Formaldehyde's Insecticidal Potential on Immature Stages of Red Palm Weevil (Rhynchophorus ferrugineus)

Abstract

: Red Palm Weevil, Rhynchophorus ferrugineus (Coleoptera: Curculionidae) is the main date-injury palm insect in Egypt. This insect became the most destructive pest for date palms. All research seeks out safe methods for controlling this pest. This study aims to use eco-friendly and safer methods to manage R.P.W. However, the effect of Formaldehyde needs more research. The phrase "formalin" refers to the gas formic aldehyde, CH 2 O, which is a 40% solution of Formaldehyde in water. The results showed that concentration (40%) had a significant impact on larvae in their second instar and newly hatched red palm weevil among all concentrations after exposure to a toxic zone for ten days. The results revealed that there was an increase in larvae mortality by increasing the duration of exposure to Formalin, and this may depend on the accumulation of Formalin on target organs. Data reported that Formalin is effective for the larvae. Therefore, Formalin could interrupt the life cycle of red palm weevil and might be suitable for integrated pest management of this pest as a protective or curative agent. In terms of LC 50 and LC 90, the relative toxicity of the tested concentrations at the LC 50 and LC 90 levels showed that the toxicity of Formalin on newly hatching was the most effective among other larvae of red palm weevil. Regarding LT 50 and LT 90 values, formalin application demonstrated great activity against R. ferruginous , and the needed time causing 50 and 95% mortality (LT 50 and LT 90 ) decreased when the formalin concentration increased. Also, exposure of red palm weevil to ascending concentrations of Formalin showed a significant effect among all concentrations (p˃0.05) of Formalin (40, 20, 10, 5 and 2.5 %) when used on larvae of the fourth instar. In comparison to control, the total lipids and total carbs dropped. As for total lipid and total carbohydrate content, it showed a detectable decrease in treated larvae, while other biochemical components (total protein) showed a slight or no decrease. In the field application of (Formalin) on palm trees for R. ferrugineus control, the results concluded that the infection began to stop seven days after treatment of formalin concentrations (40% and 20%). Also, the treated date palm trees manifested complete recovery after 30 days of the treatment.