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Metsulfuron Potentially Damaging Oaks when Applied to Turfgrass By Scott McElroy, Ph.D., Associate Professor, Dept. of Crop, Soil, and Environmental Science, Auburn University, and Jim Jacobi, Ph.D., Extension Plant Pathologist, AL Cooperative Extension System
This
past spring, numerous complaints were made regarding damage to oak species in areas treated with metsulfuron for broadleaf weed control. Symptoms include stem dieback, delayed leaf appearance and the proliferation of stems and leaves at the base of old stems and branches. In extreme cases, trees have not fully leafed out, or leaf appearance has been delayed up to two months. More commonly, trees appear bushy due to excessive stems and leaves at the base of old stems, with the top 18" to 24" of stem failing to leaf out (see photos).
Al ab ama Tu rf Tim e s > >> Fa ll 2 013
Metsulfuron’s advantages
Metsulfuron is a sulfonylurea herbicide commonly used for broadleaf weed control in numerous turfgrass species. It is sold (and has been sold in the past) under various product names, including Amtide MSM 60 DF, Manor, Blade and MSM Turf. It is particularly effective for control of broadleaf weeds and bahiagrass. With low drift potential, it has not been previously reported to move off-target to cause damage to non-target species. It also has no noticeable odor. Sold as a 60% water dispersible with a net package weight normally measured in the ounces of product per bottle, metsulfuron is typically used at only between 0.25 and 2.0 oz./a of formulated product. With all its characteristics — low use rate, small product size, effective weed control, excellent turfgrass safety, low potential for off-target movement and no smell — metsulfuron is an ideal herbicide for turfgrass management. Further increasing its use, metsulfuron is now extremely cheap. While 20
metsulfuron is typically sold at less than $20 per acre of use, new active ingredient products typically range in the $100 per acre of product. Thus, using metsulfuron can save managers money. From our observations only, metsulfuron has gone from a higher-priced, marginally used herbicide to one of the primary broadleaf weed control herbicides used in warm-season turfgrass.
Prior to a large drop in price, metsulfuron was used minimally, with a single application of 0.5 oz./a per year being a normal scenario, and applications were made most often during the summer. In our observations for 2012 and 2013, multiple applications are now being made in spring and fall for broadleaf weed control, a practice that was not common until recently.