Phytophthora drechsleri

Phytophthora drechsleri is a destructive soil-borne pathogen belonging to the class Oomycetes. It is primarily known for causing root rot, stem blight, and fruit decay, posing a significant threat to agricultural productivity in both field and greenhouse environments.

The pathogen has a wide host range, frequently affecting Solanaceous crops such as tomatoes and peppers, as well as Cucurbits like cucumbers and melons. It is also known to infect various ornamental plants, making it a concern for nursery operations and high-value horticulture.

Symptoms typically begin with wilting and yellowing of the lower foliage, often misidentified as drought stress. A closer inspection reveals dark, water-soaked lesions on the root crown and taproot. Under high humidity, the affected plant parts may show a faint white mycelial growth, while fruits touching the soil develop firm, dark rot.

Disease development is highly dependent on environmental conditions, specifically prolonged soil moisture and temperatures ranging from 20°C to 28°C. The pathogen survives in the soil and plant debris as resistant oospores, which allow it to persist through adverse conditions and re-infect subsequent crop cycles.

Management strategies focus on preventing moisture accumulation through improved drainage and careful irrigation scheduling. Cultural practices such as crop rotation, use of certified disease-free transplants, and strict sanitation of farming equipment are essential. Chemical control using effective fungicides can be implemented if preventive measures are insufficient.