INCIDENCE AND SEVERITY OF DAMAGE AGENTS ON ESTABLISHED TREES IN URBAN GREEN AREAS

Abstract

Trees in urban green areas (UGAs) face various stress-inducing factors that, together with the incidence and severity of damage agents, reduce their growth and health condition. The objective of this study was to characterize the incidence and severity of damage to trees located in 21 UGAs in the city of Texcoco, Mexico, as well as the relationship between their health, green area typology, and urban infrastructure. Using tree damage indicators, the incidence of two damage agents per tree was determined, and seven damage groups were identified: biotic agents, parasitic and epiphytic plants, insects, animals, abiotic agents, and anthropogenic factors. A damage severity index (DSI) was estimated at species level and by green area. Chlorophyll fluorescence was used to assess stress as an indirect measure of tree health condition in UGAs, and surrounding urban infrastructure was classified. A total of 1543 trees were assessed, and 23 damage agents were identified, affecting 9.95 % of the foliage, 10.24 % of the branches, 4.47 % of the trunk, and 0.45 % of the root collar and roots. As for incidence, 60.01 % showed no damage at all, 29.49 % showed only one agent, and 10.5 % showed two agents. Most of the trees at the UGAs were found to be under stress (≤ 0.78) and uncorrelated with DSI; however, the index was different by species and UGA (p ≤ 0.05). Insect damage and poor management practices were associated with the presence of buildings, busy roads, and people congregation areas inside UGAs.