Q: We were planning on planting several new trees this spring, but we were told by some friends that this summer, cicadas are coming, and they could kill small trees. Do you think is it worth the effort to plant trees this year, or should we wait?
A: I say plant away. Trees are not made in a factory when you want one. The tree you want to plant is already growing at the nursery right down the road. Someone will need to care for the tree this year. It would be better to plant the tree and start getting the benefits from it.
Let’s go back to the cicadas for a minute. I have already seen the ridiculous headlines about how they are going to cause all kinds of problems for plants, people and pets. Here is the real story.
Worldwide, there are around 3,000 species of cicadas. Wherever there are trees, there are cicadas. Most cicada species live from one to 10 years. In North America, many species of annual cicadas live one to three years. Every year, they come out of the ground in late summer.
In North America, seven species in the genus Magicicada are among the longest-lived insects. They live 13 or 17 years. During the appropriate year, they emerge from the ground in April along the Gulf Coast and as late as June in the northern states — when the soil a foot deep reaches 64 degrees Fahrenheit for a few days. Some individuals of all cicadas may come out of the ground a year early and some come out a year late.
There are three species of 17-year cicadas and four species of 13-year cicadas. In most years, some of the species have an emergence. In 1893, Charles Marlatt began keeping track of emergences, calling the first group Brood I (one) using Roman numerals. At one time, there were around 30 broods before it was realized that some broods were the same and over time some broods have gone extinct. There are now 12 broods of 17-year cicadas and three broods of 13-year cicadas. A brood can have more than one species hatch at the same time. To make it even more confusing, some of the 17-year cicadas have occasionally emerged in only 13 years.
Some broods cover only a few U.S. counties, while others range over several states. Just because they are in your state doesn’t mean they are in your area. If your area didn’t have trees 13 or 17 years ago, you will have very few cicadas. If a tree grows in an area which gets these cicadas and it is older than 17 years, than it has already survived at least one emergence.
For the entire time they are underground, cicadas feed on tree roots by sucking sap, kind of like being a mosquito for a tree. They can be found several feet deep in the ground, but they don’t move very far from where they started.
When they emerge, they molt their old skin and have wings and sexual parts that they didn’t have as larva. The new skin and wings may take a few days to harden. Then the chaos begins. The males have a structure called a tymbal that makes a lot of noise. They can be as loud as a vacuum cleaner. Thousands of them together can be really annoying.
After mating, the female lays eggs in the tips of tree branches. A few inches of the branch tip may die. A lot of females laying eggs can cause a longer section of branch to die. On large trees, the damage just amounts to some pruning and is not a problem.
Six weeks after the egg laying, tiny grains of rice-sized cicada larvae will slip out of the tree branch and fall to the ground to start their life underground.
If you live in an area that suddenly has lots of cicadas, you will know it. Cover small trees with a netting that has small holes, such as cheesecloth. You will only need to do this for a month and then the adult cicadas will all be gone. If there are a lot of them, they may need to be cleaned up as they will stink as they decay. Insecticides don’t work all that well to protect trees as the cicadas will just fly away and new ones will arrive. Insecticides on dead cicadas can harm other animals that eat the cicadas.
Speaking of eating cicadas, many cicada larvae are edible and have been used as food. I am not saying they are safe to eat, but recipes are at www.tullabs.com/cicadaworld/cicadarecipes.pdf. You may want to stop your pets from eating them, as the cicada exoskeleton is very hard to digest.
Just in case you get close enough to notice, almost all periodical cicadas have red eyes and almost all annual cicadas have black eyes. If you want to contribute to the citizen science about cicadas, check out this website: project.wnyc.org/cicadas/form.html
Email questions to Jeff Rugg at firstname.lastname@example.org.
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