Lichens can indeed spread between plumeria plants, as they can with other types of plants. However, understanding the nature of this spread and its implications is important for managing plumeria care.

How Lichens Spread to Plumeria Plants

1. Reproduction and Dispersal:
   • Fragmentation: Small pieces of lichen can break off from an existing colony and get carried by wind, water, or animals to new locations, including other plumeria plants.
   • Soredia and Isidia: These are specialized reproductive structures that contain both the fungal and algal components of the lichen. They can be dispersed by wind or water to new plumeria plants.
   • Spores: Fungal spores can be produced by the lichen and, if they land on a suitable surface with the right algal partner, they can form new lichen colonies.
2. Environmental Factors:
   • Humidity and Moisture: Lichens thrive in humid environments. Plumeria plants grown in areas with high humidity or frequent watering might provide an ideal habitat for lichen establishment.
   • Air Circulation: Poor air circulation can create a more favorable microclimate for lichens to grow. Pruning plumeria plants to enhance airflow can help manage lichen spread.

Impact on Plumeria Plants

• Non-Parasitic: Lichens are not parasitic and do not extract nutrients from the plumeria plant. They grow on the surface and do not penetrate the plant tissues.
• Aesthetic Concerns: While lichens do not harm plumeria plants, they may affect the plant’s appearance, which could be a concern for those growing plumerias for ornamental purposes.

Managing Lichens on Plumeria Plants

If lichens are present on your plumeria plants and you prefer to manage or reduce their presence, here are some steps you can take:

1. Physical Removal:
   • Gently Scrubbing: Use a soft brush or cloth to gently scrub the affected areas. Avoid using harsh tools that could damage the plant’s bark.
   • Water Pressure: A gentle spray from a garden hose can help remove lichens from the surface of the plant.
2. Improving Air Circulation:
   • Pruning: Regularly prune your plumeria plants to improve air circulation around the branches and leaves.
   • Spacing: Ensure proper spacing between plants to reduce humidity levels and improve airflow.
3. Managing Moisture:
   • Watering Practices: Avoid excessive watering and ensure good drainage around your plumeria plants.
   • Mulching: Use pine bark mulch, which you prefer, to help manage moisture levels and improve soil drainage.
4. Chemical Treatments:
   • Fungicides: While not typically necessary, some fungicides can help manage lichens. However, this should be a last resort and used with caution, as it can also affect beneficial organisms.

Conclusion

Lichens can spread between plumeria plants, but they are generally harmless and primarily a cosmetic concern. By managing environmental conditions such as moisture and air circulation, you can reduce the spread of lichens and maintain the aesthetic quality of your plumeria plants. Regular monitoring and gentle physical removal can also help keep lichens in check without harming your plants.