Rhizoctonia burden in seed potatoes. Effects on yield and quality.

摘要

Rhizoctonia solani control is difficult in potato production. In conventional systems, only 60% efficiency is found under optimum conditions and in organic systems, no permitted treatments are available. Therefore, prevention has to be the main control strategy. In 2002 and 2003, on-farm trials on three organic farms in Niedersachsen, Germany were carried out. Seed potatoes with three infection levels (below 1%, 5-8% and above 10%) were used on all farms. Results show significant lower yields with more infected seed potatoes. An effect on size classes was not found. Clear effects however, were found on potato quality measured as skin deformations. Minor deformation with no effect on marketable yield and major deformation, making potatoes un-marketable for human consumption, were significantly higher with increased infection levels. It is concluded, that seed potatoes should be free from Rhizoctonia (below 1%). Tubers with a higher infection level should not be used for planting in organic and conventional systems.