Australian pines were first brought to the United States in the early 1900's as lovely ornamental shade trees, thought to be a perfect solution for many yards in hot, sunny sites. The "pine" is now a troublesome invasive plant that has escaped into the wild in south Florida, the Virgin Islands, Puerto Rico and Hawaii. The plant, which is not related to our north American pines, has become a highly invasive problem weed that is choking out native species in southern US coastal areas, and it is a particular problem in Florida's Everglades National Park. It is commonly referred to as ironwood, horsetail tree, or Australian pine.
There are actually three different species of Casuarina -- C. equisetifolia, C. glauca, and C. cunninghamiana, but the three look so much alike that it is very difficult to tell them apart. Scientists at USDA's Agricultural Research Service are now conducting research to positively identify each species by its specific DNA and then finding insects for each one that might be used as biological control agents.
ARS scientists have traveled in recent years to Australia, where they collaborated with Australian colleagues to collect DNA samples from native Australian trees and to identify insects that might be used to stop the spread of the plant in the United States and its territories. ARS entomologist Greg Wheeler says that although Casuarina has some "fine qualities ... its negatives far outweigh its positives." Wheeler and Australian scientists collected over 300 insects that might be used to control the weed, and narrowed the field of potential control agents to just 12, including a wasp that eats the plant's seeds and a moth that attacks the foliage.
By the end of this year, the researchers expect to complete their DNA studies, which will allow them to positively identify which species is which -- and then match them with an insect that will help stop the spread of a now-deadly plant that inhibits the growth of native American species.
(image: ARS, courtesy Amy Ferriter, S. Florida Water Management District, Bugwood.org)
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