Economic levels for Sunn pest, Eurygaster integriceps Put. (Het.: Scutelleridae) on wheat in Iran

Sunn pest, Eurygaster integriceps Put. is the most destructive and damaging pest of wheat and barley in the most parts of Iran. It reduces both yield and yield quality of the crop. To develop an integrated pest management (IPM) strategy for Sunn pest control, it was necessary to determine the economic injury level (EIL) of the pest. To determine the loss assessment and EIL for the over-wintered Sunn pest, a factorial experiment based on a randomized complete block design was carried out at Feiz-Abad Research Station of Qazvin province, Iran. Factors comprised wheat cultivars (Alvand and Zarrin) and over-wintered Sunn pest density at 10 levels of 2, 4, 6, 8, 10, 12, 15, 17 and 20 insect per square meter and an insect free plot as the control. Large screen cages of 28 meshes with the dimension of 2×1.5×1.8 meter were established over plots. Adult insects were collected from their over-wintering sites in last winter, and cages were infested with predetermined number of adults of equal sex ratio. After 20 days, number of plants with damaged terminal buds and dried spikes were counted. Results revealed a positive significant correlation of yield loss with over-wintered Sunn pest density. Yield loss ranged from 247 Kg/ha (4%) at 2 over-wintered Sunn pest to 773.1 Kg/ha (12.38%) at 20 over-wintered Sunn pest per square meter for Alvand variety. It also ranged from 167.1 Kg/ha (2.35%) to 923.6 Kg/ha (13%) at above mentioned over-wintered Sunn pest densities for Zarrin. Using Pedigo et al. (1986) equations, the calculated mean of EIL for E. integriceps on Alvand and Zarrin wheat varieties was 10.65 and 10.94 over-wintered Sunn pest adults per square meter in aerial chemical control, and 13.63 and 14.01 over-wintered Sunn pest per square meter in land chemical control method, respectively. Besides, according to Pedigo (1989), EIL was estimated 14.1 and 18 over-wintered Sunn pest per square meter for aerial and land chemical control methods on Alvand and 11.6 and 14.8 over-wintered Sunn pest per square meter on Zarrin.