Pests of paradise

Mike Harris

Software bugs are irksome enough but when a real one crawls out from behind the keyboard space bar and makes a dash for freedom in the flag locker, instant action is called for. Late night computer sessions are sure to bring them out and the small can of insecticide I keep to hand is effective; but you have to be quick. It was some four years ago in the Canary islands that the cockroaches first moved aboard and in spite of several attempts at mass extermination, they still make regular night patrols around the sink, the bulkheads and the chart table . I suppose that with time, we have become more adapted to the idea of living with roaches but at one time the possibility seemed too dreadful to contemplate. This was before we had settled to the life of long term cruising and, on reflection, a good many of the natural hazards we thought to be important proved to be benign, whereas one or two we had not suspected turned out to be more serious. It's impossible to give a complete catalogue of all the hazards to health one might encounter during a long cruise in the tropics. Sharks and similar marine hazards are of course well known but list that follows is a personal perspective on a few that we encountered in the Caribbean and Pacific that are perhaps less obvious, misunderstood or underrated.

Cockroaches come in various types and sizes. Fortunately, the larger 'mahogany sparrow' (Periplaneta Americana) that can reach 50 mm in length do not normally inhabit boats though are often seen beneath palm trees and in buildings ashore. The German cockroach (Blattella Germanica) is common aboard boats. Even the cleanest, most well kept boats can have them and if you spend long enough in the tropics, sooner or later you'll probably have them aboard. They are often found in food warehouses and like to live in the small recesses of cardboard boxes which gives them a good means of transport to new locations. To avoid capture cockroaches prefer to run away rather than fly though they are perfectly capable of flying if the need arises. For the most part cockroaches are fairly harmless pests, but one that most would rather do without, so how might they be controlled or eradicated? Firstly, prevention is better than cure, so be scrupulous about removing cardboard packaging from food stores before they are brought aboard. Start your eradication campaign at the first sign of a roach, as the chances are that a fair number of others have already set up home behind the woodwork. This could include:

  1. Sprinkling boric acid powder, diatomaceous earth or proprietary roach tablets in their favourite draws, cupboards, or surfaces.

  2. Deploy 'roach motels' in popular locations. These are thin plastic insecticide filled domes that are mounted on a 50 mm X 50 mm self adhesive base. The dome has small roach size tunnels and the insecticide remains active for many weeks.

  3. Have a regular 'bombing' session. This involves removing a good deal of the boat's furnishings, lifting floor and removing head linings. Cockroach 'bombs' are aerosol cans of insecticide. With the boat evacuated and all hatchways sealed the 'bomb' is set to release its vapours which circulate and penetrate the boats more inaccessible parts.

Unfortunately cockroaches are amongst the most resilient life forms on the planet. Able to thrive under high levels of ionising radiation and, even after decapitation, they can live on for days still following their usual circadian rhythms. In the aftermath of nuclear war they would surely be the first life form to emerge and take over.


Before eating their ship's biscuit, seamen of the nineteenth century developed the technique of gently tapping them on the table to shake out the weevils. Even after years of shoreside life the habit was hard to forget and served as an amusing way to pick out old salts at smart parties. I can safely say that it is a trick I will not fall into; our biscuits are totally weevil free as they get eaten too quickly though the same has not always been true of the ingredients. Though weevils are tiny, they are not usually difficult to spot. Their dark colour generally contrasts well against the types of food they like to infest. Also the 'wood worm' like holes they bore in pasta, rice or papodums are unmistakable. Buy stores of pasta, beans and flour carefully and in quantities that are consumed quickly and weevils are not likely to be a problem. On the other hand, if you are preparing for a long voyage or need to stock up because prices are low, you need to be especially careful. Buy a small sample and inspect it most carefully before you commit your self to a large quantity from the same supplier. Subdivide bulk foods and store in watertight rigid plastic containers. Do not use hessian, polypropylene or paper sacks. Instigate a regular inspection routine so that any infestation is detected early and can be dealt with promptly.

