Herbicides to Control Tree Roots in Sewer Lines

Abstract

The use of metham (methylcarbamadithioic acid) to control tree roots obstructing municipal sewer lines faces possible restriction by the U.S. EPA. In an effort to find a herbicidal alternative to metham, eight presently available herbicides (asulam, DCPA, EPTC, MSMA, glufosinate, glyphosate, sodium chlorate and triclopyr) were screened for efficacy in killing roots without visibly damaging other portions of the tree. Exposed roots in containerized seedlings of four species: water tupelo (Nyssa aquatica L), wax myrtle (Myrica cerifera L), wateroak (Quercus nigra L), and chinaberry (Melia azadarach L), were exposed to herbicides at rates equal to or 10 times the cost of operational rates of metham. Five weeks following treatment, triclopyr, glufosinate and sodium chlorate showed herbicidal activity against roots. Only glufosinate had activity against roots without damaging foliage. Glufosinate was effective at a 10x rate, but not 1x, the cost of metham. While these chemicals may have the potential to be developed as alternatives to metham, increased material costs would likely result.