Space sprays

Space-spraying relies on the production of a large number of small insecticidal droplets intended to be distributed though a volume of air over a given period of time. When these droplets impact on a target insect, they deliver a lethal dose of insecticide. The traditional methods for generating a space-spray include thermal fogging (whereby a dense cloud of insecticide droplets is produced giving the appearance of a thick fog) and Ultra Low Volume (ULV), whereby droplets are produced by a cold, mechanical aerosol-generating machine.


Since large areas can be treated at any one time this method is a very effective way to rapidly reduce the population of flying insects in a specific area. Since there is no residual activity from the application it must be repeated at intervals of 5-7 days in order to be fully effective. This method can be particularly effective in epidemic situations where rapid reduction in mosquito numbers is required. As such, it is commonly used in urban dengue control campaigns.

Effective space-spraying is dependent upon the following specific principles:

• Target insects are usually flying through the spray cloud (or are sometimes impacted whilst resting on exposed surfaces). The efficiency of contact between the spray droplets and target insects is therefore crucial. This is achieved by ensuring that spray droplets remain airborne for the optimum period of time and that they contain the right dose of insecticide. These two issues are largely addressed through optimizing the droplet size.
• If droplets are too big they drop to the ground too quickly and don’t penetrate vegetation or other obstacles encountered during application (limiting the effective area of application). If one of these big droplets impacts an individual insect then it is also ‘overkill’ since a high dose will be delivered per individual insect.
• If droplets are too small then they may either not deposit on a target insect (no impaction) due to aerodynamics or they can be carried upwards into the atmosphere by convection currents.
• The optimum size of droplets for space-spray application are droplets with a Volume Median Diameter (VMD) of 10–25 microns.

Bayer introduced an innovative spray technology called FFAST (Film Forming Aqueous Spray Technology) which reduced the need for use of hydrocarbon solvents in space spray application. FFAST formulations are primarily water-based, are diluted with water and achieve optimal efficacy. These formulations have been proven effective in many situations around the world.

For further information on FFAST please refer to the Aqua K-Othrine® or Aqua Reslin® Super product brochures.

Environmental Science offers the following insecticides for space-spray application:

Within this list only Aqua K-Othrine and Aqua Reslin Super are evaluated and recommended under the WHO Pesticides Evaluation Scheme.

The following products are also available in certain countries:

Product	Active ingredient	Chemical class	Application rate of active ingredient
Deltacide	Deltamethrin	Pyrethroid	0.5 – 1.0 g/ha
Aqua Resigen (Aqua Reslin Super)	Permethrin S-bioallethrin	Pyrethroid	5 – 10 g/ha
Kingfog	Deltamethrin	Pyrethroid	0.5 – 1.0 g/ha
Resigen		Pyrethroid