Effect of soybean varieties on nutritional indices of beet armyworm Spodoptera exigua (Lepidoptera: Noctuidae)

The effects of three soybean varieties (Williams, BP and L17) on nutritional indices of Spodoptera exigua(Lepidoptera: Noctuidae) were determined at 25 ± 1°C, 65 ± 5% RH and a photoperiod of 16:8 (L:D) h. Nutritional indices of overall third to sixth larval instars indicated that, Williams and L17 varieties of soybean are more nutritionally rich food and even small amount of this food could successfully support maximum relative growth rate (RGR) as evidenced by high value of efficiency of conversion of ingested food (ECI), efficiency of conversion of digested food (ECD) and approximate digestibility (AD) among the soybean varieties. The lowest values of these parameters were found on BP variety. The larvae reared on Williams variety, had the highest value of larval, pre-pupal, pupal and adult weights. The results indicate that, Williams and L17 variety was the most nutritive and as a susceptible varieties among soybean varieties, in due to the highest value of RGR,ECI, ECD, AD, pre-pupal, pupal, and adult weights, in conversely, BP variety were recorded as partially resistant and the least nutritive for S. exigua, this is due to the fact that the least value of RGR and Feces produced (FP) were recorded.   Key words: Nutritional indices, Spodoptera exigua, food consumption, resistance, biomass.