Hawaii ranchers are hopeful that a small beige-colored moth will be able to control the fireweed, an invasive plant that is toxic to livestock and has caused havoc on the state’s prime pasturelands, according to state officials.
For more than 13 years, entomologists and researchers at the Hawaii Department of Agriculture have literally searched the world for a natural enemy of the weed that would be safe to release in Hawaii. The most promising turned out to be an insect called Secusio extensa (Arctiidae), the Madagascan Fireweed Moth, the larvae of which voraciously eats the leaves of fireweed.
It is believed that the weed came to the islands in hydromulch material imported from Australia where it is a serious pest. Entomologists on Oahu have begun stepping up production of the moth after receiving the long-awaited approval from the U.S. Department of Agriculture, which came on Dec. 6. The state approved the release of the moth in 2010, but also required approval of a federal permit. The first release of the biocontrol insects is slated for early 2013, depending on the rearing of the insects in the laboratory.
"Years of extensive research have been conducted on this biocontrol program," said Russell S. Kokubun, chairperson of the Hawaii Board of Agriculture. "Control of this weed is one of the more important issues to Hawaii ranchers, and we are hopeful that it can be controlled by this natural process."
"Fireweed has become an even more aggressive pest during this extended period of drought," said Dr. Tim Richards, president of Kahua Ranch on Hawaii Island. "So it’s even more critical to our industry’s sustainability that an effective control prevents additional loss of productive pasturelands."
In 1999, the state began looking for a biological control for the pretty but deadly plant with yellow daisy-like flowers, also known as Madagascar Ragwort. It is estimated that the weed has infested more than 850,000 acres, mainly on Maui and Hawaii Island.
Although there are effective pesticides, it is expensive and impractical to use across hundreds and thousands of acres. Besides Hawaii, fireweed has spread through many parts of the world killing animals in Australia, Brazil, Argentina, Colombia, Venezuela, Uruguay, and Japan. Secusio will be the first biocontrol agent to be released against Madagascar fireweed in the world.
The Department of Agriculture’s exploratory entomologist, Dr. Mohsen Ramadan, traveled to Australia, South Africa and Madagascar in 1999 and returned with 14 insects and one fungus, which were researched and tested under quarantine conditions. Some were found to be ineffective, while others were found to harm other native or beneficial plants. Dr. Ramadan traveled to the region again in 2005, 2007, 2011 and 2012 to look for more potential biocontrols for fireweed and other pests, such as coffee berry borer, small hive beetle and the protea mealybug.