Pythium Damping-off at the Soil line of Cucumber

Pictures courtesy of Mike Roegge

Pictures courtesy of Mike Roegge

Pictures courtesy of Mike Roegge

No greenhouse operation is immune from possible disease problems.  The U of I Plant Clinic received this cucumber sample from a greenhouse that was growing cucumbers in a soil-less medium.  The symptoms were rotting in the lower part of the stem, near the soil line, of most of their cucumber crop.

The rotted tissue at the soil line was examined under the microscope at the U of I Plant Clinic and many oospores were found embedded within that tissue.  The symptoms, along with the presence of oospores embedded within the diseased plant tissue, is most likely due to pythium damping off at the soil line.

Oospores seen within the rotted tissue under the microscope

Plants will develop a watery rot in the taproot and hypocotyl at or near the soil  line.  Decline, necrosis, or sudden wilt (collapse during the heat of the day) are some symptoms that can occur after infection takes place.  Several species of Pythium can be involved.  Conditions favorable for disease development can differ depending on the pathogen species, but most likely cool and wet conditions are favorable for disease infection.

I consulted with Dr. Babadoost, U of I Extension Fruit and Vegetable Plant Pathology Specialist, to provide possible management solutions for this disease in this particular greenhouse operation.  He recommended that first and foremost, that they cut back on watering these plants as much as possible.  In addition, they may want to increase the temperature in the greenhouse, if possible.  As always, sanitation is very important.  They will not be able to save the infected plants, but to provide protection for unaffected or future cucumber plantings, they may want to apply Phosphite products or metalaxyl (Apron, Ridomil, Subdue) fungicides.