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Northern Michigan FruitNet 2009
Weekly Update
NW Michigan Horticultural Research Station

Nikki Rothwell District Horticulturist

Erin Lizotte District Fruit IPM/IFP Agent

Bill Klein Farm Mgr, NWMHRS

Duke Elsner Agricultural & Regional Viticulture Agent

March 31, 2009

Welcome to the 2009 FruitNet!  We are giving you a bonus issue this season as we collected branches of cherries and winegrapes to look for potential winter damage; results are enclosed in this first FruitNet.  Regular issues will begin April 28th.

 

NEW FEATURE ON MSU’S CHERRY WEBSITE

Nikki Rothwell and Karen Powers, NW Michigan Hort. Research Station

Joy Landis and Tracy Aichele, MSU

 

The new MSU cherry website (www.cherries.msu.edu) has many attributes that will benefit Michigan growers.  Due to the complex nature of producing cherries, growers rely on up-to-date horticultural and pest management information from Michigan State University (MSU) extension staff and specialists.  In order to simplify growers’ internet search time, all Michigan cherry information has been merged into a single internet location.  Our goal is to have a well-organized, relevant site where growers have access to important and timely resources. 

 

Later this spring, we will add another useful feature to this website: new data sheets on sweet cherry varieties.  Data from all promising sweet cherry cultivars will be posted in a consistent manner, and growers can access these pages to help design sweet cherry blocks.  Growers can read about tree and fruit characteristics that have been compiled by MSU researchers over many years.  We hope to have these pages up by the beginning of May, so keep your eyes out for this new website upgrade.

 

SENSITIVITY OF AMERICAN BROWN ROT TO STEROL INHIBITOR FUNGICIDES, 2008

Erin Lizotte, IFP/IPM District Educator, NWMHRS

Dr. George Sundin, MSU Department of Plant Pathology

 

American brown rot (ABR) is caused by the ascomycete fungus Monilinia fructicola, and is an important pathogen on cherry (particularly sweet cherry varieties), peach, apricot, nectarine, and plum.  The fungus attacks fruit, blossoms, spurs, and shoots with ideal infection conditions initiating epidemic inoculum levels in as little as 24 hours.  ABR causes fruit rot before and after harvest, greatly reducing the quality and quantity of the yield, particularly in heavily bunching sweet cherry varieties.

 

During the 2008 growing, season many factors contributed to the high level of ABR observed in sweet cherry orchards around the state.  Pollination problems, unusually long retention of unfertilized cherries, and wind and hail damage combined with ideal conditions for disease development leading up to harvest creating epidemic levels of ABR infection in many sweet cherry blocks around the state.  Due to the high levels of ABR, the efficacy of sterol inhibitor (SI) fungicides, such as Indar, Orbit, and Elite, were called into question.  Field trials testing Elite and Indar were conducted at the Northwest Michigan Horticultural Research Station in Traverse City , Michigan during 2008.  Disease pressure was extraordinarily high because we inoculated trees with the ABR pathogen.  Despite this high pressure, Indar adequately suppressed ABR Elite was not as effective as in previous trials and will be tested again in 2009 to confirm these observations.

  

In addition to field efficacy trials, in vitro sensitivity of M. fructicola to Indar and Orbit was assessed in 2008.  Twenty-one sweet and 9 tart cherry orchards were screened, from northern Leelanau County south to Benton Harbor .  Thirty M. fructicola samples were collected at each orchard and were then single-spore isolated in the lab.  Fungicide resistance studies use reduced mycelial growth to measure sensitivity; in this case we examined growth of the fungi on agar amended with SI’s, relative to normal growth of the fungi in the absence of the SI.  Propiconazole concentrations used in our tests were based on a discriminatory dose (0.3µg/ml a.i. propiconazole) established in peaches (Schnabel, et al. 2004), a stone fruit generally less susceptible to ABR.  This discriminatory dose defines sensitive M. fructicola isolates as those that do not grow on agar amended with 0.3µg/ml a.i. propiconazole (the discriminatory dose).  Resistant M. fructicola isolates are defined as those which have a relative growth of greater than or equal to 50% on agar amended with the discriminatory dose of 0.3µg/ml a.i. propiconazole, compared to a control.  In the case of Indar, the discriminatory dose of 0.1µg/ml a.i. of fenbuconazole was based on a discriminatory dose that we established in 2007 by sampling an abandoned Michigan orchard, representing a fungal population with minimal exposure to SI fungicides. 

 

None of the orchards screened confirm resistance to propiconazole (Orbit) but many orchards, particularly sweet cherry orchards are approaching 50% relative growth, characteristic of resistant M. fructicola isolates in peaches.  Currently, this screening process cannot confirm or reject the presence of fenbuconazole (Indar) resistance as practical field resistance has not been conclusively proven.  Indar sensitivity levels can be used to gauge changes in sensitivity over time and to compare the average sensitivity of orchards based on the history of SI use.

 

Interesting patterns emerge from the data when orchards are sorted based on past SI use.  There are few sites available with limited or no history of SI use, so sampling is limited to organic/organic-transitional sites, and abandoned blocks.  Despite the small sample size, significant differences in M. fructicola sensitivity exist based on SI history. These data point to SI fungicides having a definite effect on M. fructicola population sensitivity, the same pattern which was confirmed in a 2007 survey of ABR.

 

The results of the in vitro, M. fructicola SI sensitivity trial produced two indicators that SI’s are influencing shifts in the fungal populations.  First, there is an overall variability in M. fructicola sensitivity, an indicator that the population is being affected by the fungicide.  Second, there is a significant difference in the population’s sensitivity based on the past exposure of the fungi to the fungicide. 

