November 16, 2007

Fall conditions have been great for pennycress, mustards, henbit and downy brome to get a start in alfalfa. Check your fields and you might find lots of small henbit plants or mustard rosettes or short grass seedlings of downy brome. This density and robust start suggest heavy weed growth next spring. If left uncontrolled these winter annuals could grow rapidly, reducing alfalfa yield, thinning stands and lowering forage quality.

To avoid problems next spring, spray fields now before soils freeze. Probably the three best herbicides to use now are Sencor, Sinbar and Velpar. All three do an excellent job of controlling pennycress, mustards and downy brome. Raptor may be a better choice if henbit is your biggest problem.

Fall control is often recommended because spring spraying must occur before alfalfa greens up or plants would be injured. Usually, there are only a few days in spring where alfalfa is dormant, weeds are actively growing, and it's not too wet or windy. Often fields are sprayed late and alfalfa is injured or they don't get sprayed at all.

Bruce Anderson
Extension Forage Specialist