Weed control with herbicides as alternatives to methyl bromide in herbaceous perennial and conifer seedling production

Methyl bromide (MeBr) has been used in agriculture for many years to control nematodes, soil-borne pathogens, and weeds. In 1992, MeBr was declared a stratospheric ozone depleting substance and 180 countries signed a treaty to discontinue its use by 2005, except for import and export shipments and critical and emergency use. Michigan growers have relied on MeBr for control of pests in herbaceous perennial and conifer seedling beds. The removal of MeBr from the market has made it difficult for growers to control weeds. In this project, we examined 12 herbicide treatments and one alternative fumigant that may be used as alternatives to MeBr for weed control in five ornamental herbaceous perennial species and 12 herbicide treatments and one alternative fumigant that may be used as alternatives to MeBr for weed control in five conifer species seedling beds. Research was conducted in two fields over two years in Benton Harbor, MI and one field for one year in Holt, MI. Project goals were to: (1) determine alternative weed control treatments that are safe on the crops, and (2) determine treatments that provide weed control similar to MeBr. Each herbaceous perennial species responded differently to the treatments. Weed control in the herbaceous perennials varied from year to year with the treatments and was less than MeBr. The conifer seedlings were tolerant of most of the treatments tested. Weed control in the conifer seedlings was consistent from year to year, and many treatments provided similar weed control as MeBr.