A Detailed Guide to the Latest Control Methods for Potato Leaf Blight
Potato leaf blight mainly damages the leaves. In most cases, the senescent leaves on the lower part of the plant are the first to become diseased during the middle and late stages of potato growth. At first, the leaves show greenish-brown necrotic spots, and sometimes the stems and vines are infected, forming irregular grayish-brown necrotic spots. In the late stage of the disease, small brown granules are produced on the diseased parts. Now let us take a look at the control methods for potato leaf blight!
Symptoms of Damage
When potato leaves are infected, the disease starts near the leaf margin or leaf tip. Initially, greenish-brown necrotic spots form, which gradually develop into nearly round to V-shaped large necrotic spots ranging from grayish-brown to reddish-brown, with indistinct concentric rings. The outer edge of the lesion is often chlorotic and yellowed, and finally the diseased leaves become necrotic and scorched. Sometimes a few dark brown small dots (the fungal pycnidia) can be produced on the lesions. When stems and vines are infected, irregular grayish-brown necrotic spots form, and later small brown granules can be produced on the diseased parts.
Occurrence Characteristics
Potato leaf blight is caused by infection with the fungus Macrophoma sp., a deuteromycete. The pathogen overwinters in the soil as sclerotia or as mycelium with diseased plant residues, and can also overwinter on the residues of other hosts. When conditions are suitable the following year, rain splashes the pathogen from the ground onto leaves or stems and vines, causing primary infection. After the disease occurs, sclerotia or pycnidia produced on the diseased parts are spread by rain splash to cause repeated secondary infections, leading to the spread and expansion of the disease. Warm and high-humidity conditions favor the occurrence and epidemic of this disease.
Control Methods
1. Agricultural control: Choose relatively fertile plots for planting, and maintain a reasonable planting density.
2. Strengthen management: Apply more organic fertilizer and appropriately supplement phosphorus and potassium fertilizers. Water and topdress in a timely manner in the late growth stage to prevent premature aging of the plants.
3. Chemical control: Spray for control at the early stage of the disease. The agents can be 70% thiophanate-methyl wettable powder at 600 times dilution, or 70% mancozeb wettable powder at 600 times dilution, or 50% iprodione suspension concentrate at 1200 times dilution, etc.