Chemical composition of Rhododendron luteum essential oil and its larvacidal effectiveness on Diprion pini larvae

Abstract Diprion pini is known as a significant forest pest that damages pine needles in many countries of the world today. Due to the risk of chemical contamination of synthetic pesticides applied against insects, essential oil use is becoming more popular. In this research, the chemical composition of Rhododendron luteum essential oil was analyzed by using GC-MS, and its larvicidal effects on six D. pini larval stages were investigated. The research was conducted in the Artvin Coruh University Central Laboratory under laboratory conditions settings 25±1ºC temperature, 65±5% relative humidity, and a photoperiod of 14:10 h (L:D) in 2019-2020. β-caryophyllene (15,39%), benzyl benzoate (11,05%), δ-cadinene (7,06%), benzyl salicylate (6,08%), and α-pinene (4,14%) were found as the primary components of R. luteum oil. It is observed that the applications of R. luteum essential oil at the doses of 10, 15, and 20 μL/Petri and the controls at 24h, 48h, 72h and 96h induced fatalities at varied rates (20,1-100 %) on six D. pini larval stages (L1, L2, L3, L4, L5, L6). The highest toxicity was identified at L1 (0,72 μL/larva) and the lowest toxicity was determined at L6 (11,92 μL/larva) according to LD50 and LD90 values. To sum it up, R.luteum essential oil showed high toxicity against L1 and L2 larval stages of D. pini.