Effect of pruning and control of olive psylla, Euphyllura straminea Loginova (Hem: Aphalaridae) on biennial bearing of olive trees

Olive psylla, Euphyllura straminea Loginova (Hemi: Aphalaridae) and the alternate bearing are two important factors that lead to decrease of yield in Tarom olive orchards in north of Zanjan province. In order to achieve to appropriate method of pest control and investigation on effect of pruning and this pest on alternate bearing of olive trees, two above factors were examined in the base of factorial trials in a randomized complete block design with three replications during 1999-2001. Results showed that, spring pruning decreased the pest density and increased the rate of drying mesocarp oil with significant effect (α=0.05) comparing to autumn pruning and control. Also, olive psylla decreased the rate of drying mesocarp oil (about three percent, equal to 30 lit/ha) with significant difference (α=0.05) in comparison to control. On the base of these results, the spring pruning is recommended in the olive orchards. Results of this study indicated that, in spite of pruning and psylla decreased the alternate bearing of olive trees during the three years, but this decrease had no significant difference.