Effect of exclusion net and apple variety on the population density of leaf-mining moths

Leaf-mining moths are known as pests on many fruit trees. With intensifying the chemical control in commercial orchards, their economic importance has increased. Exclusion net proved to be a promising alternative to chemical insecticides in suppressing the population densities of some apple pests. The study aimed to assess the effect of exclusion net on the rate of infestation by leaf-mining moths in the region of Plovdiv and their preference for some new apple varieties. The experiment was set up in two locations (in Plovdiv and the village of Brestnik) each with four rows of apple trees – two rows with exclusion net and two without net. In 2020 on the leaves of 8 apple varieties a total of 5 species of leaf-mining moths were observed: 2 species from the Lyonetiidae family-Leucoptera malifoliella and Lyonetia clerkella; 2 species from the Gracillariidae family - Phyllonorycter blancardella and Phyllonorycter corylifoliella, and 1 species from the Nepticulidae family - Stigmella malella with Phyllonorycter blancardella and Stigmella malella being predominant in both sites. Adult moths showed a pronounced preference for laying eggs on the leaves of the Crimson Crisp, Rosella and SuperChief varieties, in the open and under exclusion net. The new varieties Enterprise, Pinova and Fujion were the least preferred. In both sites, the rate of infestation was higher on the apple trees with exclusion net. Keywords: exclusion net, Phyllonorycter blancardella, Stigmella malella, apple varieties