Essential oil products have both a direct and a fumigant effect on reducing serrated tussock seed germination

Essential oil products derived from pine trees and oranges were assessed for germination effects on seeds of serrated tussock in a three-replicate randomised complete block Petri dish trial. The trial compared pine oil, orange oil and a commercial orange essential oil extract (Haulage-DC) applied at concentrations of 0%, 0.01%, 0.05%, 0.25%, 1.25% 2.5% and 6.0% in direct and indirect (fumigant) dose response applications. The trial also assessed the fumigant effects of the pine oil on seed germination by periodically removing Petri dish seals at 1, 3, 5 and 7 days after application. Compared with the untreated control, 0.25% or greater concentrations of essential oil products applied directly to serrated tussock seeds reduced germination by more than 90%. Fumigant effects of pine oil and orange oil products, but not Haulage-DC, reduced serrated tussock germination by 91% or more when applied at concentrations of 1.25% or above. An assessment of sequential opening of Petri dish seals to release pine oil va...