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ŠUMARSKI LIST 9-10/2023 str. 52     <-- 52 -->        PDF

Spring defoliation in oaks can lead to the decrease of the diameter increment (Muzika and Liebhold, 1999). Most of radial growth in oaks occurs in the first part of the growing season (Szőnyi, L., 1962; Járó and Tátraaljai, 1985; Hirka, 1991), while oak lace bug attack happens in the second part of the growing season. Therefore, Paulin et al. (2020) concludes that oak lace bug attack will express itself cumulatively in the following years. Bălăcenoiu et al. (2021) showed that, in Romania, oak lace bug occurrence has two peaks during the growing season in July and August. Considering the above mentioned, our experiment was continued in 2020 and 2021 with the aim to test the cumulative effect of the oak lace bug on the growth of the oak seedlings.
In 2020 measurements showed significantly higher average height of the seedlings grown unshaded, when compared to shaded on both treated and untreated subplots (Fig 5, 7). Also, the height of the treated shaded seedlings was significantly higher than the shaded seedlings that were not treated by 35,3%. Such results confirm the hypothesis on the effect of the insect attack in 2019 on the growth in the following year. Average height of the unshaded plants did not significantly differ between the untreated (85,9 cm) and treated plants (93,1 cm).
Similar results were obtained in the autumn of 2021 where shaded treated plants had significantly higher height values of the shaded untreated plant by 44,6 % with the average