Northern Michigan FruitNet 2004
Weekly Update
NW Michigan Horticultural Research Station

Jim Nugent                      Position Vacant                  Bill Klein
        District Horticulturist           District Fruit IPM Agent         Farm Mgr, NWMHRS

    Duke Elsner                                                      Jim Bardenhagen
            Agricultural Agent                                              Leelanau Extension Director

GROWING DEGREE DAY ACCUMULATIONS as of July 19, 2004 at the NWMHRS
 

Year	2004	2003	2002	2001	2000	14 yr. Avg.
GDD42	1619	1742	1754	1897	1902	1818.6
GDD50	933	1040	1142	1179	1133	1132.1

WEATHER:
Temperatures this past week finally warmed to more normal July levels. Scattered, light rainfall on 7/16 of 0 to 0.1 inches resulted in scab and leaf spot infections in some localities in NW Michigan.

GROWTH STAGES at NWMHRS (7/19/04)

Apple: Red Delicious -- 40 mm
Sweet Cherry: Napoleon – 18 mm
Tart Cherry: Montmorency – 21 mm
Apricot: 34 mm
Plum: European type – 25 mm
Grapes: Chardonnay – buckshot

CROP REPORT

Cherries: 
Tart and sweet cherry harvest is getting underway. Tart and sweet maturity is overlapped more than normal. This overlap is due at least in part to a generally heavy sweet crop and generally light tart crop. Heavy crops of either sweets or tarts take longer to mature than normal, while light crops mature slightly quicker than normal. It is also possible that tarts have a slightly lower temperature developmental threshold than sweets, but we have no data to confirm this. Brown rot is a major concern at this time on sweet cherries. Alternaria rot is present in some of the cracked sweet cherries. If it is necessary to control Alternaria rot, suggest using the strobilurin plus boscalid fungicide, Pristine. We have not collected data on this disease in Michigan, but Pristine is registered for Alternaria on stone fruits. If Pristine is unavailable, then suggest another strobilurin fungicide (Flint or Cabrio) as this class of fungicides are generally quite effective on diseases caused by Alternaria sp. on other crops. Unfortunately both Flint and Cabrio are weak on fruit brown rot, which is generally much more of a threat to the crop than is Alternaria. The SI fungicides have never provided Alternaria control.

Cherry leaf spot continues to spread in some area orchards. This has been a challenging year for control of this disease. All cherry orchards with any inoculum present will want to be treated with Bravo after harvest. Powdery mildew is becoming prevalent. 

Cherry Fruit Fly (CFF) numbers seem to be remaining fairly low this year. Likely, the one good thing to have come out of the 2002 total crop disaster is the CFF populations crashed in NW Michigan and are taking some time to recover. This is not to say they aren't present, but their numbers are lower than we were seeing by this time of the season in years prior to the 2002 disaster. In 2002, not only were commercial cherry crops wiped out, but so were much of their alternate hosts (particularly the forest black cherry). Mites remain very low. Yesterday I observed a young block of cherry that was badly infested with greater peach tree borer (GPTB). This pest does most of its damage below ground on the tree collar, so it can easily go undetected. GPTB will attack uninjured trees. High populations will cause tree death by girdling. It is currently either in the pupal or adult stages. At this time, look for their cast pupal case sticking out of the soil at the base of the tree. Eggs are laid at the base of the trees and newly hatched larvae find their way to the trunk generally below ground. Control should ideally go on for this pest shortly before or after the beginning of adult emergence (about 3 weeks ago). If the problem is found at this time, a pesticide applied to the base of the tree as soon as possible should still provide fairly good control.

Apples:
Apple maggot has been trapped in NW Michigan. Codling moth adult trap catches remain low in most sites as second generation has not yet begun emergence. Oblique banded leafroller adult trap catches are rising. White apple leafhopper populations are generally low; potato leafhopper are more plentiful than normal. Rosy apple aphids are pretty much done with apples for the season. Green apple aphid populations have generally been low.

Apple scab in unsprayed blocks is causing significant defoliation from this season's severe scab infection. Fireblight shoot strikes are appearing in some susceptible varieties, particularly in areas that retained moisture for longer periods. Suggest making sure that potato leafhopper populations are kept low in blocks with fireblight shoot strikes.

Grapes: 
Berry set looks to be quite variable thanks to some cool and damp weather during the peak of bloom. Gewurztraminer appears the worst of the varieties I have checked. Overall, cluster numbers look pretty good, and some vineyards will need to cluster thin to achieve desired crop loads. Potato leafhopper adults and nymphs are getting numerous in the unsprayed row at the Hort Station vineyard. Larvae of sphinx moths and the eight-spotted forester moth are appearing in low numbers at the station vineyard. I have not had reports of them in commercial vineyards as of yet. Foliage condition still is generally great, with little powdery mildew and almost no black rot on the station’s unsprayed vines. Remember that warm and humid weather encourages powdery mildew, as does dense leaf canopies—we are just getting into these conditions. 

Announcements:

2004 CA Clinic To Be Held.
The 2004 CA Clinic will be held this year at the Clarksville Horticulture Experiment Station in Clarksville, MI, Friday, August 13, 2004. Registration will start at 8:00 a.m. and the day's program will conclude at 4:45 p.m. The registration fee for the clinic is $75, before August 6 and $85 AFTER August 6. For additional information or a registration form, call Sandy Allen at 517/355-5191 ext.1339.

Found
A key to a Kubota tractor was found in Suttons Bay on July 19. The key has a tag attached that says "Ginop Sales, Inc." If it belongs to you, it can be picked up at the NWMHRS.

CIAB Weekly Raw Product Report, July 20, 2004:
http://www.cherryboard.org/week3 2004.htm

Please send any comments or suggestions regarding this site to: 

Bill Klein, kleinw@msu.edu
Last Revised: 7-20-04