What’s the buzz?
Published 3:35 pm Monday, September 24, 2018
What’s all the racket about? That high-pitched whine heard most frequently on the hottest days of summer and sounding like a dentist’s drill or the call for the college semester to begin. Well, that would be the male dogday cicada, singing for a willing mate. Somewhat unusual in nature, the females are always silent. The dogday, aka harvest fly, is not to be confused with the periodical cicada (both the 17- and 13-year.)
The annual dogday cicada has a larger dark brown body with a green band at the back of the head stretching into its wing margins. Their population is much smaller, and they don’t have a swarming habit. The life cycles of annual cicadas are two- to five-years. Yet, some adults emerge every summer, and their appearance is scattered over the summer season.
From the home gardener’s perspective, an important distinction between the dogday and the periodical cicada is that the annual cicada ordinarily doesn’t cause much harm to our trees. These cicadas are usually associated with mature, well-established hardwoods like oaks and maples (see VCE publication 444-276).
Periodical cicadas, though related to the dogday, are smaller and black with red eyes and orange legs. They are the longest lived species of insect in North America and emerge en masse. They cause significant damage to young trees that have branches perfect for egg laying. Periodicals target the slight branches of newly-planted fruit and ornamental trees including apple, dogwood and pear.
The female periodical cicada lays her eggs in the small twigs of these trees. She inserts her saw-like, egg laying tube into the branches and places her eggs under the thin bark, splitting the twigs. These small branches wither and die. A female may lay up to several dozen eggs in a single branch, depositing eggs in 40-50 sites. That is a lot of eggs!
The immature cicadas do not feed on the twig where they hatch but drop and burrow to the tree’s root system, staying there for 13 or 17 years. These nymphs damage the tender roots by sucking root sap. After serving their time below ground, mature nymphs tunnel up from the soil to climb onto nearby plants and vertical structures to molt. As they transition to the winged adult stage, their familiar outer shells are left behind on tree trunks and birdhouse poles much like a snake leaves its skin behind after shedding.
Cats and dogs are known to find cicadas to be tasty treats. Cicadas are high on bird, snake and raccoon menus, too. Identify other harmful insects destructive to trees, shrubs and forbs by contacting the Master Gardener Helpline. Volunteers are available Wednesdays, 10 to noon, 356-1979 (through September.)
KRISTI HENDRICKS is a member of the Western Tidewater Master Gardeners. Contact her at GardenontheJames@yahoo.com.