How to Treat Pythium in Soil

You can spread pythium around your garden by moving soil from one spot to another.

Pythium root rots are caused by several fungi of the Pythium spp. According to the University of California, they are prevalent in soil and can survive under a variety of conditions. Pythium fungi attack young root tissue in wet soils. As more and more roots succumb to the disease, plants begin to wilt, become necrotic and eventually die. Young plants rapidly growing roots can fight off the disease if their soil is allowed to dry out between waterings. One effective method for killing pythium fungi in the soil is solarization. Solarization heats the soil to a temperature that kills the fungi.

Things You'll Need

• Rake
• Shovel
• Clear plastic sheet, enough for your garden, 1 mil thick
• Black plastic bag
• 2-foot by 2-foot piece of wood
• 4 tin cans
• Soil thermometer

Instructions

Outdoor Plots

1. Prepare your garden beds by raking them smooth and removing any rocks, debris or large dirt clods.

2. Irrigate the soil to a depth of 12 inches. According to the University of California, wet soil heats better and makes the fungi more susceptible to the high temperatures.

3. Dig a trench 4 to 6 inches deep around the planting bed. If you are working with a raised planter, dig the trench at the edge of the raised soil or wooden border.

4. Lay one edge of a sheet of 1 mil, clear plastic sheeting in the trench and cover it with soil. Stretch the plastic tight across your garden and lay the opposite edge in the trench. Cover it with soil and stretch and bury the final two edges. Solarization works best when the plastic is as close as possible to the soil. For raised planter beds, it is best to use a separate sheet of plastic for each bed.

5. Leave the plastic on the soil for between four and eight weeks, depending on where you live. You need to maintain a temperature of between 110 degrees and 125 degrees Fahrenheit daily for four weeks. In colder areas, it may take longer for these temperatures to be reached initially.

6. Remove the plastic after the temperature and time requirements have been met. Or, you can leave the plastic as mulch and cut holes in it for planting.

Soil for Containers

1. Pour the desired amount of soil in a black plastic bag.

2. Build a raised platform by placing a square piece of wood at least 2 feet by 2 feet on top of four tin cans and place it in the sun.

3. Place the soil-filled plastic bag on the platform. Leave the bag on the platform until the soil temperature remains at 160 degrees for 30 minutes or 140 degrees for one hour. Use a soil thermometer inserted into the center of the soil to monitor the temperature.

References

• UC IPM Online; Pythium Root Rot; March 2009
• UC IPM Online; Soil Solarization for Gardens & Landscapes; J. J. Stapleton, et al.; October, 2008