THE DYNAMICS OF COMMON PINE SAWFLY (DIPRION PINI L.) FOCI AREAS IN EASTERN LITHUANIA

Abstract

Pine sawflies are one of the most common pests of pine forests in Europe (Meshkova V. et al., 2019). In Lithuania, there have not been many mass reproduction outbreaks of the pine sawfly (Diprion pini (L.)), and there is a lack of information about the foci dynamics. Therefore, the article aims to use the knowledge of various authors, research data and discuss the development of the common pine sawfly foci that has formed in 2022–2023 in eastern Lithuania.

During three generations of the common pine sawfly, the area where pine crown defolation recorded increased from 2 351 ha area in 2022 to 6 803 ha area in 2023. The maximum focal area was determined after the end of the development of the second generation of common pine sawfly in 2023. In 2022, the average defoliation intensity – 33.9±2.3 %, after the end of the development of the first generation in 2023 – 61.8±3.4 %, after the development of the second generation of common pine sawfly in 2023 – 37.9±2.1 %. In 2022, due to the development of the second generation of pine sawfly, a focus of mass reproduction was formed. 81.2 % the area is slightly damaged (defoliation up to 50 %). The first generation of pests in 2023 did the biggest damage. 71–100% defoliated stands accounted for 39.8 %. territory (it is considered the culmination phase). Later, some of the pines grew needles and the intensity of defoliation decreased. The primary foci went into the extinguishing stage, but spread and formed a secondary foci. It is likely that in 2024 weak–moderate damage may occur in the territory of both the primary and secondary foci, but the damaged area should not increase.