I’m not sure if it’s because we have many new people moving to the area from other states, people new to gardening, or a wonderful rush of new GardenLine listeners, but I’m getting many questions like this one from Chris S. in Cypress: “Randy, I have this strange white fungus all over my hibiscus (or other plant), and fungicide has done nothing. Do you have any suggestions on how to control it?”
Well, it’s not a fungus, as many people new the area or new to gardening assume. It’s an insect known as mealy bugs. We often get “Mealy Bug Mayhem” once our high temperatures get into the 90s, accompanied by heavy rains. And I think the recent combination of heat, humidity and rain has been keeping people from regularly walking their gardens and landscapes and catching these annoying pests in their early stage.
That’s when they are easy to kill or control with a simple blast of water from a hose. But when they get as bad as pictured here, you’ve got to get on some kind of spray control, synthetic or organic.
Mealy bugs are white, soft-bodied insects that suck plant juices. And they are related to the family of insects that include scale. So, mealy bugs are a soft, cottony version of scale. They are often found nestled in the nooks and crannies of your plants, where it’s hard to spray. Most commonly they attack new growth, so they are usually found near the growing tips and where leaves join stems or along leaf veins. The bugs are covered with white, waxy threads that protect them from predators and give them the fuzzy, cottony appearance. And that’s why many calls and emails I get say the problem looks like “snow” or “a white furry fungus.”
I’m not immune to these things, either. The plant pictured above is mine. On one of my prized hibiscus, the mass of mealybugs was ignored for only one week. (I was out of town.) That should give you a good idea of how prolific they can be in the absence of a control.
While malathion is the hands-down best method for controlling scale and mealy bugs on evergreens and trees, BEWARE – it is deadly on houseplants, hibiscus, and tropical plants like the croton. NEVER, EVER, EVER spray malathion on tropicals.
Nevertheless, there are still many ways to beat this nuisance, depending on the plant in question. There are various organic remedies that will work. And even simply blasting them off with a hose every morning for a week or so can be effective. That’s what I did for my hibiscus and crotons.
As for minor infestations on house plants, using cotton swabs dipped in rubbing alcohol seems to be the best control, along with applying soapy water. But this must be an ongoing process because the bugs’ eggs are often not eliminated with organic controls. Be consistent in your care, and check bug-prone plants regularly. Remember these insects are under a protective hairy covering, and many insecticides don’t deliver complete elimination.
For highly sensitive plants that can’t take malathion, below are two homemade controls that have worked with varying degrees of success on tender foliage. You should find success with at least one of them.
Randy's Homemade Mealy Bug Control
I came up with this formula 18 years ago for tropical plants on my back patio that were infested with mealy bugs. We just had our first child, and I was obsessed with keeping the area 100% organic. I knew soapy water worked a little, and I knew rubbing alcohol worked on mealy bugs, but only if you swabbed them. Neem oil alone was not working 100%. So, I came up with this recipe by tweaking the three ingredients.
***Warning: Test it first on the leaf of a sensitive plant to see if it works without causing damage. You should know within 24 hours if it’s safe to use on the rest of the plant.
In a one-quart spray bottle:
1 tablespoon of Neem oil
¼ to ½ cup of rubbing alcohol
4-5 drops of dish soap (not detergent)
Fill the rest of the container with water
Gardenline's Homemade Scale Control
This concoction is exclusively for landscape plants – shrubbery and trees. While it can smell bad for the first few minutes, the odor will go away in under an hour.
In a one-gallon sprayer:
(1) cup each of:
Agricultural molasses
Garlic oil
Seaweed extract
Fill the rest of the container with water
If it makes you feel a bit safer, go with ½ cup of each of the three ingredients. Then do a test. You should know if it’s safe to use within 24 hours.
There’s a side benefit to this one, too. In addition to being an all-natural insecticide, this mix is a great soil amendment. As it drips to the soil below, the molasses and seaweed extract will supercharge nature’s own microorganisms.