Another Way to Stick it to Weeds

Tony Koski, Extension Turf Specialist

Since it was first introduced in 1974, Roundup (glyphosate) has always been sprayed on weeds. Because it is largely non-selective (will kill or harm any plant that is sprayed) in what it controls, using Roundup and its generic counterparts near desirable plants has to be done carefully to avoid unintended injury. The introduction of Roundup Precision Gel Weed and Grass Killer potentially makes it easier to apply glyphosate to individual weeds – without the concern of overspray, wind drift, and other application errors that could harm desirable plants. But a question we have, as with all new technology, is: does it work?

The application process reminds one of using a gel deodorant stick. A button on the bottom of the stick is clicked until the gel (containing a 1% concentration of glyphosate) is extruded through holes on the top of the stick. You then apply the gel by wiping the leaves of the weed. Sounds easy, right? What I

found, however, was that – to get a decent application of herbicide to a weed’s leaf surface – you have to support the leaf with your other hand while applying the gel. Of course, a rubber glove should be worn to avoid wiping your hand with the gel in the process. (Gloves should ALWAYS be worn when using any pesticides, whether natural/organic or synthetic types).

Because glyphosate is a systemic herbicide, complete leaf coverage isn’t essential to get good weed control. With the gel, you get streaks of gel on the leaf surface – which should be sufficient to control the weed. I tried this on some plantain growing in a groundcover bed outside of my office. The series of photos

shows the progressive death of the plantain. While plantain is admittedly one of the easiest landscape weeds to kill, the Roundup Gel worked well on this weed. For those of you expecting “instant gratification” weed control, you will have to be patient with this product. In the case of this plantain, it took about 16 days from application to death. I will next test this on quackgrass growing in juniper beds and perennial beds, which could be an excellent use for this product.

Roundup Gel applied on 23 June

Injury appears the next day thanks to the pelargonic acid that is also in the
gel stick; complete leaf coverage (I did try!) would have burned the leaves
down more quickly.

Complete death is achieved after about 2 weeks