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Avoiding biting insects

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What is the issue?
Biting insects can be a scourge in certain sailing geographies. Mosquitoes are the largest problem and they can act as vectors for many disease-causing viruses and parasites.

Why address this?
Insect bites are not just painful, sensitive humans usually have extreme allergic reactions to the biting insect's saliva. The primary culprit, mosquitoes, can carry horrific diseases such as Zika, Dengue, and Malaria. One should always make sure that you protect yourself from these small predators as much as possible.

How to address this?
One of the joys of sailing is that you can get away from biting insects to some extent, making your environment that much more enjoyable. When it comes to dealing with biting insects there is not one fix to solve the problem, but a whole range of solutions to hopefully minimise it. To begin, a little knowledge about biting flies will help.


Anatomy of an adult mosquito
Photo: CC0

There are several types of biting flies, such as Sand Flies, Black Flies, Biting Midges etc. but mosquitoes are still responsible for most of the bite cases. Mosquitoes, in particular, are always found where there is stagnant water as this environment is the species, perfect host. There are much heavier concentrations in enclosed and sheltered areas such as in forests rather than out in the open terrain.

Biting flies, as a whole, can fly a long way from where they thrived as larvae. They tend to be active all day with concentrated activity in the first two hours after sunset and again at dawn. They locate animals and humans by sensing the moisture and the carbon dioxide in their breath, perspiration, warmth, movement, and dark colours. Once they find their mark they insert a piercing and lacerating mouthpart into the skin. They then inject their saliva, which contains anticoagulants that prevent blood from clotting as they feed and to make room in its gut for more of the solid nutrients.

Staying well offshore in a good breeze avoids the biting insects
Photo: CC0


One of the great advantages of cruising is that you can anchor off to get away from it entirely or at least the worst of it. If you are surrounded by the ocean, you do not need to worry about it:

  • Anchor well offshore : Stay out as far off the shoreline as is comfortable.

  • Go for the breeze : Avoid narrow, tree enclosed river anchorages that trap the air, or anchorages right on top of mangroves. These are thick with insect life. Pick areas where there is a strong likelihood of a breeze such as anchoring off a stretch of beach with an open valley before it as opposed to a sheer bluff.

  • Get downwind :If there is a choice of anchorages available go for one that is downwind of land. Keep insects upwind wherever possible as they have an unparalleled sense of scent. Given any lead, they will come and find you. Downwind anchorages make it difficult for them to pick up the scent and have the added benefit of offering the most protection.

  • Read the blogs and forums: There are places where mosquitos are more prevalent, near inland marshes, woods and rainforest etc. Usually, people will have signalled the problem locations well in advance so they can be avoided.

If you have to come inshore make the vessel uninviting
Photo: CC0


If you have to come inshore or into a port or marina you should make the boat an unwelcolme environment to biting insects:

  • Clenliness : Eliminate any form of sustenance by following the below deck suggestions for dealing with cockroaches Experience. If you eliminate the substances that support biting insect nurseries you will stop them getting a toehold aboard.

  • Use warm-coloured LED Lights : According to recent scientific research External link the least appealing light to insects is a warm coloured LED light that produces a yellow/orange hue, rather than cool blue light. The worst lighting by far were the traditional incandescent bulbs.

  • Screen off : By far the best line of mosquito control is to have screens, with a finer mesh than the standard screens if possible, on every opening and the companionway Experience of the yacht. At the very least seal the boat up just before dusk, and if possible, stay down below behind the screens during the hours when insects are most active.


Even if we are not in charge of the vessel there are a lot of things we can personally do to dramatically reduce the chances of being bitten.

  • Avoid the worst of it : Mosquitoes are most active after dawn through to mid-morning and become highly active for a couple of hours after sunset. Stay below decks and behind screens during these times as best you can.

  • Do not broadcast your position : Mosquitoes are drawn to moisture and the carbon dioxide which is unavoidable, but also sweat, dark colours, perfumes, scented soaps, sunscreen and hairspray which should be avoided. Reduce the amount of sugar in your diet as sweet-smelling skin attracts mosquitoes.

