Fabrics

FABRICS
Practical advice on materials for making traps
for tsetse and other biting flies

If you don't want to know all the nitty-gritty details...

	Use white, highly transparent, ultraviolet-resistant, polyester mosquito netting with only a minimal sheen; avoid using dark or very shiny netting.
	Use opaque, well-textured, non-shiny blue fabric that matches the deep, brilliant blue shown below [Phthalogen Blue cotton in the tropics; Pacific Blue # 6001 acrylic awning fabric (Sunbrella), or Top Notch Blue #563 polyester marine canvas (MarChem Coated Fabrics) in the north.
	Use an appropriate, deep black fabric. Sunbrella acrylic or Top Notch polyester are recommended for light-fastness, but some less expensive fabrics are also suitable.
	Choose fabrics designed for outdoor use that will not fade with time. Light-fastness is critical; see Weathering of Fabrics for some examples.

The "right stuff" can increase the catch of many biting flies considerably, so it is important to strictly follow this advice. Many readily-available retail fabrics are not suitable.

I have tested "seconds" of Sunbrella as an alternative to new material and they are suitable (see Fabric Warehouse in Maine). There may be other options I am not aware of.

I have a basic interest in the phthalogen blue and other metal phthalocyanine dyes that are used to produce deep, brilliant blue or greenish-blue colours on various textiles by various methods. I'd be happy to comment on any fabric samples or exchange reference materials to learn more about what is available on the market around the world.

Contact me at smihok@rogers.com.

Other Practical Options
Detailed instructions for making traps out of other materials are provided at
Making a Plywood Trap

Portable and collapsible painted plywood trap that can be stored flat in winter

Plexiglass trap with an inner wooden frame for permanent, fixed applications

The "Right" colour of BLUE
See Blue Fabrics or Blue Dyes for technical information and other examples

Below is an example of the heavy cotton drill (= bull denim) used in tsetse traps in Kenya relative to reference phthalogen blue dyeings (Dystar). The blue spectrum of phthalogen type IF3GM has a single, simple reflectance peak in the middle of the blue region, with low reflectance in the ultraviolet. The twill weave in this fabric produces a rough texture with almost no sheen. At 175 g/m², the cloth is opaque when it is wet or dry, even in bright tropical sunlight.

Kenya drill
Type IF3GM

Dystar Cloth @4%
Type IF3GM

Dystar Thread @4%
Type IF3GK

The colour "Phthalogen Blue" is a generic term for a series of copper and other heavy metal phthalocyanine dyestuffs patented by Bayer in the 1950s. This dyeing process produces exceptionally brilliant and light-fast blues (based on Cu) which can be shifted to blue-greens (Ni) or darker blues (Co) depending on the metal in the dye complex. When CuPc is solubilized (e.g. as in the sulphonated reactive dyes), brilliant turquoise colours result. These turquoise shades are unique in terms of dye chemistry. When CuPc is halogenated as in some paint pigments, "thalo greens" result.

Phthalogen dyes are still sold by Dystar in Germany for printing and dyeing of thread, but are not in common use for solid-shade dyeing of retail fabrics. Nevertheless, suitable phthalogen-dyed fabrics are still available in the tropics, mostly through dyes obtained from Indian chemical manufacturers.

"Phthalogen Brilliant Blue IF3GK or IF3GM" is shown above. The history of the Bayer dyestuffs is outlined in the following publication:

Vollmann, H. (1971) Phthalogen dyestuffs, Chapter V. pp. 283-311 in Venkataraman, K. (Ed) The chemistry of synthetic dyes, Volume V. New York, Academic Press.

Except for Sunbrella "Pacific Blue", this uniquely brilliant blue is unavailable in North America in any readily-available outdoor fabric. However, a useful turquoise variation for use in biting fly traps can be obtained by dyeing cotton with Procion Turquoise M-G (Reactive Blue 140), or Cibacron Turquoise F-G. See Blue Dyes if you are interested in dyeing cloth for experiments with these or similar dyes.

