Movement behaviour of Nephotettix virescens (Distant), a vector of rice tungro virus disease, on rice varieties with different levels of resistance

The movement pattern of the green leafhopper, Nephotettix virescens (Distant), on some rice varieties having different levels of resistance was evaluated under caged conditions. Insects released on the seedlings of different rice varieties were provided two options i.e., the forced or free choice feeding, and tungro transmission efficiency was estimated. The movement of inseeb under forced choice was comparatively more on resistant varieties than the GLH susceptible varieties. Settlement period of caged insects did not differ much in most of the IR varieties. One viruliferous insect transmitted as high as 1.70% tungro infection in IR-54 and the lowest was 1.01% in IR-50, IR-60, IR-70, ARC-11554, and Utrimerah. In the free choice conditions, GLH rested up to 93 min on IR-20 and for 48 min. on IR-29, IR-70 and IR-72. Also, under free choice, the leafhopper transmitted tungro virus in TN-1, IR-20, IR-36, IR-45, IR-60 and IR-70, the per cent infection being 28, 24, 12, 8, 4 and 4, respectively. Further, it was observed that the infectivity of GLH increased simultaneously with the increase of host and insect population in the cage.