Thinking about using a grass herbicide such as Select Max (clethodim) for pre-plant burndown? Have you seen any data suggesting this is a wise decision?
Interestingly, there is a lot of buzz about using grass
herbicides to burndown small grain cover crops and annual ryegrass because of the glyphosate price/shortage issues. Most of the
conversations also include tank-mixing the grass herbicide with either 2,4-D or
dicamba and applying as a March/April burndown.
Prior to making the effort and spending a significant amount
of money, it might be wise to review the grass herbicide label itself for the
level of control the product potentially offers.
Additionally, you may find value in the data we generated in 2021
(Figure 1). A couple of important clarification notes regarding this research are
as follows: 1) the application was made
on February 28 (2021) when conditions were cooler; 2) we did not tank-mix with dicamba
or 2,4-D, which could negatively influence grass control (i.e.
antagonism); and 3) this is data from only one location.
When considering your burndown treatment for 2022, a significant
amount of research suggests that the value of glyphosate may be at its maximum
for the pre-plant burndown application if grasses are present in the field.
Thus, we would encourage staying with the burndown program that you know is
successful if anyway feasible. Planting into weed-free fields, with the potential lack of
some postemergence herbicides this year, will be extremely important.
Once grassy weeds, as well as other broadleaf weeds are
mature, Gramoxone (paraquat) + diuron + COC (cotton) or Gramoxone + Valor +
2,4-D amine + COC (peanut) are fantastic options (small grains must have seed
heads). It appears, at least currently, that most of our winter weeds are
maturing at a faster rate than in the past so these treatments may be very timely
options.
Tillage is also a very effective option as you well know,
just be cognizant implementing steps to avoid soil erosion.
Another possible negative. If Select Max is used prior to planting field corn, the plant-back restriction would be 30 days. The rate needed for burndown control (marginal) is much higher than the rate needed for volunteer corn control thus warrants a longer restriction.
