By Irene Shonle, CSU Extension in Gilpin County
Three out of my many houseplants each have mild-moderate infestations of a different insect. My lemon verbena has spider mites, my Amazon lily has mealy bugs, and my Bay Laurel has scale. Even though I inspected them when I bought them, it became evident in each case that the bugs were hiding in not-very-visible nooks and crannies. And given that it wasn't that easy to find these plants, I couldn't do the sensible thing and throw them out.
While I’ve mostly kept the insect populations in check with diligent applications of neem oil spray and the occasional shower/water spray, I have never succeeded in eliminating them entirely. I have been so frustrated that there have been times when I have sworn to get rid of the insects even if I kill the plant doing it -- they STILL come back! If I’m a bit negligent, the populations explode, and I have to be careful they don’t spread to my other plants (but so far, I’ve been able to quash any incipient populations on new plants).
Frankly, I was getting sick of it!
So, the other day, I was in the shower, and inadvertently drowned a spider. I was astonished at how quickly it died – I had every intention of rescuing it after I dried off, but despite the fact that it was at the edge of the shower and that I take quick showers (mountain wells, you know), it still was dead when I shut the water off. Somehow, my pre-caffeine mind made the connection between drowning spiders and drowning scales. After all, spraying with horticultural oils works by suffocation. I decided to submerge my whole Bay Laurel in water for a while to drown the scale insects. Since I was at the point of heaving the plant anyway, it wouldn’t be a big deal if my plant didn't survive.
I got a 5 gallon bucket, taped a plastic bag around the pot to keep the soil in, and turned in upside down in the water, submerging the entire foliage and trunk. I left it for 24 hours, but I suspect that was overkill. Remember - I was frustrated!
|Drowned scale on bay laurel -- the whitish residue is from the dead scale.|
Over the next couple of days, it became obvious that all the scale had died. The insects scraped off easily, or even showed signs of rot (see whitish residue on picture above). Yippee! It’s been about a month and a half, and I still see no signs of new scale or the tell-tale sticky honey dew they leave behind. However, I probably should have changed the potting soil (or submerged it as well), in case there were any crawlers in the soil. If they come back, that’s what I’ll do.
After the fact, I checked to see if others recommend it, and did find it in a few places here and there, but it's surprisingly seldom mentioned, especially within Extension (for example, horticultural oils and syringing are recommended here amongst other methods, but not submerging: http://www.ext.colostate.edu/pubs/insect/05595.html. Obviously, this would only work for plants small enough to submerge, and succulents might not appreciate it. Otherwise, it seems like a cheap and non-toxic method to try.
|Here goes my lemon verbena - next up is the Amazon lily!|