Biology and insecticide sensitivity of rice white backed planthopper, Sogatella furcifera (Horvath) (Hemiptera:Delphacidae) in Kerala

Abstract

Among planthoppers infesting rice, white backed planthopper (WBPH), Sogatella furcifera (Horvath) (Hemiptera: Delphacidae) has become a menace to rice growers recently. Biology of the S. furcifera studied during winter (December) and summer months (March) showed a shorter incubation period and nymphal duration in summer when compared to the winter. The developmental cycle was longer in December. The fecundity of S. furcifera was more during March. But the per cent hatchability was higher in December. However, there was no significant difference in the per cent survival of WBPH over two seasons. The sex ratio exhibited significant difference in two seasons with more number of males during March than that in December. Population build up studied under laboratory condition recorded a reduction in fecundity of WBPH in the second generation. Feeding study conducted by honeydew test revealed that adult females produced more feeding damage than the adult males and any other stages of WBPH. The insect excreted two amino acids (glutamic acid and aspartic acid) along with the honeydew. The important natural enemies recorded were spiders (Argeops sp., Lycosa pseudoannulaata, Oxyopus spp., Thomisus spp. and Salticus spp.) and mirid predator, Cyrtorhinus lividipennis (Reut.). Two entomopathogenic fungi isolated from WBPH were identified as Aspergillus flavus (Dirk.) and Penicillium oxalicum (Currie & Thomb). This is the first report of above mentioned entomopathogenic fungal infection on WBPH. Imidacloprid and lambda cyhalothrin were more toxic to WBPH nymphs and recorded lower LC50 values. Among the tested insecticides, higher relative toxicity (compared to imidacloprid) was exhibited by lambda cyhalothrin. Under laboratory condition, phosphamidon and monocrotophos were more persistent insecticides which persisted for seven days while the DDVP persisted only for three days. There was a slight reduction in total protein content in insecticide treated samples compared to the untreated ones.