 

What methods can be used to limit further shifting in the ABR populations that will lead to resistance to SIs?  Tank mixing and fungicide rotation are a MUST to preserve SI efficacy for as long as possible.  Full rates and good coverage are also very important.  Iprodione (Rovral® 50WP) may be applied for the spring, blossom-blight application to help limit the number of SI sprays used in a season.  Iprodione is a protectant fungicide that affects the fungus differently than sterol inhibitors and may help reduce the speed at which SI resistance is developing.  Pyraclostrobin and boscalid mixtures (Pristine®) and trifloxistrobin (Gem) are also rated as providing good control of American brown rot under lower disease pressure and can be utilized as a rotational partner during some seasons.  We are also awaiting word on a special Section 24(c) label for Indar which will increase the allowable rate used in orchards from 6 fl oz per acre to 6-12 fl oz per acre.  Since differences in SI sensitivities are quantitative in the ABR population, increasing the rate of Indar should be effective in controlling strains with shifted phenotypes. 

 

The most important factor in limiting further shifting in ABR populations is to effectively kill the fungus in orchards and limit exposure to SIs.  This can be best accomplished as stated above by rotating modes of action (especially to Iprodione during bloom).  In addition, increasing the rate of Indar initially to at least 8 fl oz per acre would increase the effectiveness of the best tool for killing ABR fungi.  We will pass word along of the Section 24(c) label when it becomes available.

 

CHERRY BUD DAMAGE

N.L. Rothwell and K.L. Powers, NWMHRS

 

On 30 March, we collected Montmorency, Balaton, and sweet cherry branches to investigate potential winter damage.  The following results for percent bud mortality are below:

 

Montmorency:  4/145 = 3%

 

Balaton:  0/154 = 0%

 

Emperor Francis:  37/96 = 39%

 

Napoleon:  0/136 = 0%

Ulster :  10/134 = 7.5% (Many damaged buds where 1 or 2 flowers in a bud are dead)

 

Gold:  3/144 = 2%

 

WINEGRAPE COLD INJURY PRELIMINARY REPORT

Duke Elsner, Wine and Grape Agent

 

I took a few sample canes out of the vineyard on Friday, March 20.  I let them hydrate a bit in a cool garage over the weekend.  Here are the results of dissecting the buds today:

"dead" = apparent cold injury to buds OR whole bud apparently missing or never fully formed (common at distal ends of canes, looks like they never were really set last fall).

Riesling, from guard vines in the Spacing trial:

Canes arising from upper fruiting wire of Scott Henry system
11 canes, 115 nodes total
10.4% primaries only dead or missing
14% primaries or more dead, mainly due to one thin cane from the sample
2.6 % primary, secondary & tertiary bud dead or missing

Canes arising from the lower fruiting wire (and directed downward), Scott Henry system
12 canes, 125 nodes total, only 10 nodes with no bud present
5.6% primaries only dead or missing
38% primaries or more dead,
29 % primary, secondary & tertiary bud dead or missing


Riesling from the variety block, heavily infected with powdery mildew in 2008:
11 canes, 186 nodes total, 43 with no bud present
8.1 % primaries only dead or missing
43% primaries or more dead,
33 % primary, secondary & tertiary buds dead or missing

Pinot Noir from the variety block, heavily infected with powdery mildew:
9 canes, 173 nodes total,
5.8 % primaries only dead or missing
39% primaries or more dead,
32% with p,s & t dead or missing

In all samples, very few buds contained primary & secondary buds dead only..... it was either a dead primary or all three dead most cases.

It looks like the powdery mildew weakened the vines significantly-- many nodes without any buds present on the more distal portions of the sample canes.

 

MSUE KICKS-OFF THE YOUNG FARMER LEADERSHIP PROGRAM

Rob Sirrine, Nikki Rothwell and Erin Lizotte

 

Recent social, economic, political, and environmental changes have had an impact on agricultural and rural communities in northwest Michigan .  During these times, it is critical that agricultural interests are well represented and articulated in the years to come.  The Northwest Michigan Young Farmer Leadership Program aims to identify and prepare our local up-and-coming farmers to assume a leadership role in the community and ensure that agriculture remains an economically viable, socially responsible, and environmentally sound industry.

 

A preliminary meeting of 19 young farmers took place on March 16^th, and a rough agenda for the upcoming two-year program was outlined.  The program is set to officially begin in the fall of 2009 with an introductory meeting at the Kettenun Center in Tustin , Michigan .  Highlights of the program include attending the Great Lakes Fruit and Vegetable EXPO, assisting the 2010 International Fruit Tree Association post-tour in Traverse City , and an out- of-state trip determined by the group.  Topic areas for the program include running a successful business, communications, labor issues, social responsibility and public policy.  For more information, visit http://www.maes.msu.edu/nwmihort/youngfarmer1.pdf

 

Applications for the program will be forthcoming.  If you know anyone who would be interested in the program who has not yet received information, please give Jackie a call at 231-946-1510

This issue and past issues of the weekly FruitNet report are posted on our website at: http://www.maes.msu.edu/nwmihort/faxnet.htm

ACTUAL AND PREDICTED DEGREE-DAY
ACCUMULATIONS SINCE MARCH 1, 2009

 

Please send any comments or suggestions regarding this site to:
Bill Klein, kleinw@msu.edu

Last Revised: 4-1-09