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Northern Michigan FruitNet 2009
Special 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

May 27, 2009

Following are two articles to help manage your apples this time of year.

 

APOGEE IN A NUTSHELL

Nikki Rothwell, District Horticulturist, MSU-E

       Apogee is a plant growth regulator that helps regulate shoot elongation in apple trees.

       Apogee helps control tree vigor, which can reduce the amount/intensity of pruning, decrease internal shading, and reduce canopy density for thorough pesticide coverage.

       Apogee is a reliable tool for minimizing impacts of shoot blight caused by the fireblight pathogen.  Shoots that have less growth are not as susceptible to fire blight.

Timing

       Apply when vegetative shoot growth is less than three inches.

       Optimal timing is king bloom petal fall.

       Two more applications should be made at two-week intervals following the king bloom petal fall application.

Rate

       Rate per acre is usually calculated on a tree row volume basis.

       A two-thirds' rate is used season-long and is the starting rate for growers without experience using Apogee.

       For example, if trees are at 75% tree row volume, then 24 ounces per acre is the seasonal rate (48 * 0.75 * 2/3).

       Best results are achieved when the seasonal rate is split into three or four sprays: 8 + 8 + 8oz per acre for a total of 24oz per acre per season.

       When fire blight is a severe risk, the first application at king bloom petal fall timing should be increased--the rate should be increased from 8oz per acre to 12oz per acre. If the first spray rate is increased, the second and third sprays should be reduced (12 + 6 + 6 = 24oz instead of 8+8+8=24oz).

Thinning

       Apogee tends to increase fruit set, hence more aggressive thinning is often needed.

       If using Apogee, growers should increase thinning products by 10 or 15%.

Compatibility

       Apogee is not compatible with calcium or boron in the tank.

       Apogee should be applied after thinner applications. If the two-week timing interval is also the ideal time to thin, make the thinning application first and follow with Apogee a few days later.

Fireblight

       Limits shoot blight strikes

       Reduces # cankers

       Controls shoot blight even if streptomycin-resistant strains present

 

THINKING ABOUT THINNING

Nikki Rothwell, District Horticulturist, MSU-E

Phil Schwallier, District Horticulturist, MSU-E, and

Coordinator, Clarksville Horticulture Experiment Station

 

Factors to Consider:

 

     Crop from last year.  Light crop last year results in increased flowering in present year.  Blocks where fruit was light will have increased bloom and an increased tendency to set fruit.  We have observed tremendous bloom in apples around the region.

       Frost damage.  Some apple blocks were damaged on the evening of 3 May. If the frost took out the king bloom, thinning becomes more difficult.

       Pollination and bee activity.  Growers have reported improved hive quality this season over past years.  Apple pollination weather has been excellent.

       Weather conditions during thinning.  Cold temperatures and sunny weather increase fruit set. Cloudy conditions increase thinning capabilities (See Table 1). 

       Tree vigor and growth.  Trees that are growing vigorously with lots of leaves and lush growth present are harder to thin than less vigorous trees.

 

This year’s apple crop for Michigan and the United States is expected to be large, and growers should be diligent with thinners as it will be important to produce larger apples to avoid growing juice apples.  Plan on applying good thinning combinations of Sevin plus NAA or Sevin plus MaxCel where set will be heavy. Be ready at petal fall to apply thinners if warm weather occurs at that time. Petal fall is the first good time to thin when heavy fruitset is expected. A second thinning can then be applied at 10 mm if needed.

 

 

 

This year, we have a new tool from Drs. Terrence Robinson and Alan Lasko of Cornell University .  This tool is designed to help with thinning decisions using the theory that fruitset is based on carbohydrate supply and demand.  Fruitlets need energy (carbohydrates) to set, and if they become deficient of energy, they more readily drop from the trees; fruitlets with less carbohydrates are also easier to thin. Stress at fruitset timing either from thinners, weather conditions, or tree energy levels will cause increased fruit drop.  This new carbohydrate model helps predict energy levels based on current weather conditions as well as predicted forecasts to determine optimal times to thin. 

 

 

 

5/26/09 - This model output is based on the energy supply of apple trees at the NWMHRS beginning at petal fall.  The premise behind this model is that when the fruitlets are in an energy deficient situation (demand is greater than supply), the fruitlets are sensitive (easier) to thin.  When the tree has excess energy (supply is greater than demand), fruitlets are more resistant to thinning. The

 

 

 

NWMHRS model output suggest that tree demand is higher than the supply, hence, we had opportunities for good thinning earlier in May, but as we approach the end of May, those lines move closer together (supply is equal to demand), fruitlets will be more difficult to thin. 

 

Most times the model will predict normal conditions, normal energy levels, normal tree sensitivity and normal thinning responses. However, thinning sensitivities can be abnormal during the thinning window, and the model is intended to help reduce mistakes of both over-thinning and under-thinning. If normal conditions are predicted, then growers can use their judgment of thinning level desired and adjust thinning aggressiveness to achieve ideal thinning. This model is under testing for Michigan conditions and should be used as a guide this year.

 

WEBSITES OF INTEREST

Insect and disease predictive information is available at:
http://www.enviroweather.msu.edu/home.asp  

60 Hour Forecast
http://www.agweather.geo.msu.edu/agwx/forecasts/fcst.asp?fileid=fous46ktvc

Information on cherries is available at the new cherry website:
http://www.cherries.msu.edu/

Fruit CAT Alert Reports
http://www.ipmnews.msu.edu/fruit/

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: 5-27-09