Abstract

The gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae) is one of the most important pests in Hyrcanian forests, north of Iran. The objective of this research was to determine the effects of diameter at breast height (dbh), oviposition place and oviposition orient on number of egg masses gypsy moth. Sampling was carried out in Golestan State region, during 2008. Data and means were compared using Duncan’s multiple range tests. By global position system (GPS) device with using polygons with width of 20 m and determined azimuth, defoliated trees were recorded. Results showed that the diameter at breast height was not significantly affected by the number of egg masses. Maximum of egg masses were observed at 110-120 cm dbh (2.37 egg masses/tree). The effect of oviposition place on number of egg masses gypsy moth were significant (P<0.01). The highest number of egg masses (2.148 egg masses/tree) was observed at trunk of defoliated trees, also, minimum (1.65 egg masses/tree) occurred in branches of defoliated trees. The effects of oviposition orient were significant (P<0.05). The comparison of means showed that the maximum rates of egg masses was occurred in south (2.04 egg masses/tree), the least of defoliation was related to north (1.57 egg masses/tree).

Key words: Defoliation, egg masses, gypsy moth, Lymantria dispar, oviposition.