SW Michigan Fruit Update
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Southwest Michigan, May 25, 2009

Mark Longstroth, Bill Shane

Weather

Last week was warm with highs in the 70s and 80s and lows in the upper 50s.  Scattered showers fell Sunday.  The warm weather increased insect activity and plant growth.  Cooler temperatures with several chances of rain are forecast for the next week.

Southwest Michigan Growing Degree Day Totals March 1 through May 24, 2009				Grapes, from April 1
Location	GDD 42	GDD 45	GDD 50	GDD 50
SWMREC:	728	581	377	346
Fennville:	646	510	321	302

You can find weather and IPM information for Southwest Michigan at the Enviroweather website.  Here is a link a table of SW Michigan’s Growing Degree-Days from March 1 to May 24, 2009.  Our heat accumulations are still lagging behind recent years. 

Tree fruit

Tree fruit should be protected from plum curculio.  Curculio egg laying scars were found in sweet and tart cherries Monday.  Leafroller larvae of all sizes have been found in tree fruit.

Apricot fruit are 18 to 24 mm in diameter.

Peaches are out of the shuck and are 10-14 mm in diameter.  Peach leaf curl symptoms are scarce.  Copper damage to peach leaves is present in some orchards where copper sprays were used to suppress bacterial spot.  The first generation of Oriental fruit moth is past peak egg laying and we should be seeing injury to peach shoot tips.  Growers need to protect peach fruit against rusty spot once it emerges from the shuck.  Rusty spot is caused by the apple powdery mildew pathogen and causes fruit blemishes on some peach and nectarine varieties.

Sweet cherries fruit are 12 to 14 mm in diameter, with some fruit drop underway.  Fruit blemishes due to winds as the fruit emerged from the shuck are becoming more obvious.  Plum curculio egg laying scars can be found in cherry. Sweet cherry fruits are always susceptible to brown rot, warm rains are good infection periods.  Growers also need to protect against cherry leaf spot.

Tart cherries are 10 to 12 mm in diameter.  Growers need to protect against cherry leaf spot and plum curculio.

In Plums, European plums are 8 to 10 mm in diameter.  Oriental plums are 12 to 16 mm.  Growers should apply fungicides to reduce black knot.  Growers need to protect against plum curculio and continue to suppress black knot.

Apple fruitlets are 12 to 18 mm in diameter.  Most fruit are 13 to 15 mm in diameter.  Thinners applied at this time are usually effective, but cooler weather this week will not be favorable for apple thinning.  No warm periods are forecast for the upcoming week.  This means that thinners applied this week will have little effect on the natural drop of the fruit.  Growers should carefully assess the fruit set in their apple orchards and determine which orchards will need thinning.  Growers will need to apply thinners during a warming trend in early June.  Apple scab symptoms are becoming easier to find.  All the primary scab spores are mature and almost all have been discharged.  Grower should inspect their orchards for leaf scab and determine if they need to continue using protectant sprays.  Apple scab symptoms for the mid May infection events should be visible this week.  This week’s rain will probably end primary scab season.  Growers with scab in there orchards will want to continue protecting the fruit until it is about one inch in diameter and waxy.  These fruit are resistant to scab infection.  Warm weather and scattered rain on Sunday were a fireblight infection for apple orchards with open bloom.  A few blossom blight symptoms were found near Paw Paw Monday May 25, 2009 in Jonathan apples.  This infection probably occurred on April 27, at the very beginning of apple bloom, when warm weather with highs near 80 was followed by a two day wetting event.  Only the earliest blooming apple varieties would have been open for the April 27 event.  Rain May 24 and 25 could have infected late blooming varieties with open bloom.  Insect activity increased last week.  Codling moths were been trapped in good numbers last week. It appears that codling moth Biofix was May 19 or 20 for most of the region.  We are just over 100 GDD base 50 since Biofix and past the application window for Rimon and Esteem.  The 125 GDD window is Wednesday and the 250 GDD window will be in the middle of next week.  Growers and scouts should monitor codling moth traps to see if the cool weather shuts down the flight codling moth flight this week.  Leafroller larvae can still be found.  Spotted tentiform leafminer adults are flying and laying eggs.  European red mite eggs have hatched.  Oriental fruit moths are still flying in good numbers. 

Pear fruit are 12 to 14 mm in diameter.  Pear Psylla eggs and nymphs are hard to find.

Small fruit

Blueberry bloom is ending.  Jersey and other late varieties are at petal fall.  Mummyberry shoot strikes are common in some fields and some growers have mistaken them for frost injury.  There was some freeze injury in unirrigated fields from last Monday’s (May 18) freeze.  Cherry fruitworm and cranberry fruitworm are flying and laying eggs.  Insecticides to protect against these pests should be applied in fields where they are a problem.  The Michigan Blueberry IPM Newsletter is posted at the MSU Blueberry IPM web site . 

Grape shoots are about 8 to 12 inches long; flower clusters are elongating and separating.  Wild grape may bloom in some areas later this week.  We expect grape growth to slow during this cool weather.  Bloom is probably about two weeks away.  Next week will be the time for growers to apply their prebloom fungicides to suppress grape disease development, especially phomopsis.  An SI material such as Rally or Elite should be included to control powdery mildew.  Downy mildew lesions were found on wild grape last week.  Eutypa symptoms were also found.  Early in the season, Eutypa symptoms are easiest to find.  Affected vines should be marked and removed.  A few grape berry moths have been trapped but since bloom is over a week away this is not a concern.  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 May 25, 2009.  Freeze damage was generally light and scattered.

Strawberry bloom is winding down and the largest fruit are thimble sized.  Freeze damage occurred in some fields last week.  Growers should be applying fungicides to protect against fruit rots.  Tarnished plant bug and spittlebug are out and may require controls.

Raspberry flower clusters are emerging and bloom in earliest varieties has begun.  Black raspberry bloom is almost finished.  Primocanes are 12 to 24 inches tall.

Miscellaneous

The Fruit Code-A-Phones in Van Buren County (269) 657-8217 and Berrien County (269) 944-4126 ext 1 are being updated.  The next Monday Fruit IPM Update meeting will be, Monday June 1, at the Fruit Acres Farm in Berrien County.