Soil Fumigants to Replace Methyl Bromide for Weed Control in Ornamentals

Abstract

A field study was conducted to evaluate fumigant alternatives for methyl bromide (MB). Iodomethane (IM), chloropicrin (CP), 1,3-dichloropropene (1,3-D), metham sodium (MS), and MB in various combinations were applied to a sandy soil field site in Sept. 2002. Some treatments were tarped. Plant injury, plant growth, fresh weight, and dry weight were evaluated for seven ornamental species: cushion spurge (Euphorbia polychroma), globe thistle (Echinops bannaticus ‘Blue Globe’), common lavender (Lavandula angustifolia ‘Hidcote Blue’), hosta (Hosta ‘Twilight PP14040’), silvermound artemisia (Artemisia schmidtiana ‘Silver Mound’), shasta daisy (Leucanthemum ×superbum ‘Snow Lady’), and thread leaf coreopsis (Coreopsis verticillata ‘Moonbeam’). Weed control was evaluated in Apr. 2003, July 2003, and May 2004. All treatments gave almost complete control of all annual weeds, except for IM 50% + CP 50% (200 lb/acre, tarped) and MS (75 gal/acre, 1:4 water, not tarped), which did not give adequate control of common chickweed (Stellaria media), mouseear cress (Arabidopsis thaliana), common lambsquarters (Chenopodium album), or common purslane (Portulaca oleracea). None of the treatments caused visual injury to any crop species. Treatments did not affect plant size in Nov. 2003. However, some treatments resulted in larger thread leaf coreopsis and silvermound artemisia plants in May 2004. There was no difference in dry weight at harvest between treatments for all species.