Investigations on the frequency and density; of Amaranthus palmeri and its chemical control options in some important agricultural crops in the Gediz Basin

Purpose: The aim of this thesis is mapping of an alien weed species, Amaranthus palmeri that has become widespread and increasingly important in Türkiye in recent years, in the Gediz Basin and to investigate the possibilities of chemical control in order to prevent its spread. Materials and Methods: The studies were carried out as survey, pot and field studies. The survey was carried out in the entire Gediz Basin. In the survey, when A. palmeri was found in the agricultural areas during the survey, its coverage area was calculated; when A. palmeri was seen on non-agricultural areas, their total number was counted in an area of 1 m2. Sunflower, tomato, corn and cotton as cultivated plants; Amaranthus palmeri S. Watson was used as a weed in pot and field studies. In the chemical control studies carried out on A. palmeri, pre-emergence (14) and post-emergence (19) herbicides registered for broad-leaved and annual weeds were used. The effects of herbicides in pot studies were determined by the number of emerged A. palmeri in pre-emergence applications; the height, visual effect percentage and biomass values of A. palmeri in early and late post-emergence applications. The herbicides that were effective in pot studies were tested under field conditions for two years in Aydın and one year in Manisa. In field conditions, hoeing was also added to the treatments for comparison. The evaluation of the effects in the field was determined by the number of A. palmeri emerging in the pre-emergence treatments; the number of A. palmeri emerging, the percentage coverage rate and biomass values in the post-emergence treatments. Results: The frequency of occurrence of A. palmeri in the Gediz Basin was 44.48%, 38.35% of the areas were in agricultural areas and 61.65% in non-agricultural areas. The density was found to be 0.58 plants/m2 in non-agricultural areas and 34.35% in agricultural areas. In chemical control studies, post-emergence herbicides were not successful in controlling A. palmeri in sunflowers, tomatoes, and cotton, and highly effective enough to be recommended were not successful pre-emergence due to soil type, irrigation, and regional differences. In maize, 280 g/l Dimethenamid-p + 250 g/l Terbuthylazine, 312,5 g/l S-Metolachlor + 187,5 g/l Terbuthylazine and 225 g/l Isoxaflutole + 90 g/l Thiencarbazone-Methyl + 150 g/l Cyprosulfamide were effective against A. palmeri before emergence. After emergence, 280 g/l Dimethenamid-p + 250 g/l Terbuthylazine, 330 g/l Terbuthylazine + 70 g/l Mesotrione, 326 g/l Terbuthylazine + 50 g/l Mesotrione were more than 90% effective against A. palmeri in both regions. Hoeing application reduced the amount of A. palmeri for a while immediately after hoeing, the population increased rapidly again with new germinations. Conclusion: In this study, it was determined that A. palmeri is dense in some regions of the Gediz Basin. The effects of herbicides to be used in the control of A. palmeri in sunflower, tomato, corn and cotton plants were determined. Thus, results have been obtained in this study that will contribute to the chemical control of this weed in Türkiye.