Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 23, 2011
Publication Date: April 4, 2011
Citation: Wood, B.W. 2011. Influence of aminoethoxyvinylglycine (AVG) on yield and quality of nut crops from a commercial pecan orchard. HortScience. 46(4):586-589. Interpretive Summary: Excessive fruit drop is a often a major problem for pecan farmers. This study assessed efficacy of a commercially available natural product plant growth regulator (AVG or ReTain) for use as a horticultural tool for crop-load regulation in an alternately bearing commercial pecan orchard. ReTain was found to increase nut yield in low crop-load years, but not in high crop-load years; and that a production increase in one year causes a production decrease the following year. This research identifies ReTain as useful tool in orchard management under specific circumstances during the “off” year of alternate bearing cylcles.
Technical Abstract: Excessive fruit-drop (i.e., June-drop) can limit orchard profitability of certain pecan [Carya illinoinensis (Wangenh.) K. Koch] cultivars. The present study examines efficacy of aminoethoxyvinylglycine (AVG; formulated as ReTain®, Valent BioSciences, Libertyville, IL), a natural ethylene inhibitor, for increasing nutmeat yield in a commercial ‘Desirable’ pecan orchard over a two-year period. The 30 ha experiment consisted of two treatments (Nontreated vs. ReTain) in the first year, an “off” year in the orchard’s alternate bearing cycle. The second year’s study, an “on” year, consisted of four treatments (i.e., “08 Nontreated + 09 Nontreated”, “08ReTain + 09 Nontreated”, “08 Nontreated + 09 ReTain”, and “08ReTain + 09 ReTain”). AVG, as ReTain [132 mg•L-1 a.i. (11.7 oz/acre)], was applied as two post-pollination canopy sprays (937 L.ha-1) two weeks apart in both years. During the “off” year, ReTain increased nut yield parameters, with ReTain increasing kernel yield by 36% (704 kg.ha-1 vs. 516 kg.ha-1) over that of nontreated trees. In the subsequent “on” crop year, the trees exhibiting a ReTain associated previous year yield increase of ˜ 36%, exhibited a reduction in yield parameter of ˜ 25%; thus, largely negating the previous season’s yield increase when view over a two-year alternate bearing cycle. Additionally, ReTain treated trees during the “on” year failed to exhibit an increase in yield parameters over that of the nontreated control. Due to a lag effect on subsequent year yield parameters, ReTain offers limited potential as a crop-load management tool for ‘Desirable’ orchards in “off” years, such as a year of relatively high nutmeat price followed by a year of relatively low price. There appears to be no positive effect on yield when used in a heavy crop-load “on” year of an alternate bearing cycle. Additionally, kernel quality (defined as percentage of nut weight as kernel) of “on” year trees was not as sensitive to units of yield increase as nuts of “off” year trees; thus, implying that the rate of assimilate partitioning to reproductive structures in “off” year trees is not as great as that in “on” year trees.