ISSUE 13 July 26, 2001
ANNUAL GRASSY WEEDS MAKING AN EARLY SHOWING IN MOST LAWNS
With the extended, recent hot weather, the growth cycle of many of the annual grassy weeds has been accelerated. This includes crabgrass, foxtails, barnyard grass and others. Questions have been coming in about what to do - spray them with what? My answer typically is, "wait and let Mother Nature do the work for you!" This simply means that within 60 days we will have a killing frost that will take out the annual grasses that are so obnoxious in the lawns right now.
I suggest this because I believe that herbicide use should be limited whenever possible. Applying a post-emergence herbicide right now would kill off the plants, but their seeds would still remain available for germinating next spring, when a pre-emergence herbicide should be applied. Why not simply make the pre-emergence application when the forsythia are finishing bloom in your community? There are plenty on the market that are very effective – more so than most post-emergence, with little to no collateral effect on the desirable grasses. Since turfgrass in lawns is not an economic crop that needs to be harvested, the only problem is aesthetic, not economic.
A word or two about a new product from Riverdale for controlling weeds: Millennium Ultra Plus. It is the latest in a new generation of herbicides and is highly effective against controlling many broadleaf and grassy weeds. The active ingredients are 2,4-D, Dicamba, Clopyralid, and MSMA. This formulation will be murder on crabgrass, clover, nutsedge, broad-leaf plantain, and many others, but it will not control quackgrass. Quackgrass is a tough perennial that persists in most lawns, and does not have any registered herbicide for selective control. At this point, if quackgrass is a problem, either use Roundup for spot control, kill everything off and start all over again, or simply live with it.
Horticulturist and Turfgrass Specialist
Department of Plant Science