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Dealing with cockroaches

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What is the issue?
Cockroaches are a common infesting insect in warm climates. They make boating life unpleasant, unhealthy, loathsome and lonesome.

Why address this?
Once a few cockroaches have arrived aboard and established themselves they are prolific breeders. With the tiniest amount of food and water they are capable of producing thousands of offspring annually and building an infestation very quickly.

Roaches can passively transport pathogenic microbes on their body surfaces that cause food poisoning. They can leave an offensive odour and one of their proteins, called tropomyosin, has recently been found to trigger allergic reactions and is also linked with asthma. They are also known to burrow into human ears, causing pain and hearing loss.

Justifiably most people find them repulsive, and once it is known that you have them aboard your vessel you will become a social outcast in sailing circles. Friends will no longer want to visit and worse still they will live in fear that you visit their vessel carrying roach eggs aboard.

How to address this?
The great news is that cockroaches can be largely prevented and eliminated so they are not a problem to deal with. It really comes down to working in three areas: preventing an outbreak, making the vessel inhospitable to an outbreak and killing them should they get aboard despite your best efforts.


The commonly invasive roaches
Photo: CC0

  • A The German roach, or Croton bug, Blattella germanica (length 15mm or 9/16 inch).

  • B The American cockroach, Periplaneta americana (length 35mm or 1⅜ inches).

  • C The Australian cockroach, Periplaneta australasiae (length 32mm or 1¼ inches).

  • D The wingless female of the Oriental roach, Blatta orientalis (length 22mm or 1⅛ inches).

  • E The winged male of the Oriental roach (length 25.4 mm or 1 inch).

The German cockroach is the most common invader of the seagoing vessels. They have wings but do not fly having in evolutionary terms long since forgotten how to - big roaches can fly, but they rarely come aboard to infest a boat. Nocturnal creatures, they scurry about at night and hide during the daytime hours. They are scavengers that eat anything organic and flourish where food and moisture are readily available. Likewise, they can live for a few days up to a month without food, so just because no cockroaches are visible it does not mean they are not there. Unfortunately, with ample food and water, they can breed rapidly. A German cockroach and her extended young can produce 300,000 more roaches in a single year.


With a little due diligence and forethought, you can avoid introducing cockroaches to the vessel in the first place. A few simple precautions can make a world of difference:

  • • Most cockroaches arrive aboard yachts during provisioning runs. They, both as insects or eggs, are introduced in grocery boxes, bags, product cardboard wrapping, within fruit and vegetables etc. The solution is to make a policy of not allowing cardboard bags/boxes/product wrapping aboard the vessel under any circumstances. Discard any cardboard packaging on the dock before it even gets near the cockpit. Wash all fruit and vegetables before taking them aboard.

  • • In some cases, cockroaches can simply wander onto a vessel along the dock lines from marina pontoons or harbour walls. This may be best be addressed by lying to anchor offshore in tropical areas as much as possible.

  • • Sometimes they are carried aboard on footwear. If you have walked in areas where roaches have been seen, or indeed upon roaches, make certain to wash off your shoes before returning to your vessel as they could contain eggs. A basin with some bleach water will help clear the soles of your shoes.

  • • Roaches are also capable of hitching a ride from one boat to another by way of your bags and even your person. If you know someone has got roaches aboard treat them like they have the plague. Stay away from their boat and avoid having them aboard at all costs. Sorry, it's brutal, if you don't, you will be the next pariah!


The next area to work on, should you not be able to stop them arriving on your vessel is to create an inhospitable roach environment aboard. Cockroaches need to have food, warmth and moisture to take hold. Sanitation is an important step in prevention and control, don’t throw a party to welcome them aboard:

  • • Search out all the hidden nooks and crannies for any little pools of water from spills, condensation or rain leaks.

  • • Thoroughly clean up any crumbs or spillages aboard. All surfaces and areas around the galley area, including the stove, should be scrupulously clean.

  • • Use href="http://eoceanic.com/sailing/tips/ALL/200/">food storage containers that have an air-tight seal Experience. Likewise, all staples, flour, rice etc should be stored in heavy plastic sealed containers.

