By Webb Callicutt
Delta County Weed Program
The lovely green vegetation that can now be seen after the snowmelt will be a problem by early April. These plants are the first of the 2012 weed crop.
These early emerging plants are mostly winter annuals. Winter annuals will germinate early fall through late winter, depending primarily on available moisture. The winter annual will complete its life cycle by early to late spring. Broadleaf winter annuals in the area are primarily in the mustard family. These include flixweed, tansy mustard, blue or purple mustard, shepardspurse, clasping pepperweed, tumble mustard, yellow alyssum, and black mustard. Grassy winter annuals include cheatgrass, jointed goatgrass, and hare barley. The early warmth this year is also promoting early whitetop growth.
To control winter annuals with herbicides, the weeds need to be treated before they exceed approximately three inches tall. This will require scouting for winter annuals as early as February and treating no later than March in alfalfa, grass pastures and grass hay fields. Once winter annuals exceed that three inches in height, produce flowers and/or seed, the herbicides labeled for use are fairly ineffective.
Mowing will not be effective. The plants merely set seeds at lower heights. Tilling or chopping below the root level can be effective. Herbicide treatments for non-agricultural settings (driveways, disturbed areas, bare ground) are as follows: Mustards may be treated with 2-4D or glyphosphate (Roundup). The grassy weeds like cheatgrass or hare barley require glyphosphate. Remember that glyposphate is non-selective and kills all vegetation it contacts. Do not use in a lawn. The 2-4D products are selective and will not kill grass. Always read the label on any herbicide product before using.