Screening walnut and apple trees against Leopard moth, Zeuzera pyrina (Lep.: Cossidae)

Leopard moth, Zeuzera pyrina L. (Lep.: Cossidae), is a xylophagous pest which feeds on several host plants such as apple, pear, walnut and quince trees. Its activity results in withered branches and yield loss, finally causing death of trees. Detecting resistance mechanisms in resistant trees and deploying resistant varieties can be useful in managing leopard moth and conserving the environment from detrimental side effects of pesticides. In this research, resistance of 9 walnut and 17 apple varieties in orchard collection of Seedling and Seed Research Institute (Kamal-Shahr, Alborz province) was studied during 2009-2010 based on a completely randomized block design. For walnut varieties, 6 cohort trees for each variety were chosen and the number of larval entrance holes in six branches (four outside and two inside of canopy)/tree, were studied. For apple varieties, 3 cohort trees for each variety were chosen and the amount of larval feces at the base of each apple tree (based on the amount of larval fecal pellets which can be held in a tablespoon) and the number of larval entrance holes from base of the apple trees up to 1.5 m-height were studied. The maximum and minimum number of larval entrance holes in walnut varieties were observed on ''Z30'' (6.16±0.45) and ''Z63'' (1.25±0.49) respectively. Therefore, ''Z63'' is recommended for further study regarding the detection of resistance mechanisms. In apple varieties, the maximum number of larval entrance holes (11.0±3.1) and maximum amount of larval feces (7.0±1.3 tablespoons) were recorded on ‘Richard Delicious’. ‘Northern spy’, ‘Jonathan’, ‘Prime Gold’ and ‘Red spur cooper’ varieties received the least damage (near zero) compared to the other varieties and they are recommended for further studies.