Some areas of the world where Malaria was once highly active are now less risky, yet in other parts such as the Solomons, unpleasant strains have emerged. With new treatments, prophylaxis, eradication techniques and new patterns of disease, the malaria story is still unfolding. When planning a trip to an area where the disease is prevalent always seek informed medical advice well in advance as prophylactics may need to be taken several weeks before you arrive. Even if you are taking prophylactics, you are by no means guaranteed immunity. Also, as several other unpleasant diseases are also spread by mosquitoes (eg. Dengue fever) your first line of defense must include precautions against being bitten. Here there are several strategies that, when built into a tropical life style, become second nature:

  1. Clothes. In evenings and early mornings wear long loose shirts and trousers covering wrists and ankles.

  2. Bed Nets. Sleep beneath mosquito nets. Nets stretched around light wooden frames that fit portholes and hatchways can help keep the boat free of insects. Use an insecticide spray to finish off any that you find inside. If ventilation is a problem consider using a wind scoop to force air through a forehatch net. Nets are made much more effective if they are regularly soaked or sprayed with a pyrethroid insecticide (eg. Deet). The treatment needs to be repeated every 2 to 4 months.

  3. Mosquito coils These consist of flat spirals of compressed sawdust soaked in an insecticide and potassium nitrate. When set alight they smoulder keeping mosquitoes at bay for about 8 hours.

These South American mosquito coils are made from wood dust soaked in gum, insecticide and potassium nitrate.

The dish on the left contains a smouldering coil setup for use at night.

In many parts of the tropics the candle nut tree provides a source of natural soaps and cosmetics. When crushed and burnt the oily kernels smoulder producing a smoke that keep insects at bay for hours.

This tree is in Vava'u, the northern island group of the Kingdomof Tonga

Vampire bats.
Vampire bats are quite common in parts of the Caribbean, particularly around the Venezuelan coast. The risk here is not, as in the horror movies, that you might yourself be turned into a vampire, but that the bats can carry a variety of rabies. There have been several reports of people bitten whilst sleeping beneath open hatchways so the risk cannot be ignored. In areas where vampire bats are prevalent the local inhabitants are aware of the risk so enquire locally for advice. For once, the traditional method of draping garlic around the hatchway is no good at all though a simple mosquito net should keep them out.

Cruising boats are not often bothered by rats but on boats I have known that have experienced them, the devastation has been such that crews now go to great lengths to keep them off in future. Rats of course are not exclusive to the tropics and are commonplace in many commercial harbours, particularly those shipping animal feeds or other things they like to eat. Alongside berths are particularly risky, so grills over ventilators and open hatches are a good idea. On my own boat, I also like to make sure that all floor panels and engine covers are always in place as any wandering rodent would then have at least 12 mm of plywood to nibble through before it could gain access to the bilge and more inaccessible parts of the boat.

For Mike Ambrose, a single hander over-wintering in the Canaries, scratching sounds from the bilge were the first indications that he was no longer alone. As with most boats, the bilge contained a ready made ratty lair of passageways between pipe-work, spares and stores. The thought of having a rat build a home from chewed sail bags and insulation was dreadful and were it a gravid female the future prospects were too horrible to contemplate. Drastic and immediate action was clearly called for but how best to tackle the problem was by no means clear. Already it had easy access to enough food to last for months so traps and poison baits were immediately ruled out without a second thought. Some of us whose boats did not have rats on board suggested that perhaps a Jack Russell, or maybe a ferret (readily available from the local market) might be used to entice it to leave but, not having a liking for blood sports, Mike rejected these ideas as well.

At first light the next morning, instead of continuing his usual leisure activity of oil painting, Mike began the long job of methodically clearing the bilge. Lots of long forgotten gear was hauled up and piled on deck, barriers were erected and by mid afternoon the rat was reported to be located in a far corner. It appeared unwilling to leave the boat but when it made a sudden dash to for a more inextricable part of the boat, Mike made a desperate grab for the most handy object to clap on top of it. Sadly, this turned out to be the stretcher holding his most recent artwork - a portrait that had taken many hours and which was very near completion. Now, with one hand fully occupied securing the rat his choice of further action was severely limited. It is at this stage that his account of events becomes unclear; however, in the subsequent action neither rat nor oil painting survived.

Rat guards - a simple deterrent for mooring lines

The name covers a multitude of sand flies and other tiny biting insects that cause small irritating lumps to appear on exposed areas of skin. In the Marquesas Islands of French Polynesia, where they are known as No-no's, they have a reputation for being particularly vicious and have survived repeated attempts at eradication. If No-see-ems are present, it's often children playing on the beaches that are most badly bitten. The spots always look worse if they are scratched and can quickly become infected. In Polynesia, the bright red mercurial ointment used to treat them makes them appear absolutely dreadful. So if your island paradise has children with red spotty arms and legs, the best beach gear could be a long-sleeved shirt and trousers with elastic cuffs at the ankles. Anchor well offshore and keep mosquito screens in place at night.

