Determination of Glyphosate Resistant Horseweed (Conyza Canadensis (L.) Cronquist) in Apple Orchard in Isparta

Isparta is one of the most important apples producing areas of Turkey. Disease, pests, and weeds that result in problems in apple orchards may restrict apple production. Although the direct impact of the weeds on apples is limited, they can be significant, especially at an early stage due to competition for water, nutrients, and light. The most preferable method to prevent crop losses is herbicide use. If the herbicides were used in the same place without a rotation, herbicide resistant populations may become apparent. Implementation of resistance management following herbicide-resistant population covers more long-term and extensive studies. This study was conducted to determine Glyphosate resistance horseweed (Conyza canadensis) population in apple orchards of Isparta from 2015 to 2019. Bioassay techniques were employed to determine the resistance. In the screen test, the recommended rate of glyphosate was applied to the horseweed populations that were grown in the growth chamber and their resistances were determined. In the dose-response experiments, logarithmic rates of glyphosate were applied to horseweed populations and the impact was identified by non-linear regression analysis. I50 values of suspected glyphosate resistant populations were 96.087 and 83.126ml commercial ingredient/da and 106.48 and 98.82ml commercial ingredient/da for F1 and F2 populations, respectively. The populations separated as suspected glyphosate resistant horseweed have been considered as high-level herbicide tolerant.