Yes, you can mix diatomaceous earth water spray at a ratio of 4 tablespoons per gallon. The water serves as a carrier to help DE reach places where dry powder cannot stick. Once the water dries, the DE coating works just like dry dust would.
I use this wet diatomaceous earth method on vertical surfaces all the time. Greenhouse walls, tree trunks, and fence posts hold wet DE far better than dry powder. The spray sticks in place while it dries and leaves a thin protective layer behind.
The key to good DE spray application is stirring your mix often. DE settles fast in water and sinks to the bottom of your sprayer in minutes. Shake or stir your container every minute or so to keep the DE spread through the water.
Getting your diatomaceous earth spray ratio right matters for coverage. Mix 4 tablespoons (about 60ml) of DE into each gallon (3.8L) of water. This gives you enough coverage without clogging your sprayer nozzle. A pump sprayer works better than a trigger bottle for larger jobs.
I tested this method on the undersides of my squash leaves where dry dusting always made a mess. The spray went on clean and dried to a light white film within two hours. The beetles stopped coming around after that first coat dried.
The wet method works best in these situations. Use it on walls, posts, tree trunks, and hard-to-reach cracks. Spray into crevices where dry powder would just blow away. Coat the undersides of plant leaves where pests like to hide from view.
Dry dusting still beats spraying for flat ground barriers and raised bed edges. Dry DE starts working right away while wet DE needs hours to dry before it can kill bugs. Choose your method based on where you need the coverage to go.
Give your sprayed areas 2-4 hours to dry before you expect pest control to start. Hot sun speeds this up while shade and humidity slow it down. You can tell DE is dry when the white coating looks powdery again rather than damp.
Clean your sprayer right after use since dried DE can clog the nozzle and hose. Flush fresh water through the system and let it dry open. I learned this the hard way when a clogged sprayer cost me a full afternoon of cleaning work. Your sprayer will last much longer with this quick care routine.
Read the full article: Diatomaceous Earth Garden: Complete Guide
