Effect of soil amendments, intercropping and planting time in combination on the severity of cassava bacterial blight and yield in two ecozones of West Africa

Abstract

The severity of cassava bacterial blight at two sites in the forest-savanna transition (FST) and dry savanna (DS) zones of West Africa were studied by assessing the effects of: (i) shift of planting date; (ii) potassium fertilizer application and mulching; (iii) intercropping cassava with sorghum or cowpea vs. cassava monoculture; and (iv) the combination of these measures. Disease severity of bacterial blight in two genotypes was generally reduced by 20 -60% by late planting, without a negative effect on cassava root yield, in monocropping systems in most treatments in the FST zone (reduction in four treatments, and increase in two treatments, out of 19) and the DS zone (two of eight treatments in 1 year). Late planting led to crop failure in the DS zone in the second year. Intercropping cassava with sorghum reduced bacterial blight severity significantly, up to 80% at normal (all treatments) and late planting time (three out of six treatments) in the FST zone, and in some treatments (four out of seven) at normal planting in the DS zone. Intercropping of cassava with cowpea in the DS zone also reduced disease severity. Cassava-sorghum intercropping generally had no effect on root yield compared with cassava monocropping at both planting times in the FST zone and provided an additional harvest of the intercrop, while yield was affected by intercropping in the DS zone at late, and in some treatments (three out of seven) at normal, planting time. Mulching and potassium treatment had no effect on disease severity, but increased or decreased root yield in some treatments in both sites. Analysis of combined data showed that cropping system, year, site, and site combined with planting date were the highest significant determinants of variation in bacterial blight development.

Cassava Bacterial Blight: A Devastating Disease of Cassava

“…Also, for control of cassava bacterial blight, the shift to a late planting date was observed to reduce disease incidence and severity [87], and in our study, disease severity of bacterial blight was generally reduced by late planting in the last third of the rainy season with no effect on cassava root yield [79].…”

“…The effect of intercropping on cassava bacterial blight severity may vary with intercrops used and across ecozones. In our study in Benin, intercropping cassava-sorghum reduced cassava bacterial blight severity significantly up to 80% in three soil amendment treatments, at normal and late planting time in the forest-savannah transition zone and at normal planting time in the dry savanna zone, with few exceptions [79]. Also, the effect of intercropping cassava-maize and cassava-taro on cassava bacterial blight was investigated in Togo.…”

Towards understanding factors that govern fertilizer response in cassava: lessons from East Africa

“…Adjusting the procedure of Zinsou et al (2004) to capture disease progress during the growth cycle into one number, we then determined the area under disease severity index progress curve (AUSiPC) for each disease in each plot as:…”

“…Previous reports on the effect of fertilizer on bacterial blight and mosaic disease were contradictory. Some authors (Mollard 1987;Obigbesan and Matuluka 1977) reporting an increase, others (Zinsou et al 2004;Sseruwagi et al 2003) reporting no effect of fertilizer, while Odurukwe and Arene (1980) and Adeniji and Obigbesan (1976) found a decrease due to fertilizer application. Nonetheless, changes in pest and disease pressure due to fertilizer were small in our trials and did not affect the yield response of cassava to fertilizer use.…”

Effect of Intercropping on the Development of Cassava Bacterial Blight

“…Ahohuendo & Sarkar (1995) reported partial control of African cassava mosaic disease by intercropping, but intercropping cowpea with maize or cassava did not show a clear effect on cowpea bacterial blight, though an additional yield from the minor crop could compensate losses (Sikirou, 1999). However, Zinsou et al (2004) observed a reduced severity of cassava bacterial blight when soil amendements were combined with intercropping practice and planting date. Bacterial diseases are generally disseminated in the field by rain splash and aerosols combined with wind.…”