How to Protect Trees from Damage by 13-Year Periodical Cicadas

Periodical cicadas are fascinating insects known for their unique life cycles, emerging in massive numbers every 13 or 17 years. While these cicadas are a natural part of many ecosystems, their mass emergence can cause significant damage to trees, especially young or newly planted ones. In particular, the 13-year periodical cicadas present a cyclical challenge for gardeners, orchardists, and homeowners who want to protect their trees from harm.

This article will explore effective strategies for protecting your trees from damage caused by 13-year periodical cicadas, including understanding the cicada life cycle, recognizing the types of damage they cause, and implementing practical protective measures.

Understanding 13-Year Periodical Cicadas

Periodical cicadas (genus Magicicada) are remarkable insects that spend most of their lives underground as nymphs, feeding on the sap from tree roots. After 13 years (or 17 years for some broods), they emerge synchronously in huge numbers to mate and lay eggs.

The 13-year cicadas belong to specific broods that appear at predictable intervals. Their emergence causes a sudden increase in the number of adult cicadas on the landscape, leading to widespread oviposition (egg-laying) activity in tree branches.

Why Are Cicadas a Threat to Trees?

While adult periodical cicadas do not eat leaves or bark and are not harmful in the traditional sense of pests, their egg-laying behavior can injure trees. Female cicadas use their saw-like ovipositors to cut slits into small twigs and branches where they deposit their eggs. This process can cause:

• Flagging: The most visible damage where oviposited twigs die and turn brown or red before dropping off.
• Twig breakage: Weakened branches may break due to structural damage.
• Reduced growth: Excessive egg-laying may reduce photosynthesis and overall vigor, especially in young trees.
• Increased susceptibility: Damaged branches may be more prone to diseases or secondary pests.

Mature trees typically tolerate this damage without lasting harm, but young trees and saplings are more vulnerable. Protecting these valuable trees during cicada emergences is critical.

Identifying Damage Caused by Cicadas

To effectively protect your trees, you need to know what signs to look for:

• Flagging twigs: Small branches with dead leaves that hang limply or fall off.
• Slits or cuts on twigs: These are oviposition sites created by females.
• Sudden leaf dieback: In severe cases, multiple twigs may be affected.
• Presence of adult cicadas: Large numbers of noisy cicadas around the tree during emergence season (usually late spring to early summer).

If you notice these symptoms during a known emergence year of 13-year cicadas, it’s time to take action.

Preventive Measures to Protect Trees

1. Physical Barriers: Netting and Mesh

One of the most effective ways to protect trees from oviposition damage is by using fine mesh netting or floating row covers. The goal is to prevent female cicadas from reaching the branches.

• Material: Use a nylon or polyester mesh with openings smaller than 1/4 inch to prevent cicada access.
• Application timing: Install netting before adults emerge, typically early spring or when soil temperatures reach about 64degF (18degC) as this signals nymph emergence.
• Coverage: Cover entire young trees or vulnerable fruit trees, securing edges tightly at the trunk and ground level.
• Duration: Keep netting on for about six weeks until adults disappear after laying eggs.

Pros:
– Simple and chemical-free
– Highly effective if applied correctly

Cons:
– Labor-intensive for large trees
– May impact aesthetics or airflow if not managed well

2. Pruning Damaged Branches

Removing flagging twigs can help the tree recover more quickly after egg-laying has occurred.

• Prune immediately after emergence ends (usually mid-summer).
• Cut back damaged twigs several inches below visible damage.
• Disinfect pruning tools between cuts to prevent disease spread.
• Avoid heavy pruning as it stresses the tree further.

This method does not prevent damage but limits long-term impact.

3. Chemical Controls

Insecticides are generally not recommended against adult periodical cicadas because:

• Adults only live for a few weeks.
• Large-scale spraying is environmentally harmful.
• Cicada nymphs live underground where insecticides do not reach effectively.

However, some targeted treatments during peak emergence may reduce oviposition activity:

• Use systemic insecticides labeled for sucking insects on trees in early spring before adult emergence.
• Apply contact insecticides like pyrethroids only if recommended by local extension services and applied carefully.

Always follow label instructions and consider nonchemical options first.

4. Tree Health Maintenance

Healthy trees withstand cicada damage better than stressed ones. Maintain tree vigor through:

• Proper watering during dry periods
• Mulching around the base to retain moisture and moderate soil temperature
• Fertilizing according to soil test recommendations
• Controlling other pests and diseases promptly
• Avoiding unnecessary stress such as construction damage or soil compaction

A robust root system also helps trees recover from twig dieback faster.

5. Timing Plantings

If possible, avoid planting new trees just before an expected brood emergence year. Newly planted saplings are most susceptible to serious damage because they have fewer branches overall and less ability to compensate for losses.

Plan plantings so that young trees have at least one full growing season before an anticipated brood appearance. This approach minimizes initial vulnerability.

Specific Considerations for Fruit Trees and Ornamentals

Fruit-bearing species like apple, cherry, peach, and plum are particularly susceptible because:

• Twigs damaged by egg-laying may reduce fruit yields.
• Branch breakage impacts future harvest potential.

For these species:

• Consider netting individual branches if covering entire tree is impractical.
• Coordinate protective measures with your overall pest management plan.
• Monitor carefully during emergence years for early signs of damage.

Ornamental shrubs like dogwood or redbud may also be affected but usually tolerate minor defoliation unless heavily infested.

Monitoring Cicada Activity

Effective protection begins with knowing when cicadas will emerge locally:

• Consult regional extension services or entomology departments for brood maps and predictions.
• Soil temperature monitoring: Adult nymphs typically emerge when soil reaches about 64degF at a depth of ~8 inches.
• Early spring observations: Watch for nymphal exoskeletons on tree trunks as a sign of imminent emergence.

By anticipating emergence windows accurately, you can apply protective measures timely and efficiently.

Long-Term Outlook: Why Cicadas Are Not Always Bad

While damaging in the short term, periodical cicadas play important ecological roles:

• Their nutrient-rich bodies enrich soil when they die off en masse.
• Feeding activity aerates soil and stimulates root growth indirectly.
• They are a key food source for many birds and other wildlife.

Protecting valuable trees does not mean eliminating cicadas but managing their impact responsibly.

Summary: Best Practices for Protecting Trees from 13-Year Periodical Cicadas

1. Use physical barriers like fine mesh netting around young and vulnerable trees starting early spring.
2. Maintain good tree health through proper watering, mulching, fertilizing, and avoiding stressors.
3. Prune damaged branches after egg-laying ceases to promote recovery.
4. Minimize chemical insecticide use; rely on systemic treatments only when justified and applied properly.
5. Time new plantings so that saplings have time to establish before a brood emerges.
6. Stay informed about local cicada emergence forecasts via extension services or scientific resources.

With these strategies in place, you can safeguard your trees through the noisy yet natural spectacle of the 13-year periodical cicadas while maintaining healthy landscapes year after year.

By understanding the biology, timing your interventions carefully, and combining physical protection with strong cultural practices, you ensure your valuable trees survive, and thrive, despite one of nature’s most impressive insect events.