Rhizoctonia

Rhizoctonia affects a wide range of crop, pasture and weed species. Barley and wheat are most susceptible. Roots of infected plants will be stunted and often present ‘spear tip’ characteristics which are a diagnostic feature. Infection is most severe in cold, dry soils, compacted soils or in situations where root growth is inhibited, such as where group B herbicides have been used.

Maximum inoculum buildup occurs under cereals or grassy pastures. Grass free canola, mustard and medic pastures have been found to reduce inoculum levels, leading to higher yields in the following cereal crop. Others factors which reduce inoculum levels include, frequent summer rainfall, control of summer weeds and control of the autumn green bridge.

Short term management techniques that reduce the impact of Rhizoctonia include: – Sowing early, into warm, moist soils – Soil disturbance below the root zone – Adequate crop nutrition, particularly Nitrogen – Avoiding herbicides that prune seminal roots and hinder early growth, such as Group B’s – Avoiding low disturbance disc seeding systems – Zinc application has been found to reduce Rhizoctonia symptoms, although yield responses have not been demonstrated