ARS | Publication request: POTENTIAL CHEMICAL THINNERS FOR THE 'GOLDRUSH' APPLE CULTIVAR

Submitted to: Annual Cumberland Shenandoah Fruit Workers Conference
Publication Type: Proceedings
Publication Acceptance Date: January 25, 2006
Publication Date: February 20, 2006
Citation: Miller, S.S. 2006. Potential chemical thinners for the 'goldrush' apple cultivar. Vol 81., pg 174-177. 2006. . Annual Cumberland Shenandoah Fruit Workers Conference.

Technical Abstract: Information is lacking regarding the response of the new apple cultivar ‘GoldRush’ to chemical thinners. This preliminary trial examined two chemical thinning treatments for thinning efficacy on 5-year-old ‘GoldRush/M.26 trees. Thinning treatments were applied on 23 May at the 10-12 mm fruit stage. A combination of 6-benzyladenine (MaxCel) at 125 ppm and carbaryl (Sevin XLR Plus) at 4.73 ml/3.78 l (1 pt/100 gal.) reduced crop load (measured as fruit/sq. cm trunk cross-sectional area) and increased fruit size (weight and diameter) at harvest compared to an untreated control. A combination of carbaryl at 4.73 ml/3.78 l and naphthaleneacetic acid (NAA, Fruit Fix 200) at 10 ppm also reduced crop load, but had no effect on fruit size. Both chemical thinning treatments reduced fruit density (fruit/cu. ft. canopy volume) and yield per acre. The larger fruit size obtained with MaxCel + Sevin XLR appeared to be achieved with a significant reduction in yield. MaxCel + Sevin XLR is a promising thinner for ‘GoldRush’, but additional studies at lower dose levels are needed to determine the optimum thinning rate for obtaining large fruit and economical cropping levels.