The effect of salt stress on lime aphid abundance on Crimean linden (Tilia ‘Euchlora’) leaves

Abstract

Many authors claim that trees planted along streets are weaker because of environmental pollution, especially high soil salinity, which results in greater susceptibility to attacks by pathogens. The Tilia ‘Euchlora’ (Crimean linden) is described as one of the urban greenery species that is most prone to the effects of salinity. The aim of this research was to assess the influence of salt stress on the lime aphid abundance on the leaves of Tilia ‘Euchlora’. The average number of aphids was lower for trees growing along the street and subjected to de-icing salt than in the controlled park area. It was strongly negatively correlated with the Na and Cl level in the leaves, whereas it was positively correlated with the content of N and P. The study showed that the aphids’ abundance was most strongly influenced by the N and Cl content in the leaves (although in opposite ways). When the amount of nitrogen increased by 1.0% (from 2.0 to 3.0%), the abundance of aphids increased by 116%. An increase by 1.0% (from 1.0 to 2.0%) in the Cl content in the leaves resulted in a decrease in the abundance of aphids by 36%. The toxic Cl level (over 1%) was exceeded only in the leaves of trees growing along a busy street (79% of the examined individuals in this location), whereas it ranged from 0.23% to 0.40% for the trees from the park. There was concluded that aphids probably prefer trees with healthier leaves for their feeding, i.e. leaves of lower amount of Cl and Na, while with higher concentration of N.