در شرايط آزمايشگاهي برروي گياه چغندرقند Steinernema Carpocapsae به نماتدهاي )Spodoteva ex: gaH.( بررسي حساسيت مراحل لاروي ، شفيرگي و پيش شفيرگي پروانه برگخوار چغندرقند

Studies on the susceptibility of different larval, prepupa and pupa stages of beet armyworm (Spodoptera exigua H.) to Steinernema carpocapsae on sugar beet under laboratory conditions

The present study was conducted to determine LC50 values of different concentrations of Steinernema carpocapsae on various larval instars and compared the efficacy nematodes on prepupa and pupa stages of beet armyworm(Spodoptera exigua).The beet armyworm were reared in the laboratory on artificial diet. The nematodes were isolated from apple orchards soil by Galleria trap and reared on last instar larvae of greater wax moth (Galleria mellonella L.). Infective juveniles (3"ʹd stage nematode larvae) collected after emergency from the larval cadavers. Different concentrations of nematodes prepare to determine LC50 values and used in bioassay tests on the leaves of sugar beet. The estimated LC50 values of five larval instars of armyworm were 164, 342, 396, 450 and 481 nematodes per 0.1 ml respectively. The effects of nematodes concentrations ranging from 4x 103, 2x 104 and 4x104 nematodes per liter on prepupa and pupa stages were investigated. The percentages of mortality three concentrations were 26.6, 50 and 80 for prepupa and 16.6, 23.3 and 33.3 for pupa respectively. These results indicated that prepupa stage was more susceptible than pupa stage. In addition to larval instars, we propose to use the nematodes on prepupa stage of this pest.