IPM Run Amuck!

The Harmonia lady beetle, Harmonia axyridis, was introduced into this country from Asia because of their voracious appetite for aphids. According to Louis Tedders, formerly with the USDA Southeastern Fruit and Tree Nut Research Lab in Byron, GA, a single beetle eats over 300 aphids before it reaches maturity¹.

The beetles were purposely introduced as biological control for aphids, but it is suspected that most of the population now causing problems in the eastern US is not the lab-reared types that were released originally, but more aggressive wild populations that were accidentally introduced through the port of New Orleans around 1988. They now have spread to all states east of the Mississippi, and also to parts of Texas and Oklahoma.

Harmonia lady beetles are very effective in controlling a wide range of aphid populations, including ones that affect fruit trees, crape myrtle, roses, peaches, and pecans. In fact, they have all but eliminated the need for spraying pecans in the southeast for aphid control, saving growers millions of dollars in pesticide costs.

The problem is that the beetles tend to swarm in the fall, and form overwintering colonies in structures.... particularly in homes! Tends of thousands of the beetles swarm on houses, climbing into walls, entering attics, forming colonies in walls and in chimneys. Having personally experienced a swarm while on vacation in North Carolina one October, I can tell you it is a very unsettling experience!

People are reluctant to destroy the lady beetles... after all, they are lady beetles... and we have been taught since youth that they are entirely beneficial. Spraying and killing the insects in place in homes does more harm than good, because other problematic insects are attracted to their decaying bodies. Dr. Tedders1 is working on a nondestructive trapping system that uses a weak UV light source to attract the insects into a mesh bag, so that they can be released outdoors.

Even the best plans for biological control may have unintended consequences!

1Tangley, Laura. 1999. Ladybug, fly outta my home. U. S. News and World Report, January 25, 1999.

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