All about cicadas

Question: Dear Master Gardeners, can you tell me more about the Cicadas I keep hearing about?

Answer: Yes, cicadas can be found all over Tennessee, we have many species that emerge every year. What makes this year so special is that there are two different broods emerging at the same time. There are the 17-year cicadas which consists of three different species and there are the 13-year cicadas of four different species. When these cicadas emerge, they are called broods, and there can be many combinations of the different species in a single brood.

Here in Tennessee, we will be dealing with what is called Brood X1X only, also known as the Great Southern Brood of the 13-year cicadas. They last came out in 2011. Another Brood called X, The Great Eastern Brood of the 17-year cicadas, that is mostly found in Eastern Tennessee, and they came out in 2021 and returns in 2038. Another 17-year cicada named Brood X1V came out in 2008 and won’t return till 2025. The Great Mississippi Valley Brood of the 13-year cicadas which mainly affects West Tennessee and came out in 2015 and will return in 2028. Cicada adults have black bodies, with their eyes, legs and wing veins are reddish-orange and are medium sized (1-1.5 inches in length). The top eight inches of soil is where the mature nymphs can be found. When the soil temps reach 64 degrees F, nymphs will begin digging to the surface.

Early May is when emergence starts. The count varies greatly in quantity in an area ranging from 20,000 to 3.7 million acres. After five days and depending on temperature the cicadas start flying and singing. Males produce the music by two-drum like membranes on the side of the abdomen to attract females. After mating the female will use her knife-like ovipositor to deposit eggs into slits she makes on young twigs and branches sizes range in (0.12 — 0.55 inches) in diameter.

This is when the most damage to trees, vines, and shrubs by cutting into them. She can lay 24 to 28 eggs in each slit; she repeats this process several times along the same branch. During her 4-to-5-week lifetime she can lay 400 to 600 eggs.

Once the eggs hatch into ant-like nymphs they fall to the ground and dig until a suitable root is found, they then feed on the xylem sap. They continue to feed and develop over the next 13 or 17 years, depending on species. The final year is when they emerge, molt on a vertical surface, and go on their mating flights to start the life cycle all over again. Cicadas have been observed in over 200 woody tree species. Here is a short list of some of the trees, and shrubs they will affect. American hornbeam, Ash, Cherry, Cypress, Dogwood, Peach, Pear, Oak, and Grapevines. You can protect small limbs and twigs by enclosing them in cheesecloth, tobacco canvas, mesh screenings of less than ½ inch to 3/8-inch openings. Netting has seen the best results. Cover protection should be applied just before emergence and kept on until the adults are gone, usually 6 to 8 weeks later. Chemicals that show some effectiveness are pyrethroids, but it must list periodic cicadas on the label for control. Thank you for your question. Happy Gardening!