Rose Atoll National Wildlife Refuge. Photo credit: USFWS
By Danille Lampe, Americorps Intern, Pacific Reefs National Wildlife Refuge Complex
Dominating the scenery, Pisonia trees (Pisonia grandis) inhabit some larger islands of the Pacific Reefs National Wildlife Refuge Complex, particularly Palmyra Atoll and Rose Atoll National Wildlife Refuges. They reach heights of up to 98 feet and provide many seabirds with important nesting sites. However, Pisonia forests are at risk due to a variety of factors, including invasive species like the Urbicola soft scale insects (Pulvinaria urbicola).
Pisonia tree. Photo credit: USFWS
The scale insect outbreaks have negatively affected Pisonia trees on both Rose Atoll and Palmyra Atoll Refuges. The insects latch on to the leaves and stems, sucking the sap and up to 25% of essential nutrients from the phloem, the inner most layer of bark. They then force out the extra carbohydrates as a sticky substance called honeydew which causes mold to grow over the leaves, preventing photosynthesis and resulting in the leaves being dropped from the trees (Nonner and Woodward, 2006).
Urbicola soft scale insects (Pulvinaria urbicola) on a Pisonia leaf. Photo credit: USFWS