During the past two weeks, our weather has been cooling down and we have been blessed with a few more trade-wind showers.

It has been a pleasant change from the hot, dry summer. It just so happened that this ever-so-slight change in weather coincided with the arrival of autumn in late September.

As we become experienced orchid and plant growers, it is important to be aware of the changing climatic conditions. With the wetter months come certain pests that will become more problematic.

One group that can cause serious damage to our collections is mollusks — which includes slugs. The most damaging are the brown slug (Vaginulus plebeia), the two-striped slug (Veronicella cubensis) and the black slug (V. leydigi). They love to feed by scraping off the tissue of young orchid shoots, leaves, flowers and root tips. The damage can literally happen overnight — with the telltale signs of damage and a trail of sticky slime. To make matters worse, the slugs have equally hungry relatives such as the giant African snail (Achatina fulica) and the brown garden snail (Helix aspersa).

These nocturnal bad guys are busy eating on our collections while we sleep, usually appearing out on nowhere after an overnight rainfall. During the day, they seek shelter beneath wood, plants, pottery, rocks, leaves and mulch. While slugs are extremely sensitive to drying out, snails, in times of drought, take refuge within their shells and can remain dormant until damp conditions recur. Often they will bury themselves within the orchid planting medium or crawl into the bottom of the pot from the drainage hole, remaining unseen and protected during the day.

Slugs and snails are legless and move by means of a "foot." Glands in the foot secrete mucus to facilitate movement. This is where it gets confusing — both are hermaphroditic (have male and female sexual organs), but still need to mate, and both animals have the ability to lay eggs. (Talk about a sexual revolution!) Depending on the species, they can lay up to 200 oval, translucent eggs. Eggs are laid in moist soil and hatch in 14 to 30 days. So, this tells you that you will need to constantly monitor for these pests during the rainy season.

There are several ways to manage the slug and snail populations.

The safest, cheapest and surest way is through cultural controls such as sanitation — eliminate the critters' hiding and breeding areas.

Another strategy is to trap them and dispose of them. Place raw potatoes or fruits, or pieces of lumber, in moist problem areas. Collect the culprits at night or in the early morning. Then drop them into a bucket of soapy water; they'll die right away (although you will lose major karma points).

Be extremely careful when handling African snails — they carry rat lungworm (Angiostrongylus cantonensis), which can cause eosinophilic meningitis in humans. People can become infected if snail mucus comes into contact with human mucous areas such as the eyes, nose and mouth, or by ingesting improperly cooked snail meat. (The snails were originally brought to Hawai'i as food.)

Slugs are just as dangerous — they can carry E. coli.

So when handling snails and slugs, use disposable gloves and wash your hands thoroughly with soap and water.

Another method is to pour fresh beer into shallow pans. The pests will crawl in there and die quite happily. I have tried this method, but, frankly, I can find better uses for beer.

Biological control for slugs comes in the form of toads, predatory beetles and birds such as ducks and chickens. The rosy predator snail (Euglandina rosea) is one of three species brought in to combat the African snail.

If the cultural and biological controls fall short, you may have to resort to chemical controls. Most garden shops carry very effective slug and snail bait containing methaldehyde. As with any chemical, carefully follow label directions and keep animals out of treated areas.

For the most complete effect, use all of the above methods in conjunction with a commercial slug and snail bait containing methaldehyde.

You need to be diligent and monitor your collection, because your neighbors may not, and their guys may come over one evening for a visit.

If you have more questions on controlling orchid pests, check out the annual Honolulu Orchid Society Show, "Orchids in Paradise." You'll find five guest orchid society displays, and a miniature orchid display, potting sessions and a full slate of orchid lectures.