Cicadas expected to emerge by the millions
Posted: Friday, March 25, 2011 8:22 am
This is the year.
The 13-year cicada is expected to emerge from soils across much of Tennessee.
Sometime this spring, when soil temperatures reach about 67 degrees at a depth of four inches, large numbers — millions — of cicadas are expected to emerge from the soils of more than one-third of the state’s 95 counties. The greatest population concentrations are expected to be in Middle Tennessee.
The target date is early May, and four or five days after they emerge, the adult males will start “singing” said University of Tennes-see Extension entomologist Dr. Frank Hale. “In some locales, the sound may seem deafening,” he said.
The periodical cicada, Magicicada species, has the longest developmental period of any insect in North America. There are numerous sub-species and broods of the insects, but the brood designated as XIX, which has a 13-year life cycle, is the group that usually attracts the most attention in Tennessee.
Hale said the high-pitched, shrill-sounding songs of the males may be distracting or irritating, but it’s the activities of the females that can cause damage to the landscape, especially young trees. “After the males attract females with their song, mating occurs and females begin laying eggs inside the branches of woody plants,” he said. “A female cicada has a knife-like ovipositor that she uses to slit twigs before she lays eggs inside the slits.
“A single female cicada can lay anywhere from 24 to 28 eggs in each slit she cuts, and she can cut anywhere from five to 20 slits in a single twig.”
He explained that each female can lay a total of 400 to 600 eggs and that the egg punctures pose a threat to young trees.
“Apple, pear, dogwood, oak and hickory are their favorite hosts, but you can see the puncture marks on many tree species,” Hale said. “The punctures can damage young transplanted trees in nurseries and orchards causing the twig tips to wilt and die.”
In areas having a previous history of high populations of periodical cicadas, Hale said certain preventative measures should be followed. “Delay pruning young fruit trees until after cicada emergence so damaged branches can be removed and a proper scaffolding of branches can be established,” he said. “When feasible, small, valuable shrubs and trees may be covered with a loose woven or spun fabric such as cheesecloth or floating row cover for protection while cicadas are present.” He said insecticides have not proven to be effective for preventing cicada egg-laying damage.
Cicadas cannot sting, and adult cicadas live for only four to five weeks. Eggs hatch six to seven weeks after they are laid and the newly-hatched nymphs (which are white and ant-like in appearance) drop to the ground and work their way into the soil. Nymphs grow slowly and they feed on sap from roots until the spring of their 13th year, when they emerge to start the cycle again.
If you live in an area with high populations of the 13-year cicada, expect a noisy late spring.
Hale recommended earplugs for anyone who finds the song of the romantic male cicadas is not music to their ears.
Published in The Messenger 3.24.11