Cannabis Chronicles

Before finishing our current coverage of insecticidal soaps, we thought we’d pass along some information we originally found at LivingWithBugs.com, a website created and run by an individual with a PhD in Entomology.  It seems we can’t help ourselves from calling Jack DeAngelis, a “bug doctor”.

Dr DeAngelis has some great advice on how to determine if an insecticidal soap is oxidized and therefore no longer suitable for use, read on to learn about his “jar test”, then we’ll come back with a few final comments of our own . . .

Summary: Insecticidal soap can be used as a safe and inexpensive alternative to garden insecticides in many pest management situations. Old, oxidized soap can damage your plants but a simple test is available.
Jack DeAngelis, PhD
OSU Ext. Entomologist (ret.)

What is insecticidal soap?

Insecticidal soap is a very safe and effective alternative to conventional insecticides in many garden situations. It is used mainly for soft bodied pests like aphids, thrips, scale crawlers and spider mites. It is also a very effective leaf wash to remove aphid honeydew, sooty mold and other leaf debris.

All soaps are made from the “fatty-acid” portion of either plant or animal oils. Chemically, soaps are salts of the fatty acid portion of fats and oils. Insecticidal soap is simply a highly refined version of liquid soap. However, do not jump to the conclusion that you can substitute household soaps, or homemade soaps, for genuine insecticidal soap. Doing so will damage your plants and probably won’t be very effective.

Insecticidal soaps will not harm beneficial species and are generally very safe to use. Soap concentrates are less expensive in the long run, and easier to store, than “ready-to-use” packaging. However, always do a “jar test” (above, right) to be certain that the concentrate has not spoiled

Do a “jar test”!

As soap concentrate ages it oxidizes which causes it to turn dark brown. Old, oxidized soap has the potential to burn foliage. Solutions made from old soap concentrate often exhibit a white precipitate (jar on right, above) when mixed with water and should be discarded. Old soap concentrate can be used as a cleaner like ordinary liquid soap just don’t put it on your plants!

Mix the soap concentrate as a 1-2% solution and pour into a jar. A 1-2% solution is about 1-2 oz. of concentrate in 1 gallon of water (always follow label instructions). The precipitate will form almost immediately if the concentrate has gone bad.

Fresh 2% soap solution (left). The slight milky color is normal. If the solution turns cloudy, or a white precipitate forms (right), don’t use it.

Using insecticidal soap in your garden

Insecticidal soap is generally used as a 1-2% solution (1-2 oz. per gallon). Mix soap concentrate in a clean 1 gallon sprayer. Plan to treat in the morning of a warm day when the plants will be able to dry before evening. Spray plants with a coarse spray of plain water from the garden hose. Next, thoroughly spray plants with soap solution covering all surfaces. Finally, wait 30 minutes then wash soap off with water. The last step will prevent soap solution from damaging tender leaf tissue.

Dr DeAngelis finishes his article on insecticidal soaps by encouraging users to get a fresh supply every year, an obvious way to help avoid using oxidized soaps.  He also mentions that any soap concentrate that’s left at the end of the season can be used to clean greenhouses and spray tanks, making leftover insecticidal soap a good candidate for use in a periodic cleanings of indoor grow rooms as well.

We’d like to add one caveat of our own concerning Dr DeAngelis’ statement that insecticidal soaps will not harm beneficial species.  We believe this statement is based around the fact that insecticidal soaps work on contact, and are not systemic insecticides, in other words it’s necessary to literally spray pests with the soap solution for it to be effective.

Insecticidal soaps aren’t necessarily discriminating in the species they effect, but rather they are generally safe because they do not persist and only effect bugs they contact.  It’s probably worth noting that beneficial species that are literally “caught in the line of fire” and sprayed with an insecticidal soap will likely suffer a similar fate as the intended pests.