PATHOGENICITY AND MORTALITY BIOASSAY OF SPODOPTERA LITURA FABRICIUS (LEPIDOPTERA: NOCTUIDAE) INFECTED WITH FOUR STEINERNEMA SP. ISOLATED FROM DIFFERENT AGRO-ECOSYSTEM

The four Steinernema sp. isolated from Palladam, Erode, karur and Madathukulam areas were tested for its pathogenicity against 4th instar larvae of Spodoptera litura with 100 IJs/ 20 larvae under laboratory conditions. The mortality was observed after 24 hrs of infection with 87%, 88%, 86% and 83% respectively in Palladam, Erode, karur and Madathukulam. In the larval mortality study 0.5 ml inoculam with 1, 5, 10, 15, 20, 25, 30, 35, 40, 45 and 50 IJʾs per twenty larvae of treatment of T1, T2, T3, T4, T5, T6, T7, T8, T9, T10 and T11 respectively for each Steinernema sp. isolated from Palladam, Erode, Karur and Madathukulam with five replication for each treatment along with untreated control were identical treatments except with no IJs. Larval mortality was recorded for 48 hrs. The LC50 value to 4th instar larvae of S. litura was 4.46, 6.20, 5.56 and 4.21 and LC90 with 13.80, 10.62, 12.40 and 7.74 in Palladam, Erode, karur and Madathukulam respectively. When compared to early studies, the four isolates of Steinernema sp. has showed virulence to S. litura in low dosage of inoculum in this study. So this isolated Steinernema sp. is a potential bio control agent S. litura