By Ralph E. Mitchell
Imagine for a moment that you look identical to something else – this can have both good and bad consequences. If you are a predator, perhaps a you could sneak up on your prey if you looked just like it – a wolf in sheep’s clothing if you will. However, if you look exactly like a classic pest insect such as a mealybug, you may have mistaken identity problems. Such is the life of the humble mealybug destroyer. This ladybird beetle larva looks exactly like a mealybug, one of its favorite foods. However, people trying to control mealybugs often target it for elimination because of its similar appearance – a tragic consequence! The first step in any Integrated Pest Management (IPM) program is positive identification.
Mealybug destroyer history goes back to 1891 when this insect was brought in from Australia in to manage citrus mealybugs in California. Since then it has naturalized in several states including Florida where it is a now a common biological control agent. The adult beetle is small (one-sixteenth of an inch) with dark brown to black wing-covers and a red thorax and head. Both adults and larvae eat mealybugs, aphids, and some scale insects.
It is essential that you be able to tell the difference between these beneficial insects and the mealybugs they feed on. The mealybug destroyer beetle larvae are covered with significantly more white waxy material and are about one-half inch long. This white waxy material forms long “tendrils” that cover the body of the predator. Also, the mealybug destroyer moves around a great deal more than mealybugs do. If you flip over a mealybug destroyer, you will see three sets of little legs which are actively moving about. While real mealybugs have legs and can move, they move less and are in general more sluggish and/or stationary.
What do you do when you see real mealybug destroyers doing their job on an infested plant? First determine how many are actively feeding on the pest insect of concern. If there are sufficient mealybug destroyers, then you could let nature take its course. If there are not that many, perhaps spot treat with a least-toxic product like insecticidal soap as per label directions around the existing mealybug destroyers.
Adult mealybug destroyers and young larvae prefer to eat pest insect eggs, while older larva tend to attack all stages of mealybugs. The good news is that one mature mealybug larva may have eaten up to two-hundred and fifty mealybug nymphs. Populations of mealybug destroyers occur naturally in our area and will be drawn to mealybug infestations.
What is the bottom-line? Make sure to get positive identification before you take any control action! The mealybug you think you killed may actually be a mealybug destroyer! For more information on identifying all types of beneficial organisms, please call our Master Gardener volunteers on the Plant Lifeline on Mondays, Wednesdays and Fridays from 1 to 4 pm at 764-4340 for gardening help and insight into their role as an Extension volunteer. Don’t forget to visit our other County Plant Clinics in the area. Please check this link for a complete list of site locations, dates and times – http://charlotte.ifas.ufl.edu/horticulture/Plant%20Clinics%20Schedule.pdf.
Sadof, C. ( 2017) Know Your Friends – Mealybug Destroyer. Purdue University.
Gray, B, (2006) Beneficials in the garden – Mealybug Destroyer. Galveston County Master Gardeners, Texas A & M University.
Balaban, J. & J. (2004) BugGuide. Iowa State University, Department of Entomology.
Osborne, L. S. (2010) Pink Hibiscus Mealybug Management , Mid-Florida Research & Education Center. The University of Florida, IFAS.
Frank, J. H. & Mizell, R. F. III, Lady Bugs of Florida. University of Florida Extension Service, IFAS.
(2014) Mealybug destroyer. Agriculture and Natural Resources, University of California.