Sumatran fleabane (Erigeron sumatrensis Retz.) resistance to herbicides in peach orchards in Çanakkale

Sumatran fleabane, Erigeron sumatrensis Retz. is considered an invasive and troublesome weed in Europe and many countries with Mediterranean climate. Glyphosate is an active ingredient that has been widely used to control annual and perennial weeds successfully including fleabane species (Erigeron spp.), and is the most used herbicide in Turkey. Therefore, the findings and complaints of the resistance to glyphosate in weeds are continuously increasing. In order to determine if Sumatran fleabane is resistant to glyphosate in Çanakkale, dose-response studies were conducted using four fleabane populations grown under the appropriate conditions of which seeds were collected from peach orchards and non-crop areas. Glyphosate isopropyl-amine and potassium salt formulations were applied separately at 0, ¼, ½, 1, 2, 4, and 8 times the use rate of 1.080 g ae ha-1 when the plants were early (BBCH 15-16) and late (20-22 cm tall) at vegetative stages. Experiments were terminated 21 day after herbicide treatments, and evaluated by visual injury followed by above ground biomass weighted after dried at 65℃ for 72 hours. Effects of both glyphosate formulations were combined due to no significant interactions between them statistically. According to visual injury ratings, the resistant populations showed higher resistance 3,8 to 6,6 and 5,3 to 7,8 times at early stage and late stage, respectively, compared to the susceptible population. In parallel, they showed higher resistance 1,3 to 1,6 and 2,9 to 4,7 times at early stage and late stage, respectively, compared to the susceptible population based on dry weight reduction. Furthermore, glyphosate-resistant populations were treated with chlorsulfuron and metribuzin at 0, ¼, ½, 1, 2, 4, and 8 times use rate of 7,5 and 350 g a.i. ha-1, respectively at the early stage. The glyphosate-resistant populations also exhibited from 2,4 to 3,8 times more resistance by visual injury and 2,6 to 12,7 times more resistance by dry weight reduction to chlorsulfuron compared to the susceptible population, but were adequately controlled with metribuzin.