The Pesky Problems of Boat Pests

Ever since I fell under the spell of E.B. White’s classic tale “Charlotte’s Web,” I’ve been more than reluctant to stomp on every bug we see on deck—especially spiders. I know my arachnid empathy might come back to bite me, literally. Nevertheless, when someone on board shouts, “Spider!” I still reach for a clear plastic container (to trap the uninvited guest) and sheet of notebook paper (to slip under the plastic dome, for extraction).

Each time I do, I imagine prominent American philosopher and famous bug lover E.O. Wilson nodding with approval.

I know that my love of bugs is not universal—especially for those bugs regarded as pests, so for those who’ve not the time or inclination to trap and release tiny creatures who bite, sting, or devour property, here are some other ways to deal with pests on board.

Grain Weevils. We described in detail the treatments (microwaving, baking, CO2, etc.)  for grain weevil in PS November 2018, so we won’t repeat those tips here.

Spiders. Fundamentally, we’re both on the same side. They eat insects. However, at some point they become annoying. The best way to remove them from the cabin is to eliminate their natural food source by eliminating insect pests. Because they are at the top of the food chain, they are more susceptible to pesticides that most insects, so any pesticides applied for insects will probably kill the spiders.

At certain times of year and in certain areas, spiders can descend on the wind, each predator dangling from a single thread of silk. The lifelines create a natural framework, and the breeze delivers a steady supply of mosquitoes and small flying insects. The dark corners of the cockpit are naturally attractive to no-web spinning spiders.

There seems little point in trying to poison them on deck; fresh ranks arrive daily. But repellents have proven reasonably effective, at least in the cockpit and around the companionway. We’ve used Star Brite Spider Away with considerable success, focusing on dark corners and the edge of the companionway. They are less effective on the lifelines, but if you go sailing, the wind and spray will generally take care of that.

Ants. Because they need a fresh water source, these are typically only an issue on the hard or when there is fresh water in the bilge. Eliminate the water source. If they persist, we found Terro Liquid Ant Bait trays to be quite efficient. Some of the ants will die in the tray or in the immediate vicinity, but others will carry the poison back to the nest, eliminating the nest. They should be placed as close to the nest as practical and where the ants run. If there are small children or pets on the boat, locate them so that they are inaccessible.

Fruit Flies. The simplest cure is prevention. Keep fruit either in a basket draped with netting or in a net laundry bag. Monitor your store rigorously for signs that something is getting overripe and eat it first.

In a house, vinegar traps and sticky paper work. But a brisk sail with the hatches open usually blows them out, if there is no over ripe fruit to hold them. At night, a vacuum cleaner is quite effective at collecting the flies and mosquitoes that gather around cabin lights (after you put the netting up).

Bees and Wasps. Prevention is best. Seal up holes, particularly in spars. Try to remove the nest at the very beginning, when they are relatively harmless.

The best answer for a bees nest is a bee keeper. Most of the bees in the Caribbean and Mexico are Africanized; they get mad, swarm, and don’t stop stinging. The keeper will move the queen to a box, along with some comb, wait for the workers to return in the evening, and remove the box after dark. Try moving the boat mid-day; the workers that are out will be unable to find the boat-repeat as needed.

Wood-boring beetles leave pinholes and worm-like trails where they’ve been at work.

Roaches. We’re a fan of boric acid and borate-based cleaners such as Formula B (Homemade Mildew Preventers That Really Work, PS Blog May, 2018), in part because they are effective biocides, but also because bugs hate them. Thus a little boric acid in the pantry makes sense to us. The roaches do not eat it directly, but it does get on their legs, and when they clean themselves they die.

When borax-based cleaners have not worked, we’ve found that either Terro Liquid Ant and Roach Bait trays are effective, sometimes using both.

Termites. Cabinet damage is bad, but if they get into the glassed-in wood, the boat may become a total loss is short order. Bug bombs don’t work-the galleries are too deep. DIY injections are sometimes effective against minor infestations, but often as not they fail to reach the whole colony. Our advice is act immediately; while you fiddle around with do-it-yourself solutions, the bugs are chewing wood and devaluing your investment. Better to admit that its time to call in the professionals.

For more on dealing with pests, including some eco-friendly preventions that won’t put the environment or your crew at risk, see PS August 2019, “Giving Bugs the Big Goodbye.” If you do get bit by a spider the NIH offers an identification guide, and advice on treatment.

Finally, if you have a favorite insect preventative or entertaining insect story to share, I’d love to hear about it in the comments section, or you can send it direct by emailing me at [email protected].