Infection rate of two Poplus deltoides clones with gypsy moth, Lymantria dispar (Lep.: Lymantriidae) in Astaneh-e- Ashrafiyeh in Guilan Province

Gypsy moth, Lymantria dispar L., is considered as an important pest of broad-leaved trees and conifers in Guilan province. About 400 species of trees including poplar are reported as host plant for the pest across the world. Due to suitable climatic and soil conditions of Guilan province, poplar
plantation are highly appreciated and vastly practiced by the farmers and villagers. In the course, a survey conducted on the pest in Astaneh-e-Ashrafiyeh of Guilan province in 2003, we examined a poplar plantation parcel planted with P.d. 69155 clone which were highly infested with this pest. Larval feeding of the poplar leaves had caused total defoliation of the trees. The parcel area aveiage, tree height, and diameter were' 6500 m2, 19 ±1 m and 25±2 cm, respectively. Lawae survival mean on ten selected poplar stands (P.d. 69/55) located inside and outside of the parcel were 2.75 and 6 respectively. Mean of larvae death on these trees were 38 and 43 respectively. Effect of tree height on survival rate of larvae were evaluated by counting larval numbers on four different height of trees (from collar up to 50 cm, from 50 cm up to 100 cm., from 100 cm up to 150 cm from 150 cm up to 200 cm). Mean number of the survival larvae in theses height were 12.02,12.12,9.87 and 5.75 for trees inside the stand and 12.75,14.37,12j5,8.87 for peripheral trees. Analyses of variance on the data, didn't show a significant different between larval number of the height. Another plantation of poplar with P.d. 77/51 clone that located twenty meters far from the first one, showed less infestation to the pest. This parcel with 4750 square meter area had an average trees height and diameter of 18±1 meter and 2l ± 5 cm, respectively. Mean of egg clusters deposited by female moths were2.7 and 4.1 for P.d. 69/55 and P.d.77/51, respectively. While poplar trees are generally considered as a preferred host for L. dispar L., but there supposedly are great differences between clones in terms of resistance or susceptibility to the pest attack. This difference can be athibuted to the genetic variability of poplar species and clones which in turn can affect morphological and biochemical differences.