EFFECT OF ETHEPHON ON MISTLETOE REMOVAL

Abstract

The parasitic eastern mistletoe, Phoradendron serotinum is a perennial evergreen that infests trees including the deciduous pecan [Carya illinoensis (Wangenh.) C.Koch]. Various chemical and/or mechanical methods of mistletoe eradication have been studied. An efficient method of mistletoe removal in deciduous trees involves the use of ethephon, an ethylene-releasing compound. Mistletoe in dormant `Stuart' trees and `Desirable' trees at bud break were treated on 15 Mar. with 0, 2500, 5000, 7500, or 10,000 ppm ethephon [pH of treatment solution adjusted with 1.2 ml/L of a buffering agent (pH +, Stoller Chemical Co.)]. `Desirable' trees at the prepollination stage of development were treated with 0, 312, 625, 1250, or 2500 ppm + 1.2 ml/L of the buffering agent on 27 Mar. 1991. All ethephon treatments except 312 and 625 ppm resulted in >95% defoliation on 18 Apr. All chemical treatments resulted in abscission cf some mistletoe branchlets. There was a negative correlation between ethephon concentration and mistletoe regrowth on 2 Dec. for both cultivars. The most effective treatment was 2500 ppm applied at prepollination on `Desirable'. This treatment resulted in no mistletoe regrowth on 80% of the trees. No phytotoxicity to the pecans was observed.