Effect of NPK Fertilization on Cassava Mosaic Disease (CMD) Expression in a Sub-Saharan African Region

The influence of NPK fertilizer on the incidence, severity and gravity of cassava mosaic disease (CMD) was investigated using eight genetically improved cassava varieties and eight local farmer’s varieties. The study was carried out in a savannah region (Gandajika) in D.R. Congo at two locations. The varieties were planted with and without NPK fertilization. Application of NPK fertilizer significantly (P<0.05) increased CMD incidence, severity (AUDPC) and gravity overtime compared to the trials without fertilizers for all the improved cassava varieties evaluated. The CMD incidence remained below 30% of infected plants for improved cassava varieties and reached 100% of plants for local varieties during the six months trial. The same trend was observed for CMD gravity (number of infected leaves per plant) that was below 50% for improved varieties while reaching 100% for all the local varieties at 6 MAP. High incidence and gravity of CMD were observed on local varieties just one month after planting. NPK fertilizers increased significantly the CMD incidence and gravity compared to control site during the first month after plantation. Thereafter, the effect of NPK fertilizer on CMD symptom expression was not noticeable since all the plants from local varieties were infected regardless of the fertilization regimen.