DATE: 2/18/05

CONTACT: Clemson Extension Home & Garden Information Center, 1-888-656-9988

WRITER: Chuck Burgess

CHEMICAL CONTROL OF BROADLEAF WEEDS

CLEMSON – Because broadleaf weeds, such as dandelion, are not grass-like, they really stand out in the lawn. In the quest to control these weeds, people scour the shelves of retail establishments in the spring but many come away confused and unsure of their purchase. Below is a review of what you might find this spring.

For years, manufacturers of broadleaf weed control products have combined several herbicides in one product which is why you hear the term three-way. These have commonly included 2,4-D, mecoprop, and dicamba, which are common names of the herbicide. These products are combined because together they control more weeds than any one of them would alone. For example, MCPP provides better control of clover and chickweed than does 2,4-D, and dicamba provides better control of ground ivy.

Many products are available in liquid and granular formulations with these three ingredients. Included are Ortho Weed-B-Gon Weed Killer For Lawns, Southern Ag Lawn Weed Killer with Trimec, Ace Spot Weed Killer, Ortho Basic Solutions Lawn Weed Killer, and Bayer Advanced Southern Weed Killer for Lawns. One reason for the popularity of these products is that most of these can be applied to all of the commonly grown turfgrasses in South Carolina including tall fescue, bermuda, centipede, zoysia, and St. Augustine.

Some of the confusion with products can be attributed to label changes. A good example is Ortho’s new Weed-B-Gon Max Weed Killer for Lawns Concentrate. The active ingredients in this product are different from Weed-B-Gon Weed Killer for Lawns. It contains MCPA, triclopyr, and dicamba and is not labeled for use on centipede or St. Augustine lawns. However, the Ready to Use and Pull ‘n Spray versions of Weed-B-Gon Max contain MCPP, 2,4-D, and dicamba and with the exception of Floratam St. Augustine are labeled for use on fescue, zoysia, bermuda, centipede, and St. Augustine.

Many retailers will also offer Image. Image can safely be applied to warm season grasses, but not fescue. It will not control as many broadleaf weeds as a three-way product but has the added benefit of controlling nutsedge. If your warm season lawn is riddled with dollarweed, sandbur, wild garlic, or several others, Image may be a good choice.

Atrazine (Hi-Yield Atrazine) is labeled for St. Augustine and centipede. It will control some broadleaf weeds as well as some grassy weeds such as crabgrass and annual bluegrass. Because it is also a preemergence herbicide, treated areas cannot be reseeded for four to six months.

Ortho recently introduced Weed-B-Gon Chickweed, Clover, and Oxalis Killer for Lawns. The active ingredient, triclopyr, is a relatively new herbicide and is supposedly very effective against ground ivy, oxalis and a few other broadleaf weeds. This product is labeled for zoysia and fescue lawns only.

Basagran T/O is a broadleaf weed killer that has the additional advantage of controlling nutsedge. As with most herbicides, this product can harm ornamental plants, but it can be applied over the top of some ground covers. Listed on the label are ajuga, English ivy, liriope, pachysandra and others

The importance of reading the label cannot be overemphasized. For example, you will find that because centipede and St. Augustine are sensitive to 2,4-D, the labels of some products containing 2,4-D will have different mixing rates and spot spraying may be suggested. Also, the Southern Ag Lawn Weed Killer with Trimec label does not mention zoysia. A product is legally applied only to the types of turf on the label. Lastly, there may be variety exceptions. For example, you cannot apply Bayer Advanced Southern Weed Killer for Lawns to Floratam St. Augustine.

The bottom line is that if weeds pop up and cultural controls are not controlling them, there should be a product appropriate to your situation. Be sure to look for your weeds and your turf on the label and to heed all other precautions.

For answers to your gardening, pest and food safety questions, visit the Clemson Extension Home & Garden Information Center website at http://hgic.clemson.edu or call us toll-free at 1-888-656-9988.

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