Coffee Board of Kenya Monthly Bulletin July 1973

Abstract

Five field experiments were carried out to investigate the abscission and fruit ripening properties of 2-chloroethane phosphonic acid (CEPA) on mature Coffea arabica growing at Ruiru, Kenya. A single application of formulation ACP-68-250 at 1400 ppm removed about 60-65% of young expanding berries between 4 and 6 days after spraying but had no significant additional effect after the 6th day. At this concentration about 10% of the leaves were also shed, but no other appendages, including open flowers and berries at other stages of development, were affected substantially. CEPA could replace hand-thinning of fruit in the first fruiting year of young trees and might subsequently be used in some areas to prevent over-bearing and also to influence the annual fruiting pattern by selectively removing the products of unwanted flowerings. CEPA accelerated the onset of ripening of mature green berries; thus, in one experiment berries on trees sprayed with CEPA at 1400 ppm and 700 ppm began to ripen four and two weeks earlier, respectively, than untreated berries. The quality of the beans was unaffected. CEPA might be used to synchronize, stagger or prolong the harvest period and so increase the efficiency of hand-picking. Concentrations higher than 1400-1500 ppm were excessively phytotoxic.