Tropical ulcers
Here's a problem to be taken seriously. Occasional cuts and grazes are such a normal part of the cruising lifestyle that many people are inclined to ignore them. It seems silly to fuss over a minor scrape, but in the tropics there is always the risk of it developing into a tropical ulcer.

The example of a fellow cruiser in the Pacific has often been repeated. Being vaguely aware of the problem, after scratching his leg on a rock he simply stuck a plaster over the damage and carried on enjoying life as usual. On pulling it off a couple of days later a large lump of skin also came away leaving, a much bigger wound with a soft centre. 'Let the air get at it' he thought might be the solution, but as the days went by it got larger and showed no sign of healing. At last the idea dawned that without serious treatment the whole leg might become infected so a drastic change of strategy was called for. Thorough washing with antiseptics, daily treatment with an antibiotic powder and careful dressing did the trick, though it was a long time before new flesh covered the wound.

The message here is not to leave wounds to look after themselves but to make sure they are thoroughly cleaned with antiseptic as soon after they have occurred as possible (weak hydrogen peroxide is my personal favourite) and thereafter, to keep them as clean and dry as possible. The same treatment should also be applied to insect bites which, if scratched, can also develop into an ulcer.

Sea snakes
Some sea snakes are highly venomous though the only one commonly found in the Caribbean is reputed to be harmless. Not all are inclined or able to bite. The black and silver banded Flat Tailed Sea Snake (Laticauda colubrina), common in parts of the Pacific, has a small head with fangs set well to the back of its mouth. This limits the size of object it can bite and in humans it's reputed to be dangerous only if it is able to bite a thin fold of skin such as that between thumb and forefinger. I once watched some Tongan lads taking advantage of this principle as they handled such a snake on the road outside of a village shop. With minds on other matters, they casually allowed such a snake to drape itself over bare forearms and fingers. Be that as it may, it is as well to remember that sea snake venom can be extraordinarily powerful causing death within minutes. Surely reason enough to keep out of their way.

Coral reefs
Walking over coral reefs at low tide is a fascinating experience. A chance to observe at first hand an enormous variety of exotic plant and animal life that most people only get to see on TV documentaries. Here the risks are mainly of encounters with poisonous jellyfish, stinging coral or of stepping on sea urchins or venomous fish such as the Zebra fish (Sinanceja horrida). Rather than open sandals wear a good pair of wellington boots or closed reef shoes and the risks are minimised. It doesn't matter if they have holes, as any water that comes over the top will just drain out more quickly.

Ciguatera is a toxin carried by fish. It doesn't seem to affect the fish but if you eat them you may suffer numbness and tingling sensations about the lips, tongue, hands and feet, possibly followed by prostration, paralysis and coma. The problem is associated with reef fish rather than those caught in open waters. The local people are usually well aware of the risks and can advise where to fish and what types can be eaten. I am frequently amazed by fellow cruisers who heartily enjoy catching and eating every kind of fish going without giving the subject a second thought. On visiting a new location it may not be a bad idea to live on canned food for a day or two until you find out which species are safe to eat.

In conclusion
When visiting a new country, part of the enjoyment is seeing how people manage their everyday affairs in a different environment with different values and priorities. For the traveller it's often the simplest, ingrained habits that mark the locals from themselves. I once watched the King's birthday celebrations in Nuku 'Alofa, Tonga. The sun was high in the sky and long before the parade of bands and dancers were due, the roadsides had filled with hot well wishers all looking for somewhere to rest their legs. Like a bank holiday weekend on Brighton beach, groups of people filled every available space save for the handy shady spot I found beneath a palm tree. The procession was late and, as time passed, I noticed that beneath every other palm tree there were other vacant shady spots. As families passed, mothers and grandmothers would peer anxiously into the tree above my head and at the full bunches of ripe coconuts, at the coconuts that had already fallen and at the idiot sitting underneath. Look after the coconuts and the vampires will take care of themselves.

� Mike Harris March 2005