The Butterfly Effect: The impact of an invasive disease on native butterfly populations

By on July 16, 2014

If we lose the redbay tree, we may also lose the Palamedes Swallowtail, which feeds almost exclusively on redbay as a caterpillar (caterpillar pictured left; adult pictured right).  Images: Left: J. N. Dell, University of Georgia, Bugwood.org; Right: J. Payne, USDA, Bugwood.org.

If we lose the redbay tree, we may also lose the Palamedes Swallowtail, which feeds almost exclusively on redbay as a caterpillar (caterpillar pictured left; adult pictured right). Images: Left: J. N. Dell, University of Georgia, Bugwood.org; Right: J. Payne, USDA, Bugwood.org.

Laurel wilt disease, a disease caused by a fungal pathogen, has already had major impacts on redbay trees across the Southeast. The pathogen is spread from tree to tree by the non-native redbay ambrosia beetle, a small insect that seeks out healthy redbays. A single beetle attacking a tree can spell doom and trees may die in as little as a few weeks. Already known to occur in six N.C. counties, the disease continues to spread.

While the death of redbay may not garner as much attention as, say, the death of a valuable lumber species such as walnut or ash, the ecological effects of losing redbay could be quite significant, especially for one of North Carolina’s most charismatic butterflies.

The Palamedes swallowtail feeds almost exclusively on redbay as a caterpillar. In turn, many fear that losing the redbay also means losing the Palamedes swallowtail. To determine if this is true, the N.C. Forest Service Forest Health Section has teamed up with Dr. John Riggins at Mississippi State University to survey the populations of swallowtails in areas both affected and unaffected by laurel wilt. By comparing the population dynamics in these areas over time, a population trend of the butterflies can be determined.

Are the populations indeed decreasing? Preliminary data seems to suggest so, but only time will tell. This summer marks the second year that NCFS will conduct the survey. For more information about laurel wilt, visit NCFS’ laurel wilt FAQ page.

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