An Assessment of the Use of Botanical Extracts and Pheromes for the Off-Host and On-Host Control of Amblyomma Variegatum Tick

Abstract

The livestock tropical bont tick, Amblyomma variegatum Fabricius, is a pest of major economic importance in Africa where it is the vector of Cowdria ruminantium that causes Headwater, disease in cattle. Its control has relied mainly on commercial acaricides, which have many problems associated with, environmental pollution, development of resistant strains of ticks against acaricides and escalating costs. It has, therefore, become necessary to look for alternative methods of tick control, which are environmentally friendly, relatively cheap and which involve farmers directly. In this regard, the purpose of this study investigated the potential of pheromones in attracting ticks to a trap off-host and toxicating them with Neem products and the repulsion of ticks on-host using repellent plant. The use of pheromone components comprising Attraction-Aggregation-Attachment Pheromone (AAAP), 1-octen3-ol and 2,6-dichlorophenol to attract A. variegatum to traps containing botanical extracts on the vegetation was explored. The possibility of enhancing attraction of ticks to AAAP with 1-octen-3-ol and 2,6dichlorophenol was first investigated in a T-tube olfactometer in the laboratory. Whereas males were attracted to increasing proportions of 1-octen3-ol, females were repelled. A combination of 8 ng of 1-octen-3-ol with 1.1 mg of AAAP was adopted as an optimum for the attraction of both sexes, enhancing the attraction of ticks by 20% (p<0.0001). Unlike 1-octen-3-ol, 2,6dichlorophenol did not improve the attraction of A. variegatum in the laboratory (p=0.0667). In the field, the attraction of A. variegatum to different doses of AAAP+1-octen-3-ol combination from various distances was investigated. The longest distance from which ticks were significantly attracted was 7 m. The effects of continuous and intermittent release of carbon dioxide (CO2) on the performance of AAAP and 1-octen-3-ol in attracting ticks in the field were also investigated. The results showed that CO2 increased the range of attraction to 8 m and the continuous and the intermittent release of CO2 were not significantly different. The efficacy of traps treated with Neem Cake Extracts (NCE) and baited with AAAP, 1-octen-3-ol and CO2 was evaluated. The attraction to the traps as well as the modality of A. variegatum were significant (p<0.0001). The modality of attracted ticks was dependent on the concentration of NCE and the time of exposure. 98% modality was recorded for a concentration of 30% of NCE. The volatiles of two of the predilection feeding sites of A. variegatum (scrotum and lower dewlap) were tested against the odour of the ear. The scrotum and the lower dewlap were found very attractive to the ticks. The possibility of using plant extracts with repellent properties in reducing the number of ticks arriving and attaching at predilection sites was also investigated. Boscia senegalensis, Ocimum suave and Ocimum kilimandscharicum were tested as repellents. Ocimum kilimandscharicum was found to repel adult A. variegatum by 33%. This technology of using botanical traps baited with pheromones and CO2 as well as repellent plants could be improved and can be transferred to farmers where it can be incorporated in an Integrated Tick Management Strategy.