It always seems that once high temperatures reach the 90s, and are accompanied by heavy rains, insects known as mealy bugs begin to proliferate. Interestingly, though, few people realize the problems they cause are actually from an insect. I often get questions like, “What is the white, cottony fungus on my hibiscus?”
Mealy bugs are white, soft-bodied insects that suck plant juices. In fact, they are just a soft, cottony version of scale, an insect to which they are related.
They are often found nestled in the nooks and crannies of plants, where it's hard to spray. Most commonly, they attack new growth, so they’re usually found near growing tips, where leaves join stems, or along leaf veins. The bugs are covered with white, waxy threads that protect them from predators and give them their fuzzy, cottony appearance. And that's why many of my callers and emailers reference something that "looks like snow" or “a white, furry fungus” on their hibiscus or the backs of tree leaves.
I’m not immune to such infestations - the plant pictured on the right above … one of my prized hibiscus … has a mass of mealy bugs that was ignored for only one week – that’s how quickly they can procreate in the absence of a control measure. The picture below is of one of my crotons.
While malathion is the hands-down best method for controlling scale and mealy bugs on evergreen plants and trees, BEWARE! It is deadly for houseplants, hibiscus and other tropicals like the croton. So, NEVER, EVER, EVER spray malathion on tropical plants. For them, various organic remedies will work. You can even try blasting them off with a hose each morning for a week or so – that’s what I did for my hibiscus and crotons.
As for minor infestations on house plants, rubbing alcohol applied with cotton swabs seems to be the best control, along with soapy water. But this needs to be an ongoing response … the eggs are often not eliminated with one application. These insects are under a protective hairy covering, and that’s why many insecticides don’t deliver complete elimination. Be consistent in your care, and check bug-prone plants regularly.
For highly sensitive plants that can't take malathion, I also have two homemade controls. Both have had varying degrees of success on tender plants, and you may find that one of them will work for you.
Randy’s Homemade Mealy Bug Control (For one-quart spray bottles)
- 1 tablespoon of neem oil
- ¼ to ½ cup of rubbing alcohol
- 4-5 drops of dish soap
- Fill the rest of the bottle with water
I originally designed this formula 18 years ago when my back-patio tropicals were infested with mealy bugs. We just had our first child, and I was obsessed with keeping the patio 100% organic. I knew soapy water worked a little, and I knew rubbing alcohol worked on mealy bugs, but only if you swabbed them. And neem oil alone was not working 100%. So, I tweaked the ingredients for this recipe. Warning: With a sensitive plant, test on a small spot or a single leaf before you spray it everywhere. You should know within 24 hours if it’s safe to use on the rest of the plant.
GardenLine’s Homemade Scale Control
This concoction is exclusively for landscape plants - shrubbery and trees.
- 1 cup agricultural molasses
- 1 cup garlic oil
- 1 cup seaweed extract
Pour into a one-gallon sprayer and fill the rest with water. (To be on the safe side, try ½ cup of each of the main ingredients, and do a test. You should know if it’s safe to use within 24 hours.) While this formula can initially smell bad, the odor goes away in under an hour. There’s also a side benefit - as this mix drips to the ground below, it is a great soil amendment. The molasses and seaweed extract will supercharge nature’s own micro-organisms.
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PHOTOS: Randy Lemmon