Know Your Friends

Mealybug Destroyer

The mealybug destroyer, Cryptolaemus montrouzieri, is a small (1/5") black lady beetle with a tan front end and a voracious appetite for mealybugs and some soft scales. This beetle was imported into the United States in 1891 from Australia by one of the early biological control pioneers, Albert Koebele, to control citrus mealybug in California. Though this beetle initially devastated the citrus mealybug populations in citrus groves, it was unable to survive the winter, except in coastal areas. Consequently, techniques for mass rearing this beetle were developed for its release into groves during the warmer months. This predator is readily available from natural enemy suppliers. In the Midwest, the mealybug destroyer can be used to reduce populations of citrus and long tailed mealybugs in interior-scapes and greenhouses. Both species of mealybugs feed on a wide variety of ornamental plants. This predator readily feeds on some soft scales including hemispherical scale and its relatives, but reproduction is substantially greater on mealybugs.

Adult female beetles lay their eggs among the cottony egg sack of adult female mealybugs. Eggs hatch into larvae in about 5 days at 80F. These larvae, whose waxy covering makes them superficially resembles mealybugs, feed on mealybug eggs and young crawlers. It takes another 24 days for these beetles to go through three larval stages and a pupal stage before they become adults. After four days, adult beetles begin to lay up to 400 yellow eggs during their two month life span. When releasing these beetles in the winter be aware that cool temperatures will slow development and reproduction.

When the temperature is below 50F these beetles remain alive but do not produce many offspring. Beetles take 29 days to go from egg to adult at 80F and take 47 days at 70F. In the summer beetles thrive at 90F, but fail to reproduce at extremely warm temperatures (104F). Like most lady beetles, the mealybug destroyer has a tendency to fly when you release them from the container. Release adult beetles near mealybug infestations and keep windows and vents closed on the day of release. Mealybug destroyers feed on both mealybugs and their sugary liquid excrement, commonly called honeydew. Recent studies show that adults and larvae will spend more time searching a leaf for mealybugs if it has honeydew than if honeydew is absent. In small greenhouse areas, where mealybugs can easily be found by predators, mealybug destroyers will not persist after the mealybug population has been devastated. Beetles do persist in more complex areas, such as conservatories, atriums or interior-scapes where there are multiple infestation sites, and alternate hosts such as hemispherical scale. In one such area in Indianapolis, a single release of 100 beetles has persisted for over 5 years. Though the complexity of the conservatory is helpful, be warned that birds in the conservatory will make a great sport out of eating adult beetles.

Finally, it is important to remember that larvae of mealybug destroyers superficially resemble mealybugs. This can cause some problems for growers getting ready to ship their crop, or when large numbers of larvae are in close view of people eating in shopping mall restaurants and cafes. The ability of this beetle to consume large numbers of mealybugs can offset this disadvantage in many cases.

- Cliff Sadof, Purdue University

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