What is the best way of treating targets with insecticide?
Always discuss the regime of insecticide treatment with the insecticide supplier or manufacturer.
If you are using deltamethrin sc the manufacturer will usually recommend that the dip/spray for the targets contains about 0.05% of active ingedient for every month that the insecticide deposit is required to last, ie, 0.15% and 0.30% for applications at intervals of three and six months, respectively. For other insecticides, such alphacypermethrin, the recommended concentrations may be about twice as great as for deltamethrin.
Some people treat the targets once per year, others once per month but most people adopt intervals between these two extremes. The main benefit of long treatment intervals is that it minimises the hassle. The main disadvantage is that that high concentrations of insecticide need to be applied to maintain an effective deposit between infrequent applications, so that if the target gets destroyed or lost soon after treatment then much insecticide has been wasted. Intervals of 3-6 months offer a reasonable compromise.
However, even if you adopt a long treatment interval, you should still visit the targets every three months to repair/replace them and to ensure that the clearing around them is not overgrown. Regenerating vegetation will obscure the target and hinder its attractiveness. Moreover, vegetation brushing against the target will remove insecticide.
If you buy target cloths that are ready made you may find that that the supplier will offer you targets that are already treated with insecticide to last a "long time". However, be wary of this unless the manufacturer offers you clear, independently verified proof that the insecticide as supplied really does persist as an effective deposit for long periods. Bear in mind that most tsetse will touch the target only briefly, so that the insecticide must be transferred quickly to the flies. In general, an sc formulation deposited on the surface of the cloth transfers much more rapidly than an ec formulation, or some other "slow-release" formulations that are incorporated inside the cloth fibres themselves.
If the project is to treat the targets itself, there are the options to treat at the site where each target is erected, or to treat centrally and take the treated targets out for deployment.
Treatment at site
This is usually performed by a presurised knapsack sprayer taken to the site, and spraying to the point of run-off. To get an even application it is usually best to use a nozzle that delivers the droplets in a "fan", as against a "cone". Be sure to adjust the pressure and droplet size so that the maximum amount of spray soaks into the cloth, as against bouncing off or getting blown away.
One advantage of this is that it can be more readily supervised to ensure that the treatment is correct.
You might find that a combination of treatment options is most convenient, treating centrally when the targets are first deployed, and spraying at the sites when replenishing the insecticide. This saves the inconvenience of removing the target cloth from its frame, transporting it to and fro and then erecting it again.
The central treatment of targets is best performed by dipping, brushing or using a paint-roller, rather than spraying.
This method is the simplest if the whole of the target cloth is to be treated with insecticide. Fill a large tub with enough dip to treat about ten targets and add the targets, using a wooden stick to move the targets around, so ensuring even uptake.
Brushing or paint-rolling.This method is the best if only part of the target cloth is to be treated.
Tsetse Plan provides advice on how to construct systems for the mass treatment of targets.