Fending off alien plants and animals is a constant, uphill battle in Hawaii but it must be sustained for the health of the agricultural industry and the tourism economy as well as the native environment.

Limited funding, manpower and political will have left the islands porous to harmful species. The state needs to put together an improved system of checks and inspections, which may cost more up front, but save both businesses and taxpayers the expense and difficulties of eradication or containment.

A recent survey of 40 plant nurseries around the state, conducted by a University of Hawaii at Manoa biosciences research program, found all of them were infested with alien slugs and snails.

Of equal concern was that nursery operators had no idea of the infestations and were moving their products from island to island and elsewhere, possibly spreading the pests.

Five of the 29 alien species discovered had never been reported in Hawaii previously and many had not been reported on particular islands before. Some nurseries unknowingly had as many as 17 invasive species.

The report of the survey in the International Journal of Pest Management comes as the state goes through the annual hit-or-miss exercise of checking imported Christmas trees for pests through eyeballing them and the low-tech method of shaking or pounding evergreens to displace bugs and whatnots.

In some years, the holiday trees, mostly from the Pacific Northwest, have arrived with wasps and other insects and been turned away. In others years, lizards and snakes have escaped officials' notice, much to the alarm of the residents who found them in their homes.

This year, slugs have made appearances, which Robert Cowie, a snail-slug specialist at the university who also was involved in the survey, described as “;potentially quite serious pests.”; Though the environmental risks aren't known, some of the infested nurseries were supplying plants to restore native habitats in particularly vulnerable places like Kahoolawe.

The slugs and snails could also prove damaging to vegetables such as lettuces and cabbages, specialty fruits and floral crops.

The survey found a pattern for the gastropods among the nurseries - arriving first on Oahu, escaping to establish themselves around the island, then being transported to neighbor islands through horticultural traffic.

Cowie suggests the state study horticultural distribution networks to find a way to put controls at key points. That could be productive, but the state should take a comprehensive look at how it could best intercept invasive and alien species, much as California and other states head off island produce for fruit flies.