Control of Rootsuckers on Apple Trees with Growth Regulators1

Abstract

Naphthalenacetic acid ethyl ester (NAA ethyl ester) applied to actively growing rootsuckers on ‘Oregon Spur Delicious’ apple trees (Malus domestica Borkh.) at 0.5 and 1.0% provided effective sucker suppression 70 days after treatment. Combination sprays of NAA and N -butyl- N -ethyl- a,a,a -trifluro-2,6-dinitro- p -toluidine (benefin) or NAA and straight chain fatty alcohols (Off-Shoot-T85) gave good control of rootsuckers. Lower rates of NAA and NAA plus Off-Shoot-T85 were equally effective when a paraffin based petroleum oil spray adjuvant (Agicide Activator) was added. NAA at 1.0% was the only treatment to provide effective rootsucker supression in the season following treatment.