Ben Beale, Extension Educator, St. Mary’s County
The recent rains and numerous days of continuous wind has made it difficult to get herbicide applications made when needed. Ideally, we really like to wait until planting to spray, or have good confidence that the herbicide application will occur right after spraying. Sometimes it doesn’t work out, and what we like and what we get are two different things. With most weeds you will be ok, but Palmer and other resistant weeds can be another story. In our trials, residuals from pre-emergent herbicides provided 2-5 weeks of control for Palmer. That allows you to get in with an early post emergence product such as Reflex plus Glyphosate or Flexstar around 21 days after planting. This will help to keep the field clean until the beans canopy. If you take away a couple of those weeks, you can be in real trouble with weeds coming in before canopy closure.
One option is to review what residual was used early and if there is the potential to add something else in. Products such as Dual, Zidua or Metribuizin may be options. If you used a single active ingredient product like Valor SX (flumioxazin only) or Authority (sulfentrazone only), then it may be possible to add in another mode of action at planting. This option really depends on what herbicides were used ahead of planting and at what rates. You cannot double up on rates of most of the products. There are also restrictions on what can be applied in the same season. For instance, any of the Valor products require at least a 14 day interval before applying Dual. Take some time to read the label to determine what options are available. Another option is to switch to a Liberty Link system or Xtend system.
The most important thing will be to watch those fields closely and get the post-emergence product on before the Palmer gets out of hand. That may only be 2 weeks after planting. Also, be sure to kill any Palmer that may have emerged if it’s been two weeks since the last burndown application. It is critical to start the season clean.
