CFC 10998
Potato / Late Blight Late blight Overview
Potato late blight is considered to be the most serious potato disease worldwide. It occurs almost everywhere potatoes are grown. In developing countries alone, yield loss due to late blight is estimated to add up to US$ 2.75 billion each year. In addition, much money is spent on fungicides. For example, of 196 potato fields surveyed in northern Ecuador, farmers spent, on the average, $120 per hectare on fungicides, about 10 percent of their overall production costs.
CIP's project for integrated management of potato late blight aims to reduce losses in potato production in developing countries due to late blight and damage to human health and the environment caused by the use of fungicides. The project is developing and deploying potato varieties with stable resistance to late blight, and developing agroecosystem-specific integrated management strategies for LB, suited to the needs of farmers in developing countries. This work is done in the context of and integrated disease management approach.
CIP’s research on integrated management of LB (IPM-LB) is aimed at developing flexible and farmer-friendly IPM-LB strategies, and working with local institutions to make relevant knowledge, skills and technology available to farmers. Participatory research and training programs are being developed in collaboration with national research and extension organizations. Our approach emphasizes the use of varieties with genetic resistance to the disease and helping farmers make better disease-management decisions.
To manage LB well, farmers need basic knowledge and access to technologies such as resistant varieties. Baseline surveys have indicated that resource-poor potato farmers in developing countries have a general idea of how environmental factors affect disease development, but they are unaware that a microbe is involved. They are generally poor at diagnosis and decision-making. To allow farmers to learn about disease and other key aspects of potato pest and crop management, and to get their input into the latest stages of the breeding program, CIP is working with diverse partners to develop farmer field schools for potato producers in areas where LB is a major concern.
Late blight is caused by the fungus-like oomycete Phytophthora infestans. Spores transported in the wind or infected tubers carried to new areas can cause infestation. Late blight first appears as a few grayish specks on the plant’s leaves, and then a cottony film appears. Under certain climatic conditions (high humidity and cool to warm temperatures), the disease can easily lead to the destruction of a whole field of potatoes. The disease also affects tubers, and can make the crop unfit for storage.
The disease can be controlled using resistant varieties, and cultural practices such as fungicides. However, many developing country farmers do not have the sufficient knowledge to manage the disease well. On top of that, the level of resistance in current potato cultivars is only intermediate, and access to resistant varieties by farmers is often limited. Moreover the use of fungicides is often too costly for resource poor farmers.
Phytophthora infestans began as a local pest of the wild relatives of the potato (and tomato) in the central Mexican valley of Toluca. It was unknown to European and American farmers and consumers who adopted the South American potato as a staple. In the 1840s, the microorganism spread all over Europe, and later over the rest of the world. On several occasions, the disease has reached disastrous proportions. Well documented is the Irish Potato Famine of 1845 to 1851 when, as a result of a late blight epidemic, one million persons of a total of eight million inhabitants died and another 1.5 million left the country.