Colours are typically reproduced poorly by computer monitors. To view Phthalogen Blue, visit an art supply store, and examine a paint that contains ONLY "Pigment Blue 15:1" (e.g. PB15:1) or alpha copper phthalocyanine. An example is Winsor & Newton Finity Artists' Acrylics "Phthalo Blue Red Shade". When mixed with white pigment, "phthalo" paints will produce a close match to Phthalogen Blue cloth. The turquoise colour produced by Procion Turquoise M-G is similar to many cyan inks; it be viewed on a test page from any inkjet or colour laser printer.

There are many forms of copper phthalocyanine (CuPc) and many qualitative terms used in the paint, ink and textile industry for this colour of blue (phthalo blue, peacock blue, royal blue, marine blue, ocean blue, etc.), so always look for the specific pigment (PB 15). Many "phthalo blue" paints are also made from a slightly greenish version of this pigment beta copper phthalocyanine (PB 15:3). The shade difference is subtle and not significant. With simple chemical manipulations, CuPc can also produce brilliant turquoise and cyan colours. Hence, it has major applications in paints, inks and plastics.

Excellent technical information on pigments and the colours they produce is provided by Handprint. Pure pigment powders for experiments can be obtained from stores that supply materials to professional artists, e.g. Stevensons in Canada. You can also view paint colour cards at Winsor & Newton and can download a detailed colour chart in Adobe PDF format. However, it is far better to see colours in person. The retail market is quite diverse.

Although there is no exact match to Phthalogen Blue dyed cotton in printing inks, you can view some reasonable matches by examining Pantone� spot colours. Pantone� 286 is probably the best overall match. Pantone� 293, 2935 and 2945 resemble some of the brighter fabrics. Letraset� Pantone� Tria� marker pens (in art supply stores) are a convenient source for colour examples.

In the tropics, the white polyester mesh used in mosquito bed-nets is usually appropriate for the netting components of the Nzi trap. There are an infinite number of products with various weaves, mesh sizes and fibre types. Purchase only long-lasting materials suitable for outdoor use.

Fine white Mosquito Netting 9k In the north, one useful example of similar netting is type IN-06 from Barre Army/Navy. Note that most types of polyester netting, even when uv-protected, will not last more than a few seasons. There are better long-lasting options from the horticultural industry that come at a much higher price. These are mostly in smaller mesh sizes.

See the sections on Netting and Mesh Sizes for many other practical options.

Insecticide-impregnated netting (synthetic pyrethroids incorporated into polyethylene or polyester) is now also being produced on a very large-scale for use in bed nets for malaria control (World Health Organisation), but these special materials are not yet readily-available to the consumer. Products that have obtained full or interim approval from WHO are Olyset �, Permanet � 2.0 and Interceptor �. See the WHO Pesticide Evaluation Scheme (WHOPES) for up-to-date information. This is a rapidly evolving field in various contexts, with new products (e.g. ready-made, impregnated clothing) starting to appear on the consumer market (Buzz Off Insect Shield).

The "Nitty-Gritty"

Traps can be made out of many things (not just cloth), but choose materials with caution following the detailed advice provided here.

The choice of the right kind of black fabric may not be critical.

Alternatives to cotton have not been tested extensively, but there appears to be considerable latitude in the use of nylon, polyester, acrylic, or blends for the black component of the trap, even if somewhat shiny. Use of a light-fast fabric synthetic fabric is advantageous, given the poor ability of cotton to retain a deep black colour for a very long period of time. Most retail cottons and polyester/cottons will fade to various shades of grey after one season.

The choice of the right kind of blue fabric is absolutely critical.

Traps made out of shiny blue fabrics (non-texturised synthetics in nylon or polyester, e.g. with smooth textures and a very fine weave) often perform poorly, sometimes extremely poorly.

Nearly all biting flies react best to traps made from heavy-weight, opaque (drill), textured (twill weave), "pure blue" (see swatch above), 100% cotton (fabric used in pants, uniforms, overalls in the tropics).

