About the only pest to attack cactus is the caterpillar, which will take the leaves off. You don't need to spray. He uses a slow release fertilizer like Magamp or Osmacote, following package instructions. There is no native Hawaiian cactus, although the Mexican native prickly pear is faking it as panini. It was introduced here in about 1800 with the best of intentions as a cattle feed.
Mexican cattle love it.
Hawaiian cattle got indigestion, and dumb though cows may be, refused to eat it. So now it's a pest and nobody is quite sure of how to get rid of it. Please be sure to include a phone number. Evergreen by Lois Taylor is a regular Friday feature of the Honolulu Star-Bulletin. All rights reserved.