FIELD SAMPLING OF THE TICK AMBLYOMMA-VARIEGATUM (ACARI, IXODIDAE) ON PASTURES IN GUADELOUPE - ATTRACTION OF CO2 AND OR TICK PHEROMONES AND CONDITIONS OF USE/

Field experiments were conducted in Guadeloupe to evaluate the attract ion of different chemicals on a Guadeloupean strain of Amblyomnra vari egatum. Such tick sampling techniques may help to assess the size of t he tick population on pastures before, during and after an attempted t ick eradication campaign. CO2 was absolutely necessary to activate tic ks, including the larvae. In addition to activation, our data suggeste d that CO2 itself is attractive for ticks. The reactivity of the ticks varied greatly with the period of the year, the adults being insensit ive to CO2 alone or combined with pheromones for a period extending fr om December to June. For the whole period, the total captures were equ al for the males and females, but the males were relatively more sensi tive at the beginning of the season of activity (June-July), while the females dominated, but not significantly, for the rest of the period. There was also a gradient of reactivity depending on the distance fro m the trap; 28% of the ticks were captured at 0.5 m from the CO2 traps and 1.2% at a distance of 6 m. The ticks arrived rapidly at the trap. After 1 h of trapping, 55, 68 and 81% of the active nymphs, males and females, respectively, had reached the trap. Synthetic pheromones (me thyl salicylate, o-nitrophenol and nonanoic acid in the proportions 1: 2:8) or freshly detached males added to CO2, greatly increased the eff icacy of the CO2 traps. Depending on the concentration of the pheromon es, the attraction was four to 70 times higher than with CO2 alone. Th e effect depended on the sex of the ticks, males being attracted in a greater proportion by small amounts of pheromones, while the females w ere activated by higher doses. From a practical point of view, samplin g should be conducted from June to December, with CO2 and high concent rations of pheromones, the traps being in operation for approximately 1 h at least, the area concerned by effluents being located downwind a nd covering an area of approximately 36 m(2).