Potato Spraing

Potato spraing Common name Potato spraing Causal agent Potato spraing refers to a cluster of symptoms caused by two similar viruses: Potato mop-top virus (PMTV) and Tobacco rattle virus (TRV).  Both viruses have a synergistic effect when present together, amplifying the disease. Calcium deficiency in potatoes also induces a similar effect as spraing. Symptoms & Signs Spraing refers to a group of symptoms, including brown necrotic rings and streaks. It may also appear as brown concentric rings on the outer surface of the potatoes. The potato mop-top virus induces chlorosis on the middle and lower leaves. It gives a bunched, dwarfed appearance to the crop. Conversely, the tobacco rattle virus gives the plant a mottled, scorched, and stunted appearance. They both cause blotchy marks on the flesh but not on the skin. Transmission PMTV and TRV are both soil-borne. However, PMTV is transmitted by the fungus Spongospora subterranea, which releases its spores that travel by air, water, soil, and insects. However, RTV spreads via nematodes that feed on the tubers and transfer the virus to healthy crops. The nematodes usually appear on the upper soil during heavy rainfall or irrigation. Time of concern Early spring to summer Common hosts Potatoes Sugar beet Tobacco Field pansy Knotgrass Chickweed