My Hatiora salicornioides has a light infestation of soft brown scale. It reacted negatively in the past when it was sprayed with insecticidal soap. Is there a non-systemic insecticide that can be used safely with cacti? (I believe systemics are no longer available in my area.) For what it's worth the cactus does not appear to be very hospitable to the scale as they seem to die at young age. My guess is once the cactus skin hardens the scale can no longer feed and so dies. Nevertheless they eke out an existence on the younger growth.
Hello, I know your post is old... For scale on our indoor plants wee use a q-tip dipped in rubbing alcohol and lightly remove each scale insect. It will probably be something you do for as long as the plant lives as scale is very hard to deal with. Sometimes the plant scabs where we have putting the rubbing alcohol but it has definitely helped. I always remove the plant from direct sunlight for a few days after any application.
Thanks for the reply. Actually I took a chance and ended up experimenting with the plant as there had been no replies. I selected a small portion of the plant and sprayed it with isopropanol (isopropyl alcohol) 99%. After seeing no ill effects I sprayed the entire plant a couple more times. There were signs of dead scale which were previously unseen because of their young transparent shell. Out of curiosity I repeated the experiment using insecticidal soap. Again there were no ill effects. Therefore I must have exposed the plant to direct sunlight immediately after spraying the plant previously. Anyway I hope this will help others searching for a solution to this problem.
