How to Protect Trees from 17-Year Periodical Cicada Egg Laying

Every 17 years, billions of periodical cicadas emerge from the ground in certain parts of the United States, creating a spectacle that fascinates entomologists and nature enthusiasts alike. However, while these insects are mostly harmless to humans, their reproductive cycle poses a significant challenge for tree health. Female cicadas lay eggs by cutting slits into small branches and twigs, which can cause damage ranging from twig dieback to weakened trees that become more susceptible to disease and pests.

If you have young trees or valuable plants in your yard or orchard, understanding how to protect them from 17-year periodical cicada egg laying is essential. This article explores effective strategies and best practices to safeguard your trees during these periodic emergences.

Understanding the 17-Year Periodical Cicada

Periodical cicadas belong to the genus Magicicada and are unique because of their synchronized emergence every 13 or 17 years, depending on the brood. The 17-year cicadas are mostly found in the eastern United States and cover large geographic areas during their mass emergence.

Life Cycle Overview

• Nymph Stage: Cicadas spend most of their lives underground (about 17 years) feeding on root sap.
• Emergence: After 17 years, nymphs emerge en masse, molt into adults, and begin their brief above-ground life.
• Mating and Egg Laying: Adult females lay eggs by cutting slits in young branches.
• Egg Hatching: Eggs hatch into nymphs that drop to the ground and burrow into soil.
• Cycle Repeats: The nymphs remain underground for another 17 years before emerging again.

Impact on Trees

The female’s egg-laying behavior is the primary source of damage:

• Flagging: Twigs with egg slits often die back, a phenomenon called “flagging.”
• Branch Dieback: Repeated attacks can lead to larger branch dieback.
• Reduced Growth: Damage can stress trees, reducing vigor and making them susceptible to secondary pests and diseases.

Young trees (less than 10 years old) and orchard trees are particularly vulnerable because they have thinner branches where cicadas prefer to lay eggs.

Signs of Cicada Egg Laying Damage

Recognizing egg-laying damage early helps in timely intervention:

• Small twig ends turning brown or black.
• Numerous flagging twigs scattered throughout the canopy.
• Tiny slits or cuts along branches where females have inserted eggs.
• Decline in tree vigor if damage is severe.

Strategies to Protect Trees from Cicada Egg Laying

1. Physical Barriers: Netting and Mesh Covers

One of the most effective ways to protect young or valuable trees is by using physical barriers that prevent female cicadas from accessing branches to lay eggs.

How to Use Netting Effectively:

• Choose the Right Material: Use fine mesh netting with holes less than 1/2 inch (about 12 mm) wide. This size keeps out adult cicadas without restricting airflow or sunlight too much.
• Timing: Install netting just before emergence begins (late April to early May, depending on location) and keep it on until mid-summer when cicadas disappear.
• Coverage: Cover entire trees including all twigs and branches. Ensure netting reaches the ground and is securely anchored so cicadas cannot crawl underneath.
• Maintenance: Check regularly for tears or gaps.

Benefits:

• Completely prevents egg laying if properly installed.
• Supports tree health by reducing stress.

Limitations:

• Can be labor-intensive for large trees or many trees.
• May interfere with pollinators; remove after cicada activity ends.

2. Pruning and Tree Care Before Emergence

Proper tree maintenance before cicada emergence reduces vulnerability:

Pruning Tips:

• Remove weak, thin, or damaged branches prior to cicada emergence.
• Focus on branches less than half an inch (12 mm) in diameter since these are preferred sites for egg laying.
• Dispose of pruned material far from your trees so it doesn’t attract cicadas.

Tree Health Practices:

• Keep trees well-watered but avoid overwatering.
• Fertilize appropriately to promote vigorous growth before emergence.
• Minimize other stresses like pest infestations or diseases.

Healthy, vigorous trees can better tolerate some damage and recover faster.

3. Chemical Control: Limited Options

Currently, there are no pesticides specifically labeled for preventing periodical cicada egg laying. Additionally, spraying insecticides during adult emergence is generally discouraged due to potential harm to beneficial insects like pollinators.

However, some growers consider systemic insecticides applied well before emergence may reduce nymph populations underground but this approach:

• Requires expert guidance.
• May not be practical for homeowners.
• Has potential environmental impacts.

Chemical control is not the preferred method for most home gardeners or small-scale orchards.

4. Encouraging Natural Predators

While natural predation alone cannot prevent egg laying damage entirely, a healthy ecosystem supports birds, wasps, spiders, and other predators that feed on adult cicadas. These natural enemies help reduce adult populations somewhat.

To encourage predators:

• Avoid broad-spectrum insecticides.
• Provide birdhouses and native flowering plants that attract beneficial insects.

5. Monitoring Cicada Activity

Stay informed about local cicada broods by consulting state extension services or entomology departments. Knowing when emergence will occur allows timely preparation such as netting installation or pruning.

After the Emergence: Post-Cicada Care

Once cicadas finish their cycle above ground (usually within 4-6 weeks), focus shifts to recovery:

Prune Damaged Branches

Remove flagging twigs showing dieback caused by egg laying. This encourages new growth and prevents secondary infections.

Mulching and Watering

Apply mulch around tree bases to retain soil moisture and regulate temperature, this supports root recovery after nymph feeding underground.

Maintain consistent watering during dry spells but avoid waterlogging soil.

Fertilization

Applying balanced fertilizers can boost tree health but avoid over-fertilizing as stressed trees may respond poorly.

Special Considerations for Orchards

Fruit orchards with young trees face particular challenges due to economic stakes:

• Consider installing protective netting around each young fruit tree before emergence.
• Coordinate with neighboring growers if possible for area-wide netting efforts.
• Monitor regularly for signs of damage post-emergence.

In commercial settings, consult with agricultural extension agents about integrated pest management programs specific for periodical cicadas.

Common Myths About Periodical Cicadas

Understanding reality helps in managing expectations:

• Myth: Cicadas kill mature trees.
  Fact: Mature trees usually survive with minimal long-term damage unless heavily stressed by other factors.

• Myth: All cicadas emerge every year.
  Fact: Periodical cicadas emerge only every 13 or 17 years depending on brood; annual “dog-day” cicadas are unrelated species with different cycles.

Conclusion

While the mass emergence of 17-year periodical cicadas is a remarkable natural event, their egg-laying behavior can cause significant damage to young and vulnerable trees. By employing protective netting, practicing proactive pruning, maintaining good tree health, encouraging natural predators, and monitoring local cycles closely, homeowners and orchardists can effectively protect their trees during these episodes.

Remember that mature trees typically withstand cicada activity quite well. The key focus should be on protecting saplings and valuable young specimens especially during peak emergences every couple of decades. With careful planning and timely actions, you can enjoy witnessing this fascinating natural phenomenon without sacrificing your landscape’s health.

For more information about local periodical cicada broods and detailed protective measures tailored to your region, contact your county extension office or visit entomology department websites at major universities.