Hawthorn preference of orchard ermine, Hyponomeuta padella in Bâzoft forests

Pests infestation increase in central Zagros has been catalyzed by the environmental stresses such as drought and overgrazing. To assess host preference behavior in orchard ermine Hyponomeuta padella L.، six infested forest sites with topological feature variation in Bâzoft region in central Zagros were selected. Sampling was conducted in the months of June and July 2012. Each site was divided into one-hectare plots and pest infestation density، larva web thickness; tree density as well as hawthorn features (diameter at breast height، height، intercalary growth and crown asymmetry) were measured. We found no relation between infestation rate and crown asymmetry، but pest attack significantly increased by twig’s intercalary growth. Based on these results، hawthorn density and hawthorn to oak ratio were the main factors affecting pest outbreak in Bâzoft. A minimum number of 10 hawthorn trees per hectare (one third of tree cover) are enough for pest establishment in a given area. The results of this study could be used t0 identify pest infected areas and determine factors affecting the severity of pest infestation in Bâzoft forests.