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ŠUMARSKI LIST 9-10/2023 str. 50     <-- 50 -->        PDF

2021). Research conducted by Csoka et al. (2019) found that 27 of total 48 oak species are suitable for the development of oak lace bug. Besides the oak, the insect was recorded on 33 additional species from 10 plant families (Csoka et al., 2019).
Adults and nymphs cause damage to the leaves by sap feeding on the lower side of the leaves, while symptoms are expressed as yellow or pale spots to appear on the upper leaf surface and eventually spread across the entire leaf area and whole tree crown. Damage caused by this insect can result in tree weakening and defoliation (Hrašovec et al., 2013). Feeding can decrease leaf physiological activity such as net photosynthesis (-58,48%), transpiration (-21,66%) and stomatal conductance (-35,71) (Nikolić et al., 2019). In North America, in its natural habitat, there are rare reports of damage caused by C. arcuata on american autochthonous oak species. Only Connell and Beacher (1947) reported damage in the form of defoliation and tree weakening of oaks. The data on the impact of oak lace bug on the height and growth of pedunculate oak is very limited. During the initial phase of the development, young oak seedlings in the regenerated stand have high demand for the upper light in order to compete with the weed vegetation (Drekić et al., 2019). Considering the above mentioned, the idea of this research was to determine the effect of the oak lace bug feeding on the height of the oak seedlings at the beginning of forest regeneration process. This manuscript presents three-year study on the influence of oak lace bug feeding on an oak seedling’s height in two different methods of the forest regeneration.
The experiment was established in spring of 2019 in the forest managed by PE “Vojvodinašume” Forest Estate Sremska Mitrovica at the locality Varadin (N 44º 57´ 30´´; E 19º 15´ 04´´) with the aim of investigation of the influence of oak lace bug feeding on the height of young oak seedlings (Fig. 1, 2). Experimental design included two neighboring plots with different forest regeneration methods where the seedlings emerged either (i) under shelterwood system prior to the final felling (shaded seedlings) or (ii) after the final cut (unshaded seedlings).
Forest regeneration was conducted by acorn sowing in the autumn of 2017 on both plots. On each plot, we selected separated and marked 8 subplots sized 1.5 x 1.5 m of which four were treated with insecticide Actara 25 WG (thiamethoxam) in the concentration 0,02% three times during each vegetation period (10. 6. 2019; 3.7. 2019; 1. 8. 2019; 29. 05. 2020; 30. 06. 2020; 29. 07. 2020; 3. 6. 2021; 1. 7. 2021 and 6. 8. 2021) with the aim to suppress oak lace bug adults and nymphs, while four plots remained untreated. The insecticide Actara 25WG was selected for the treatment because it was in the time of investigation allowed to be used in Serbia and proven to be efficient in suppression of the pest (Drekić et al., 2019). For the application, we used portable back sprayer (Stihl SR 420). In addition, all 16 subplots were preventively treated against the powderly mildew with the fungicide Falcon (Spiroxamine + Tebuconazole + triadimenol) and Impact (flutriafol).
The assessment of the intensity of the attack was performed on 40 selected plants within the untreated subplots and expressed by the percentage of the number of the attacked leaves. Intensity of the attack assessments were performed by the end of June, July and August in 2019, 2020 and 2021. Height measurements were performed in autumn of 2019, 2020 and 2021.
Statistical analysis included two- and three-way ANOVA and Tukey`s test. Percentage of the damaged leaves was