Millions of slugs invade Rota

Millions of slugs, including “a very harmful” species from the Caribbean called the Cuban slug, have invaded and grown to epidemic proportions on Rota, an expert said.

“There’s a population outbreak of slugs on Rota. It’s a cause of alarm because it’s destroying our crops [and] trees. There’s a need for immediate assistance from the government,” said tropical horticulturist Mark J. Bonin of Rota’s Northern Marianas College-Cooperative Research Education and Extension Service.

Bonin, who was on Saipan last week for a scheduled workshop that was cancelled due to the typhoon, said the Cuban slug, scientifically known as Vernicella cubenis, is a two-striped slug.

“It has an amazing range of color from milky white which is the one present on Rota, [to] stripe, brown, and black,” he said.

So far, he said the Cuban slug has not been found on Saipan and Tinian.

“That’s good and we should keep it that way, which means we should strengthen our quarantine efforts. Likewise, there’s a huge need for public awareness,” he said.

Based on initial accounts, he said the Cuban slug on Rota came from Hawaii and Guam. The species is believed to have reached Hawaii through importation of ornamental plants about 15 years ago.

“It’s not sure when it reached Guam but it’s there and it’s on Rota, most likely through containers,” he said.

Bonin related that in a recent survey on Rota, he and his group spotted a slimy area underneath a papaya tree that was hosting some 200 to 300 slugs.

“It’s a very serious pest. It attacks almost all kinds of plants using its razor-sharp tongue,” he said.

Bonin said his office has discussed the problem with the Department of Land and Natural Resources. “We’re working in coordination with DLNR. DLNR’s assistance is most needed to carry out a serious suppressant program.”

So far, he said, the most effective method to contain the slugs is by using baits.

With the level of outbreak on Rota, he said the government’s assistance is needed to purchase enough slug baits.

“Individual farmers can buy their own bait but it’s limited. If we want to get rid of it altogether, the government should come in [now],” he said.

Slugs and snails thrive in humid and wet areas and are damaging pests of fruit trees and vegetables. They also crawl over walks, porches, walls of homes, and invade homes through doorways.

Slugs and snails are gastropods, soft-bodied animals without body segmentation.

In the Pacific region, there are 4,000 indigenous species of slugs and snails and 100 to 200 alien species.

Most of them are hermaphrodites—each has both male and female reproductive organs—and they multiply by exchanging bundles of sperm.

Eggs are usually laid in crevices in the soil or under rocks, while some species may give birth to live young. Eggs hatch within several weeks. It takes one to two years for slugs to reach maturity.

Slugs normally hide under logs and rocks, in leaf litter or under the bark of trees. Most of them feed on fungi, dead animal, and plant matters—leaves, stems, bulbs, algae.

In a report, research biologist Robert G. Hollingsworth of the U.S. Department of Agriculture-Pacific Basin Agricultural Research Center in Hawaii, said there is little doubt that snails and slugs cause significant agricultural losses in the Pacific islands.

But cost estimates are not generally available compared with other pests because “slugs and snails…have received far less attention than they merit.”

He said this is due to some factors: damage from these species are frequently confused with other pest problems; slugs and snails generally feed at night and hide during the day so their damage may be attributed to grasshopper or caterpillar pests; lack of specialized scientists in the region; and a misperception that most slugs and snails have the same feeding habits and pest status.

“This misrepresentation occurs because pest control scientists and extension workers have not been trained to identify the important pest species, and also because certain species do in fact appear very similar to one another,” Hollingsworth said.

Bonin, Hollingsworth and another colleague, David Robinson from the USDA-Animal Plant Inspection Services, visited Saipan to hold a survey and workshop on slugs and snails. Supertyphoon Chaba, however, prompted the cancellation of their work. They already left the CNMI.

Bonin said the two may drop by the CNMI when they do the survey and workshop in nearly island states.