Home // C.O.R.N. Newsletter // 2019-03 // The LL-GT27 soybean – what's legal?
- In mixtures of systemic and contact herbicides, it's important to optimize the application parameters for the contact herbicide. In this case, it's especially important to optimize the glufosinate since it's controlling the glyphosate-resistant broadleaf weeds. Optimizing glufosinate means higher spray volumes and smaller spray droplets, compared to what is needed for glyphosate alone (which works with almost any spray parameters). Both herbicides require the addition of AMS. Keep in mind also that glufosinate requires warm, sunny conditions for maximum activity. And the activity of both herbicides is reduced in late evening through early morning.
- Sources tell us that, depending upon glyphosate rate, the cost of adding clethodim versus glyphosate to glufosinate is a wash to a slight advantage for glyphosate. Higher rates of glyphosate will be needed where perennial weeds are the target. The long-term potential for herbicide resistance could also be considered as part of the cost-benefit analysis here. Populations of glyphosate-resistant annual grasses have become more prevalent in soybean-growing areas. Continuous use of glyphosate for control of annual grasses in soybeans can increase the rate of resistance development, especially where glyphosate is used as a primary POST herbicide in corn also. Paying somewhat more for clethodim in certain years of the rotation may therefore provide long-term weed management benefits compared with use of cheaper glyphosate.