Hero Image

Rest-breaking in Sweet Cherry

Dormancy, chill accumulation, rest-breaking and freeze damage(pdf)

Recommendations for rest-breaking applications in sweet cherry. (K. Glozer, 2011)

Essential points:

  1. Timing of applications
    1. Timing by the Dynamic Model (start counting chill accumulation when the Model shows it, not by calendar date)
    2. Dormex best applied at 45-50 chill portions
    3. CAN17 best applied at 47-55 chill portions
    4. Dormant oil probably best at same timing as CAN17
  2. Order of strength in response:  Dormex>CAN17>Dormant oil
  3. Order of risk for phytotoxicity (same as above)
  4. Dormex effective rate and adjuvant: 
    1. label rate of 4% and 0.5% nonionic surfactant—this tends to be too high, although still widely used.  Best to go with 2%.
    2. Choice of adjuvants:  Agridex 0.5% is fairly routine; MontereyAg CanHance at 1.5% tested well as an alternative, with 2% Dormex.
  5. 25% CAN17 + 2% N-Ter or 1.5% RNA Activator 85 have been widely tested by us and growers.  These rates can often cause bud death, especially with late freeze.  Definitely, the rate for Activator 85 should not be above 0.5%, and 0.25% is better if applied late in chill accumulation or in case of freeze.  Young or stressed trees are more susceptible than older or unstressed trees.  I advocate 12% CAN17 and 1-2% N-Ter or 0.25-0.5% Activator 85.
  6. 3% Dormant Plus (UAP-Loveland) is best choice for dormant oil treatment.  Some growers go well above the label rate, which we can’t recommend.  3% Dormant Flowable Emulsion (UAP-Loveland) is an alternative that we have also tested with success.

We are in the middle of the fourth driest winter on record in California, and I have recommended that growers irrigate their trees well before any applications, but even more importantly, spray down the trees with water just in advance of application (same day).  We don’t have hard data for this, just observations.