How to Make a Weed Dabber

The tool that I am going to tell you about is for using herbicides such as RoundUp. The biggest mistakes that people make when using non-selective herbicides like RoundUp is overspray getting the herbicide on plants that they did not intend to spray, and over applying the product. If you spray to the point of run off, you are applying way too much.

The weed dabber is a tool used for spot treating weeds without getting the herbicide on other plants.
Start by going to your hardware store and buying a piece of 1- 1/2” PVC pipe. You only need a piece 30” long, but they might make you buy a 10' section. It's pretty cheap though. You'll need a plastic PVC cap for one end of the pipe, and on the other end you'll need an adapter to convert the PVC pipe to a standard pipe thread. You'll have to let the clerk at the hardware store help you find the best combination of fittings to use. What you need to do is to get the PVC pipe reduced down to a male garden hose type fitting. Hardware stores sell brass fittings that convert standard pipe thread to the same thread used on garden hoses.
Probably what you'll end up with is an adapter that will convert the 1-1/2” PVC to 3/4” male pipe. Then an adapter to convert the 3/4” male pipe to a male garden house fitting. They also make a cap that you can install on the end of a garden hose, you'll need one of those. This cap must have a rubber garden hose washer in it so it seals properly.
The PVC fittings have to be glued on so you'll have to pick up some PVC pipe glue and cleaner. You have to use the cleaner to remove the film and gloss from the PVC pipe and fittings before you glue them. Once you have them cleaned, just apply a coating of glue to both the pipe and the fitting, slide the fitting on and twist it at the same time. Hold the fitting tight for 60 seconds and it will be glued tightly.
Cut a piece of pipe 30” long and glue the pipe cap on one end, and the PVC to pipe thread adapter on the other end. Apply a small amount of pipe dope or Teflon tape to the threads of the adapter, and screw the male garden house fitting onto the adapter. Screw the garden hose cap to the male garden hose fitting.
Now back to the end of the pipe that you glued the pipe cap to. Drill a very small hole right in the middle of the pipe cap. You might have to experiment a little with the size of the hole you need, but make sure you start with a very small hole. I'd start with 1/16”. Cut a piece of regular household sponge in a square about 1-1/2” square. What you are going to do is place this sponge over the small hole you drilled in the pipe cap, and secure it there by covering it with a piece of lightweight screen or mesh cloth. Maybe even a piece of an onion bag. You can secure the mesh to the PVC pipe with a hose clamp, or electrical tape.
Remove the garden hose cap from the other end of the PVC pipe, and fill the pipe with pre-mixed (ready to use) RoundUp. Replace the garden hose cap and you have yourself a weed dabber. The RoundUp will seep out the hole in the end of the pipe cap and be absorbed by the sponge. As long as the garden hose cap is tight the vacuum in the pipe will keep the herbicide from running out too fast. Once the sponge is damp, you can start dabbing weeds. Remember, you only want the weeds damp and not dripping wet. As long as you are leaving some RoundUp on the weeds as you dab them, the herbicide should kill them.
Depending on the temperatures, it could take a week or so before you can see the effects of the herbicide. If the sponge gets too dry you can loosen the cap a little to release the vacuum and more herbicide will be released onto the sponge. Or you can simply turn the tool upside down and that should let some air into the chamber, thus releasing the vacuum. As always, read the label and follow the directions on the herbicide package.