Intercropping with cereal in groundnut fields will minimize the incidence of the disease.
TOBACCO STREAK virus is a devastating pathogen, seriously affecting groundnut and sunflower. In groundnut it causes the peanut stem necrosis disease (PSND), The symptom was observed in Anantapur district of Andhra Pradesh during the monsoon season of 2000, according to Dr. D.V.R. Reddy, Consultant Virologist at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) near Hyderabad.
The virus causes complete necrosis of the plants unlike the bud necrosis, and it affects almost all varieties of groundnut. The virus finds haven in parthenium weed, which is a silent host, and is transmitted through the pollens.
The disease also spreads through white fly, which is a new enemy to groundnut. Since the disease is seed-borne, farmers should avoid using seeds from infected crops. The virus has also seriously affected sunflower in Karnataka, and scientists are working on new strategies to effectively manage the infection.
"The virus causes tip necrosis in groundnut. The drying and dying of root tips is a characteristic symptom of this disease. Affected pods show black lesions on the pod shells, and kernels become smaller. The marketability of the pods and kernels is seriously affected by the disease," explained Dr. Reddy.
ICRISAT has developed a package of integrated disease management practices that effectively contained the spread of this crippling scourge, according to him.
The incidence of the disease can be prevented by following some simple cultural practices. The removal of the pernicious parthenium weed in the vicinity of groundnut crop will greatly help in minimizing the virus infection.
The virus can also be contained by growing some cereal crops such as maize, sorghum and millets along the border of the field. The fast growing crops should be raised for at least ten rows along the border for effective management of the disease.
The smaller groundnut plant shows the characteristic drying of tips induced by the tobacco streak virus, while the large plant exhibits symptoms of peanut bud necrosis disease.
Inter-cropping with pearlmillet, sorghum or maize at a rate of one row of cereal crop for every six rows of groundnut will prove to be rewarding in keeping the pathogen at bay. Farmers should not resort to the use of any insecticide to eliminate the vectors, as it may lead to resurgence of the pest and epidemic spread of the infection. Simple and effective biological control of the pests will be the best option.
The disease can also be managed well by using crop varieties that are resistant to the virus. ICRISAT scientists are working on the conventional approach and the frontier biotechnological approach to develop resistant varieties.
The virus can also pose a serious threat to other commercial crops such as cotton, okra (bhendi) and chrysanthemums.
Scientists are making all out efforts to study the virus in detail with help from advanced laboratories in the U.S., and come out with practical and inexpensive technologies for the benefit of small farmers in the developing countries, according to Dr. Reddy.