Insecticidal activity of alpha-cypermethrin against small banded pine weevil Pissodes castaneus (Coleoptera: Curculionidae) in forest plantations and thickets

Scots pine (Pinus sylvestris) plantations and thickets damaged by biotic and abiotic factors are particularly attractive to small-banded pine weevil Pissodes castaneus, whose larvae excavate feeding tunnels in the stems of young trees, causing their death. There are no chemical methods that can be applied to protect forest plantations and thickets against this pest. Therefore, the studies were undertaken aimed at the assessment of the efficacy of alpha-cypermethrin used to reduce the numbers of this pest within restock areas. The scope of work included laboratory and field estimation of insecticidal activity of alpha-cypermethrin.

In laboratory, the beetles of P. castaneus were reared on P. sylvestris twigs treated with five concentrations of alpha-cypermethrin (0.0001–1%) formulated as Fastac Forest 15 SC. Insect mortality was calculated during 7-day rearing and median lethal concentration LC₅₀ was calculated. The field treatments consisted of spraying of four-year old Scots pines with the insecticide in concentrations of 2% and 4%.

In laboratory conditions, the insecticide used at five different concentrations caused a 7–95% mortality of the beetles (LC₅₀ = 0.266%), while field sprays resulted in a 1.5–3.5-fold reduction in the colonization of trees and in higher pest mortality rates.

The results indicate the possibility of using of alpha-cypermethrin in protecting the forest against P. castaneus and can be the basis for the development of chemical method used in the forestry practice.