Diprion pini L. (Hymenoptera, Symphyta, Diprionidae) population dynamics in the Low Dnieper region

Pine sawflies (Hymenoptera, Symphyta, Diprionidae) are the most spread foliage browsing insects of pine forests in Europe, especially monovoltinous European pine sawfly Neodiprion sertifer (Geoffroy, 1785) and common pine sawfly Diprion pini (Linnaeus, 1758), which develops in one or two generations per year depending on weather. The outbreaks of both pine sawflies are the most frequent and intensive in the Steppe zone of Ukraine, especially in the Low Dnieper region, where pine forest (Pinus sylvestris Linnaeus and Pinus pallasiana D. Don) was planted on moving sands in the sixties of the 20th century. This research is aimed at the evaluation of the parameters for D. pini outbreak dynamics in the Low Dnieper region. Outbreak severity, specific foci area and mean score of stand threat by D. pini were evaluated from the regional statistical reports. In the regional scale for 1979–2017, notable outbreaks of D. pini were registered in 1982, 1993, 2002, 2006 and 2017. An interval between maximums was from 4 to 11 years, in average 9 years. The growth of foci area in 1979–1998 as compared to 1999–2017 as well as correlation between pine stand area and annual area of this pest’s foci in different forests was not statistically significant. Graphical analysis of dynamics of D. pini focal area for 2010–2017 was done based on individual threat levels. Our study confirms the fact of three outbreaks for this period in three forest and hunting enterprises (FHE), two outbreaks in one FHE and one outbreak in one FHE. An interval between the outbreaks makes three or six years. The causes of such shortening of interval are discussed.

GIS-based prediction of the foliage browsing insects' outbreaks in the pine stands of the SE "Kreminske FHE"

To improve the detection and prevention of foliage browsing insects' outbreaks it is very important to reveal the forest plots, which are the most favorable for these pests. The aim of this research was to predict using GIS technologies the spatial dynamics of foliage browsing insects' outbreaks in the pine stands of the State Enterprise "Kreminske FHE" (Luhansk region). Forest inventory databases of Production Association "Ukrderzhlisproekt" were analyzed for the SE "Kreminske FHE" as of 2001 and 2011. Rating of forest plots preferences for common pine sawfly (Diprion pini L.) and European pine sawfly (Neodiprion sertifer Geoffr.) considered the type of forest site conditions, age of stand, density of stocking, and the part of pine in the stand composition. If forest plot bordered with clear-cut, then 1 point was added to the general score of the threat. It was shown, that the area with high threat of European pine sawfly and common pine sawfly outbreaks for 2001–2011 increased in the forest fund of the SE "Kreminske FHE" by 702.8 and 2004.2 hectares respectively. The part of foci area made up 27.5 and 32 % from forest fund area, 42.5 % and 49.5 % from pine stands area for European pine sawfly and common pine sawfly respectively. The areas of pine sawflies foci increased mainly in result of decrease the stocking density of pine stands and increase the number of plots which border with clear-cuts. The survey for pine sawflies is recommended to carry out first of all in the plots with high threat of foci appearance.

The dynamics of the spread of pine sawfly in the forests of the Bryansk region

On the basis of forest pathology survey of pine plantations of the Bryansk region for the period of 2011-2014, the nature of the centers of the European pine sawfly is studied and the reasons for their change are established. Works are made in the definition of the number of larvae per one tree in the growth phase of the outbreak, cocoons, male adults, and the sanitary conditions of pine forests on 5 plots in pest outbreaks are evaluated. The area of distribution of foci ranged from 896.6 to 8176.8 ha depending on the year of survey and prevailed in maturing pine plantations. There was a wide range of defoliation of trees - from mild to complete. Average condition category of plots in pine plantations, partially restored after damage was 1.84-2.42. The average number of sawfly larvae per tree has reached an average of 308 pieces. Previously unknown method for selecting the place of their cocoon - a thicker crust of fodder trees is discovered. Relatively low density of sawfly cocoons in the forest litter - 1-17 pcs/m2 is set. At the regional level for the first time, to assess the intensity of the flight of the European pine sawfly and prognosis of foci used pheromone traps were used. The number of males caught in traps varied over wide limits. Mixed results when comparing the two observation periods in 2013 and 2014 are got and the dependence of flight on the weather conditions at that time is shown. Broad ecological plasticity of this species in its ability to form foci in various conditions is confirmed.