Efficacy and Costs of Using Breeding Traps to Monitor the Small Banded Pine Weevil Pissodes Castaneus (de Geer, 1775)

Pissodes castaneus (Coleoptera, Curculionidae) is one of the most dangerous pests to Scots pine Pinus sylvestris reforestations and thickets weakened by various biotic (root diseases and herbivorous mammals) and abiotic (drought, shortage, frost, hail, etc.) factors. In the case of a massive occurrence of P. castaneus, the growth of shoots can be inhibited, but the feeding of larvae is more harmful to trees as it leads to the death of trees during growing season. In the 20th century, P. castaneus was not the subject of much research in biology, ecology, and methods of population control which is due to the fact that this species was not an economic problem for a long time. The lack of effective and environmentally safe methods to protect young Scots pine stands from P. castaneus warranted conducting research to develop methods to monitor and limit its population. The objective of the study was to evaluate the effectiveness of using the breeding trap method for monitoring the number of P. castaneus. The research was conducted from 2020-2022 in P. sylvestris reforestations aged 3-7 years and located in the Wyszkow Forest District (central Poland). The traps consisted of stems of live Scots pines without branches, 5-15 cm in diameter and about 1.5 m in length, dug in May each year at a depth of about 0.5 m in rows of up to 10 pieces/ha. After 6 months, the traps were dug up and the sections in the soil were debarked to a depth of 20 cm along with the aboveground section to a height of 20 cm. The larvae and pupal chambers of P. castaneus were counted in the debarked sections. The obtained results were converted to 1 dm2. In addition, the relationship between the number of P. castaneus and its pupal chambers was found, and the diameter of the piles was determined. In addition, the cost of the tested method was compared with the cost of the previously used method to control P. castaneus which consisted of uprooting and removing infested trees. The evaluation of breeding trap colonization revealed that P. castaneus inhabited only the under- ground section of the breeding traps (from 0 to -0.2 m) as evidenced by the presence of larvae in feeding tunnels and pupal chambers as well as pupal chambers left by beetles - up to a maximum of 8 pieces/dm2 and on average 3.8 +/- 1.5 pieces/dm2. The analysis of the relationship between the number of larvae and pupal chambers and the diameter of the traps showed a higher prob- ability of colonization by P. castaneus in traps with a diameter of 10-15 cm. The tested method, with the use of up to 10 traps per 1 ha, was characterized by lower implementation costs compared to the costs of P. castaneus controls by uprooting and removing of infested trees. The results indicate the usefulness of breeding traps for monitoring the occurrence of this pest in young Scots pine stands.