As we reported last Friday, there appears to be a negative interaction of Echelon herbicide and urea (46-0-0) on tall fescue. This interaction showed up as injury on tall fescue. Echelon is a pre-package mix of prodiamine and sulfentrazone. Echelon has been tested in many university trials in recent years and, at the proper rate, turfgrass tolerance has not been an issue. However, when Echelone 4SC (sprayable Echelon) was mixed with 46-0-0, several lawn care operators have called to say they have observed injury on tall fescue. We followed these complaints up with a research trial at the Lake Wheeler Turfgrass Field Laboratory and we have confirmed that there was some injury on tall fescue.
The data we reported last Friday at 5 days after treatment can be seen in the following chart. Note that the most injury was found with sprayable Echelon with 46-0-0. Also note that the addition of Fe tended to act as a safener for this mixture.
This same test was evaluated this morning (May 9) and I can report that the fescue has almost totally recovered from this early phytotoxicity. The chart below shows fescue injury at 14 days after treatment.
There is still a minor amount of phytotoxicity that remains with the four-way combination of Echelon + 3-way + Urea + Fe. However, almost total recovery from Echelon + Urea has occurred between 5 days after treatment and 14 days after treatment.
It is important to keep this negative interaction in perspective. This interaction with Echelon 4SC and 46-0-0 did not kill tall fescue. It did not cause any thinning of the fescue stand. It can best be characterized as a temporary discoloration of tall fescue. This interaction has nothing to do with Echelon 4SC applied alone. It is also irrelevant to Ecehlon 2G since this granular formulation cannot be mixed with 46-0-0. Therefore, this interaction has nothing to do with Echelon 4SC use alone or Echelon 2G use.
|PLOT 102||PLOT 105||PLOT 112|
|Echelon (0.75 lb ai/a) + urea (0.5 lb N/M)||Echelon (0.75 lb ai/a) + urea (0.5 lb N/M) + Trimec Classic (3.5 pt/a) + 4-4-5 fertilizer with 6% Fe (2 fl oz/M)||Echelon (0.75 lb ai/a) + urea (0.5 lb N/M) + Trimec Classic (3.5 pt/a)|