Signs of 17-Year Periodical Cicada Egg Laying on Plants

Periodical cicadas are one of nature’s most fascinating and mysterious insects. Known for their synchronized emergence every 13 or 17 years, these remarkable creatures have captivated scientists, gardeners, and nature enthusiasts alike. Among the two major broods, the 17-year periodical cicada is particularly notable for its predictable, large-scale appearance. One critical stage in their life cycle is the egg-laying process, during which female cicadas deposit eggs into plant tissue. This behavior can have significant effects on plants and is often a clear indicator of an impending cicada emergence. In this article, we will explore the signs of 17-year periodical cicada egg laying on plants, how to identify them, and their implications for plant health.

Understanding the 17-Year Periodical Cicada

Before diving into egg-laying signs, it’s important to understand the cicada’s life cycle:

• Life cycle duration: Approximately 17 years underground as nymphs.
• Emergence: Adults emerge synchronously in late spring or early summer.
• Mating and egg laying: Adult females lay eggs in tree branches.
• Larval stage: Eggs hatch into nymphs that drop to the soil and burrow underground.
• Nymph development: Nymphs feed on root sap below ground until maturity.

The extremely long developmental period makes their synchronized emergence one of the most dramatic natural events in many parts of North America.

Why Focus on Egg Laying?

The egg-laying phase is critical for cicada population sustainability. However, it can cause damage to host plants due to the way females insert their eggs:

• Females use their ovipositors (egg-laying organs) to cut slits into small branches or twigs.
• Eggs are deposited inside these slits.
• This process can weaken branches, causing “flagging,” where tips of branches wither and die.
• Heavy egg laying can lead to branch breakage.

Recognizing these signs early can help gardeners and foresters monitor cicada activity and take steps to protect valuable plants.

Identifying Signs of Periodical Cicada Egg Laying

1. Slits or Cuts on Branches

One of the clearest indicators of cicada egg-laying activity is the presence of small cuts or slits on young branches or twigs. These cuts are made by female cicadas as they insert their eggs.

• Appearance: The slits typically appear as shallow V-shaped or linear cuts along the length of a branch.
• Size: The incision is usually about a few millimeters long.
• Location: Most commonly found on small diameter branches from 1/4 inch to 3/4 inch thick.

Inspecting young tree growth carefully during cicada emergence years provides clear evidence of egg laying.

2. Dead or Wilting Branch Tips (“Flagging”)

After females lay eggs inside branches, the plant tissue surrounding the eggs often dies due to disruption caused by the incision and egg deposition.

• Symptoms: The tips of affected branches turn brown or black and wilt.
• Extent: Often only the distal several inches die back.
• Result: Branch tips may break off over time if damage is severe.

This phenomenon, called “flagging,” is the most visible sign that confirms recent cicada egg laying.

3. Presence of Cicadas on or Near Plants

While not a direct sign on plants themselves, seeing adult periodical cicadas actively crawling or flying around trees suggests ongoing mating and egg-laying activity.

• Female cicadas tend to land on suitable host trees before cutting slits for eggs.
• Large numbers of adults clustered on trees increase likelihood of egg laying damage.

Observing insects can help focus your search for damaged branches.

4. Accumulated Dead Twigs Underneath Trees

Since some heavily damaged branch tips break off due to weakened tissue, you may notice an accumulation of small dead twigs beneath trees experiencing egg laying.

• This debris is often an indirect sign suggesting extensive flagging above.
• Regularly checking under host trees during emergence can provide physical clues.

5. Host Plant Preference Patterns

Periodical cicadas typically prefer certain deciduous hardwood trees for oviposition:

• Species like oak, hickory, maple, ash, birch, elm, and fruit trees such as apple and cherry are commonly targeted.
• Conifers and very young saplings are generally avoided.

Focusing monitoring efforts on these preferred hosts increases chances of spotting egg-laying signs if periodical cicadas are active in your area.

Impact of Egg Laying on Plants

While periodical cicada emergences can be noisy and startling, the actual damage caused by adult feeding is minimal; it mainly occurs during egg laying:

Branch Flagging and Dieback

Repeated insertion of ovipositor slits weakens branch tissues causing dieback as described above. While this might look concerning:

• Moderate damage typically does not kill mature healthy trees.
• Trees usually recover well by growing new shoots after emergence ends.

Breakage Risk

In extreme cases where many slits accumulate on a single limb:

• Branches may break under wind or weight stress due to weakened structure.
• This can result in minor pruning needs or aesthetic damage to ornamental trees.

Effects on Young Trees

Younger or stressed trees may suffer more significantly from flagging because they have less energy reserve for recovery. Protecting these vulnerable specimens during emergence seasons is advisable.

How to Monitor and Protect Plants During Cicada Emergence

Monitoring Tips

1. Timing: 17-year brood emergences occur predictably; local universities or extension offices often publish expected dates.
2. Regular Inspections: Check susceptible trees weekly during peak emergence months (typically May-June).
3. Branch Inspection: Look closely at new growth tips for slits and discoloration.
4. Record Observations: Document extent and location of damage for future reference.

Protective Measures

While total prevention is challenging given massive emergences:

1. Physical Barriers:
2. Use lightweight mesh netting (1/2 inch mesh) draped over young or high-value trees before cicadas emerge.
3. Secure edges to prevent access while allowing light and moisture penetration.
4. Pruning:
5. Remove flagged branches promptly after emergence to encourage healthy regrowth and reduce breakage risk.
6. Avoid Heavy Fertilizing Before Emergence:
7. Excessive nitrogen encourages soft twig growth preferred by females; moderate fertilization supports overall tree health without attracting excessive oviposition.
8. Maintain Tree Health:
9. Well-watered, mulched, and pest-free trees recover faster post-emergence damage.

Conclusion

The 17-year periodical cicada’s mass emergence is an awe-inspiring natural event that leaves unmistakable marks on host plants through their distinctive egg-laying behavior. By recognizing key signs such as characteristic branch slits, branch tip flagging, accumulation of dead twigs, and monitoring adult insect presence, gardeners and arborists can better understand when this phenomenon occurs in their region.

Though some damage to branches may occur during oviposition, mature healthy trees generally tolerate this well with minimal long-term impact. With awareness and preparation, including careful monitoring and protective measures, plant owners can manage cicada-related stress effectively while enjoying the unique spectacle these remarkable insects provide once every seventeen years.

Understanding these indicators not only aids in mitigating potential plant damage but also fosters appreciation for one of nature’s rarest synchronized events, the grand return of the periodical cicadas.