The effectiveness of consistent roguing in managing banana bunchy top disease in smallholder production in Africa

Abstract

The removal of infected individuals is a common practice in the management of plant disease outbreaks. It minimizes the contact between healthy individuals and inoculum sources by reducing the infectious window of contaminated individuals. This requires early detection and consistent removal at landscape scale. Roguing of mats with symptoms of banana bunchy top disease (BBTD) in Cavendish banana production systems has been tested in Australia, using trained personnel, but has never been tested in smallholder systems. We studied the effectiveness of long‐term consistent roguing in prolonging the productivity of banana orchards under smallholder farming systems in highland banana and plantain dominated production systems in Africa. We assessed the possibility of low‐risk seed sourcing from the managed plots. Roguing reduced BBTD incidence to 2% in managed farmer fields and to 10% in experimental field plots, while a nonmanaged field eventually collapsed in the same period. With roguing, new infections decreased monthly compared to an exponential increase in a nonmanaged field. The emergence of new infections in both managed and nonmanaged farms followed a seasonal cycle. BBTD managed plots were a source of low‐risk seed for replacing the rogued mats in the same fields, but perhaps not safe for use in nonendemic areas. We conclude that it is possible for smallholder farmers to recover and maintain banana productivity with rigorous roguing, which would entail early identification of symptoms and early removal of diseased mats. Studies are needed on the intensity of roguing under different disease and production conditions.

Spatial parameters associated with the risk of banana bunchy top disease in smallholder systems

“…Brief historical information of the garden (age of the plot and cropping management) was sought from the proprietors. For all analyses, the response variable was the BBTD symptomatic plants observed, assuming that the number of plants showing BBTD closely estimated the actual number of plants infected with BBTV [20].…”

“…Within the cropping management, the diverse kind of banana production (plantain or sweet banana) differed in their BBTD prevalence and calculated risk, as did the identity of the associated crop, the distance between fields, and the presence of barriers. This study isolates some potential combinations of approaches that could help keep banana production in BBTD endemic regions [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36]. The results of this study suggest a set of tools that could be better refined and tested alone or in combination to determine their potential in BBTD control.…”

“…Conversely, intercropped fields have a lower plant density compared to monocrop bananas, both resulting in lower canopy connectivity. The individual and additive effects of these measures would be interesting to test in controlled experiments, to identify priority packages for BBTD control in smallholder systems [20]. Previously, [37] had observed the role of canopy connectivity in BBTD spread at a plantation edge in Australia (subtropical systems).…”

“…Thus, within an endemic region, BBTD infection risk at the plot level depends on local factors influencing vector movement and seed movement. Banana production would still be possible within the BBTD affected areas if strict protocols were followed [20]. However, reducing the risk at the landscape level is desirable to make reinfection less likely.…”

“…Studies on BBTD epidemiology are mostly based on subtropical large-scale monocultures [28,29]. Some of these studies have yielded a useful framework for BBTD management in smallholder systems in Africa [20]. [30] designed a model for understanding BBTD prevalence using hypothetical model farms, based on distance from the point of infection.…”