Detection of weed population in cotton and determination of phytotoxicity of some corn herbicides in cotton

One of the adverse effects of herbicides on crops is the damage referred to as phytotoxicity. Herbicide drift, non-target misapplications, herbicide tank residue, herbicide transport, no calibration before application, phytotoxicity of the herbicide used in the crop rotations in the next product, the absence of herbicides in the recommended phenological period and the incompatibility of environmental conditions during application are the main causes of phytotoxicities. In the first stage of this study, weed species that are problematic in cotton cultivation areas were identified, and in the other part, different doses of some herbicides used in corn plant may cause damage to the cotton plant due to the above-mentioned possible conditions (phytotoxicity), it was made to detect and investigate the damage amounts, yield losses and possible symptoms. As a result of a survey conducted in 2023 to determine the population densities of weeds in cotton fields in our region; 26 weed species belonging to 12 plant families have been identified. Purple nutsedge (Cyperus rotundus L.), redroot pigweed (Amaranthus retroflexus L.), respectively and field muskmelon (Cucumis melo var. agrestis) was found as the most common species. Applications were done when cotton was in the 2-4 leaves, pinhead square, and early bloom stages. In the study, four different doses [quarter of the recommended dose (N/4), half of the recommended dose (N/2), recommended dose (N), double the recommended dose (2N)] of herbicides containing 225 g/l Isoxaflutole + 90 g/l Thiencarbazone-methyl + 150 g/l Cyprosulfamide (safener) and 50% Dicamba + 25% Tritosulfuron active ingredients were applied. In all plots treated with 225 g/l Isoxaflutole + 90 g/l Thiencarbazone-methyl + 150 g/l Cyprosulfamide (safener), chlorosis (yellowing) in leaves and plant tissues, stunted plant growth, die back, and in plots treated with 50% Dicamba + 25% Tritosulfuron, wilting, necrotic (dark brown or red, plant tissue) lesions on stems and petioles, inhibited plant growth, stem thickening and callusing, and die back symptoms were observed At the end of 28 days, the 2N and N doses of both herbicides were found to be the most effective on cotton height, yield, and above-ground dry biomass compared to the control plant. The herbicide with the active ingredients Isoxaflutole + Thiencarbazone-methyl at 2N, N, and N/2 doses had the most adverse effects on cotton chlorophyll content compared to the control plant. The effects of these doses were statistically different from the other treatments. On the other hand, the herbicide with the active ingredient Dicamba was found to have no significant effect on chlorophyll formation. As a result, the necessary precautions must be taken during applications and herbicide applications must be carried out in accordance with the rules.