Phytochemical composition and biopesticidal potential of Pinus mugo Turra essential oil

Pinus mugo Turra (sensu lato) is an alpine species distributed at high altitudes in the mountains. The species represents a resource for obtaining essential oil (EO). Pinus essential oils (EOs) show great potential as biopesticides in agriculture. To date, there is no comparative study of the EO from various plant parts of P. mugo across the Bulgarian flora. This study aimed to investigate the phytochemical compositions of P. mugo EOs from different plant parts; leaves, twigs, wood, and cones, and evaluate their bioactivity. The botanical pesticides potential of twigs EO against Sitobion avenae, Rhopalosiphum padi, and seeds of weed species Agrostemma githago L., Anthemis arvensis L., Avena fatua L., and Papaver rhoeas L. were tested in Petri dishes. The statistical analysis results showed different EOs yield in different plant parts (0.10–0.63% in leaves, 0.40–1.00% in tips of twigs, 0.1–0.71% in twigs, 0.2–1.43% in wood of one-two year twigs, 0.21–0.6% in male cones, and 0.17% in female cones). The predominant constituents in P. mugo EO were α-pinene, α-phellandrene, β-phellandrene and β-caryophyllene. These constituents were found in all analyzed shrubs from the six populations but in different amounts, depending on the plant part. The tested twigs EO at concentrations of 5%, 4.5%, 3.5%, 2.5%, 1.5%, and 1% had significant insecticidal activity against two aphid species. The efficacy of all concentrations of the EO was 100% on both aphids 24 h after the treatment. The EO demonstrated repellent activity only in high concentrations of 3.5%, 4.5%, and 5% for S. avenae, and 4.5%, and 5% for Rh. padi, respectively. The germination energy, germination, sprouts length, and root length of A. githago, A. arvensis, A. fatua, and P. rhoeas seeds were completely inhibited by low, and high doses (1 µL, 2 µL, 5 µL, 10 µL, and 20 µL) of P. mugo EO. Furthermore, the botanical pesticide capabilities of EOs against six phytopathogens; Alternaria alternata, Botrytis cinerea, Diaporthe nobilis, Fusarium oxysporum, Rhizoctonia solani, and Phytophthora cryptogea were evaluated. The EOs of all investigated parts of the species had strong antimicrobial effect against Salmonella enterica subsp. enterica, and Escherichia coli. The needles tissues extract of P. mugo contained polyphenolic compounds with pronounced antioxidant activity. The findings of this study provide strong support for considering P. mugo EO as a valuable ingredient in the formulation of diverse biopesticides.