Potato Late Blight Description Symptoms & Control

Potatoes are the third-largest food crop in the world. At present, China’s planting area and output both rank first in the world. Late blight is a devastating disease in potato production. It causes huge losses every year and seriously affects potato production. Planting disease-resistant varieties are the most economical, environmentally friendly, and effective way to prevent and control late blight, and it can fundamentally solve the problems of pesticide residues and environmental pollution.

With the continuous expansion of the potato planting scale, potato late blight has occurred in all potato-producing areas. Potato late blight is a devastating disease that occurs on potatoes, and it occurs all over the world. The potato yield reduction caused by this disease is generally 20% to 80%, which has become the most serious disease of potatoes.

Potato late blight is a serious fungal disease caused by Phytophthora. Phytophthora infestans have become the most harmful pathogen in potato blight due to the death of potato stems and leaves and tuber rot.

Potato late blight Phytophtora

Potato Late Blight Occurrence Characteristics

Potato late blight is a fungal disease caused by Phytophtora infestans, which brings huge losses to global potato production every year.

Potato late blight is believed to be the main culprit leading to food shortages in Europe in the 1850s. Over a million Irish people suffered starvation or even death as a result. Potato late blight mainly infects leaves, stems, and tubers, and its typical symptoms are: When the leaves are damaged, The leaf tip or leaf margin first produces water-stained lesions with irregular edges. There is often a light green halo around the spots. When the humidity is high, the lesions can quickly expand to the whole leaf. The gray-brown or dark-brown lesions will expand as the stalk elongates.

After the tuber is infected, small brown spots appear on the surface and gradually expand, forming a sunken light brown to grayish purple irregular spot. The diseased potato is often rotted with other pathogen infections under the conditions of high temperature and high humidity.


Seed tuber infection has been reported as the most important factor leading to potato late blight at the field level, and it is also affected by the following factors:

Climate: The prevalence of late blight is closely related to climatic conditions, especially the number of rainy days. In rainy, foggy, humid air, the relative humidity is above 85%, and the temperature is 10-15℃. It is easy to get epidemic.

Varieties: There are great differences in the resistance of different varieties to late blight.

Growth period: strong disease resistance in the early stage of growth, and the most susceptible to disease in the later stage of growth, especially at the end of flowering, especially the continuous rainy weather at the beginning of the flower to the end of flowering, which is conducive to the outbreak of late blight.

Integrated Control Technology

The prevention and control of potato late blight should be based on the promotion of disease-resistant varieties and the selection of disease-free seed potatoes, combined with the elimination of central diseased plants, chemical control, and improved cultivation techniques for comprehensive control.

1. Choose Disease-resistant Varieties of Potatoes

Establish a disease-free planting area and select disease-free seed potatoes in the two-season cultivation area. The incidence of autumn-sown potatoes is light, and the autumn potatoes are vigorous and have strong species, which are suitable for retention as seed potatoes. In the one-season cultivation area, the disease-free planting field should be more than 2.5 km away from the field to reduce the chance of spreading and infecting pathogens, and various prevention and control measures should be strictly implemented.

The selection of disease-free seed potatoes is also an effective measure for disease prevention, and disease-free plants can be selected for single harvesting or single storage in the lighter-infected plots and reserved for seeding.

2. Strengthen Cultivation Management

Combine the management of the prevention and control of virus diseases, rationally fertilize, keep the plants strong, enhance the disease resistance of the plants, choose a sandy loam with higher terrain and good drainage, and rationally irrigate. The central diseased plant should be removed immediately, or the diseased leaves should be removed. Cultivating the soil in the later growth period to reduce the chance of pathogens infecting the tuber, reduce the plant spacing, or spray the mass concentration of 90 mg/L paclobutrazol at the bud stage to control the growth of the above-ground plants and reduce the field microclimate humidity, which can all reduce the disease.

3. Biocontrol Microorganisms

The use of biocontrol microorganisms to control plant soil-borne diseases has been successful in many plants.

The parasitic effect of biocontrol microorganisms is manifested by antagonizing the parasites to specifically recognize the target pathogens and inducing cell wall lytic enzymes to degrade the cell walls of the pathogens so that the parasites can enter the hyphae of the pathogens to exert antibacterial and killing effects.

Chemical control has made pathogens resistant to chemicals, reduced the control effect, and caused pollution to the environment. Therefore, finding and researching biological products is a trend in disease control. Breeding and popularizing disease-resistant varieties are the basic measures to prevent and control late blight.

Bacillus subtilis can effectively control the occurrence of plant soil-borne diseases. Relevant studies have shown that Bacillus subtilis has effectively prevented the potato late blight (Phytophthora infestans), and the incidence of late blight has been reduced by 20.0%; The rot rate of potato (Solanum tuberosum) tubers was reduced by 14.9%.

The Trichoderma harzianum strain has carried out research on the prevention and control of potato late blight. After the potato seeds are treated with the Trichoderma solution, the incidence of potato late blight has been reduced by 45.8%, and the rot rate of potato tubers has decreased by 38.4%.

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