Isolation of Steinernema feltiae and its pathogenicity on rice weevil, Sitophilus oryzae (Col.: Curculionidae)

Extreme use of pesticides on stored grains is hazardous for non-target organisms and result in resistance of the insects to the pesticides, pollution of the environment and etc. Nowadays, nonchemical methods, including biological agents are considered as safe methods to control the stored grain pests. Entomopathogenic nematodes are one of the most important biocontrol agents. A survey was designed to investigate the presence and efficiency of entomopathogenic nematodes in the soils of Kohgiluyeh and Boyer-Ahmad province, Iran. Sixty nine soil samples were collected from different regions of the province in 2010. Steinernema feltiae, S. carpocapsae and Panagrolaimus sp. were isolated. Because of danger in the use of chemical pesticides to protect the stored products, this study was performed to determine the efficiency of S. feltiae on adults of rice weevil, Sitophilus oryzae (L.), one of the most important pests of stored products. Under laboratory condition, adult insects were received different concentrations of infective juveniles (Ij) (0, 250, 500, 1000 and 2000 per ml) at different temperatures (25, 27.5, 30 and 32.5ºC). Insects were placed on a double layered filter paper saturated with 1 ml of IJs suspension in 9 cm petri dishes. Mortality of the insects recorded every 24hrs, for three days. The best result (77.5% mortality) observed after 72 hours of exposure at concentration of 2000 IJs in 30ºC.