What's best timing for wheat herbicides? I am often asked when it is best to apply the various herbicides for wheat. For ryegrass control, Hoelon and Achieve are best applied in the fall. In our research plots, we have had the best results with applications made from mid-November through mid-December.
The optimum timing will depend upon the planting date and upon the emergence date of the ryegrass. If the wheat was planted very early and the ryegrass is getting large in the fall, mid-November to early-December applications work well. On wheat planted in October and early November, the early-December to mid-December applications seem to be the best compromise between having ryegrass small enough to kill and spraying late enough to prevent much re-infestation.
On both susceptible ryegrass (where both Hoelon and Achieve work well) and Hoelon-resistant ryegrass (where both fail), we don't see much difference between Hoelon and Achieve applied in the fall to small ryegrass. As the susceptible biotypes of ryegrass get larger, Hoelon outperforms Achieve in our research.
We have seen no consistent benefit to adding any type of surfactant or oil to Hoelon. Supercharge adjuvant is specifically recommended for Achieve.
With Hoelon, rates down to 1.33 pints per acre have performed well in the fall. If the ryegrass is three-leaf or larger (it has grown fast this fall), raise the rate to 2 pints per acre.
With Achieve, use the rate of 0.24 pound active ingredient per acre (0.6 pound of 40 DG).
Cheat Cheat has been an extremely elusive weed for us in our research plots. We chase it all over the state and fail to get a good infestation in our plots. If you have it and want to control it, a fall application of Sencor is the only way. There are two ways to go in the fall. A reduced rate of Sencor - 2 to 3 ounces per acre (use 3 ounces) - can be applied when the plants have two leaves and 1-inch secondary roots. The other way to go is a 5- to 10-ounces per acre rate of Sencor DF after the wheat has developed three tillers and four secondary roots at least 2 inches long.
With either method, make sure you have a variety that will tolerate Sencor. Your county agent has a list of those.
In our limited experience of getting cheat up in our plots, I like the low rate applied early better than the higher rate applied later. Cheat gets too large to kill in a hurry, and for the most part, spring applications are a waste of time.
Garlic We get some calls about applying Harmony Extra in the fall for garlic control. We have done a lot of comparisons between fall, spring and split (fall-spring) applications of Harmony Extra. A single treatment in the spring has been better than a single fall treatment and about as good as a split.
The exception might be in no-till wheat where a burndown herbicide was not used and the garlic is extremely large in the fall. In that case, a split application might be better.
A lot of Finesse was going to be used at wheat planting. It is good on ryegrass as a pre-emerge and very good on garlic and a lot of the broadleaf junk weeds. If a lot was used, a lot likely has not had rainfall for activation. Watch it closely when it is activated and be ready to back it up if necessary. It is an excellent pre-emergence herbicide but pre-emergence herbicides don't usually work if it doesn't rain within a week or so after application.