Paul Gans - Plant Health Management

Most (92.6%) isolates of Rhizoctonia solani from potato crops belong to anastomomosis group 3 (18 April 2007)

How can this help potato growers? It is now technically feasible to test soils for the presence of Rhizoctonia solani, which causes black scurf and stem canker of potato. However it is important to know that the test is carried out for the right strain or strains. It is also known that some strains are more sensitive than others to particular fungicides.

Rhizoctonia solani causes diseases on a wide range of crops. This has led to specialization within the species. Subgroups within the species can be recognized in the laboratory by the way in which hyphae of isolates belonging to the same group will fuse, an event which is described as anastomosis. On this basis at least 11 anastomosis groups have been recognized. Worldwide only a few of these have ever been found in association with potatoes.

According to a research paper published in this April issue of Plant Pathology most (92.6%) isolates of, belong to anastomosis group 3 (AG3). Another 6.7% belonged to AG2-1 (a subgroup of AG2) and a single isolate out of a total of 135 belonged to AG5. The researchers at Harper Adams University College and SCRI also made significant improvements to a molecular method to detect these two groups.

French scientists found similar proportions of the 3 groups in their country. Significantly, they established that AG5 and AG2-1 are highly sensitive to flutolanil, iprodione and pencycorun (the active ingredients found in Rhino, Rovral and Monceren respectively).