This blue fabric is easy to obtain in the tropics, but it is not available in the northern hemisphere. The outdoor awning fabric Sunbrella (Pacific Blue, # 6001) is the best alternative. Quality sportswear fabrics may be a practical retail alternative (e.g. a medium-weight, 65% polyester and 35% cotton twill), but there will almost surely be some sacrifice in catches of biting flies.

Pure synthetics or blends are used by some researchers for both the blue and black components of the trap as they are durable and colour-fast. Synthetics like polyester and nylon also absorb and retain insecticides better than cotton (a major consideration in Africa for control of riverine tsetse).

Some fabrics are very durable and are resistant to fading in bright sunlight. Some synthetics may be suitable for the black component of the trap, despite being shiny (e.g. 200 Denier Dupont Solar Max^� nylon). More opaque nylon fabric is also available at reasonable cost, e.g. 420 Denier nylon pack cloth. I have yet to experiment with substitutions of many alternative black fabrics.

However, I have done extensive studies of the effects of substitutions of blue fabrics. Synthetics with a smooth texture (shiny) reduce the catch of biting flies, especially stable flies, horse flies, and savannah species of tsetse. To date, I have only found one useful fabric with the right properties as a substitute for cotton: Sunbrella acrylic awning fabric in Pacific Blue #6001.

Some synthetics perform extremely poorly.
So beware. For some really bad examples, see "Poor Choices".

This is a critical point to consider when one is tempted to make traps out of a convenient retail fabric "off the shelf". Even if you can find a fabric that has been texturised to resemble cotton ("natural-feel" fabrics), and the colour is close to Phthalogen Blue, it may perform miserably. However, if you still want to test alternative synthetic fabrics, a good site for practical information, colour swatches, mail order, etc. is Beacon Fabrics in Florida, USA. I have largely abandoned working with the more economical synthetics from retail sources vary too much in quality and/or colour through time.

Always test trap performance and durability relative to a standard Phthalogen Blue cotton trap before making major commitments.

See Blue Dyes for an alternative phthalogen standard outside the tropics.

Non-fabric options (plastic, fibreglass, fibreboard, painted metal or wood) may be appropriate for some flies (particularly Tabanidae or horse flies). Unfortunately, minimal research has been conducted on materials other than cloth to provide generic advice.

Fabric Quality
Colour and texture variation

Blue Fabrics 12k

Large Image (70k)

Fabrics #1 a-c represent variation in Phthalogen Blue IF3GM cottons from Kenya; they only differ in terms of depth of shade.

Fabric #2 is nominal "Phthalogen Blue" cotton from the Awassa Textile Factory, Ethiopia.

Fabric #3 shows the shininess of plastic in "United Nations Blue" from Uniplastics in Nairobi.

Fabrics #4 to 9 are some 100% polyesters from Vestergaard Frandsen with various textures and shininess, tested in early experiments.

A final consideration is the question of durability vs cost - relative to expectations of weather, damage by animals, and the very real problem of theft. Always test fabrics under realistic conditions before making major purchases.

When exposed outdoors to sun and rain, many generic retail fabrics fade within a few months. Synthetic netting materials also vary greatly in quality; only ones that contain ultraviolet protectants are suitable for use in traps (e.g. outdoor insect screening).

Practical examples are provided in Fading of Fabrics.

Below is just one example of the colour fastness of two fabrics
used in tsetse traps in East Africa in the 1990s.

Weathering
Weeathered Traps 25k

The trap on the right was made from Ethiopian cotton drill from the Awassa Textile Factory, dyed "Phthalogen Blue". The trap on the left was made from polyester, dyed to a similar colour.

After exposure to high temperatures and bright sunlight in the Rift Valley of Kenya for 2.5 months, the cotton faded considerably. This was either due to poor dyeing or the use of another process (Weaves).

This example illustrates how difficult it is to ensure consistent quality when apparently similar fabrics are obtained from different sources. This Ethiopian cotton was clearly not light-fast, even though "true" phthalogen blue cotton from other sources has excellent light-fastness.