Release of bio-control insects to eradicate invasive weed OK’d

The U.S. Department of Agriculture has allowed the islands of Guam and the CNMI to breed and release a non-indigenous insect that is said to help control infestations of an invasive weed throughout the islands.

According to the USDA, the non-indigenous insect with the scientific name Heteropsylla spinulosa is used to reduce the severity and extent of infestation of a non-indigenous plant in the CNMI called the Mimosa dilotricha.

The M. dilotricha is a major pest of agriculture, pastures, wastelands, and roadsides. It scrambles over and smothers other plants.

Thickets of the tangled stems can injure humans and trap animals. The USDA stated in its March 2008 environmental assessment that, “it is a serious tropical plantation weed in the Pacific islands infesting rubber, coconut, and sugarcane fields.” Also, when the plant dies and dries up it becomes a fire hazard.

The M. diplotricha has sharp, hooked prickles. Leaves are alternate, bright green feathery and fern-like. Leaflets close up when disturbed, injured, or at nightfall. Their stems bunch, often scrambling over other plants.

The M. diplotricha is not indigenous to the CNMI.

The USDA decision last week would allow the introduction of laboratory rearing and release of Heteropsylla spinulosa.

Northern Marianas College-Cooperative Research Extension and Education Services entomologist Dr. Jaoquin Tenorio said the M. diplotricha is all over the place in agricultural areas throughout the CNMI.

“Because these plants grow very tall in a vine or in a bush, many farmers have to wear thick clothing or they get thorns everywhere. They are also a nuisance to cattle that roam farm areas and are very hard to control,” Tenorio said.

It has been estimated that over 350 acres on Saipan, 370 acres on Tinian, and 300 acres on Rota are infested with this nuisance weed.

Tenorio said that NMC-CREES is currently waiting for the official permit from the USDA before going ahead with the release of the bio-control. The permit is expected to arrive by the end of this month or early next month.

“When we receive that permit, we will then go out and gather these insects from their original areas,” Tenorio said.

He said that NMC-CREES is planning to gather them from either Pohnpei or the Federated States of Micronesia.

When asked that if these non-indigenous insects will someday become a nuisance in the CNMI, Tenorio said that the USDA received all the testing of the insect from Australia, Pohnpei and Palau and has decided that “they do not and will not become a nuisance.”

“Nothing will become approved for introduction by the USDA if it does not complete necessary assessment,” Tenorio said.