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ARS Home » Southeast Area » Fort Pierce, Florida » U.S. Horticultural Research Laboratory » Subtropical Insects and Horticulture Research » Research » Publications at this Location » Publication #270746

Title: NAA thinning of ‘W. Murcott’

Author
item ATWOOD, RYAN - Keyplex
item FARYNA, NICK - Faryna Grove Care And Harvesting
item Stover, Eddie

Submitted to: Proceedings of Florida State Horticultural Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/17/2012
Publication Date: 6/12/2012
Citation: Atwood, R., Faryna, N., Stover, E. 2012. NAA thinning of ‘W. Murcott’. In: Proceedings of the Florida State Horticultural Society. 124:76-78.

Interpretive Summary: This study was conducted to determine if the growth regulator NAA may be useful for reducing excessive cropload in Florida ‘W Murcott’. Trials were conducted in two groves of ages 4 and 6 years. NAA was applied on 13 May, 2010, when fruitlets averaged 10-12 mm in diameter. Applications were made using standard grove sprayers. Three spray variants were used. Fruit were harvested on 7 Feb 2011 and data were collected on number of boxes per tree, number of fruit per tree, and limb breakage. Prior to harvest, a random 20 fruit per tree sample was collected to determine fruit size distribution. In the 4th year trees, non-thinned fruit averaged 158 g.fruit-1 and peaked sizes of 80 to 100 fruit/carton (quite large), while in the 6th year trees non-thinned fruit averaged 127 g.fruit-1 and peaked on sizes of 100 to 120 fruit per carton (medium sized). Mean fruit weight was significantly increased by each NAA treatment in both groves, ranging from 9 -12% increase in the 4th year trees and 22-38% increase in the 6th year trees, substantially shifting fruit into larger sizes. Boxes per tree were not affected by NAA treatment in either grove. Economic analyses indicate that crop value was significantly increased by NAA treatments in the older trees but not the younger trees.

Technical Abstract: This study was conducted to determine if NAA thinning may be useful for managing cropload in Florida ‘W Murcott’. Trials were conducted in two groves of ages 4 and 6 years. NAA was applied on 13 May, 2010, when fruitlets averaged 10-12 mm in diameter. A randomized complete block design was used, blocked by cropload and location. Airblast applications were made using non-ionic surfactant at 0.05%. Three spray variants were used: 250 ppm NAA, 2.4 kph, and 1170 L.ha-1; 500 ppm NAA, 2.4 kph, and 1170 L.ha-1; and 500 ppm NAA, 4.8 kph, and 585 L.ha-1. Fruit were harvested on 7 Feb 2011 and data were collected on number of boxes per tree, number of fruit per tree, and limb breakage. Prior to harvest, a random 20 fruit per tree sample was collected to determine fruit size distribution. In the 4th year trees, non-thinned fruit averaged 158 g.fruit-1 and peaked on 80 to 100 carton size, while in the 6th year trees non-thinned fruit averaged 127 g.fruit-1 and peaked on 100 to 120 carton sizes. Mean fruit weight was significantly increased by each NAA treatment in both groves, ranging from 9 -12% increase in the 4th year trees and 22-38% increase in the 6th year trees, substantially shifting fruit into larger carton sizes. Boxes per tree were not affected by NAA treatment in either grove. Economic analyses indicate that crop value was significantly increased by NAA treatments in the older trees but not the younger trees.