EFFECTS OF WINDROWING, IRRIGATION AND DEFOLIATION OF POTATOES ON SILVER SCURF (HELMINTHOSPORIUM-SOLANI) DISEASE

Field experiments with the potato variety Desiree at Cambridge, UK, in 1988-90 examined the effects of windrowing on the development of blemishing diseases during storage on tubers from crops grown with differing irrigation regimes and dates of defoliation and harvest. Irrigation reduced levels of silver scurf (Helminthosporium solani) at harvest in all three years and increased black dot (Colletotrichum coccodes) in one year. Early crop defoliation slightly increased silver scurf at harvest in one year only. Silver scurf developed less during storage at 3-degrees-C than at 7-degrees-C and disease levels on tubers after storage were related to levels present at harvest. The effects of leaving tubers for up to 6 h in a windrow at harvest on silver scurf after storage were small and inconsistent between years despite similar drying conditions. The results suggest that windrowing may be of little practical use in controlling silver scurf during storage.