Population Fluctuation and Spatial Distribution Pattern of the Nut Scale, Eulecanium tiliae (L.) (Hem.: Coccidae) on Cherries of Western Iran

The nut scale, Eulecanium tiliae (L.) is a potential pest, infesting deciduous trees in Iran, where it is common in urban horticultural areas and usually present in high population on some stone fruit trees, such as Prunus spp., including Prunus cerasus. It has higher occurrence and population in sustainable orchards. This pest has one generation per year and second nymphs overwinter on one or two-years old branches. High populations of this pest can cause death of branches, twigs and degeneration of leaves chloroplasts. In this research, the spatial distribution pattern and population fluctuation for all stages of E. tiliae were investigated in a cherry orchard of Kermanshah region during two studied seasons from ۲۰۱۶ to ۲۰۱۸. Four different methods were used to calculate distribution pattern including index of dispersion, Morisita’s index and regression methods (Taylor’s and Iwao’s). Sample size was determined for the first time, according to a primary sampling date and corrected for other sampling dates according to the data of the previous sampling date. Data analysis was performed using Minitab۱۶ and Office Excel ۲۰۱۶ statistical softwares. Most used methods revealed aggregated distribution pattern of the pest in both years. The results obtained from the Morisita’s index during activity showed the random distribution of the second nymphs (in ۱۶ April ۲۰۱۶, Z= -۱.۲۱۸, Iб= ۰.۴۴۰) (in ۱۶ April ۲۰۱۷, Z= -۰.۱۷۹, Iб= ۰.۹۴۲) (-۱.۹۶< Z< ۱.۹۶). These changes showed that the spatial distribution could change during the season. Knowledge of the pest spatial distribution pattern can be used to arrange sampling program in pest management.

Keywords:

Iwao’s Patchiness Regression , Morisita’s index , Sampling program , Seasonal activity , Taylor Power Law.