Purpose. To determine the laws of manifestation of abnormal changes in growth and development of sunflower plants as affected by herbicide Euro-Lightning applied at various rates. Methods. Field, laboratory, analytical, and statistical. Results. On the basis of these studies it can be stated that application of different doses of Euro-Lightning affects the shape of sunflower calathium, but further germination of seeds of plants from the calathium allowed to obtain normally developed progeny. Most often, we face different kinds of calathium deformation as resulted from the application of the high rate of the herbicide, namely 14.0 plants with deformation per 1,000 plants, that was by 6.7 more than under the application of recommended by the manufacturer doses. The obtained equations allow high-precision forecast (88–92%) of occurrence of phenotypic changes in sunflower stands as affected by Euro Lightning application. The correlation coefficient between herbicide application rate and the number of plants with deformed calathium has a close positive bonding force (r = 0.92), indicating that increased doses of herbicide results in increasing the number of plants with deformed calathium. Conclusions. The application of high consumption rates of herbicide Euro-Lightning (2.0 l/ha), as well as uneven application, results in the increased number of abnormal changes in populations resistant to the herbicide regardless of sunflower hybrid. The established regression equations between the doses of herbicide and abnormal calathium allow to predict the occurrence of abnormal changes resulted from herbicide Euro-Lightning application in sunflowers stands with 88–92% precision.