Hot Water Drench Treatments for the Control of Burrowing Nematode, Radopholus Similis, in Tropical Ornamentals

Abstract

Hot water drench treatments were investigated for their potential application as quarantine treatments against Radopholus similis, in two palms, Rhapis excelsa and Caryota mitis, and in potted Anthurium. Drenches with 50°C water were applied for 10 to 16 minutes to both R. excelsa and C. mitis. R. similis were eliminated from C. mitis in all treatments longer than 10 minutes. In R excelsa, a 16-minute hot water drench achieved 99.6% mortality of R. similis. In Anthurium, previous applications of hot water drench treatments resulted in a few survivors being detected 2 months after treatment. An experiment was designed to test cultivar effects, duration of time between treatment and nematode assay, and location of surviving nematodes after hot water drench treatment on four cultivars Anthurium. No cultivar differences were found in the reproductive factor of R. similis. Surviving nematodes, 1 week after treatment, were only found in stem sections above the soil line. Four weeks after treatment nematodes were found in roots and stems below the soil line, Migration into stem tissue is a proposed mechanism for escaping lethal temperatures. Conditioning treatments applied to Anthurium may also enhance thermotolerance in R. similis and decrease the efficacy of subsequent eradication treatments. R. simils did not survive challenge heat treatment after receiving a variety conditioning treatments in vitro. Probit regression estimates of conditioned and unconditioned R. similis mortality rates in potted Anthurium was similar. However survivors in conditioned potted Anthurium suggest that efficacy of eradication is compromised, although development of thermotolerance has not been confirmed.