Dynamics of deterioration of phytosanitary indicators of tubers with an increase in potato productivity during the pre-harvest vegetation period

Determining the optimal harvest time for potato plantings is one of the main problems of potato growing. An essential task in this case is to study the dynamics of the development of massive soil-dwelling pests and phytopathogens during the pre-harvest period in order to reduce the loss of tuber quality against the background of an increase in crop yield. The research was carried out in 2022–2024 in the grain–and–grass crop rotation of the agroecological study area (Leningrad region) in the planting of the early-ripening Meteor potato cultivar (the predecessor is rapeseed). Observations of phytosanitary parameters, the number and weight of tubers were carried out according to generally accepted methods in dynamics – on the 70th, 80th, 90th day after planting. According to the research results, during the pre-harvest period, the number of tubers damaged by the larvae of click beetles increased from 20.7 to 38.3 %, the incidence of scab and rhizoctoniosis increased from 17.3 to 30.5 % and from 16.7 to 38.0 %, respectively. The maximum intensity of these processes was observed from the 80th to the 90th day after planting: damage to tubers by larvae of click beetles increased 1.4 times, the degree of development of scab – 1.3 times, rhizoctoniosis – 2.5 times. It was found that in the conditions of the Leningrad region, harvesting an early Meteor cultivar 70 days after planting is not justified due to the low mass of tubers from the plant (72 % compared with harvesting on the 90th day). High rates of increase in potato productivity are observed in the period from the 70th to the 80th day after planting, with an average of 88.1 % of the maximum possible yield. The expediency of longer cultivation of the crop was seen only in one year out of three. Thus, the optimal solution for cultivating the Meteor cultivar in the research region is harvesting 80 days after planting, which significantly reduces the loss of marketability of the tubers of the crop with a high final level of productivity.