Answer: It may be hard for you to believe but your Hoya plant may have had mealybugs when you purchased it, even years ago. It just took this long for the circumstances to be just right for the population to explode. Now that there is a huge population, you'll begin to see the damage they can cause. The key to eradicating mealybugs on stems and leaves is getting complete coverage.
A spray mixture of 5 parts water and 1 part rubbing alcohol with a little liquid soap added is effective. However, you have to really drench all of the leaf and stem surfaces until they are dripping wet. The mealy babies are nearly invisible and they hide in nooks and crannies where they are out of sight. I suggest that you repeat this thorough spray treatment again in a week. If you see any early signs of their return in the future, re-spray. With diligence and thoroughnesss you should eventually have success.
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