Peanut Grower Magazine May Column Peanut Notes No. 18 2018
May brings many important early season management decisions, and making sure weeds are controlled is one of the most important things we will do. The majority of peanut in the V-C region are planted in conventional tillage systems and it is always a good practice to incorporate some herbicide prior to planting. This takes time, especially to incorporate uniformly, but in some springs this investment will be well worth the effort. At least some weed control will be obtained with incorporated herbicides even under dry conditions. A DNA herbicide (herbicides that contain pendimethalin or ethalfluralin) is a very good start for pigweed control and control of several other broadleaf weeds and annual grasses (especially Texas millet, also referred to as Texas panicum.) Chloroacetamide herbicides (products that contain metolachlor, acetochlor, or dimethenamid) can be incorporated but for some of these make sure the rate matches the soil texture/organic matter content. For some growers the time required to till and incorporated is simply not there. For those in conservation tillage, the ability to incorporate is challenging. In these cases it is a good idea to apply residual herbicides (the chloroacetamide herbicides) at several timings early in the year. This increases the likelihood of catching a rain for activation. Preplant, preemergence, at cracking, and early postemergence timings (within the first few weeks after peanut emergence) are good times to get herbicides with residual activity in the field. A new chloroacetamide herbicide, Zidua, fits in the postemergence timings quite well. Of course, if some weeds are up applying these herbicides with an appropriate contact herbicide (paraquat, for example) is critical. The extra money spent early in the season on weed management will often pay for itself through protection of peanut from weed interference and by reducing the need for “extra” postemergence sprays later in the season. As these applications are being made it is generally okay to apply acephate to control thrips along with these herbicides if systemic insecticides applied in the seed furrow did not perform well. Be careful not to apply paraquat if peanut injury from thrips is excessive. In most instances if a systemic insecticide was applied in the seed furrow at planting there will be enough protection from thrips to allow paraquat to be applied with no concern over excessive injury. But if there is considerable thrips injury applying paraquat will reduce yields. From a resistance management standpoint, the herbicides I have focused on here have held up quite well in terms of evolved resistance in weeds. Although the DNAs and chloroacetamide herbicides do not have significant postemergence activity, and paraquat (with Basagran) needs to be applied when weeds are small, these herbicides also serve as good tools to reduce selection pressure on ALS inhibitors (imazapic and diclosulam) and PPO inhibitors (acifluorfen, flumioxazin, and lactofen).