Chemical Thinning ‘Fuji’ Apple in the Midwest

‘Fuji’/M.7 apple trees in a commercial orchard were treated with a range of chemical thinners over 7 years to determine their effectiveness. NAA and NAD did not adequately thin and did increase pygmy fruit. Multiple sprays of ethephon and scoring increased return bloom. Although carbaryl or BA (Accel) did not generally reduce fruit set when applied alone, the combination caused significant thinning 2 out of 5 years and 4 out of 5 years increased return bloom. In 2 of 3 years of limb treatments, Endothall applied at bloom reduced set.