Management of Common Bean Rust (Uromyces appendiculatus) through Host Resistance and Fungicide Sprays in Eastern Ethiopia

Abstract

In Ethiopia, common bean rust ( Uromyces appendiculatus) is the most destructive
disease constraining common bean production. Field experiments were carried out
at Hirna Research Sub-Station of Haramaya University in the 2010 main cropping
season to elucidate reaction o f released common bean varieties to rust infection and
to study the effect of integrated use o f host resistance and fungicide foliar sprays
on incidence o f the disease and its control. For the evaluation of common bean
varieties to rust disease the experiment was laid out in randomized complete block
design with three replications and 15 varieties and the experiment was laid out as a
randomized complete block design in factorial arrangement with three replications
for the management part. In the fungicide spray, three contact (i.e. Chlorothalonil,
Mancozeb and Copper hydroxide) and one systemic (Triadimefon) fungicides were
tested on a susceptible (Mexican-142) and a moderately resistant (Awash-1)
varieties. The research results obtained indicated that the evaluated common bean
varieties varied significantly in severity, area under disease progress curve, disease
progress rate and grain yield. Three reaction groups o f common bean varieties were
identified, viz. susceptible, moderately resistant and resistant. The resistant
varieties produced the highest grain yield. At Hirna the varieties, Kufanzik,
Haramaya, Melkadima, Gofta, Chore and Awash Melka were found to be resistant
to the disease. These varieties were also high yielders. However, in case seeds o f
resistant varieties are inadequate to cover the major growing areas, farmers can use
the moderately resistant varieties with fungicide sprays wherever the disease is a
pervasive and pressing problem. In the management study, lower rust incidence,
severity, area under progress curve and slower disease progress rate occurred on
the moderately resistant variety sprayed with Triadimefon than on the susceptible
variety with Triadimefon and/or with other fungicides. The integrated use o f
moderately resistant variety (Awash-1) with Triadimefon proved to be the best
management option producing the highest (2306.25 kg h a 'l) grain yield.
Triadimefon foliar spray reduced relative grain yield loss by 10.84% on the
moderately resistant variety Awash-1 compared to the susceptible variety Mexican-
142. In conclusion, integrated use o f Awash-1 with Triadimefon spray was found
to be the most effective bean rust management option.