American-Eurasian J. Agric. & Environ. Sci., 12 (1): 30-36, 2012 ISSN 1818-6769 © IDOSI Publications, 2012 Corresponding Author: Mehrdad Ghodskhah Daryaei, Department of Forestry, Faculty of Natural Resources, University of Guilan, Somehe Sara, Iran. 30 Effect of Feeding on Four Different Forest Trees on the Biology and Feeding Indices of Lymantria dispar L. Massome Assadi, Mehrdad Ghodskhah Daryaei, Jalal Jalali Sendi and Hossei Barani Biravand 1 1 2 3 Department of Forestry, Faculty of Natural Resources, University of Guilan, Somehe Sara, Iran 1 Department of Plant Protection, College of Agriculture, University of Guilan, Rasht, Iran 2 Department of Biology, Azad University of Khorramabad, Iran 3 Abstract: Gypsy moth, Lymantria dispar L. is one of the main phytophagous pest of decidous and coniferous trees in north of Iran. Due to the importance of this pest, the biology and feeding efficiency of this pest has been undertaken on four species; Quercus castanifolia, Alnus glutinosa, Parotia persica and Acer velutinum. The results showed that, gypsy moth spends the shortest period of its life cycle by feeding on Q. castanifolia (50.31 days) and the longest period on A. velutinum (61.62 days). The highest attraction was observed on Q. castanifolia and the least attraction was observed on A. velutinum. The results revealed that the highest relative consumption rate (RCR) belonged to A. velutinum (34.92%) and the lowest to A. glutinosa (21.37%). The highest relative growth rate (RGR) belonged to Q. castanifolia ( 17.11) and the lowest to A. velutinum (13.83). The efficiency of conversion of ingested food (ECI) belonged to A. glutinosa (93.83) and the lowest to A. velutinum (57.87). The highest approximate digestibility was that of A. velutinum (36.03) and the lowest to Q. castanifolia (14.78). The significance of the results is discussed. Key words: Lymantria dispar L. Gypsy moth Biology Feeding Preference Feeding efficiency INTRODUCTION influence the host preference of L. dispar, as Foss [7] on Lymantria dispar is one of the major pests of various species of oak concluded that the balance of deciduous trees and some of gymnospermopsides in chemical components present in the leaf cause the whole northern hemisphere [1, 2]. The largest distribution susceptibility of the trees to this pest. The primary hosts and plenty of hosts has enabled this pest to feed on more of L. dispar are broad leaf species specially oak. In spite than 477 hosts of various plant family [3]. Therefore, of pines being secondary hosts to this pest but when reaching a suitable management for this pest is essential being targeted by this pest their damages are quite high for reducing the population. The use of resistant varieties [8]. The amount of food eaten by this pest during their in integrated pest management is recognized as a known development is considerable. The mean leaves eaten by strategy [4]. The studies on severity of damages on a single larva during its development are 856 cm [9]. The herbivory of L. dispar on several species including; oak, L. dispar has several hosts in Iran and until now 38 red oak, black oak, elm, poplar, mulberry, beech, ash, pine, species of and ornamental plants has been reported for in Pensylvania performed showed that oak species this insect and among the useful and economic plants the specially red oak has the maximal preference and poplar, seed fruit and stone fruit trees is economically more mulberry and beech are intermediates while the lowest important [10, 11]. The presence of L. dispar in every area preference was observed in pines [5]. Davidson [6] in their has environmental, economical and outing impact on studies on the relationships among species combination the area. and herbivory of L. dispar in coastal plains in broad leaf The largest extend of distribution and plentiful hosts habitat mixed with pines concluded that the mean falling have enabled this pest to cause irreversible damages on leaves in pine and oak habitats reached 42-60%, while in trees. The innumerable damages caused by this pest in maple-pine habitats almost 32.8%. Different factors some parts of north-eastern America have been estimated the survey of the larvae of L. dispar on the preference of