Keywords

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Two diseases, one of sweet potatoes and one of potatoes, are commonly called scurf.

Monilochaetes

Deuteromycetes, Hyphomycetes

Hyphae and conidiophores dark, spores hyaline, one-celled, oblong-cylindric, in chains.

Monilochaetes infuscans

Sweet Potato Scurf. Small, circular, brown or black spots are formed on all underground parts, often forming a uniform patch over the whole potato or a black patch on red-skinned varieties. The skin cracks, and potatoes shrink in storage. The black conidiophores stick up from the surface of the lesions like bristles. The fungus winters on the roots and on decaying vines.

Control

Scurf, formerly present in 50 % of New Jersey sweet potatoes, is now rare because of proper care. Set only healthy sprouts, grown from potatoes bedded in sand that has not grown sweet potatoes before.

Helminthosporium (Spondylocladium)

Deuteromycetes, Hyphomycetes

Conidiophores dark, straight, septate, the upper cells bearing whorls of conidia; conidia dark with three or more cells.

Helminthosporium solani

(formerly Spondylocladium atrovirens). Silver Scurf of potatoes. Scab, Dry Rot, present in almost all potato districts but not too important. Light brown lesions become somewhat blistered, giving the skin a marked silvery appearance. The disease is only skin deep, and control measures are seldom used.

Spondylocladium atrovirens

(see Helminthosporium solani). Silver Scurf of potatoes. Scab, Dry Rot, present in almost all potato districts but not too important.