Brown Spot (Cochliobolus Miyabeanus) Factsheet for R Ice D

Brown Spot (Cochliobolus Miyabeanus) Causal agent: Fungus Geographical Distribution Management Strategies . This disease can occur in all rice 1. Cultural control growing areas of East Africa (refer to • Water stress can be prevented by Rice Production Areas Factsheet) application of alternative wetting-drying Fig 1. A spore of C. meyabeanus Crop damage and associated loss technique of irrigation. Source: Martin-Felix et al., 2017 Brown spot Roots of rice crop, infested • Infection by this fungus causes a • Soil nutrient stress can be avoided by serious damage on the leaves of both application of fertiliser at the appropriate Favourable conditions for disease young and adult rice plants, hence rates (see Water and Nutrient development reducing the photosynthetic area Management Factsheet). • Damaged seedlings have small, Fig 3. Brown lesions on rice • Inoculum reservoir can be destroyed by • The optimum conditions are: a leaf Source: Dr Lusike removing and/or burning of left-over temperature range of 16°C-36°C and a circular, yellow brown or brown lesions Wasilwa debris and any infected rice from the high relative humidity ranging 86-100% . that may girdle the coleoptile and distort field. • For infection to occur, the leaves must be primary and secondary leaves. • General crop health can be maintained wet for 8−24 hours. • Lesions on leaf sheaths are similar to by reducing rice-weed competition using • The disease is more common in fields those on the leaves. Infected glumes timely removal of weeds in the field. have water and nutrient deficiencies. and panicle branches have dark brown • Get rid of seedborne inoculum by using • Besides rice, the fungus attacks several to black oval spots. hot water treatment method of seeds at grasses, including rice, wild rice, cutgrass • The brown spot lesions on leaves can 53-54°C for 10- 12 minutes. and maize. be mistaken for foliar rice blast disease. 2. Resistant cultivars • The fungus can survive in the seed for The major characteristic of brown spot • Use resistant varieties such as MWUR 2 more than four years. is the circular brownish spots which and MWUR 4 (available KALRO MWEA) • The fungus can also survive in volunteer have a gray center. Factsheet for Rice Diseases in East Africa East in Factsheet Diseases for Rice 3. Chemical Control rice, infected rice debris and weeds. • If spikelets are infected, grain filling is • Seeds can be dressed using Seed Plus • In a season with favourable conditions, disrupted and the damage leads to 30 WS (Imidacloprid 10%; Metalaxyl the inoculum is spread by wind, water partial or complete loss of the crop. Fig 3. Symptoms on 10%; Carbendazim 10%) at a rate splashes or via seed. spikelets Source: Dr Lusike • Generally, if the disease is unmanaged, Wasilwa between 2.5-5.0 kg/ton of seed. it can lead to 50% yield loss in all rice growing regions. Contact experts: Mutiga, S, ([email protected]), Mwongera, D; Kirigua, V; Otipa, M; Kimani, J; V. Mugambi, C; Ngari, B; Ochieng, V; Wasike, V; Wandera, F, Wasilwa, L; Too, A; Nyongesa. O. (IRRI); Zhou, B (IRRI)); Mitchell, T. (OSU); Wang, G. L (OSU); Were, V. (TSL); Ouedraogo, I. (INERA); Rotich, F. (UoEm); Correll, J. C. (UARK) and Talbot, N. J. (TSL). E-Guide for Rice Production in East Africa (2019).

Load more