Study on allelopathic effects of volatile oil from E. grandis × E. urophylla on fungi and pest insects.

We studied the allelopathic effects of the essential oil of E.grandis × E.urophylla on the fungi and insects pest on the chemical composition. Our experimental results indicated that the leaf oil emulsion of E.grandis × E.urophylla inhibited the growth of four fungi tested. As the concentration went higher, the inhibition also became stronger. When the concentration of leaf oil was at 1600 ug/ml, the inhibition effect was highest on epiphytes. The inhibition rate of four fungi Fusarium oxysporum, Pyriculerie grisea, Glorosprium musarum, Phytophthora capsici was 58.08, 79.24, 75.27 and 92.18%, respectively. Also the leaf oil of E.grandis × E.urophylla inhibited the pupation and feeding behavior of the pests insects. The same concentration effect as in fungi was observed. When the concentration of leaf oil was at 2500 ug/ml, the inhibition rate of Spodoptera litura Fabricius and Helicoverpa armigera Hubner was highest and the anti-feeding rate was 52.26% and 86.6%, while, the pupation rate was 45.28% and 7.45%, respectively. We analyzed the leaf oil of E.grandis × E.urophylla by GC/MS. The main components, whose concentration was >3% were α-pinene (13.63%), Alloocimene (43.22%), Gamma.-terpinene (5.49%), 2,6-Octadien-1-ol,3,7-dimethy-,(3.58%), B-fenchyl alcohol(4.58%), 2-amino-3,5-dicyano-6-(4-methoxyphenoxy)-pyridine (3.67%). Most components identified were terpenes, classified as allelochemicals. It can be concluded that the E.grandis×E.urophylla had certain allelopathic effects on the pest insects and fungi. The allelopathic potentials of leaf oil of E. grandis × E. urophylla needs further research under field conditions.