Pythium dissotocum

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Pythium dissotocum is a water-loving plant pathogen that causes root rot in many crops, especially strawberry and rice, and can threaten plants grown in greenhouses or hydroponic systems.

How it reproduces
- Asexual phase: It makes sporangia that release swimming spores (zoospores). The zoospores swim to roots, infect them, and start a network of fungi that damages the plant.
- Sexual phase: If two mating types meet, their hyphae fuse to form thick-walled oospores that can stay dormant for months. Oospores can germinate later to begin new infections.

Spread and impact
- It spreads mainly through water. Wet conditions in greenhouses, irrigation systems, and hydroponics greatly increase the risk.
- It can infect many crops, including lettuce, spinach, peppers, parsnip, parsley, tomato, sugar cane, carrot, and hydroponic cannabis.
- It causes root necrosis and lesions, yellowing, and damping-off of young plants, leading to yield losses.
- It is found in the Americas, Europe, and Asia, and globalization can help it spread to new areas.

Detection
- RT-PCR tests are available to detect the pathogen.

Management
- Prevent over-watering and keep roots drier when possible.
- Sanitize tools and water to reduce spread, especially in irrigation and hydroponic systems.
- Fungicides such as mefenoxam and phosphonates can help, usually used together.
- Biocontrol with Pseudomonas chlororaphis shows potential but results are variable and it doesn’t reliably block infection.
- If infection occurs, trim damaged roots and sterilize the healthy ones.