ALUMINUM AMENDMENT OF POTTING MIXES FOR CONTROL OF PHYTOPHTHORA DAMPING-OFF IN BEDDING PLANTS

摘要

Control of preemergence damping-off caused by Phytophthora parasitica Dastur was investigated on three bedding plant species in a 1 peat : 1 vermiculite medium (v/v) limed at 3 kg . m(-3) and drenched with aluminum at 10, 25, or 50 meg Al/100 cm(3) medium. Aluminum as Al-2(SO4)(3) was applied as a drench at 0.75, 1.9, or 3.75 g/150 mi water to the surface of infested medium in 650-cm(2) plug trays (1300-cm(3) tray volume). All concentrations of aluminum were effective in controlling preemergence damping-off of snapdragon (Antirrhinum majus L.) and vinca (Catharanthus roseus G. Don, Madagascar periwinkle), but only 50 meg Al+3/100 cm(3) medium was effective for petunia (Petunia x hybrida Hort. Vilm.-Andr.). At 4 days after seeding and drenching with aluminum sulfate, exchangeable aluminum was 0, 0.5, and 2.03 meg Al+3/100 g medium, respectively, for the three concentrations used. Control of damping-off of snapdragon and vinca with 10 meg Al+3/100 cm(3) medium with no detectable exchangeable aluminum 4 days after application suggests that P. parasitica was suppressed by aluminum early in the host-pathogen interaction, whereas petunia was susceptible to damping-off for a longer period before seedling emergence. Aluminum was not phytotoxic to vinca, snapdragon, or petunia grown in a limed medium.