Insecticidal effect of plant extract of lemon-scented tea tree (Leptospermum petersonii B.) on Leptinotarsa decemlineata Say (Col.: Chrysomelidae)

In this study, the efficacy of extracts obtained from Leptospermum petersonii Bailey (Myrtaceae) on Leptinotarsa decemlineata Say (CPB, Coleoptera: Chrysomelidae) using two different methods was investigated. Bioassays were used to determine the effect of varying concentrations (0.05, 0.1, 0.3, 0.4 and 0.5%) of extracts. Experiments were carried out using 3 cm diameter leaf disks of Solanum tuberosum L. (Solanaceae). Third instar larvae of about 30-35 mg weight were used in leaf disc dipping and larvae dipping methods. In addition, the effects of extract on L. decemlineata reproductive capacity was investigated. For this purpose, 3- to 5-day-old adults were used. The highest effect occurred at concentration 0.5% while the smallest effect was at 0.05%. In leaf dipping method, the extract of 0.5% concentration showed the highest mortality in the larval stage (92%). In the larva dipping method, mortality at the same concentrations was 88%. At the lowest concentration, females laid lower numbers of eggs compared to the untreated.