New data on the fauna of mealybugs (Hemiptera; Pseudococcidae) inhabiting subtropical plants in the Lankaran-Astara Region of Azerbaijan

Abstract

Invasive insect species enter new environment mainly with their host plants and spread rapidly in new conditions due to the absence of natural entomophages that can effectively limit their numbers. Comprehensive studies of the invaders, including crop pest, are of great importance for agricultural practice. In this regard, we investigated mealybugs (Pseudococcidae) in the orchards of five subtropical species, viz. lemon (Citrus limon) mandarin (Citrus reticulate), orange (Citrus sinensis), persimmon (Diospyros kaki), and pomegranate (Punica granatum) in the Lankaran-Astara Region of Azerbaijan. The research was conducted in 2016‒2019 in various seasons. Three mealybug species were recorded from the area in question: Pseudococcus comstocki Kuwana 1902, Pseudococcus viburni Signoret 1875, Pseudococcus calceolariae (Maskell, 1879). An annotated list of species provides collecting localities, their geographical coordinates, dates of collection, and the number of individuals found. We obtained data on species distribution, biology, host plants and signs of infestation. Ps. viburni was registered in the fauna of Azerbaijan for the first time; a developement period of its larvae and imagoes is provided. The highest infestation of the vegetative organs was observed on the citrus plants: on average, 30 % of trees were damaged by Ps. comstocki, 27 % by Ps. viburni, and 21 % by Ps. calceolariae. Two mealybug species (Ps. comstocki, Ps. viburni) were found on the persimmon and only one species (Ps. comstocki) on the pomegranate. Ps. comstocki population density was the highest in the study area (3–5 larvae per 10 cm of branches, and 4–5 colonies per 100 leaves during flowering). All three species were found together on the stems and leaves of citrus crops; Ps. comstocki was observed on the fruits of mandarin and persimmon, and Ps. viburni was only on the persimmon. Based on the data obtained, the degree of harmfulness of the above species was determined: for Ps. comstocki – 3–5 larvae per 10 cm of branches, and 4–5 colonies per 100 leaves during flowering; for Ps. viburni – 2–3 larvae per 10 cm of branches, and 3–4 colonies per 100 leaves during flowering; and for Ps. calceolariae – 2–3 larvae per 10 cm of branches, and 2–3 colonies per 100 leaves during flowering.