Specifics of life cycle and damage of Oligonychus ununguis (Acari: Tetranychidae) on introduced species of coniferous plants in conditions of megalopolis

Population of the spider mite Oligonychus ununguis (Jacobi, 1905) was monitored on introduced species of coniferous plants in the Fomin Botanical Garden, Kyiv, Ukraine in 2012–2019. The mite material was collected by shaking method, fixed, mounted on slides and then processed according to standard techniques. Severity of damage (R, %) was calculated. Eight varieties of the introduced genera Pseudotsuga and Picea of coniferous plants were chosen as study objects. The pest was found on Pseudotsuga plants for the first time. It was revealed that different species and varieties of conifers differ in attractiveness as host plants for this pest species. The mite O. ununguis was the most numerous on plants of Pseudotsuga menziesii, Ps. menziesii var. viridis Franco, and Picea glauca (Moench.) Vossf. «Conica». The dependence of shoot growth parameters on pest density is strong according to the value of the coefficient of determination, R2 = 0.8781. The populations of spruce spider mites mostly increase in spring and autumn in Kyiv. In summer, the increase of air temperatures about 30–32 ℃ slowed the mite development, suppressing its density and the levels of damage on the conifers. Two species of Phytoseiidae, Typhlodromus laurae and Amblydromella inopinata and their activity in colonies of the pests on plants were observed in 2019. These predaceous mites can colonize the investigated coniferous plants together and control the O. ununguis population.