How to keep spud plantings ahead of disease risk

Threat more prevalent this season

Changing rotations and reduced tillage could explain why a key disease is becoming more prevalent and damaging in potato crops.

Potato growers need to be alert to the threat of Rhizoctonia solani this spring – especially farms moving less soil between crops. Reduced tillage has been shown to encourage survival the pathogen in the soil.

There are also more species of plants being grown in some rotations, whether that is driven by a greater area of cover crops, environmental schemes, or more cash crop options.

In theory, this diversity could reduce the amount of available Rhizoctonia inoculum for susceptible crops – including potatoes. But it also provides more hosts for soil-borne persistence.

Farming systems have changed rapidly over recent years and this has created a knowledge gap that needs filling, says Rumiana Ray, professor of plant pathology at Nottingham University.

“Growers and agronomists need to know the current soil-borne disease situation to assess the impact of these practices and implement alternative or corrective measures, if needed,” says Prof Ray.

Identifying risk

Hutchinsons agronomist and potato specialist Andrew Goodinson says currently that leaves good husbandry, combined with the application of soil- and seed-applied fungicides, as the main control measures where risk is identified.

Where soil-borne risk is identified, Mr Goodinson recommends the use of in-furrow fungicides like azoxystrobin or fluxapyroxad – combining them with a seed treatment where needed.

There are liquid seed-treatment options like flutolanil-based RhiNo and Andrew sees these becoming much more popular in the future as seed is treated in the shed over a roller table ahead of planting.

This takes an operation off a busy planter operator already grappling with accurate seed spacing and in-furrow applications of fungicide and fertiliser, before even considering powder seed treatment application.

But Mr Goodinson says many of his potato growers are still using powder flutolanil formulation RhiNo DSG, as it gives flexibility, particularly where seed is delivered just-in-time for planting.

“But whatever seed treatment you decide to use, effectiveness does rely on excellent coverage. That makes correct setup, calibration, and maintenance of on-planter applicators crucial,” he adds.

Early nutrition

Planting conditions and adequate early nutrition are the final considerations, with timely cultivations and seed-bed preparations that avoid soil compaction key to seeing the crop grow away from the threat of Rhizoctonia.

“Anything that can reduce stress and encourage crop development is a good thing and we are using phosphite-based products as well,” says Mr Goodinson.

“Other biological products will play an increasingly important role in potatoes, but we are still learning about how and when they are best applied for consistent success.”