Vegetative growth control can be achieved by application(s) of Apogee or Kudos 27.5 WDG, both containing the active ingredient prohexadione-calcium. In addition to providing growth control, early application can suppress fire blight of shoots.
Application details for Apogee or Kudos 27.5 WDG on apples
- Apply beginning at late bloom to early petal fall; earlier applications seem to give better results (Ed. note: in 2019, Kudos was approved for use beginning at pink bud stage @ 6 oz. per acre. This application in particular may help suppress fire blight and result in improved growth control, although follow-up applications may still be necessary. Only the Kudos formulation of prohexadione-calcium has the specific pink timing recommendation. The Apogee label still says application beginning at 1-3 inches of shoot growth.)
- Apply at rates of 3 to 12 oz. per 100 gallons of dilute spray water depending on the amount of growth control desired and number of anticipated applications
- Repeat applications at 1 to 4 week intervals may be necessary for season-long growth control
- Do not apply more than 48 oz per acre within any 21-day interval, and there is a maximum of 99 oz per acre per season
- Always use a water conditioner such as ammonium sulfate, Choice, or Quest.
- Do not tank mix with sprays containing calcium
- Chemical thinning efficacy may be decreased when using prohexadione-calcium
- Direct spray to top of trees if only vigor control is desired in the top of the tree
- Not recommended for use on Empire, may cause russetting
For more information on Apogee/Kudos/prohexadione-calcium, see UMass Fact Sheet F-127R Apogee—A New Growth Retardant for Apples
Also see UMass Fact Sheet Controlling Growth of Apple Trees