2.16 Effects of common scab on potatoes Common scab affects the quality and marketability of the tuber but has no effect significant on the yield obtained (Slack., 1992; Hao et al., 2009). However, some researchers have reported that the disease can also cause yield losses (Chater, 2006). Common scab can have a more negative effect on farmers who produce seed potatoes, as these are condemned by certification agencies. When the incidence of infected seed tubers is 3-5%, seeds are rejected (Verma and Sharma, 1992) and there is also an increase in peeling costs (Wale et al, 2008) in the case of table potatoes. yield losses are higher in infected tubers as storage life is reduced (Zadeb et al., 2008). Some authors have mentioned that when infected tubers are marketed locally they can still fetch their normal price, but problems arise when the potatoes have to be exported and the washing processes will make the tubers visibly unsightly and therefore difficult to market.2.17 Control measures for common scabiesManagement of common scabies is very problematic and there are no effective control methods so far (Dees et al., 2013). However, there are certain methods that have proven effective in mitigating the effects of this disease. Common scab can be controlled by the use of certified seeds, seed treatment agents such as pentachloronitrobenzene (PCNB) or mancozeb dust (Agrios, 2005). However, freshly cut tubers can be affected by high concentrations of mancozeb (Pung and Cross S, 1999). Potato monoculture should be avoided to reduce inoculum and crop residues should be destroyed after harvest. Common scab thrives in dry soil conditions, application of adequate water from tuber formation at about 6-8 weeks can greatly...... middle of paper ......ato Advice. Ref: R248.Slack, SA, 1992. A look at potato leaf curl virus and PVY: past, present and future. Valley Potato Grower 57, 35-39. Shi, QH and ZJ Zhu., 2008. Effects of exogenous salicylic acid on manganese toxicity, element content and antioxidant system of cucumber. Environmental and Experimental Botany 63: 317–326. St-Onge, R., Gadkar, VJ, Arseneault, T., Goyer, C., Filion, M., 2011. The capacity of Pseudomonas sp. LBUM 223 to produce phenazine-1-carboxylic acid affects the growth of Streptomyces scab, the expression of thaxtomin biosynthesis genes and the biological control potential against common scab of potato: effect of PCA production capacity on S scabies. FEMS Microbiol. Ecol. 75, 173-183. doi:10.1111/j.1574-6941.2010.00992.x. Suzuki, H., 1940. On the relationship between susceptibility of rice and penetration into host plants.