The mass emergence of periodical cicadas can be an amazing natural phenomenon that humans only have a few opportunities to witness in Wisconsin in their lifetimes. We can look at cicadas in many different ways and it’s only human nature to wonder whether the big cicada emergence will be a good thing or a bad thing. While there can be some negative impacts of periodical cicadas, these insects provide many benefits to the ecosystem and they are not generally considered pests. In addition, these cicadas are generally harmless to people and pets, do not readily bite or sting, and are not toxic.
If we take a step back and remove ourselves from the picture, the cicadas are simply doing what they’ve always done—complete their life cycle, mate and successfully perpetuate their species.
Good things:
- Soil benefits: The tunnels created by emerging cicada nymphs could have impacts similar to lawn aeration, by allowing oxygen and water to more easily get into the soil, and reducing soil compaction.
- Plant benefits: The adult cicadas aren’t particularly long lived and once they die, a large amount of nutrients will flow back into the ecosystem. This can serve as a natural influx of fertilizer for nearby lawns and plants in the landscape.
- Insect tourism: Since the periodical cicadas are restricted to certain spots in the state, many Wisconsin residents may be traveling to experience these insects for themselves. Areas such as Lake Geneva are well aware of this and will likely see an influx of visitors later this spring looking to experience this rare natural phenomenon.
- A food source for wildlife: Perhaps the biggest benefit of the mass cicada emergence will be to wildlife. Wildlife such as fish, birds, turtles, and mammals can take advantage of the readily available and easy-to-capture food source.
Bad things:
- Nuisance problems: Cicadas could be a nuisance in areas of high activity due to their sheer abundance (e.g., covering sidewalks, etc.) and noise (e.g., interference with outdoor events).
- Plant damage: Damage to trees and other woody plants can occur. To lay eggs (oviposit), females cut slits into twigs and small branches, which can kill the ends of those twigs. On large trees, this damage can be conspicuous, but only a small percentage of the canopy is affected and it has little impact on tree health. This damage can be more of a concern on small trees as a significant proportion of the canopy could be lost. If severe damage occurs, this may result in stunting of plants or it could impact the appearance and structure of landscape plants. Woody landscape ornamentals, fruit trees and grape vines can be affected. Other crops, such as corn, soybeans, and vegetables are generally ignored by these insects. See the expandable box below for more details about management.
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Management
In most cases, there is no need to attempt to control periodical cicadas and the adults will only be active for a matter of weeks. Insecticides are generally not needed or recommended for periodical cicadas and research has shown them to be ineffective in many situations.
Mitigating nuisance noise: In situations where noise from periodical cicadas might interfere with outdoor events, postponing events or relocating to another site (or indoors) can be considerations.
Protecting plants: Since cicada oviposition damage tends to be tolerated by large trees, management is usually not feasible or recommended. Management may be needed for smaller trees and shrubs. One consideration is to postpone any new planting in a year of cicada emergence until after adult activity has subsided. Small trees and shrubs already in the landscape can be protected with mesh netting during the egg laying period. Netting should have a mesh size of roughly 1/4″ or less, and should be placed over the trees when males are first heard singing. Netting should be secured to the trunk beneath the lower branches, and may be removed once adult activity has ended in July. Research studies have shown that most insecticides work poorly to prevent oviposition damage to trees.
