1International Centre of Insect Physiology and Ecology (ICIPE), Mbita Point Field Station, Mbita, Post Box. 30, South Nyanza.
2Institute fiir Pflanzenkrankheiten, Universitat Bonn, Nussallee 9. Bonn, Germany.
*Present address: Senior author: Directorate of Rice Research, Rajendra Nagar, Hyderabad-550 030.