanese beetles have been reported in raspberries.