Organic growers are severely limited in the tools that they can use to fight fungal infections since they cannot use effective chemicals. One unhappy result was severe losses to diseases in the organic potato fields of Northern California last fall.

“John Crawford, part owner of Crawford Farms, Inc. for commercial farming and Cascade Farms for organic farming in Tulelake, said everyone across the county is two weeks behind on their potatoes. … The cool spring also contributed to problems with rhizoctonia disease… Rhizoctonia girdles the roots and the stem, then the plant withers and yield is reduced.”

“Rhizoctonia was a huge problem in Crawford’s conventional potatoes and crops would have a 100 percent infection rate. Now, with the new chemical compounds, he has good control. But Crawford said he continues to struggle with rhizoctonia in his organic potatoes. ‘It’s our worst enemy in organics because we really don’t have a natural compound that is very good at fighting it,’ he said, adding in one field of organic potatoes he estimates 75 percent are infected with rhizoctonia. … Crawford estimated at least a 20 percent yield loss from rhizoctonia damage.”

Author: Kathy Coatney
Title: Rhizoctonia and wilt create challenges for potato growers.
Publication: Ag Alert. September 14, 2011. p.18