783 PB 427 LEATHERLEAF FERN DAMAGE AND BENLATE USE

Abstract

Benlate 50 DF has been implicated in causing long term damage to leatherleaf ferns. Damage to leatherleaf fern including frond distortion, discoloration and growth suppression continues to occur even after two or more years following last Benlate application. Electron micrographs of affected plants roots indicate a loss of root hairs and a proliferation of associated soil bacteria on the root surface compared to healthy plants. Plants with history of continued Benlate application have extensive bacterial colonies embedded on the root surface, but these colonies were not parasitic. Lcatherleaf fern plants which only had their rhizomes dipped in Benlate at planting lacked the embedded colonies, but were extensively covered with bacteria. Bioassays of bacteria taken from the rhizoplane and rhizosphere of the these leatherleaf ferns showed that these bacteria have the ability to produce growth regulators and/or toxins which may be detrimental to plant growth when absorbed through the root. Consequently, Benlate may be influencing fern growth indirectly by modifying bacteria composition of the growing media to favor proliferation of deleterious, non-parasitic bacteria.