Behaviour of the adult seven spot ladybird, Coccinella septempunctata (Coleoptera: Coccinellidae), in response to dimethoate residue on bean plants in the laboratory.

Abstract

The sub-lethal effects of dimethoate residue on the distribution and locomotor activity of adults of Coccinella septempunctata Linnaeus on Vicia faba plants were investigated in the laboratory. The presence of dimethoate residues on the upper half of the plant caused C. septempunctata to spend significantly less time on the plants overall. When given a choice of treated and untreated surfaces, C. septempunctata spent proportionately more time on the untreated areas of the plant. The locomotor activity of C. septempunctata was also altered following encounter with dimethoate residues resulting in a significant increase in the proportion of time spent walking and a reduction in the proportion of time spent resting. The proportion of time spent on plant parts was also affected, with a reduction in the time spent on the apex and an increase in the proportion of time spent on the stem, indicating a possible avoidance response. The proportion of time spent on the adaxial leaf surface was significantly increased following dimethoate treatment. The implications for integrated pest management are considered.