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Miss Floribunda: Brooding about bugs

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Posted on: June 2, 2020

Dear Miss Floribunda,

I was about to order some fruit trees to plant this spring when I heard that we’re going to have cicadas in our area this year. Are they anything like locusts?

Will they destroy my plantings? One of my neighbors suggested I wait till fall, till after the cicadas have passed through.

What do you think?

Hesitant on Hamilton Street

Dear Hesitant,

This is not a good time to plant trees or shrubs, but not because there will be many cicadas imminently arriving. You will hear the usual number of annual cicadas, and we may get a few stragglers from the Brood IX (9) periodical horde that is currently descending on southwest Virginia, West Virginia and North Carolina. It’s next year that we will bear the brunt of Brood X (10), which will spread over an area ranging from Georgia to New England. This system of using Roman numerals to track the emergence and progress of periodical Magicicada eruptions was established in 1898 by C.L. Marlatt, and is particularly useful in distinguishing between cicadas that emerge after 13 years underground and those that emerge after 17 years. Both Brood IX and X are 17-year cicada hordes.

Do be aware that any woody plant you introduce into your garden this year will still be vulnerable to the 2021 horde. It would be better to wait till autumn of 2021 to plant fruit trees. Learning about the cicada life cycle will help you understand why.

The cicadas’ above-ground life cycle is only about six to eight weeks — starting from whenever the soil temperature reaches 64 degrees F, and they emerge from underground. By August most cicadas will have courted, mated, laid eggs and expired naturally — or been eagerly eaten by birds, wild turkeys, bats, turtles, frogs, spiders, reptiles, squirrels, ‘possums and even your family dog, if given the opportunity. Probably one of the reasons cicadas reproduce in such huge numbers is that they are a sought-after delicacy. (Recipes exist for preparing them for human consumption.) They don’t live long after mating, anyway, and in their weakened state they are easy prey. By the end of summer, the new cicada nymphs will have hatched and gone underground to wait 17 years for their own coming of age and brief but exuberant halcyon days.

Some people find the cicada mating season noisy and annoying, though others of us find their music hauntingly beautiful. The problem they pose to gardens, however, comes from the ovipositing of the females. They cut small v-shaped slits into tree bark to deposit their eggs. Well-established trees can tolerate this, but young ones can be seriously weakened. Even with mature trees, sometimes you will see “flagging,” which means that the damage wrought by cicadas has caused leaves to turn brown and weaker branches to die. This is, in fact, a service to the tree, which will no longer have to provide nutrients to those weaker branches. And the bodies of those cicadas not gobbled up by animals provide compost for the tree, while the underground larvae aerate the soil. Unlike locusts, cicadas don’t chew the leaves and stems of plants, but they do suck a little sap during their brief life cycles, and their larvae feed on fluids from tree roots while developing. In fact, a change in the root xylem fluid signals the end of the 17-year cycle for them, while warming soil temperature tells them exactly when to come out and party. The mighty oak isn’t going to be fazed at all by this, but a young sapling isn’t strong enough to have its roots fed upon.

Cicadas and locusts belong to different taxonomic families. While cicadas are related to crickets (Grillidae), locusts are related to grasshoppers (Acrididae). What the two families have in common is that they make their “music” with stridulation, a scraping together of two body parts that produces sound the way a bow does when it passes over violin strings or a needle does on a vinyl phonograph record. Locusts, however, are a genuine menace to mankind. The terrible clouds of them descending on Kenya and other areas of Africa right now are devastating crops, which locusts devour in their entirety. Also, while climate change doesn’t really affect cicadas (although if ground temperature warms early cicadas might emerge sooner than normal), it may have a great deal to do with the scourge of locusts. My consultant in entomology, Dr. Honeywell, tells me that unusual storm activity in East Africa resulted in heavy rainfall in desert regions. This increased the locust population 8,000-fold, according to the United Nations’ Food and Agriculture Organization. While locust infestations are nothing new in Africa, the stupendous size of current swarms is unprecedented.

Curiously enough, in the 19th century the Rocky Mountain locust caused much devastation in the western United States. Late in the century it suddenly disappeared, and although theories abound it still remains an ecological mystery. Its reappearance would be a catastrophe.

As a rule of thumb, it’s best to plant trees and shrubs in the fall whether or not there are insect invasions. The Hyattsville spring isn’t long enough to establish them before the brutal heat of our summers sets in. Autumn here is long and mild, and it gives a sapling ample time to establish itself before hard frost. That sapling then gets a chance to continue its growth during the next year’s spring before the advent of dog days. If you’ve already planted your young fruit trees, be sure to keep them well-watered this summer. Before the cicadas arrive next near, cover them with plastic netting and secure it well. April is not too early to do this.

It is still not known when meetings of the Hyattsville Horticultural Society will resume. The society will post updates on our web page, hyattsvillehorticulture.org.

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