David M. Kopec, Extension Turfgrass Specialist
Many homeowners are concerned about weeds which "were not in my yard this spring," but now have become an integral part of the lawn. By late August and early September most summer annual weeds are running full steam ahead, are at full growth and are even flowering. These annual weeds include the following.
GRASSES BROAD LEAVES
southwest cupgrass spurges
indian rice grass khakiweed (perennial and annual habit)
crabgrass winter mustards (in protected areas)
goosegrass horse purslane
crowsfoot goats head (open/border areas)
Most of these weeds are at maturity and at the end of their life cycle. Although well established, they are "on the way out." These weeds are much harder to control once they are mature and harder to control once they have flowered.
These grassy weeds can be controlled in lawns by using MSMA (e.g., Bueno -6-, etc.) However, there will be some discoloration. Kentucky bluegrass and fescue at the higher elevations can be damaged initially. At the lower elevations, bermuda can show some tip burn and color change, but it will grow back quickly. A directed spray (on the weeds only) will minimize the potential damage.
Broadleaf weeds are harder to control at this time. The general pallet of 2,4-D and 2,4-D like materials are available for home owners. Remember, buffalograss does not like 2,4-D. Beware that "weed-n-feed" products have different types of herbicides impregnated on them. They can be either pre-emergence or post emergence types. For late season control of emerged weeds, do not use a product that contains a pre-emergence weed control agent. Not only will it not work, but it will most likely affect the fall overseeding of bermudagrass or fall re-seeding at higher elevations.
Issued in furtherance of Cooperative Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, James A. Christenson, Director, Cooperative Extension, College of Agriculture & Life Sciences, The University of Arizona. The University of Arizona is an equal opportunity, affirmative action institution. The University does not discriminate on the basis of race, color, religion, sex, national origin, age, disability, veteran status, or sexual orientation in its programs and activities.