I've got two kalanchoes that have scale bugs on them. Initially, I tried spraying them with neem oil, which seemed to reduce the population but never eliminated them. One person I spoke with said that remove the adult scale bugs when they form the "scale" is the best way to get rid of them, as they are easy to remove and that will prevent them from laying eggs for a new generation. I've been trying that for a couple of months now (checking them almost daily), but the plants seem to be slowly getting weaker and I still see new scales forming. :(

Another suggestion I got was a bit more drastic: submerging the entire plant (including pot and soil) in water for 24-30 hours. The idea is that the scale bugs can't survive that long without air and they'll all die.

I've never tried anything like this so I'm wondering: does anyone here have experience with this technique? I'm a bit skeptical it would work and I can't find much to support or refute this suggestion. I'm hoping someone here with more experience might know if this is a good idea.

Since these are kalanchoes that propagate easily by cuttings put in water, I was just going to cut them off at the base and throw away the soil and just submerge the cut stems.

As an aside... The original scale bugs came in on some spider plants that have been going outside for a few years now, and probably picked them up outside. By this point in the late summer, they look fine outside (probably some insects eat most of the scale bugs), but by late winter, they start to get nasty looking. Interestingly, the scale bugs never seem to cause serious damage to the spider plants, they just look bad. If submerging is a good way to get rid of scale bugs, I'll probably try that with the spider plants too.

  • Have you considered using a systemic pesticide? – Graham Chiu Aug 30 '18 at 22:52

Look, this method of drowning will drown the plant as well, cause stress. Using Neem is not a one time thing, normally. I do make up a batch of Neem in a 5 gallon pots and dunk smaller plants, upside down holding the soil in the pot. I'll spray or splash a bit on the surface of the soil but dunking and soaking the entire batch of soil, plant, pot is just going over board.

It is easy to deter scale. Scale is easily controlled, never eradicated. Scale can be very dead and still be hanging on the plant. This submerging for 24 to 30 hours will weaken the PLANT. Neem does a better job and turning a smallish plant upside down and submerging in a correct mixture of Neem and water works GREAT.

If you do not see your target species of insect you do not use pesticide. Pesticides are not preventative at all! Well, perhaps, fungicides but all else you have to ID first then treat. Pesticides are, wait, wait, wait...a BANDAID on problems we humans should have prevented. I am so serious. I rarely use Neem. I haven't used glyphosate for decades. When I did use glyphosate it was probably 2 or 3 times my entire career. I've never used another pesticide and I was licensed and tested and licensed again as a Commercial Pesticide Applicator for 3 decades, I refused to do the water cert. I tutored the Landscape Laborers so they could pass the tests.

Answer this question for me, did you use garden soil or did you use potting soil; sterilized potting soil?

  • I always use potting soil, and I assume that it's sterilized properly, since the only time I've had issues with scale is on plants that were outdoors for a few months, or plants that were adjacent to and touching the plants that were outdoors. – FrustratedWithFormsDesigner Aug 29 '18 at 22:48
  • I did try repeated applications of neem, but after a certain point, and it reduced the scale, but only to a certain point. – FrustratedWithFormsDesigner Aug 29 '18 at 22:49
  • It sounds like you are suggesting a dunk (5 minutes? 15 minutes?) in a water/neem solution instead of submerging in just water for ~24 hours, yes? – FrustratedWithFormsDesigner Aug 29 '18 at 22:52
  • A quick dunk being careful not to break your plant; swish up and down and that is enough! Submerging a plant in water is plain nuts. There are aquatic plants that wouldn't mind. This dunking is better than spraying for beneficials you do not want to kill. This is smelly irritating stuff to our skin and lungs. Follow-ups with sprays ONLY when you see the target insect, never as a preventative. – stormy Aug 30 '18 at 0:27
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    Please send pictures. This diagnosing based only on words is very tough and kind of irresponsible to do. Every situation is unique. Answers are never black and white. Please send pictures! – stormy Aug 30 '18 at 0:35

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