  • • Do not leave dirty dishes in the sink and especially don’t let them remain there overnight.

  • • Leave the sink dry and put in the plug.

  • • Use lidded trash cans, the tighter fitting the lid the better. Line the trash cans with bags and remove them regularly.


If you still manage to see one after all this, and it will be one or a maximum of two, eliminate the cockroaches with Boric Acid. There is no need to worry as this is a 100% effective solution and it will work quickly. This tried and tested white inorganic powder has the twin benefits of being both deadly to cockroaches whilst at the same time being relatively harmless to humans.

Boric Acid is widely available at hardware shops worldwide and you should be able to find it readily available in most countries. Also called hydrogen borate, boracic acid, orthoboric acid and acidum boricum, it is a weak monobasic Lewis acid derived from boron that appears in a host of household products, such as antiseptic, insecticide, flame retardant, toothpaste and mouthwash. The name may sound familiar as in the past it was used as an antiseptic eye drop.

Boric acid comes as a colorless crystals or a white powder
Photo: Courtesy of Anmol Chemicals

It has the chemical formula H3BO3, sometimes written B(OH)3, and it comes in a light white powder that has no discernible smell and, provided it is kept dry, it will remain active indefinitely as it does not deteriorate over time. Hence it is easy to get a supply and store it in readiness for any unwanted visitors. But despite its widespread domestic and healthcare uses you should always read the product label carefully prior to use.

Furthermore, a small dusting of Boric Acid required to eliminate cockroaches is harmless to humans. Before discovering Boric Acid we tried many approaches to dealing with small incursions, including a much-praised and highly acclaimed off-the-supermarket-shelf insecticide aerosol. We sprayed the vessel lockers end to end and within a day the odour made the ship's crew feel highly unwell. Consequently, we were obliged to spend the next day removing it and washing it all away, something we could not entirely achieve, and had to retreat to baiting roach traps until someone finally made us aware of the ultimate cure Boric Acid. You may in fact use Boric Acid in conjunction with roach traps to expedite a particularly bad infestation but this is not usually necessary, as Boric Acid alone will do the trick.

The key to the successful use of Boric Acid is to get the cockroaches to crawl over areas treated with a light Boric Acid dusting. The object is to get the powder to stick to the insect's legs and antenna whilst they pass over a dusted surface. Cockroaches find Boric Acid neither repellent nor attractive, they ingest the acid when they clean off the particles that adhere to them and it is this that kills them. There is no species of cockroaches that Boric Acid does not eliminate.

Here is how it should best be deployed:

  • • Empty every single locker and clean thoroughly to remove any crumbs that may have collected.

  • • Target the areas where cockroaches have been seen. They prefer to live where there is food, warmth and moisture which is typically in the galley, under the sink, the stove, inside food storage lockers, near waste disposal containers etc seeking out secluded cracks and crevices to inhabit.

  • • Avoid open and exposed surfaces in these areas, focus on their observed pathways right into corners and up against edges. Do not use Boric Acid on countertops where food is being prepared; wipe off any dust that should fall upon these surfaces with a damp cloth.

  • • Take the ready-to-use Boric Acid ‘squeeze-type’ bottle, shake it and puff a very fine layer over the selected areas.

  • • Remember the objective is to force the roaches to walk through a very fine dusting of Boric Acid. Dust a thin scarcely visible and totally unavoidable layer over the area, not large piles that they will simply walk around as an inconvenience to their pathways.

  • • If there are any areas where you see activity and suspect a nest but cannot access it, remove any fittings or drill a small hole so you may puff the boric acid in.

Then all that is required is to leave the dusting in place. By the end of two weeks, you should see your boat clear of cockroach activity. As long as the Boric Acid powder is dry it will go on indefinitely protecting the vessel.

Cockroaches are a scourge in hot climates and most people live in dread of a roach outbreak. The first mention of cockroaches will make most cruiser's skin crawl and their hairs stand on end. But it does not need to be such a concern, a few precautions will make it unlikely for them to come aboard. Should you see one, you have the peace of mind of knowing that a target dusting of Boric Acid will completely eliminate any incursion.

With thanks to:
Michael Harpur, Yacht Obsession.
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