Q: Why can’t I see the spray coming out of the truck or plane like before?

The spray you used to see during adult mosquito treatments was produced by diluting a pesticide with diesel or fog oil in a technique called thermal fogging. The mixture was heated producing a cloud of smoke. The oil acted as a carrier to help disperse the pesticide in the proper concentrations and helped pilots see where they had treated. Newer methods of spraying called ultra low volume or ULV have almost eliminated the need for the thermal applications and therefore no fog is seen during spray treatments. Pilots now rely on global positioning system (GPS)  to determine treatment paths. This newer method still provides effective control of mosquitoes, eliminates the adverse health and environmental effects of the oil, and is much more efficient. One DC-3 can now provide the same area of treatment for adult mosquitoes in one night that it would have taken 6 DC-3s using the thermal fog applications.

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