Department of Plant Pathology, Tamil Nadu Agricultural University, Coimbatore-641003, India.
Abstracts of the papers presented at the 16th Annual Convention and International Symposium of Indian Virological Society on “Management of Vector-Borne Viruses” at International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru-502324, Hyderabad, India, February 7–10, 2006.
Sunflower (Helianthus annus L.) cultivation has recently been hampered by a necrosis disease. As the disease being caused by a strain of Tobacco streak virus (TSV), the present study was focused only on Thrips sp. as they transmit TSV in different crops as reported by earlier in Melilotus alba and in Lycopersicon esculentum. As the adult thrips (black in color) cannot acquire the virus, the nymphs of Thrips sp. (yellow in color) were preferred and the study was carried out to standardize the acquisition feeding and transmission feeding methods. Among the methods tried for acquisition feeding, leaf disc method was found best as the infected disc was easily approachable by the insects. In case of transmission feeding, capsule method was found suitable wherein the thrips were not allowed to escape from the capsule. Moreover, the inoculated leaf and the thrips allowed for different periods of acquisition feeding were found positive for TSV when DAC-ELISA test was conducted. Likewise, EM examination of thrips collected from the infected plant also revealed the presence of isometric particles similar to that of ilarvirus. This finding indicated not only the fact that the virus had been acquired by the thrips in the field itself but also the possibility of transmission to other healthy plants. Based on these findings, the thrips responsible for the spread of the disease in the field was identified as Scirtothrips dorsalis Hood. A trial laid out for the management of necrosis disease was found to be almost nil when the seeds were treated with imidacloprid @ 2g kg−1 of seeds followed by spraying with 0.1% imidacloprid at 30 and 45 days after sowing as against 15.4% in control.
