Assessing the toxicity of six insecticides on larvae of red palm weevil under laboratory condition

Abstract

Objective: The red palm weevil (RPW), is one of the most threatening pests of date palm trees worldwide, causing significant economic losses annually for date palm growers, both globally and in the Middle East, including Saudi Arabia. The primary objective of this research was to assess the insecticide market in Saudi Arabia, test various insecticides claimed to be effective against RPW, and evaluate their efficacy in laboratory settings. This evaluation aims to inform further trials under field conditions. Methods: Six insecticides, including imidacloprid, thiamethoxam, fipronil, emamectin benzoate, deltamethrin, and fenitrothion, were tested to assess their toxicity against red palm weevil 8th instar larvae by diet incorporation under laboratory conditions. The insecticides were applied according to the manufacturer’s recommendations with dosages of 1000 µl, 0.20 µl, 7.5 µl, 0.25 µl, 0.25 µl, and 0.5 µl for imidacloprid, thiamethoxam, fipronil, emamectin benzoate, deltamethrin, and fenitrothion, respectively. Results: The results revealed that all tested insecticides exhibited 100 % mortality against 8th instar RPW larvae, with the exception of deltamethrin. However, the time required to achieve this mortality varied. Fenitrothion caused 100 % mortality after 72 h, while thiamethoxam, imidacloprid, and fipronil caused 100 % mortality after 96 h. Emamectin benzoate and deltamethrin resulted in 100 % and 93 % mortality, respectively, after 10 days. The variability in mortality rates may be attributed to differences in their active ingredients, which show varying levels of lethality. In conclusion, all tested insecticides showed effectiveness against RPW larvae and represent viable options for controlling this pest in date palm orchards in Saudi Arabia.

Keywords

• Date palms
• Rhynchophorus ferrugineus
• Chemical control
• Saudi Arabia