Turf Tip - August 27, 2009

MSMA and Iron: To mix or not to mix?

Recently an article was published in Weed Science documenting what happens when iron is added to MSMA to offset some of the phytotoxicity to bermudagrass. Here is a shortened summary of what they found.

Discoloration of bermudagrass often results from application of MSMA herbicide used to control southern crabgrass and other weeds. However, when products containing iron sulfate (FeSO4) are tank-mixed with MSMA, this discoloration is reduced. Experiments investigated the effect of tank-mixing organic arsenical herbicides with FeSO4 or a chelated iron source (Sprint 330) in terms of southern crabgrass control and injury to bermudagrass. Tank-mixing MSMA with FeSO4 reduced bermudagrass injury. However, southern crabgrass control was also reduced by at least 50% with the addition of ≥0.12 oz./1000 ft2 (5.4 oz./acre). Neither antagonism nor safening of bermudagrass injury was observed when the chelated Fe2+ source was used. Applying FeSO4 as a separate treatment 1 to 4 d before or after MSMA application did not reduce visual bermudagrass injury 1 wk after treatment. Tank-mixing MSMA with FeSO4 to protect against bermudagrass injury negates the benefit of applying the herbicide for weed control, and therefore is not a recommendable practice for turf managers.

This research was conducted by Joseph Massey et al. at Mississippi State University.


Joseph H. Massey, James M. Taylor, Nursen Binbuga, Kristen Chambers, G. Euel Coats, and William P. Henry. 2006. Iron antagonism of MSMA herbicide applied to bermudagrass: characterization of the Fe2+-MAA complexation reaction. Weed Science 54(1):23-30.

Posted by Aaron Patton

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