CONTROL OF KAROO PARALYSIS TICKS THROUGH VEGETATION MANAGEMENT

Karoo paralysis, caused by feeding Ixodes rubicundus females, is a maj or disease of small stock in South Africa. Control methods currently p ractised are almost exclusively chemical based. To limit overdependanc e on chemicals, vegetation management was investigated as a possible m ethod for control, to be incorporated in an integrated tick management system. Laboratory and field experiments were conducted to determine, firstly, the extent of vertical migration and survival of ticks on lo ng and short copper rods which simulated grasses as questing substrate s; secondly, the infestation burdens of sheep exposed to similar tick challenges in pens with long and short grass; and thirdly, the effect of trimming the lower crown line of wild olive trees, simulating the b rowsing effect of goats, on tick density in the immediate environment of the trees. When ticks were exposed to optimal (>45 cm) and sub-opti mal (<10 cm) length rods on which to quest, the extent of vertical mig ration over extended periods of time (up to 87 days) was significantly higher (P < 0.001) for the ticks exposed to long rods. Also, almost 3 times as many ticks exposed to long rods survived compared to those e xposed to short rods. Sheep exposed to long grass were infested by twi ce as many ticks compared to those exposed to short grass. Tick densit y at modified wild olive trees (Olea europaea africana) (0.027 ticks/m (2)) differed significantly (P < 0.05) from that at control trees (0.0 88 ticks/m(2)). It is recommended that coarse grazers such as cattle a nd horses should be used to graze down long grasses before sheep are i ntroduced into camps known to be infested with I.rubicundus. Similarly , domestic goats can, through their browsing effect on shrubs and tree s, modify the vegetation and as such play an important role in an inte grated tick management system.