Are 13-Year Periodical Cicadas Harmful to Fruit Orchards?

Periodical cicadas are among the most fascinating and unique insects in North America. Emerging in massive numbers every 13 or 17 years, these creatures capture widespread attention due to their synchronized appearances. While their presence is often viewed as a natural spectacle, many orchard owners and fruit growers worry about the potential impact these cicadas may have on their crops, especially during the emergence of the 13-year periodical cicadas.

In this article, we will explore what 13-year periodical cicadas are, their life cycle, behaviors during emergence, and most importantly, whether they pose a threat to fruit orchards. By understanding these factors, orchard managers can better prepare and manage their trees during cicada outbreaks.

What Are 13-Year Periodical Cicadas?

Periodical cicadas belong to the genus Magicicada and are known for their extraordinary life cycles. Unlike annual cicadas that appear every year, periodical cicadas spend most of their lives underground as nymphs feeding on root xylem fluids. They emerge synchronously in massive broods after precisely 13 or 17 years, depending on the species and brood.

The 13-year periodical cicadas emerge in large swarms primarily across the Midwest and parts of the Eastern United States. Their synchronized emergence is believed to be an evolutionary strategy called “predator satiation,” where overwhelming numbers reduce individual predation risk.

The Life Cycle of Periodical Cicadas

Understanding the life cycle of periodical cicadas is essential when assessing their impact on fruit orchards:

1. Nymph Stage (Underground): After hatching from eggs laid in tree branches, the nymphs drop to the ground and burrow underground, feeding on root fluids for 13 years.
2. Emergence: When ready to mature, nymphs emerge synchronously in spring or early summer.
3. Adult Stage: Adults climb onto trees and shrubs, shed their exoskeletons, and begin mating. Males sing loudly to attract females.
4. Egg-Laying: Females cut slits into small twigs or branches of trees and lay eggs inside.
5. Death: Adults live only a few weeks after mating and egg-laying before dying off.

Why Do Orchard Owners Worry About Cicadas?

Fruit orchards consist primarily of young or mature fruit trees like apples, peaches, cherries, pears, and plums, many of which can be affected by intensive damage caused by insect pests. Orchard owners worry about periodical cicadas because:

• Massive Numbers: Millions of cicadas emerging can cause visible damage.
• Egg-Laying Behavior: Females lay eggs by cutting slits into small branches, a process known as “oviposition.”
• Potential Tree Stress: Repeated injury could weaken trees or reduce fruit yield.

Considering these concerns, it is crucial to analyze whether 13-year periodical cicadas truly harm fruit orchards substantially.

How Do Cicadas Affect Trees During Emergence?

Damage from Egg-Laying

The primary way cicadas affect trees is through oviposition damage. Female cicadas use their ovipositors (egg-laying appendages) to make slits in branches roughly 1-2 cm long where they deposit eggs. This damage often appears as distinct zigzag cuts or scars on young twigs.

• Twig Dieback: The wounds disrupt nutrient flow leading to twig dieback known as “flagging.” Multiple damaged twigs show yellowing or wilting leaves followed by branch death.
• Branch Loss: In severe cases, entire branches may die due to excessive egg-laying.

Impact on Root Systems

Cicada nymphs feed on sap from tree roots underground for up to 13 years. However, scientific studies suggest that this feeding has minimal impact on mature trees’ health since root systems are extensive and resilient.

Stress on Young Trees

Young fruit trees with thin branches are more vulnerable to damage because even a few oviposition cuts can cause significant twig loss or stunt growth temporarily. Mature trees with thicker branches tend to withstand damage better.

Scientific Research on Cicada Damage to Orchards

Studies Indicate Limited Long-Term Harm

Research conducted by agricultural extension services and entomologists generally concludes that while periodical cicadas cause noticeable physical damage during emergences:

• Most healthy mature fruit trees recover fully after emergence events.
• Branch loss is typically limited to smaller twigs rather than major limbs.
• There is no evidence that cicada feeding or egg-laying reduces long-term yield significantly.

For instance, a study published by the University of Maryland Extension found that although oviposition caused flagging on young apple trees, overall tree health was not compromised over time.

Greater Concern for Young Orchards

The main concern remains for newly planted orchards or young saplings less than five years old where heavy oviposition may lead to reduced growth or delayed establishment. In such cases, temporary reduction in vigor could impact early fruit production but usually does not kill the tree.

No Evidence of Disease Transmission

Unlike some other insect pests such as aphids or scale insects known for spreading plant pathogens, periodical cicadas are not vectors for diseases affecting fruit trees.

Management Strategies for Orchard Owners

Orchard owners anticipating upcoming broods of 13-year periodical cicadas can take several steps to mitigate potential damage:

Physical Barriers

Using fine mesh netting (with holes smaller than 1/4 inch) over young trees can protect delicate branches from egg-laying females during peak emergence weeks. This method is especially useful for saplings less than five years old.

Timing Pruning Practices

Prune damaged twigs and flagging branches shortly after emergence ends (usually late summer) to promote healthy regrowth and reduce stress on trees.

Avoid Chemical Controls

Because of the synchronized mass appearance and short adult lifespan (~4-6 weeks), broad-spectrum insecticides are generally ineffective or impractical against periodical cicadas. Insecticides may also harm beneficial pollinators active during this time.

Monitoring Emergence Predictions

Stay informed about local brood emergence schedules via agricultural extension services or university resources so you can prepare ahead of time.

The Ecological Role of Periodical Cicadas

It’s important to recognize that periodical cicadas are an integral part of forest ecosystems and provide several ecological benefits:

• Soil Aeration: Nymph tunneling improves soil quality.
• Nutrient Cycling: When adults die en masse, they enrich soil nutrients aiding tree growth.
• Food Source: They serve as a vital food source for birds, mammals, reptiles, and other insects.

Thus, despite temporary damage concerns in orchards, their ecological value is significant.

Conclusion: Are 13-Year Periodical Cicadas Harmful to Fruit Orchards?

In summary:

• The primary damage caused by 13-year periodical cicadas comes from female egg-laying behavior damaging twigs.
• Mature fruit trees generally tolerate this damage well without long-term health effects.
• Young orchards with thin branches may experience more noticeable stress but rarely suffer lasting harm.
• Root feeding by nymphs underground does not significantly affect mature trees.
• No evidence links cicadas with disease transmission in fruit crops.
• Preventive measures like netting young trees during emergence can help reduce twig injury.

While the mass emergence of periodical cicadas is dramatic and potentially concerning for orchard owners, scientific research indicates that these insects typically do not cause severe or lasting harm to fruit orchards. With proper management strategies in place and awareness of emergence timing, orchard growers can coexist with these remarkable insects without significant losses.

By appreciating both the challenges and ecological importance of these 13-year visitors, orchard owners can better navigate future brood cycles while protecting their valuable crops effectively.