Cicadas’ life cycle yields clue for controlling their damage

Contributed photo (By Eric Day, Department of Entomology, Virginia Polytechnic Institute and State University)

By Judy Ferring

‘Singing’ from this year’s emergence of 17-year cicadas may annoy some, but Master Gardener Sherry Easterbrooks contends that they’re “amazing and fascinating creatures” whose tightly choreographed emergence deserves attention. Granted, these insects can do significant damage to certain woody plants, but knowledge of their life cycle gives a powerful advantage to homeowners who have just planted new fruit trees, as well as owners of commercial vineyards and orchards.

On June 10, Easterbrooks and fellow Master Gardener John Morehead will provide details in a 30-minute presentation on WHEO Radio.

The key is that it’s not those noisy males that you have to worry about. They’re singing to attract a mate. In the end, it’s the silent females that cause the problem.

Adult cicadas begin appearing in early May and the males begin their cacophonous concert. Think of as something a storm warning, likely to peak in early June. The real problems begin when the impregnated females lay their eggs. Out of their entire 17-year life cycle, it’s those last two to four weeks that things start to go badly. Even then, there’s little visible destruction underway: adults don’t eat much. Birds often snack on them instead. By July, most are gone.

Easterbrooks and Morehead will outline how to spot the emerging danger during their discussion.

Owners of vineyards and orchards, plus homeowners who planted new trees this spring, can mitigate the damage by preventing the female cicadas from reaching the tender new shoots of vines and young trees.

The experts at Virginia Cooperative Extension (VCE) recommend enveloping the trees in fine netting to prevent them from landing in the first place, and scouting the trees every 2-3 weeks for signs of egg-laying. Shoots and twigs showing such signs should be cut away, bagged and discarded.

Other creatures’ life cycles limit growers’ alternatives. Insecticides will give limited control, but often kill pollinating insects, warn the VCE experts.  Application of Sevin or a pyrethroid insecticide often cause an increase in spider mite populations.

Growers will have another month or so to diminish the 2037 onslaught by preventing Patrick County’s nymph cicadas from burrowing back into the ground. At that point, some may well look to the west.  According to VCE maps, there’s a smaller emergence expected in Carroll County in 2021.

 

 

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