Yes, you can use Ethofumesate 4SC Select Selective Herbicide in the fall at the same time as you are overseeding your fescue.
Ethofumesate 4SC Select Selective Herbicide states to use 1.59-3.18 pints per acre or 0.78-1.17 per 1k square feet. In order to determine how much water to use, you will need to calibrate your sprayer. Here is a video that will assist with that. You may also find complete rates for poa annua on page 20 of the label A surfactant is only added when tank mixing with fertilizers.
Please note: Ethofumesate 4SC Select Selective Herbicide is not intended for residential use.
No you can not apply Ethofumesate 4SC Select Selective Herbicide at the time of seeding. The label states to wait 6-8 weeks after emergence . Please find complete label instructions here.You can use Tenacity at the time of seeding.
Ethofumesate 4SC Select Selective Herbicide is not labeled to treat Poa Trivialis. Acclaim Extra Herbicide is labeled to control Poa Trivialis. Please see the label for full application instructions and to ensure your turf is tolerant.
Per the label, for preemergence and/or postemergence control of susceptible weeds, apply Ethofumesate 4SC Select Selective Herbicide prior to weed emergence or at the earliest possible weed growth stage, but not later than the 4-leaf stage. For best results, apply to moist soils. Please note Ethofumesate 4SC Select Selective Herbicide is not intended for residential use.
Per the label, Ethofumesate 4SC Select Selective Herbicide can be applied to residential lawns, by licensed or certified applicators.