Goal. Ecotoxicological and economic substantiation of the biological system of apple protection against pests and diseases, its optimization and adaptation to the weather and climatic conditions and the phytosanitary state of apple agrocenosis in the Precarpathian province of the Carpathian mountain zone of Ukraine in order to reduce crop losses and improving its quality. Methods. Phytosanitary monitoring was performed visually and using pheromone traps. The degree of hazard of pesticides was assessed by an integrated 7-point scale, the risk — by agroecotoxicological index (AETI). Results. Based on the monitoring of the phytosanitary state of the apple agrocenosis in 2015—2017, scientific and methodological parameters of ecologically safe and cost-effective protection systems for apple trees adapted to the soil and climatic conditions of the Precarpathian province of the Carpathian mountain zone of Ukraine were developed: biological and biological-chemical. They are based on 7 treatments with biological or chemical and biological preparations, carried out in the phenophases of culture critical for the development of harmful organisms. The efficiency of the biological system against harmful organisms was in the range of 65.7—72.8%, the biological-chemical system — 66.4—96.5%. It is shown that replacing a number of chemical treatments with biological ones allows to minimize the negative impact of pesticides on the apple agrocenosis. Conclusions. A model of ecologically safe protection of an apple orchard against a complex of harmful organisms has been developed. It is shown that the modern assortment of biological protection means makes it possible to develop a system that provides effective protection of the apple orchard against a complex of diseases and pests. Calculations showed that the system of biological and chemical protection was more effective in terms of profitability during the years of research (71.4—127.23%). The profit obtained from the use of this system was from 49 898.9 to 107 586.4 UAH/ha.

Goal of the research is to consider the main concepts used in the probit-analysis method, the features of its application to determine the toxicity of pesticides, in particular insecticides, acaricides and fungicides. Methods. To determine the toxicity of pesticides, the method of probit-analysis was used. It consists in determining the dose of a substance necessary to achieve a certain level of mortality of test organisms, based on the transformation of the S-shaped «dose-effect» curve into a straight line. Results. The article describes in detail the main stages of probit-analysis: selection of biological material; determination of the pesticide dose range to be used and preparation of working solutions; processing of biological material; assessing the mortality of the studied objects; processing of the obtained results. The peculiarities of its use in determining the toxicity of insecticides and fungicides of different chemical groups and with different mechanisms of action are shown. As an example, the application of the method for determining the toxicity of insecto-acaricide Vertimek 018 EC against the spider mite (Tetranychus urticae Koch.) is given. Conclusion. The results of the research show the effectiveness of the probit-analysis method in determining the toxicity of pesticides, the possibility of its application for assessing the sensitivity of pests and pathogens to pesticides, and monitoring of their resistance.