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Horticulture and Home Pest News
Horticulture & Home Pest News is filled with articles on current horticulture, plant care, pest management, and common household pests written by Iowa State University Extension specialists in the Departments of Entomology, Horticulture and Plant Pathology.

The Return of the Boxelder Bugs

This article was published originally on 7/25/2012

The number of calls and messages received already about boxelder bugs and the number of bugs reported is not a good sign.
 
The weather this year has been ideal for creating a boxelder bug outbreak of epic proportions. In the past we could expect significant boxelder bug populations when it was warm in May and dry in July. This year both conditions existed to excess. I suspect we should brace for an onslaught of boxelder bugs and boxelder bug complaints.
 
Calls and specimens received so far have been about boxelder bug nymphs and not the more easily-recognized adults. Both adults and nymphs (immatures) have bright red abdomens.  The red abdomen is concealed under the black wings in the adult stage, making the adult appear dark in color. The nymphs do not have wings to cover the bright red abdomen. See the photos below.
 
Life Cycle: Boxelder bug adults that stayed outdoors and successfully hibernated through last winter returned to the trees to lay eggs for an early summer generation. This new generation grew up and reproduced in July to produce the nymphs we see now and the adults that will be a pest this coming fall.
 
I don't know why boxelder bug nymphs scatter to so many different locations.   People have reported them in flower beds, lawns, patios, sidewalks, gardens and everywhere else in the landscape. I've learned to not be surprised when people call about pointy, bright red insects in the landscape. The book says they live in the trees where they feed on sap from twigs and seeds. It's obvious they are also other places, but as far as I can tell, they are not a pest and they cause no damage to host plants.
 
There has not been a miracle cure for boxelder bugs for the past 75 years. There is not likely to be one, now. Insecticidal soap and soapy water sprays can be applied to the congregating nymphs on the house or tree trunk for knockdown and control, but frequent reapplication will be needed to feel like you are making any headway as more keep arriving from the nearby trees (all kinds of trees and not just boxelder trees).
 
Two sizes of boxelder bug nymphs (immatures).
Two sizes of boxelder bug nymphs (immatures).
 
 
 
Mass of boxelder bug nymphs of various sizes.
Mass of boxelder bug nymphs of various sizes.