Abstract
Foliage damage by leaf-eating insects during mass reproduction causes deterioration of the sanitary state of forest and a decrease in its increment. Timely detection of pest foci allows reducing the cost of their elimination and preventing negative consequences for stands. The purpose of this study was to identify the species composition of leaf-eating insects on the territory of State Enterprise Zhytomyrske Forestry and the subcompartments with the greatest threat of foci development of the dominant species – Tortrix viridana, taking into account forest site conditions and stand structure. During the feeding period, the species composition of leaf-eating insects was identified, and after the end of oviposition, the density of Tortrix viridana egg masses was assessed on tree branches selected in subcompartments with different forest site conditions, age, the relative crop density, and proportion of oak in the stand composition. The database of forest inventory (Ukrderzhlisproekt) and the score assessment of the preferences of stands for foci development were used. Eleven species of leaf-eating insects from order Lepidoptera were identified, including 9 species from the family Tortricidae, of which Tortrix viridana dominated. The highest egg mass density of this pest was assessed in fresh dubrava conditions (D2 ), in pure oak plantations aged 40-80 years with a low relative crop density. The average score of stand preference for Tortrix viridana was assessed by forest site conditions (2.93 and 2.88 for seed plantations and coppice forest, respectively), age (3.65), the relative density of stocking (2.6), and oak participation (3.3) in the State Enterprise Zhytomyrske Forestry. The list of subcompartments with a very high and high threat of an outbreak of Tortrix viridana has been established. A survey in these subcompartments would allow timely detection of pest population increase and prevent its development
Highlights
Common oak (Quercus robur L.) is distributed on about 27% of the forest fund of the State Forest Resources Agency of Ukraine, or 62% of the area of hardwood plantations [1]
The species composition of leaf-eating insects was identified, and after the end of oviposition, the density of Tortrix viridana egg masses was assessed on tree branches selected in subcompartments with different forest site conditions, age, the relative crop density, and proportion of oak in the stand composition
The highest egg mass density of this pest was assessed in fresh dubrava conditions (D2), in pure oak plantations aged 40-80 years with a low relative crop density
Summary
Common oak (Quercus robur L.) is distributed on about 27% of the forest fund of the State Forest Resources Agency of Ukraine, or 62% of the area of hardwood plantations [1]. Hundreds of species of insects feed on the leaves of oak trees, but only some of them are capable to increase their numbers hundreds of times every few years and completely devour the crowns of trees [3; 4]. At the same time, during outbreaks of mass reproduction, some trees can be completely eaten by larvae of leaf-eating insects 2-3 years in a row This negatively affects the sanitary state of the forest and its increment [5,6,7,8,9], increases the susceptibility of trees to to colonisation with stem pests [10] and pathogens [11]
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