The first rope wick applicators for Roundup herbicide in Mid-South weed control simply used some nylon rope, 4-inch or so PVC pipe, some rubber grommets and a way to mount it on the tractor or other means to push it. You could buy them or make them yourself.
For a while the leading edge research was on what kind of rope was the best for wicking, how long the ropes should be, how much should they be overlapped, and what should the Roundup concentration be?
I still remember the best rope was one called “pistachio” from a company called Gulf Rope and Cordage. The ends of the short overlapped ropes just stuck over in the PVC pipe filled with anywhere from a 33 to 50 percent solution of Roundup.
The key was to keep the ropes as wet as possible without a lot of dripping. It was also best to wipe in two directions — down and back on the same set of rows. This was good stuff and you saw a lot of creativity on mounting systems, double pipes, etc. They actually worked — to an extent.
The weed had to be taller than the crop, which meant yield loss had already occurred and several applications were required during the growing season.
The rope wick applicator concept led to a flurry of development and entrepreneurship in the area of wiping devices. We saw different types of rope wicks, sponge wipers and several types of carpet wipers and rollers. Some of them used a wicking concept and with others the Roundup solution was either dripped or sprayed onto the wiping device.
I remember a johnsongrass demonstration with six or eight of the different devices or wiping concepts many years ago. About the time we were looking for the best way to wipe Roundup for johnsongrass control, Poast and Fusilade came along in the early 1980s, and they could be sprayed over the top of cotton and soybeans (and we preached yet another funeral for johnsongrass). As a result all of the wiping technology for johnsongrass went by the wayside quickly.
Here we are going into 2012 and what we are hearing talked about again is — carpet roller applicators for glyphosate-resistant pigweed control. Here is where history can again be a good teacher.
When the various wiper applicators were being used for johnsongrass control, we were also in the Palmer pigweed fight the first time. The pigweed problem was more isolated then, but to the folks who had the problem, it was bad. All sorts of concoctions were tried in different wiping devices for pigweed control, but there were a lot of problems.
As susceptible as the pigweeds were then to Roundup, one would have thought it would have worked well in a wiper, but it did not. Some even added things like 2,4-D to the Roundup with no better result. Even with susceptible pigweeds in those days, part of the problem was getting the pigweeds enough taller than the soybeans to wipe enough herbicide onto them.
With johnsongrass you were wiping mostly leaves whereas with pigweed a lot of the herbicide is wiped on stems. Another problem is getting enough height difference between the weed and crop which is a catch 22. The longer the pigweed stays in the field to get taller, the more it reduces yield — even if you kill it. Therefore the bigger you let it get, the more yield you have lost.
Another problem wiping pigweeds is they simply overpower the treatment. That is you get so many pigweeds you can not wipe enough of anything on any of them. I have not written this to say the research now being done on wiping pigweeds again has no merit in any crop. However it is simply an older technology that if we have to go back to it, we are truly moving in the wrong direction. It is another concept that did not work well then and will not work well in most situations now.