Seasonal population fluctuation and host preference of plum fruit moth larvae Grapholita funebrana in the environmental conditions of Karaj

Plum fruit moth Grapholita funebrana is one of the most harmful pests of plum. In this research, the seasonal population fluctuation and host preference of the damaging plum moth population was investigated. Twenty six plum germplasms were used. The quantitative and qualitative characteristics of the fruits were evaluated. The cluster analysis method was used to separate cultivars and genotypes.Tthe degree of influence of different fruit characteristics on host preference was studied by calculating correlation and multiple regression analysis. The maximum index of effective larvae day was equal to 116.5 to 42.5 larvae per day for plum germplasms in late July to early August. The maximum activity of pest larvae was recorded with a slight delay in some cultivars such as Angelo, Gholaman, Kh-Kermanshah and Zojelo in late August to early September, and in others earlier in late June such as Kermanshah. The highest and lowest three-year average value of the preference index was 2.03 and 0.23 for Zojelo and 19 genotype, respectively. Various morphological and qualitative of the fruit characteristics including pH, core thickness, firmness of flesh tissue, ratio of length to diameter, engineering diameter, surface area and TSS were effective in the occurrence of larval host preference reaction. The fruit surface area, fruit width, engineering diameter and fruit fresh weight explained 27.1%, 13.2%, 22.9% and 12.7% of the host preference changes of plum moth larvae, respectively. The results of this research are important for the selection of suitable plum cultivars for the development of cultivation in the country.