Control of Ailanthus altissima using cut stump and basal bark herbicide applications in an eighteenth-century fortress

The Cittadella di Alessandria (Italy) is a military fortification that was built in the 18th century. The site has recently been abandoned and is now colonised by weeds, including the invasive Ailanthus altissima weed. The aim of the study was to compare the efficacy of different herbicides (glyphosate, a mixture of aminopyralid+fluroxypyr and triclopyr+fluroxypyr), applied to cut stumps or to the basal bark of the weed. Before the cut stump application, plants were first cut at the base and then immediately sprayed. Untreated cut plants were used for comparison purposes. For the basal bark application, the lower 50 cm of the plants was sprayed with the herbicides. Two runs per study were carried out (in summer 2015 and in spring 2016). Efficacy was assessed up to 2018 by counting the resprouts and their height in the cut stump application and for the basal bark treatment by measuring the variation in the plant circumference after the treatment. The cut stump treatment carried out in summer greatly reduced the number of resprouts, compared to the spring treatment, to less than one sprout per plant when aminopyralid+fluroxypyr was used, and its efficacy lasted for about two years. The basal bark treatment was not able to control the species, but fewer circumference variations and a higher mortality were detected in plants treated with aminopyralid+fluroxypyr. Considering the high level of infestation of the site and the high risk of plant resprouting, repeated cut stump treatments with aminopyralid+fluroxypyr would be preferable to eradicate the species.