  • Hide in the wind : If you are out and about find a breezy spot that makes it harder for mosquitoes to locate your scent.

  • Cover Up: Wear long sleeves if you can, and two layers or ruffled materials, mesh jackets and light colours. Layers are important as they can bite through light materials or areas of your body where clothes fit you tightly, but it should not be floppy so as to entangle them.

  • Throw them off the scent : Consuming large amounts of raw garlic is also known to completely deter mosquitoes. Have some whole cloves soaked in olive oil and eat as much as would be contained in a garlic bulb as a whole. This is known to keep mosquitos at bay for up to three days and, most likely, just about everyone else. The cruising lifestyle somewhat allows this to be a realistic means of defence if all aboard take the same measure. Consuming raw onions alone or in combination has a similar effect. An alternative is to take a 1000mg capsule of Garlic a day which might also work. It has been suggested that Vitamin B1 (thiamine) which can be found in Marmite, rich in B vitamins including thiamin (B1), riboflavin (B2), niacin (B3), folic acid (B9) and vitamin B12 and very healthy to have aboard External link is also known to alter a body's skin scent enough to act as a deterrent. But, unlike garlic, it remains imperceptible to the human nose.

  • Repell them: Use an insect repellent as described below.

Mosquitos are highly attracted to people with blood type O and if you have this blood type you should be particularly cautious and take all measures possible to defend yourself.


Many types of anti-mosquito devices, creams, and sprays are available on the market. In the wake of the 2015 Zika virus, researchers at New Mexico State University tested 10 commercially available products for their effectiveness at repelling mosquitoes. Only one repellent that they tested, that did not contain DEET, had a strong effect for the duration of the 240 minutes test: a lemon eucalyptus oil repellent. All DEET-containing mosquito repellents were active. For those who are not fond of covering themselves in chemicals, it would appear DEET is a necessary evil.

OFF! Deep Woods Sportsman
Photo: Courtesy of SC Johnson
DEET is simply the common name for N,N-Diethyl-m-toluamide. It’s been in use as an effective insect repellent since it was developed by the U.S. Army in 1946 and it forms a vapour barrier at the skin surface that deters mosquitoes from landing on the skin. Fortunately, over the past several years Deet has been found to be safer than it was once thought to be and it is now deemed safe to use with children if applied as directed.

If you are planning to sail to somewhere that mosquitoes are a scourge or they have a reputation for spreading disease, then most experts will advise the use of a product with DEET in the recipe. One of the most common bug sprays that contain DEET is SC Johnson's Off!. Something like a more natural 'Repel Lemon Eucalyptus' is another other option if you are cruising in less dangerously afflicted areas. This lists ingredients including 30% by weight as citriodiol, the lemon eucalyptus component, and 45% percent ethanol. The other 25 percent ingredients are either "proprietary or non-hazardous".

The widely used 'Avon’s Skin So Soft bath' oil has an aroma that some mosquitos don’t like. Avon noted this in their slogan is “loved by moms, not by bugs”. Under test, it was found that the oil provided only about two hours of protection from two types of mosquitoes, the Aedes variety (aggressive daytime biters that can spread Zika), and Culex (nighttime biters that can carry West Nile). But it is oily and tends to stain soft furnishings, teak decking and turns fibreglass surfaces into skating rings. It can only be realistically applied ashore. It may suffice in less afflicted areas and is generally seen as a safe to use product that provides protection for upwards of six hours.

Many electronic insect repellent devices which produce ultrasounds have been developed to keep biting insects away. However, no scientific research has ever provided evidence that these devices prevent a human from being bitten by a mosquito. It should be said in passing Fly-paper does not attract biting flies only warm-blooded animals do.

The best approach is to test out a variety of things to determine what works best for you and your current environment. If anyone can provide further advice to avoid bugs please feel free below.

With thanks to:
Michael Harpur, Yacht Obsession.

Mosquito Control on a Sailboat - 10 Top Tips for Sailors

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