Damage to potato tubers by cut worms in grain-grass root-crop rotation in the north-west of the Russian Federation

Abstract

The paper presents the results of long-term monitoring of potato tuber damage by caterpillars of cut worms and study of the factors determining it. The research was carried out in grain-grass root-crop rotation in the north-west of the Russian Federation. In recent years in the domestic and world scientific literature an increase in the pest rate of cut worms on potato plantings has been observed, therefore, it is relevant to identify the factors contributing to a significant limitation of damage to potato tubers by the caterpillars of cut worms. According to the results of the studies conducted in the period 2012–2022, it was determined that the damage to potato tubers by caterpillars of cut worms varies widely – from 0.5 to 15.9%. Weather conditions have the strongest influence on tuber damage by cut worms (influence share – 24.3%). The period from planting to flowering of potatoes is determinant, which is confirmed by statistical treatment (r = 0.65, p < 0.05). Increase of tuber damage by cut worms is promoted by hydrothermal conditions during this period, corresponding to the HTC 2.1–2.3, as well as weeding of plantings with perennial dicotyledonous species and some small perennial species. The influence of vegetative mass of the whole set of growing weed vegetation was expressed by a correlation coefficient equal to 0.14 (p < 0.05), including density and mass of perennial dicotyledonous species – 0.11 (p < 0.05) and 0.13 (p < 0.05). One of the factors that significantly reduce damage to potatoes by this pest is preplanting treatment of tubers with insectofungicides. In combination with the use of herbicides, it provided a 56.8% reduction in the proportion of tubers damaged by cut worm caterpillars in the harvested crop. At the same time, application of mineral fertilizers, change of the forecrop in crop rotation and cultivation of potato varieties with different resistance did not lead to a reliable decrease in damage of tubers by caterpillars of cut worms.