Bioecology of the pear lace bug, Stephanitis pyri (F.)(Hemiptera: Tingidae) on walnut trees in Kermanshah Province, Iran

One of the most serious pests of walnut trees in recent years in Kermanshah Province is the pear lace bug, Stephanitis pyri (F.) (Hemiptera: Tingidae). Damage of lace bug is not usually economic, but serious invasions can cause considerable damage or even death to the host. A field study was carried out to evaluate the fluctuations of S. pyri population on walnut trees in Kermanshah from January to December 2015.  Data were analyzed using Taylor’s power law and Iwao's patchiness regression methods to determine spatial distribution. In order to estimate the biological parameters of S. pyri in two different laboratory and semi-field conditions, the theory of age-stage two-sex life table was used. None of the life table parameters (r: intrinsic rate of natural increase; R0: net reproductive rate; λ: finite rate of increase; T: mean generation time; and, GRR: gross reproductive rate) in the laboratory conditions had a significant difference from the field conditions, and more than 70% of individuals successfully passed the pre-imaginal developmental stages. The pear lace bug overwintered as adult within weeds until late March; after that, they migrated to the walnut trees and distributed on the leaves. As a result, there was no significant relationship between the fluctuations of the pear lace bug population and changes in temperature or relative humidity. Spatial distribution of the pear lace bug population was determined based on both Taylor and Iwao regression methods of aggregated type.