Drenching Efficacy of Imidacloprid and Thiamethoxam against Dubas Bug, Ommatissus lybicus (Hem: Tropiduchidae)

Abstract

Dubas bug, Ommatissus lybicus, is one ofthe key pests of date palmsin Iran. Chemicalcontrol is the most conventional control method of this dangerous pest. The aimof this investigation was to compare efficacy, advantages and disadvantages ofdrenching, and foliage spraying of chemical control. The study was conducted ina Randomized Complete Block Design with 10 treatments and 3 replications(trees) in a completely infested date palm grove. Treatments includedimidacloprid SC350 (Confidor®) and thiamethoxam WG250 (Actara®) by foliar spraying(4 g/tree) and by drenching method (10, 20, 80, and 100 g/tree), diazinon EC600(40 ml/tree) as recommended insecticide by foliar spraying and then the check(without treatment). The nymph population and number of honeydew drops wererecorded one day before and 7, 14, and 120 days after treatment. Insecticideresidue of date palm and cost-benefit ratio were calculated. The results showedthat all foliage application treatments had more efficacy compared to drenchingtreatments at 1 and 2 weeks after spraying but at 120 days after drenching, thiamethoxam(80 g/L) and imidacloprid (100 g/L) had 100% efficacy, while the efficacies ofthiamethoxam, imidacloprid, and diazinon foliar spraying was zero. The residueof date fruit treated by high doses of drenching was not detectable. Thehighest cost-benefit ratio belongs to imidacloprid foliage spraying (24.86)followed by imidacloprid drenching (15.67). The lowest ratio belongs tothiamethoxam drenching (3.12). Comparison of different concentrations ofneonicotinoid drenching revealed that high concentration of thiamethoxam andimidacloprid was more than two times effective.