The residual effect of deltamethrin Spot On when tested against Glossina palpalis gambiensis under fly chamber conditions.

Groups of single zebu cattle were exposed to infestations of the tsetse fly Glossina palpalis gambiensis in fly chambers following treatment with a pour on formulation of deltamethrin, Coopers* Spot On. During the experiment one animal was maintained in a stall, the other exposed at intervals to sunlight. Both mortality and knockdown of exposed flies was demonstrated. Mortality rates of greater than 90% were recorded during the period 0-20 days after treatment and values in excess of 50% during the period, 41-59 days after treatment. Knockdown was more marked with rates in excess of 90% and 65% being recorded for respectively 45 and 75 days after treatment. Exposure to sunlight did not significantly effect the performance of Spot On. Flies were observed to repeatedly land on the deltamethrin treated cattle, so contributing to the overall pick-up of effective concentrations of the chemical. It was considered that this effect of the chemical could considerably reduce the risk of transmission of trypanosomosis from the start of a tsetse campaign.