Eptam (EPTC) 7E and 20G and Summer Fallow for Nutsedge Control (May 2, 2017)
Nutsedge is one of the most difficult to control weeds in Arizona and worldwide.
It is a perennial that spreads vegetatively with below ground tubers that can stay
viable for many years. Both yellow and purple nutsedge are common throughout Arizona.
Most of it is purple which is the more difficult to control of the two. There are
few herbicides that will completely control nutsedge and it is so prolific that
even fairly high levels of control last only one season. Most herbicides need to
be used for several consecutive years to keep this weed in check.
infestations get worse every year it can become beneficial to combine summer fallow
with chemical treatment to break the cycle and get the problem under control. One
of the most effective and economical treatments for nutsedge control is Eptam (EPTC)
combined with summer fallow. This technique can be highly effective but it can also
completely fail if proper application and cultural practices are not followed. It
was developed 25 years ago but is still often misunderstood. Both the 7E and 20G
formulations of Eptam are registered in Arizona although product for the 20G formulation
is not available this season. This formulation was registered in the mid 90’s and
our trials demonstrated that granules were the most efficient means of applying
this volatile herbicide. The 7E formulation was intercepted by the crop when used
in alfalfa and if chemigated (water run) the product was subject to volatilization
and poor distribution. Both formulations are effective although the 20G can be more
efficiently and uniformly applied. We have enough product for a few 5 to 10 acre
demonstration plots. If you are interested in working with us on this please contact
either myself (928-580-9902) or Marco Pena (928-782-5871). The following six principles
are important for this technique to be effective:
1) Both above ground shoots and
below ground tubers must be destroyed. Emerged shoots will provide nutrients for
the production of new below ground tubers. Viable below ground tubers will produce
new rhizomes, basal bulbs and above ground shoots. Tillage and some herbicides such
as glyphosate can be used to destroy above ground shoots. The Eptam fallow treatment
will destroy rhizomes as they attempt to reach the surface.
2) Eptam is one of the
most volatile herbicides available. It is lost in several ways including microbiological
and photochemical decomposition but the most common means of losing EPTC in the
irrigated southwest is by contact with water. It volatizes from irrigation water,
off of wet soil and is leached deep into the soil. It should be incorporated into
dry soil where it will remain active for a much longer period of time. It should
not be irrigated after application unless the objective is to move it down to contact
deep tubers or to remove it in preparation for the planting of a susceptible crop.
3) Eptam works on those parts of the nutsedge plant that are trying to grow (rhizomes
and shoots). It works best on stressed plants but will have no effect on nutlets
that are dormant. Enough moisture should be made available to stimulate nutsedge
growth but under stressed conditions. An irrigation may be necessary. Once the top
6 inches is dry the Eptam should be applied and incorporated.
4) A chemical tarp
is created with the surface application of Eptam that will prevent shoots and rhizomes
from reaching the surface. The surface should, therefore, be left as smooth as possible.
Any untreated areas or breaks in the surface from implements, wheels or even footprints
will allow shoots to emerge.
5) Eptam should not be applied too early (April or
May) because of possible degradation prior to the period of rapid nutsedge growth
or too late (August or September) because of decreasing growth and potential injury
to fall planted crops.
6) To avoid injury to following crops, irrigate at least
30 days prior to planting. The Eptam label specifies "Do not plant cotton or crops
not listed on the Eptam label for 90 days after application."
For questions or comments on any of the topics please contact Marco Pena at the Yuma Agricultural Center.
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