Late blight

Late blight is caused by the oomycete Phytophthora infestans, a member of the kingdom Chromista. While often confused with true fungi, this pathogen acts as a water mold, capable of devastating host plants by rapidly destroying tissues through the production of enzymes and toxins.

The disease primarily targets solanaceous crops, most notably potatoes and tomatoes. Symptoms include water-soaked lesions on foliage, dark brown stem cankers, and characteristic rotting of tubers or fruits, which often leads to complete crop failure in susceptible cultivars.

The life cycle of the pathogen is driven by asexual reproduction, where sporangia produce mobile zoospores that require free water to infect host tissues. The pathogen survives between growing seasons as mycelium in infected tubers or as resilient oospores in the soil, ready to re-emerge under favorable conditions.

Outbreaks are heavily influenced by environmental factors such as high humidity, cool-to-moderate temperatures, and leaf wetness duration. These conditions promote rapid sporangia production and dispersal, which can result in severe epidemics across commercial agricultural fields.

Integrated pest management (IPM) is essential for control, focusing on the use of disease-resistant cultivars and certified pathogen-free seeds. Preventive measures include:

• Regular monitoring of weather conditions to predict infection risks
• Application of protective and systemic fungicides
• Removal and destruction of infected plant debris
• Crop rotation to reduce soil-borne inoculum levels

Effective management requires a proactive approach, ensuring that fungicidal sprays are applied before the pathogen establishes itself, particularly during periods of high precipitation and dew.