I have an enclosed patio that I use as a sort of green house. Many of the plants have mealy bugs, some species more than others. I’ve tried treating the plants on an individual basis with sprays, but nothing has much of an effect, since the eggs are laid beneath the soil and they seem to be impervious to the spray.
Is there some kind of systemic treatment, like a fumigator or fogger that kills mealy bugs?
I’ve used a systemic granual insecticide for them before. I honestly can’t tell you the name of it, but I got it at my local garden shop. Shake a tablespoon or so on each plant, water, and it gets sucked up into the plant. Then, when the bugs eat the plant, they die.
How regularly are you spraying? If you get the little buggers before they have a chance to lay eggs, you should stop the problem. Though if they’re as widespread as you say, I can see how that would be difficult. Can you maybe move them outside for awhile?
Is repotting the plants an option? My green-thumb grandmother insists that plants become “unhappy” if they live in the same soil for years at a time. Whenever the plant doubles in size, she always repots, giving them fresh soil, and a bigger “house.”
She also occasionally asks me to bring over a bag of cigarette ashes, which she puts in a sprayer bottle with water and sprays the plants to keep off parasites.
Of course, this is the woman who gives her plants cool coffee and any leftover soda pop, because she says the caffine “perks them up.” (She may be right because I’ve never seen plants grow as well as they do for her. I swear the woman could put a nickle in a pot of dirt and get a beautful plant from it.)
I would repot/root prune all plants and remove any dead or questionable vegetation. Then use a predator insect. Cryptolaemus montrouzieri is one that loves to eat mealybugs. Many nurseries sell predator insects. Good luck!
Plants heavily infested with mealybugs should be thrown out. Take healthy cuttings if possible to preserve valued specimens.
Less badly infested plants can be washed/hosed off thoroughly to lower the pest burden, then sprayed regularly with an effective spray (Neem oil and/or horticultural soap are effective and relatively non-toxic to humans and pets). Small numbers of mealybugs can be removed with Q-tips soaked in rubbing alcohol.