01. Functional response of Coccinella septempunctata L. (Coleoptera: Coccinellidae) on Ommatissus lybicus (Homoptera: Tropiduchidae)
Abstract
Dubas bug, Ommatissus lybicus (Homoptera: Tropiduchidae), is a major insect pest of date palm. Adult and nymph stages suck sap from all green parts and cause direct and indirect damage. Large number of predators feed on it; however, no information is available on their consumption rate and functional response using this prey. We aim to find out consumption rate of Coccinella septempunctata with an objective how adult female and fourth nymphal instars of C. septempunctata responds to 1st and 3rd instar nymphs of O. lybicus at various density levels under controlled condition. Both stages of C. septempunctata exhibited a type II functional response. Handling times and attack rates were significantly different between adult female and larval stage indicating that predator responds differentially to prey stage offered at same density. Estimated handling time of C. septempunctata adult female and fourth instar (in bracket) at 24 hours were 0.563(0.692) and 1.008(1.492) and estimated attack rate were 0.020 (0.014) and 0.003(0.002) on first and third instar nymphs of prey, respectively, which conclude that adult is more voracious stage than larva. However, further field studies on predator and prey stage specific in the presence of honeydew droplets on leaflets are still needed to quantify biocontrol efficiency of predator.
Keywords: Bivoltine; Coccinella septempunctata; Dubas bug; Honeydew; Predation
