The Latest Control Methods for Potato Late Blight

Potato late blight is a disease caused by the pathogen Phytophthora infestans, and this disease causes relatively serious damage to potatoes, so today we will separately discuss the origin of potato late blight, the infection process, the symptoms, and when to control it, along with related information on prevention methods, to help everyone understand late blight.

I. Disease Symptoms

When leaves are infected, water-soaked lesions appear, surrounded by a green halo; after rain, the lesions expand rapidly and turn brown, and sporangia grow quickly on the underside of the leaves, appearing as white mold-like growth. After the weather clears, the affected leaves dry up and tend to crack. When stems and leaves are infected, brown spots form, later spreading to the leaves; at this stage the symptoms differ, generally appearing as black rot, wilting, and then drying up. When underground tubers are affected, brown spots appear first, followed by rot, sunken areas, spreading, and complete decay.

II. Disease Infection

The pathogen is a type of Phytophthora infestans, which mainly produces conidia to spread and cause damage. In water it can produce swimming spores; generally the zoospores can directly penetrate the host, spreading very quickly, with favorable conditions for spread, making infection easy. Moisture in the soil, rainwater, and irrigation water can all serve as transmission media. And as temperatures rise in spring, growth and germination become especially rapid. Warm and humid conditions are the main cause of high disease incidence, and from late spring to summer is the peak period of disease occurrence.

III. Disease Triggers

In spring, successive rainy days and high soil moisture; in summer, high temperatures and heavy rainfall, with a lot of water in the field and high water mobility. In summer, night temperatures are high and do not drop, which is suitable for pathogen growth. When air humidity remains excessively high and leaves stay wet without drying, these are favorable conditions for disease development. Last year's diseased plant residues and pathogens remaining in the soil can cause repeated infection. Airflow causes the disease to occur repeatedly.

IV. Control Measures

1. Prevention

Choose soil that has never been planted with potatoes. If disease occurred in the first year, then both the diseased plant residues and the soil must be treated and disinfected. Planting on mountain land is better than in low-lying fields, as mountain land has good aeration. Drainage is convenient. It can be rotated with rapeseed-type vegetables to reduce sources of the pathogen. Ensure adequate nutrition, maintain optimal growth vigor, and resist the pathogen. The field must not be too densely shaded; expand planting spacing as needed and weed at any time, especially broadleaf weeds.

2. Medication

Potato seed potatoes can be soaked and disinfected with a 0.2% potassium permanganate solution. If disease occurs in the field, spray with 58% metalaxyl · mancozeb at 500 times dilution. In fact, there are many choices of chemicals; generally, chemicals are used alternately, once a week. After several applications, it can be treated.

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