Management of common scab of potato using planting and harvest dates

Abstract

The influences of planting and harvest dates on yields and grade-out due to tuber damage by common scab (Streptomyces spp.) were evaluated over three cropping seasons using two cultivars of potato (Solanum tuberosum) grown on land heavily infested with pathogenic Streptomyces species. Early planting and delaying the harvest enhanced yields in both cultivars, but also increased tuber grade-out due to excessive levels of scab. Delaying the harvest reduced marketable yields more than did early planting. The longer harvest was delayed after top-kill, the greater was the grade out due to scab. Increased losses to scab exceeded any increase in tuber yields obtained by delaying harvest. This study demonstrates that common scab of potato may be managed by minimizing the period the crop is in the ground, but that this method of disease management is achieved at the expense of yields. Early planting coupled with timely harvesting after kill-down of the tops appears to be an effective compromise between the objectives of maximizing yields while avoiding excessive grade-out due to common scab. Key words: Potato scab, Streptomyces scabies, Solanum tuberosum, agronomy