Determining the toxicity of the commonly used pesticides on red palm weevil


Abstract: Nine trees of date palm were artificially infested with red palm weevil adults and larvae. The trees were 7-8 years old with an average of 1.58 m trunk heig ht and 1.6 m average trunk circumference. The experiment was conducted on the research station of Abu Dhabi Food Control Authority, UAE. The aim of this study is to evaluate the movement, concentrations and effectiveness of two insecticides, chlorpyrifos and imidacloprid, using the injection technique. Ten days after the injection, dead and live weevil stages were counted as well as level of trunk damage. In addition, samples of tissue were taken at different heights to determine insecticide concentrations. The results of the injection efficiency demonstrated that chlorpyrifos is slightly more effective than imidacloprid, where mortality percentage for all the studied stages reached 48 % for the chlorpyrifos compared to 34 % for the imidacloprid. The parameter of trunk tissue damage indicated that tissue damage when chlorpyrifos was used is less than 10 %. Whereas tissue damage when imidacloprid was used is about 35 %. However, the tissue damage on the control treatment is less than 40 %, which is close to the tissue damage for the imidacloprid treatment. The very high concentrations of the two insecticides from the tissue samples in the injection zone demonstrate a slow diffusion inside the trunk after 10 days of injection, whereas very low concentrations from both insecticides were found in the leaves and in the fruits. The overall conclusion of our study found that chlorpyrifos is more effective to control red palm weevil using the injection technique.

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