 From VOA Learning English, this is the Agriculture Report. Scientists and agricultural experts recently met in Italy to talk about how to fight cassava disease. A virus that has been killing this important crop in East Africa has now spread to West Africa. Scientists are concerned that it could spread quickly throughout West Africa including Nigeria. Nigeria is the world's largest producer and consumer of cassava. Cassava is a tropical root vegetable that requires little work. It grows well in poor quality soil and high temperatures. Scientists are full of carbohydrates, vitamins, and minerals. Cassava can also be used as an industrial starch to produce plywood, textiles, and paper. Cassava is sometimes called a miracle crop for Africa. But plant diseases have been a problem for about 100 years. A particularly bad virus is cassava brown streak disease. It began infecting cassava fields in East Africa 10 years ago. Now it has spread as far west as the Democratic Republic of Congo. Cassava's streak disease is spread in two ways by white flies and by infected stem cuttings. Farmers use these cuttings instead of seeds to plant their fields. Claude Foquet is a plant virus expert. He heads the Global Cassava Partnership for the 21st Century. It is hard to see signs of the disease in the plant itself. Instead it becomes visible in the roots when the plant is harvested. He says scientists and organizations have to find a way to offer farmers virus free plant cuttings. Foquet says scientists are experimenting with a virus resistant cassava plant in Tanzania. Experts warn that brown streak disease could reduce cassava production in Africa by 50%. For VOA Learning English, I'm Mario Ritter.