Evaluation of the Toxicity of Glyphosate and its Impact on the Tolerance of Ancistrotermes guineensis to Chlorpyrifos-ethyl and the Methanolic Extract of Tithonia diversifolia

The massive use of glyphosate as a means of weed control is increasingly observed in cocoa plantations in Ivory Coast. Added to this is the ineffectiveness of the treatments. These observations led us to evaluate the level of resistance of A. guineensis to Chlorpyrifos-ethyl and T. diversifolia extract after exposure to glyphosate. The toxicity of glyphosate on A. guineensis workers was evaluated by direct toxicity. For the evaluation of the impact of glyphosate on the tolerance of A. guineensis workers, 50 workers taken at random from 75 workers previously exposed to glyphosate for 4, 6, 12 and 24 hours at concentrations 1.9, 2.14 and 3.56 g/l, were used for the bioassays with Chlorpyrifos-ethyl (22.4 mg/l) and T. diversifolia extract (10 mg/l). The study revealed no toxicity of glyphosate on A. guineensis workers. On the other hand, it showed that the exposure of workers of A.guineensis to glyphosate could modify their sensitivity to Chlorpyrifos-ethyl. This modification begins 4 hours after contact with glyphosate and at the lowest concentration. Tolerance of A. guineensis workers to Chlorpyrifos-ethyl is linked to the duration of exposure to glyphosate. After 24 hours of Chlorpyrifos-ethyl treatment, the mortality of unexposed workers and those exposed (4 and 24 hours) to glyphosate (1.9g/l) was respectively 60.00±3.65, 23.00± 1.9 and 15.00±1.15. Unlike Chlorpyrifos-ethyl, the study revealed no impact of glyphosate on the sensitivity of A. guineensis workers to the T. diversifolia extract. After 24 bioassays with T. diversifolia, the mortality of unexposed workers and those exposed (4 and 24 hours) to glyphosate (1.9g/l) was respectively 30.40±1.67, 30.40±1 .69 and 29.20±2.28. Given the cases of resistance observed with chemical products, the fight against termites must be done with natural plant extracts.