Damping Off Cuts Them Off At Their Knees

By Mary Small and Curtis Utley, CSU Extension in Jefferson County

It was finally time to start basil seedlings for our research and demonstration garden here at the Jefferson County Fairgrounds.  Containers filled? Check. Seeds planted? Check. Water applied? Check. Lights set on timer? Check.

Everything went well until shortly after the seedlings sprouted.  Then they flopped over. Looking more closely at the plants, we discovered a pinched-in area near the bottom of all the toppled stems. It was the dreaded damping off.  The crop was almost a complete loss.

Damping off is a problem that gardeners often encounter when growing their own seedlings. It is caused by soil borne fungi or fungal like organisms that thrive in wet soil. They enter the roots and secrete enzymes that break down plant tissue, creating a mushy mess. Using non-pasteurized soil for seeding and overwatering are the two most common causes of this problem.

Overwatering is easy to do in our dry indoor air.  The soil surface dries out quickly, making us think it needs some more. Excess water drives out necessary soil oxygen and at the same time enables the organisms to move easily throughout the soil, contact roots and begin their damage.

If you don’t know whether or not soil is pasteurized, you can do it yourself. Place several inches of moist soil in an oven-safe pan.  Preheat the oven to 180-200 degrees ^oF and place the pan in it. Periodically use a thermometer to check the soil temperature in the middle of the pan.  When it reaches 180 degrees, turn off the oven and keep the door closed for a half hour. Don’t mix this pasteurized soil with non-pasteurized soil or it will become contaminated.

Always surface sterilize containers and tools using a mixture of 1 part bleach to 9 parts water.  Avoid overwatering to keep soil conditions unfavorable for the growth and spread of damping off organisms.

Now you’re probably wondering what we did wrong in our basil-raising efforts.  Call it being in too big of a hurry to get growing. We overlooked surface sterilizing the containers. Now we get to plant all over again.  You can bet we’ll correct our mistake!