The common name “Mealybug Destroyer” sounds like it might be part of the advertising for an overhyped, doubtfully effective gardening product, but when applied to the predatory beetle Cryptolaemus montrouzieri, it’s actually appropriate. Here at the University of Connecticut greenhouses, we’ve been trying to minimize the use of pesticides, and rely instead on beneficial insects and other biological controls for pests, as part of an Integrated Pest Management (IPM) program. Cryptolaemus has been critical to our efforts to beat one of the worst enemies of indoor horticulture.
Cryptolaemus is a tropical lady beetle, related to the native and Asian lady beetles commonly found in gardens (and houses) in New England. Adult “crypts” are small, nondescript brown and black beetles, which eat mealybugs and mealybug eggs. Cryptolaemus larvae are what really earn the name Mealybug Destroyer, though. These are camouflaged to look like large, fast moving mealybugs, and they devour pests at a prodigious rate. They mostly go after Citrus Mealybug and Long-tailed Mealybug, but in a pinch they will settle for other insect pests; I’ve seen them make short work of an infestation of Brown Soft Scale, for instance.
Mealybug Destroyers do best in warm, humid conditions, and even in a greenhouse usually don’t survive through the winter. Adult beetles can be ordered through the mail in the spring, from specialist suppliers such as IPM Laboratories. Once a population of crypts gets established, it can quickly become a problem to find enough mealybug-infested plants to keep them fed.
Unfortunately, it is difficult to make use of Cryptolaemus in all but the largest home collections of plants. It’s fairly expensive to acquire a package of the beetles (the joke in the horticulture industry is that IPM stands for “I Pay More”), and you really need a large number of plants with a lot of mealies to support a population of Mealybug Destroyers. The beetles are far more sensitive to pesticide residues than the pests are, and probably won’t survive if systemic insecticides have been applied within the past six months, or possibly longer (pests evolve resistance to chemicals used to control them, but populations of beneficial insects have likely never been exposed to pesticides). Still, under the right circumstances, Cryptolaemus montrouzieri can be a devastatingly effective weapon in the battle against mealybugs.