The group dieback foci began to intensively spread in the pine stands of Eastern Polissya, Ukraine, after the very dry second half of the growing season 2016 and lasted for 2017–2018. Those years had extremely arid beginnings of the growing season when Selyaninov’s Hydro-thermal Coefficient was 0.1–0.5 and precipitation deficit amounted to
10–30 % in various months. After the beginning of the 2019 vegetation period, which was favorable for tree growth by the hydrothermal coefficient 1.7, the spread of pathological dieback of pine trees in East Polissya decreased significantly. It stabilized with the predominance of single and group types, as a result of excess atmospheric precipitation and reduced temperature. The renewed water supply to the trees intensified the resin exudation, which intensely hindered insects’ attempts to populate the stem at a relative height of 0.51–0.75 and below. The average production along the stems of populated trees ranged from 29 to 33 juvenil beetles per dm2.
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