Soap Bath for Pests
Homemade insecticidal soap using castile soap is a common form of soft-bodied insect control. It provides an inexpensive and eco-friendly option for dealing with pests. The fatty acids within the mixture break down the soft-bodied insect membranes, where they die by hydration.
Aphids, mealybugs, spider mites, thrips and whiteflies.
Soaking vs Spraying:
The usual method of castile insecticidal soap application is by spraying the tops and undersides of foliage with the mixture. For bushy plants or those with deep crevices, spraying may not target pests that are hidden in these hard-to-reach spots. The soil could also harbour eggs. So, sometimes a soak is needed.
I want to stress that a full plant soak is something I rarely do because it’s intense (I usually reserve it for when I bring outdoor plants back indoors). It’s my last resort. So I wanted to note a few additional things:
❶ Drying out: is absolutely essential for a drenched plant: good air circulation, a warm room, and bright indirect light for multiple days. Go as far as timing your soak to the weather forecast. Tip: run a gentle fan over the plants if you don't have adequate light.
❷ No direct sun: on the leaves on the first day as it’ll cause burns from the soap.
❸ Loose soil: yes! The soil gets loose. Just scoop it back up, or repot with the fresh stuff. Your perlite will float absolutely. Everywhere. Discard debris.
❹ Water usage: as often as I can, I re-used old bath water for this (“grey water”, devoid of body soaps) to be more environmental. One reason I don’t do full soaks often is that it takes a lot of water, be mindful of this! Pack the tub with plants, or use a smaller bucket. Make it worth it.
❺ Test: Not all plants can handle soap soaking; those with fuzzy-leaves for example are sensitive. Test the spray first in a discreet area before soaking the entire plant.
The process is very simple: fill a tub, sink or bucket with the mixture. Soak, then rinse.
〰️ Ratio: diluted 1 tsp soap : 1 cup water (I use Dr. Bronner's "Unscented")
〰️ Time: 15-20 minute soak
〰️ Rinse: a quick shower to rinse residue and clear debris afterwards
That's it! After your initial soak, you'd want to keep an eye on your plants. If you continue to see pests, spot-treat with a spray. Often, pests are persistent and need repeat application so don't expect this to be a "one-time-fix". Thrips are particularly tough to get rid of as they lay eggs within the plant tissue, which may not be affected by the initial soak so you'll have to treat them as they hatch. It pays off to be diligent.