ISHS Acta Horticulturae 653: IX International Symposium on Plant Bioregulators in Fruit Production
AUXINIC BLOSSOM THINNERS (MCPB-ETHYL AND NAA) INHIBIT RETURN FLOWERING ON FUJI/M.26 APPLE TREES |
| Authors: | S. Guak, M. Beulah, N.E. Looney |
| Keywords: | chemical thinning, ethephon, carbaryl, fruit set, Malus domestica |
| Abstract:
MCPB-ethyl and NAA were evaluated as blossom thinners for 'Fuji' in 1998 at Corvallis, Oregon. Six-year-old central leader 'Fuji'/M.26 trees were treated with each chemical at 0, 4, 8 or 16 mg L-1 a.i. All sprays were applied to run off to whole trees at 85% full bloom. This study also involved 0 or 100 mg L-1 ethephon tank-mixed with these auxins. All blossom thinners were combined with post-bloom carbaryl at 0 or 1000 mg L-1 applied at 11-mm king fruit diameter. NAA increased whole flower cluster removal and reduced total crop load linearly with increasing rate, while MCPB-ethyl proved ineffective. NAA did not reduce fruit set on the remaining clusters, resulting in the need for subsequent hand thinning. The combination of ethephon with both auxins further reduced crop load. A follow-up spray of carbaryl further reduced total crop load by both increasing whole cluster removal and reducing fruit set on individual clusters. Return flowering was not improved by the auxin treatments, despite some significant effects on crop load reduction by the NAA treatments. Carbaryl significantly promoted return flowering but this effect was often countered by the auxin treatments. Addition of ethephon appeared to overcome the negative effect of these auxins in the auxin + carbaryl treatments. | |
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