CONTROLLING ANNUAL GRASSY WEEDS

It that time of year I get call about various annual grassy weeds, including Foxtail, Crabgrass, Rescue Brome grass, Barnyard grass, Goose grass and Sand bur. These can be grouped in to two groups, winter annual grasses and summer annual grassy weeds. Winter annual grasses germinate in the late fall grow through the winter into the spring set seed then die. Summer annual grass do the same but germinate in the spring grow through the summer set seed and die. Winter annual grassy weeds include annual blue grass, rescue brome grass. Most people don’t worry about annual blue grass it is small and a weak competitor so it gets crowed out quickly as the spring warms up, warm turf breaks dormancy. Rescue brome grass is one that was classified as an annual at one time, and behaves like that in more northern latitudes; here it has been reclassified as a short lived perennial or maybe a biannual. At any rate in Eddy County it lives for more than one season. This is the robust green grass in the winter that set a sleeved seed head about now to mid-June. Like all weed the best time to control it is when it is small in late fall and winter. Controls the existing plants by preventing it from setting seed, application of a post-emergent herbicide and a pre-emergent herbicide in the fall. Summer annual weeds include barnyard grass, goose grass, crabgrass, fox tail and sand bur. Seed germination begins in early to mid-spring, when soil temperatures have risen to 55° - 60° F. for about a week. In Eddy County; this is typically late-March through mid-April. Seeds continue to germinate in the summer, and plants are killed by the first frost. Control with a pre-emergent herbicide applied prior to seed germination, and if there is a large seed production from the year before, a second pre-emergent may be helpful 90 to 100 days later. Sand bur will germinate in the middle of winter if the temperature gets warm enough so a post emergent herbicide may be tank mixed with the pre-emergent. Eddy County is un-lucky enough to have four species of fox tail, Green, Giant, Yellow, and Foxtail Barley. They all germinate at different times. They germinate in that order in the spring to late summer. Foxtail Barley is almost a winter annual grass because it germinates in late summer and will stay green into the early spring. If this is your problem a pre-emergent has to be applied every 90 days from spring to fall. Most annual grassy weed are not real good comparators with a health warm season turf grass in the summer but winter annual may take advantage of warm season tur going dormant in the fall. The best weed control is proper turf grass care, good irrigation, fertilizer practices go a long way in keeping out invasive weeds and a much more attractive lawn. Before you rush out to buy an arsenal of chemicals, read and remember this checklist! 1. Identify the weed; 2. Hand pull new weed growth before seeds are formed or clip seed heads and dispose before they are mature; 3. Correct growing conditions to favor desirable turf; 4. Understand common herbicide terms, next week article will be on this; 5. Read herbicide labels, chemical names are found under “Active Ingredients”. 6. Spot treat to limit the amount of pesticides introduced into the environment for post emergent herbicides; 7. Use and integrated weed management program that includes cultural, and mechanical practices; 8. Always remember to read and follow the label directions of any herbicide product you are using! 9. It is perfectly acceptable to have a tolerable level of weeds in a home lawn - really! In this part of the world if it is green a pleasing to the eye it may not be all that bad. Eddy County Extension Service, New Mexico State University is an equal opportunity/affirmative action employer and educator. All programs are available to everyone regardless of race, color, religion, sex, age, handicap, or national origin. New Mexico State University, U.S. Department of Agriculture, and the Eddy County Government Cooperating.