Evaluating fungicides for the management of rust (Uromycladium acaciae) on black wattle nursery seedlings in Awi zone, Amhara Regional State, Ethiopia

Abstract

Black wattle (Acacia mearnsii De Wild) provides numerous benefits for Ethiopian smallholder farmers due to its fast growth and wide adaptability. It is used for soil improvement and provides economic benefits through charcoal production and the use of wood as biomass fuel. However, in recent years, nursery stocks and young plantations have become susceptible to the wattle rust disease. No fungicides are currently registered in Ethiopia for control of wattle rust. A field experiment was conducted to evaluate the effectiveness of fungicides at varying rates for control of black wattle rust at Endewuha and Surta nursery sites, in Awi Zone, northern Ethiopia. Two systemic fungicides, namely, Amistar Top and Amistar Xtra, were evaluated at rates of 1 L·ha−1 and 0.5 L·ha−1 along with an unsprayed control in a randomized complete block design with three replications. Both fungicides at all rates significantly reduced rust infection at both sites. The lowest disease severity, along with increased plant height and collar diameter, was observed in the fungicide-treated plots compared to the untreated control. There was no significant difference in diseases intensity reduction and seedling height and root collar diameter among fungicide rates. The shortest height and the smallest root collar diameter were recorded on the untreated plots at both sites. The percentage reductions in disease damage compared to the control ranged from 94.6% to 96.72% at the Surta site and 94.6%–96.25% at the Endewuha site. Amistar Top or Amistar Xtra fungicide can effectively control acacia rust damage during the seedling stage, ensuring healthy and vigorous planting stock. The choice of the fungicide and application rate will depend on availability and cost, rather than on fungicide group. Further investigation is needed to assess the performance of both treated and untreated seedlings, as well as the progression of the disease in plantation sites.