Abstract
Due to the consequences of climate change, namely a decrease in the groundwater level, there is a massive weakening of Scots pine stands in the forests of Ukraine. Against the background of dynamic weakening of trees, annual warm winters, the establishment of warm, sunny, and dry weather in spring contribute to the spread of needle-eating pests, especially sawflies. The purpose of this study was to clarify the species composition and biological features of certain species of needle-eating insects of the Prytiasmyn Ridge and the degree of threat to plantings from needle-eating insects, namely from sawflies and related species. At the stage of reconnaissance survey of pine stands, the method of qualitative and quantitative assessment of sawflies and related species of needle-eating insects was tested. During the survey of plantings of the Prytiasmyn Ridge, Defoliating insects of the following species were found: Acantholyda erythrocephala, Acantholyda posticalis, Dendrolimus pini, Panolis flammea, Sphinx pinastri isolated, most pine stands predominate in number Diprion pini and its concomitant species Gilpinia frutetorum and Gilpinia virens. The provides results of observations on the population of Diprion pini and concomitant species Gilpinia frutetorum and Gilpinia virens in pine stands with determination of distribution, phenological and biological features. As a result of the survey of stands inhabited by needle-eating insects, it was established in which phase of the outbreak the pest population is, to which categories the breeding centres and biological features of Diprion pini and related species under these conditions belong. The population indicators of the common pine sawfly Diprion pini and concomitant species in the stands of the Prytiasmyn ridge of the Cherkasy Oblast were evaluated. It was found that the number of these species is increasing, e.g., in 2021 the average number of viable cocoons of Diprion pini females was 21%, and the density of cocoons in the detritus (or forest floor) was 0.53 units·m-2 compared to the indicators of 2020 of 12% and 0.19 units·m-2 , respectively. Similarly, the number of concomitant species Gilpinia frutetorum and Gilpinia virens is increasing, the average density of cocoons in the detritus (or forest floor) of which was 1.39 units·m-2 in 2020, and 1.87 units·m-2 in 2021. As a result of the reconnaissance and detailed surveys, foci of the needle-eating insect complex were found with a total area of 128.0 ha, the determined defoliation rate of the crown was from 30% to 50%. The obtained accounting data allow assessing the potential for the reproduction of populations of Defoliating insects and indicate the need for further monitoring observations in the pine stands of the Prytiasmyn ridge