Pacific Daily News
Editor’s note: This is the first in a two-part series about plant diseases on Guam and Micronesia.
Known by its scientific name Casuarina equisetifolia, ironwood trees are tightly integrated into Guam’s environment and local culture.
It is a hardy, pioneer, salt-resistant tree that occurs on the island’s main soil types: limestone, volcanic, and coral sand. It is propagated for windbreaks, erosion control, and urban landscapes.
Because C. equisetifolia is the dominant tree species on many of the sandy beaches of the Mariana Islands, it has become an important perching tree for the white-collared kingfisher (Halcyon chloris), the Mariana fruit-dove (Ptilinopus roseicapilla), and the white fairy tern (Gygis alba), which commonly lays eggs in the trees.
It has been continually propagated since the 1600s. Due to its buoyant cones, it likely floated to Guam’s sandy beaches thousands of years ago on currents from the central Indo-Pacific coastline.
From these cones, seeds were shed and grew into trees. Over time, ironwood became one of Guam’s prominent members of the halophytic (sea-salt adapted) vegetation type.
Based on what we now know, Guam’s healthiest trees tend to occur in natural areas, near the coastline and in areas not prone to drought.
Cocos Island and Ritidian are just a few of the places where healthy coastal stands of ironwood can still be found.
Farmer seeks help
In 2002, local grower Bernard Watson contacted University of Guam professor Robert Schlub about a group of five ironwood trees in one of his windbreaks that exhibited symptoms of rapid yellowing and death. Death occurred within a few weeks of symptom onset.