Assessment of Potato Yield Losses Due to Diseases in Busogo Sector, Rwanda

Potato (Solanum tuberosum L.) is one of Rwanda’s priority food crops, yet its productivity isconstrained by several diseases, notably late blight and bacterial wilt. This study evaluated potatoyield losses attributed to diseases under field conditions in Busogo Sector, Musanze District. Arandomized complete block design (RCBD) with four treatments and three replications wasemployed: T1 (Ridomil application), T2 (Dithane application), T3 (Ridomil + Dithane), and T4(control, no fungicide). Agronomic parameters (plant height, leaf number, and plant diameter) anddisease indices were recorded at regular intervals. Percent Disease Index (PDI) was calculated andanalyzed statistically using ANOVA. Although no significant differences were observed amongtreatments for growth parameters (p > 0.05), disease severity was reduced by fungicideapplications, particularly in T3 and T2. PDI decreased from 49.3% at week 6 to 19.4% at week 9,indicating effective disease control. Estimated yield losses were 26.19%. Preventive fungicideapplication, especially Dithane, is recommended to minimize disease impacts and improve yields