ISHS Acta Horticulturae 636: XXVI International Horticultural Congress: Key Processes in the Growth and Cropping of Deciduous Fruit and Nut Trees
PRELIMINARY RESULTS ON THE EFFICACY OF APPLE TREES TREATED WITH THE GROWTH RETARDANT PROHEXADIONE-CALCIUM (APOGEE®) IN EASTERN CANADA |
| Authors: | J.-P. Privé, E. Fava, J. Cline, C. Embree, D. Nichols, M. Byl |
| Keywords: | shoot growth control, flowering, yield, fruit quality |
| Abstract:
Experiments to evaluate the benefits of Apogee (prohexadione-calcium) on vegetative growth control, yield, crop load, fruit size and fruit quality were conducted in commercial orchard sites in Nova Scotia (NS), New Brunswick (NB) and Ontario (ON). The primary purpose was to evaluate the benefits of a new and unregistered (in Canada) growth control agent called Apogee® (prohexadione-calcium) on the vegetative and reproductive growth components of apple trees in Eastern Canada. Shoot growth and fruit production of ‘Summerland McIntosh’, ‘Macspur’, ‘Cortland’, ‘Golden Russett’ and ‘Empire’ were evaluated in NB; ‘Northern Spy’ in NS; and ‘Vista Bella’, ‘Thome Empire’, ‘Redspur Delicious’, ‘Mutsu’, ‘Reinders Golden Delicious’ and ‘Northern Spy’ in ON. Apogee treatments common to all three locations included a water-sprayed control (0 mg L-1), a low rate (75 mg L-1) sprayed twice, a standard rate (125 mg L-1) sprayed twice and a high rate (125 mg L-1) sprayed four times. Apogee reduced shoot growth, largely by reducing internode length rather than by reducing number of nodes regardless of rate, number of applications, cultivar, or location. In NB and NS, the low rate provided season long control of terminal shoot growth, while the standard rate was required in ON. Growth suppression was greatest during periods of maximal shoot growth. This reduction in shoot growth also had a significant effect on reducing summer and dormant pruning time for most cultivar/locations. Although not as significant as shoot growth, there was an increase in light interception within the lower tree canopy with increasing rate and number of Apogee applications. Neither the number of sprays nor the rate had an effect on fruit quality in ON and NS. In NB, Apogee had an indirect effect on yield and quality by reducing the efficacy of the chemical thinner. Thus, in NB, fruit quality was confounded by the variation in crop load caused by the greater retention of fruit by treated trees. | |
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