Thursday, May 22, 2008

Pythium root rots of bean and watermelon seedlings

Today was a day of root rots! Two samples of pythium root rot but both came in with complaints of foliage problems on field transplants (browning and death of bean leaves & wilting of watermelon). Luckily, the submitters had included the full root system and soil so we were able to quickly make an accurate diagnosis. Pythium agar was used to confirm the presence of Pythium spp. Note the characteristic stem lesions.
Pythium root rot on snap bean transplants:

And Pythium root rot on watermelon transplants:


IndoorHerbs said...

What treatment do you recommend in this case?

Brooke said...

At this point there is no control treatment. The root systems are unlikely to recover from this severe damage and if weather conditions are right the stem lesions will expand. Prevention is key! Fungicides are available to treat seeds and transplants in the greenhouse. Planting into well drained soils and/or on ridges to prevent excessive standing water around the transplants can also help.