Expected harmfulness of gnawing phyllophagous insects in urban stands of Kharkiv city

Abstract

Abstract Urban stands are becoming increasingly important in improving the environmental health and liveability of cities. However, they weaken as a result of technogenic air pollution and become vulnerable to pests, particularly to non-native forest insects. The aim of this research was to assess potential harmfulness (bionomically determined harmfulness [BDH]), environmentally determined harmfulness (EDH) and generally expected harmfulness (GEH) of the gnawing phyllophagous lepidopterous insects in the green stands of Kharkiv (Ukraine). All supplementary parameters were assessed by analysis of publications and the own experience of authors. BDH was evaluated as a product of the duration of larvae nutrition (p1) and an index of larvae nutrition (p2). An index of larvae nutrition (p2) was considered being proportional to their imago wingspan. EDH was evaluated as a product of the value of damaged tree species (p3), location of plant damage (p4), the period of loss decorative effect (p5) and the prevalence of certain insect species in the stands (p6). GEH was estimated as a product of BDH, EDH and the ability of insect species to the outbreaks (p7). A modified approach for evaluation BDH, EDH and GEH was suggested and implemented, considering phyllophagous leaf miner insects and phyllophagous insects with open lifestyle in the deciduous stands of streets, parks, and Forest Park of Kharkiv city. EDH of insects with an open lifestyle depends on their size and prevalence in the stand. EDH and GEH of all revealed insects with an open lifestyle increase from streets to Forest Park. Among the insects with an open lifestyle, Lymantriidae and Notodontidae had the highest BDH due to the large size and long feeding period of larvae. Among the insects with hidden lifestyle, Cameraria ohridella had the highest BDH due to the highest prevalence and the large duration of feeding period with its several generations.