Mistletoe infection in an urban forest in Mexico City

Urban forests are important lungs for urbanized environments; therefore, their study and conservation are needed. Compared with trees in natural areas, urban trees develop in more stressful conditions, which may make them more susceptible to infections by parasites such as mistletoes. Bosque de Tlalpan (BT) is an urban forest embedded in one of the largest cities of the world, Mexico City. The aim of this study was to assess which mistletoe species were present in BT, determine the intensity of the infestation, and distinguish which host species are more susceptible to mistletoe parasitism based on 20 randomly selected plots. We found that Cladocolea loniceroides was extensively distributed on the cultivated area of BT (17 plots), whereas a second species, Phoradendron brachystachyum, was found only on four plots. Seven tree species were susceptible to infection by C. loniceroides, whereas only one was susceptible to infection by P. brachystachyum. Fraxinus uhdei, the most abundant host, was the one with higher severities and larger sizes (tree height and crown length); the latter variables positively influence the severity of infection. Reforestation of the cultivated area with low diversity and exotic species appears to be a reason for the increased infestation. Therefore, we support the reforestation of urban areas with native species to provide benefits such as a lower incidence of parasitic infection and tree mortality.