Response of Container-grown Nursery Plants to Chlorine Used to Disinfest Irrigation Water

Abstract

The recycling of irrigation water may cause the dispersal of plant pathogens. Irrigation water disinfected with 2.4 mg·L−1 of free chlorine for 5 min was overhead-applied to 17 container-grown nursery plants for 11 weeks in a commercial nursery to evaluate the response of container-grown nursery plants to chlorine. No visual symptoms of injury or growth reduction were observed on the evergreen shrubs (Juniperus horizontalis, Thuja occidentalis, Buxus microphylla, Picea glauca, Rhododendron catawbiense, Taxus media, and Chamaecyparis pisifera), but there were visual injuries and/or growth reduction on some of the deciduous shrubs (Salix integra, Hydrangea paniculata, Prunus ×cistena, Weigela florida, Physocarpus opulifolius). Symptoms of anthracnose were reduced on Cornus alba plants treated with chlorinated water. The chlorine treatment did not affect leaf chlorophyll content. The chlorine treatment killed all fungi and oomycetes in the irrigation water (DNA multiscan). Although there were visible leaf injuries and growth reduction on some of the deciduous plants, chlorine injury did not render them unsalable. Results suggest that irrigation water treated with 2.4 mg·L−1 free chlorine for 5 min will effectively control the dispersal of common plant pathogens without reducing the market value of container-grown plants.