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An oil extracted from the leaves of a tropical shrub Ocimum suave was found to repel as well as kill all stages of the tick Rhipicephalus appendiculatus. In an in vitro bioassay for the larvae, the LC50 of the oil in liquid paraffin was 0.024%. A 10% solution was found to kill all immatures and more than 70% of adults feeding on rabbits. Rabbits were protected for 5 days against attaching larvae using a 10% solution. Preliminary experiments undertaken with cattle kept in the field suggest that the oil may have potential in tick control, and a role in integrated tick management.

In an experiment to investigate the effect of the tick parasitoid, Ixodiphagus hookeri, on tick numbers on cattle, 150000 parasitoids were released over a period of 1 year in a field where ten cattle infested with multiple tick species were kept. Amblyomma variegatum was reduced from 44 to two ticks per animal while Rhipicephalus appendiculatus increased over the time of parasitoid release. During the time of release 51% of the nymphs of A. variegatum collected from the animals were parasitized. The recovery of the parasitoids after the releases were stopped was only 9%. The total numbers of A. variegatum remained low up to 1 year after the parasitoid release was stopped. This study gives an insight into how I. hookeri could be used strategically for the management of A. variegatum on small-scale farms.

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In a study to develop anti-tick pastures, the climbing behaviour of Rhipicephalus appendiculatus on Melinis minutiflora (molasses grass) was investigated. Experiments were done with cut green stems of grass, grass dried in the shade, grass dried in sunshine, grass washed in solvent and grass growing in a study plot. In all cases a common pasture grass, Pennisetum clandestinum (Kikuyu grass), was used as control. All instars of the tick avoided climbing on the green M. minutiflora whereas most larvae, nymphs and adults climbed on the control green P. clandestinum grass. More ticks climbed on the stems dried in the sunshine than on air-dried grass. Acetone was found to be the best of 5 solvents used to extract the tick-repellent substance. Possibilities of using M. minutiflora as part of an integrated tick control package are discussed.

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Sixty male weaner cattle at the National Range Research Station, Kiboko, Kenya were placed in four groups of 15 animals under four different tick control regimens for 16 months. The treatment groups were: spraying with acaricide weekly, spraying every three weeks, spraying whenever group mean tick infestations reached more than 200 per animal (once only in the course of the study) and a control unsprayed group. The cattle were weighed monthly. There were no significant differences between the liveweight gains of the groups during a period of severe drought and during the following period of compensatory weight gain. The untreated group gained more weight than the other groups. Cattle died in all groups, but without significant differences between the groups; the long drought and associated malnutrition were the prime cause of death. Rhipicephalus pravus and R pulchellus were the dominant tick species with fewer Amblyomma gemma, Hyalomma truncatum and small numbers of Boophilus decoloratus and R evertsi. These ticks transmit anaplasmosis, babesiosis and cowdriosis in the study area. Total tick counts reached 750 on individual animals but group means rarely reached more than 200 because of high resistance to ticks in some animals. Host resistance ranking within groups was virtually constant throughout the experiment. The study showed that intensive tick control is not required in the semi-arid areas of Africa.