Effect of organic manure on the symptoms development of Iris yellow spot virus disease on onion (Allium cepa L.)

The effect of organic manure on the symptoms development of Iris Yellow Spot Virus Disease (IYSVD) caused byiris yellow spot virus (IYSV) (of the genus Tospovirus, family Bunyaviridae) in organic onion production was investigated. The randomized complete block design (RCBD), with three replications was used for the experiment. The treatments consisted of six organic manure combinations. These were 0% manure (control), 100% farm yard manure (FYM) equivalent to 4kg/plot, 100% poultry manure (PM) equivalent to 1kg/plot, 50% FYM plus 50% PM, 75% FYM plus 25% PM and 25% FYM plus 75% PM, denoted as T0, T1, T2, T3 ,T4 and T5, respectively. Use of PM in combination with FYM leads to fewer IYSVD incidences than when each manure was used alone. Treatments with no manure (T0) applied leads to high IYSVD incidence 26% and 37% at seven and 10 weeks after transplanting (WAT). The recommended rates of 120Kg N/ha for increased organic onion productivity were identified as; 3Kg FYM mix 0.25Kg PM/plot and 1Kg FYM mix with 0.75 PM/plot. Use of these rates resulted in high bulb and leaf yields of onion 14.58 and 18.75t ha1 respectively. The information generated in this study has greatly improved our understanding of the interactions between the three factors; the host, pathogen and the influence of organic manure, in the IYSVD-pathosystem, which would be highly useful in designing effective disease management strategies for increased organic onion production.