Assessment of electrodynamic spraying as an alternative to ultra-low-volume spraying in western Tanzania

The introduction of ULV (ultra-low-volume) spraying to cotton farmers in western Tanzania in the early 1970s was a major contribution to the cotton industry as the control of cotton insect pests was made easier and possible in many areas. However, spray drift and increased cost of ULV insecticides and batteries have been major constraints to ULV spraying in recent years, so a spraying technique allowing greater efficacy and reduced costs is needed. Trials to assess the potential of electrodynamic spraying as an alternative to ULV spraying started in western Tanzania in 1979. The present study assessed swath width, dosage rates and farmer's reaction to the ‘Electrodyn’® hand-held sprayer as compared with the hand-held spinning-disc sprayer (Micron ULVA), currently used by farmers in Tanzania, in order to identify the optimum combination package to be recommended to farmers. Cypermethrin ED applied at a dosage rate of 15·8–31·6 g a.i./ha by the Electrodyn sprayer over a swath width of 3·0 m gave good control of H. armigera. Yields of seed cotton were comparable to those with ULV cypermethrin applied at a dosage rate of 62·5 g a.i./ha. The spray volume was reduced from 2·5 l/ha applied with the spinning disc to 0·35 l/ha with electrodynamic spraying. Reduced drift, dosage of active ingredient and volume rates, and reduction in the number of batteries needed in a season, were among the major advantages of electrodynamic spraying over ULV spraying in western Tanzania.