2015 Variety Screening for Metribuzin Sensitivity
Metribuzin is a very efficacious residual herbicide, with activity on broadleaf and some annual grass weeds. It offers a unique herbicide mode-of-action–Group 5 for soybean weed control as a photosystem II inhibitor. Products that contain metribuzin are Axiom, Canopy, Boundary, Authority MTZ, TriCor, and Sencor (no longer sold under this trade name).
As great as this herbicide is, it has a significant drawback. Varietal sensitivity to metribuzin exists, especially when varieties are planted on coarser-textured soils with low organic matter following preemergence application of metribuzin, or on clay soils when the highest rate is used for enhanced control of certain weeds.
Because of increasing occurrence of GR weeds, residual herbicides are now being recommended as a soybean farming tool for weed management. Recommended residual herbicides such as those listed above contain metribuzin. Thus, producers need to be aware that varietal sensitivity to metribuzin exists.
Drs. Jeremy Ross, Jason Norsworthy, Bob Scott, and Tom Barber of the Univ. of Arkansas have published a list of soybean varieties that they screened in 2015 for sensitivity to metribuzin.
The above linked file now contains their metribuzin screening data for the 2011-2015 period. Thus, it is likely that all of the varieties now planted in the Midsouth have been screened for sensitivity to this herbicide. The new screening data from 2015 can be used with those from previous years to find the metribuzin sensitivity rating for most varieties grown in the Midsouth.
When planting soybeans on a site that has been treated with a metribuzin-containing herbicide to control HR weeds, these ratings should be consulted to ensure that the variety selected for the site has an acceptable level of tolerance to the herbicide.
The 2016 Mississippi Soybean Production Calendar has been posted on the Seasonal Resources Page of this website.
Composed by Larry G. Heatherly, Nov. 2015, larryheatherly@bellsouth.net