The phytotoxic effects of clopyralid herbicide on seed germination of austrian pine (Pinus nigra J.F. Arnold), scots pine (Pinus sylvestris L.), maritime pine (Pinus pinaster Aiton) and Turkish red pine (Pinus brutia Ten.)

Native Anatolian black pine (Pinus nigra J.F. Arnold), Scotch pine (Pinus sylvestris L.), Turkish red pine (Pinus brutia Ten.) and nonnative maritime pine (Pinus pinaster Aiton) used successfuly in many plantations are important tree species for Turkey for ecological (biodiversity, rehabilitation, erosion control) and economic (wood production) purposes. These species constitute in area more than half of the country's forests and are used extensively especially in afforestation. Their adaptability to degraded and arid habitats places particular emphasis on the value of these species when the negative effects of global climate change are considered. Herbaceous weeds make up one of the most important ecological barriers to natural regeneration and afforestation of the forest trees. Therefore, effective weed control is essential for a successful stand establsihment. Clopyralid is a systemic herbicide with a broad control spectrum and can provide successful unwanted plant control without significantly damaging the main species in many coniferous plantations, including black pine. With rapid herbicide seed screening studies, phytotoxic effects of herbicides on the main tree species can be predicted quickly, successfully and safely. In this study, the phytotoxic effects of various rates of clopyralid on seed germination of Anatolian black pine, Scots pine, maritime pine and Turkish red pine were investigated in three different modules. In the first (module) of this study, the phytotoxic effect of low-rate clopyralid herbicide on the seed germination of the principal species in five different rates (0-1%) was studied, and it was found that at lower rates, the tree species tolerated the clopyralid herbicide despite extensive fungal damage. Prior to the high-rate trials in this study, an additional sterilization procedure was needed against the fungal damage that occurred during seed germination. In the second (sterilization) study (modüle), six different sterilization treatments were applied on the seeds, and the most successful result (excluding Turkish red pine) was achieved when seeds were pretreated in 0.4% Izolkaptan fungicide solution for 24 hours before germination test. As a result of this study, all the seeds of the main species treated in high-rate clopyralid solutions in the main study were disinfected with this sterilization method. In addition, no antogonistic effects on seed germination in terms of effects of herbicide treatments were observed for the sterlization treatment. Turkish red pine seeds were observed to be resistant to fungal infection and therefore did not need sterilization. In the main and last study (module 3), phytotoxicity of eight different clopyralid (0-5%) rate-solutions on the seed germination of the main pine species was investigated. At the end of this study, for future chemical weed control preactices, it was determined that Anatolian black pine, Scots pine and maritime pine were resistant to clopyralid in phytotoxicity at rates up to 1.5% while Turkish red pine tolerated clopyralid up to 1%.