Each year 25-75% of banana and plantain yields are lost because of rhizome damages caused by banana weevil (Cosmopolites sordidus) in growing regions of sub-Saharan Africa. However, the specific plant defence response of the rhizome tissue in relation to the C. sordidus attack is unknown. Consequently, in this study, we evaluated whether plant defence substances in the rhizome are correlated with the degree of larval damage and whether applications of methyl jasmonate (MJ) elicit a greater induction of the plant defence potential against C. sordidus. Moreover, we attempted to reveal cellular modifications in response to the root feeding herbivore through histochemical staining. The banana cultivars "Km5" and "Mbwazirume" with tolerance and susceptibility to C. sordidus, respectively, were used in a pot experiment to evaluate percent rhizome damage, leaf chlorophyll content, total phenolic content (TPC), antioxidant capacity and cell morphology in response to C. sordidus attack and/or MJ applications compared to untreated control plants. We found that C. sordidus-induced rhizome damage was 30% in the susceptible cultivar but less than 5% in the tolerant cultivar. The percent rhizome damage was not related to leaf chlorophyll content but showed a significant negative linear relationship to both TPC and antioxidant capacity. Larvae feeding induced a considerably greater increase of polyphenolic defence compounds in Km5 than in Mbwazirume; however, this response was opposite in the MJ treatment, suggesting that the phytohormone induced the susceptible plant to invest more into the synthesis of defence chemicals that in turn lead to reduced C. sordidus damage. Tissue staining demonstrated a greater deposition of lignin and suberin in C. sordidus challenged rhizome, presumably to seal off healthy tissue with a physical barrier from continued pest attack. It is concluded that MJ induces polyphenolics in susceptible Mbwazirume banana that reduced C. sordidus damage.

Artificial diets rapidly establish the effectiveness of chemical-based control strategies. Diets permit preliminary evaluation of active compounds, study in-vitro larval growth cycles that are usually inaccessible and produce uniform large consistent numbers of insects as needed. With no known artificial diet, banana weevils, have always been reared on field-collected banana rhizome (corm). This study, therefore, developed and examined the effect of commercial diet recipes fortified with susceptible banana corm powder on weevil growth and development. Subsequently, corm powders from different banana cultivars were also evaluated for weevil performance. Successful laboratory rearing of the weevils to adult stage on diet was achieved in 48 days compared to 36 days in the natural banana stem. The difference in weevil larvae performance reared different corm powder, presented a novel screening method for banana genotypes. For example genotypes, Culcatta-4 (AA), Cavendish (AAA) and Kayinja (ABB) showed 0-35% of adult emergences compared to 65% in susceptible genotypes. The diet developed can be used to perform rapid bioassay experimentation to screen potential candidate proteins or molecules for a transgenic approach. It has also shown potential for rapid screening of genotypes for resistance. Keywords: Resistant banana, Laboratory weevil rearing, Resistance screening.

The banana weevil Cosmopolites sordidus (Germar) (Coleoptera: Curculionidae] is a major pest of East African highland bananas and plantains. Its larvae bore in corm tissue damaging the root system, disrupting nutrient and water uptake, compromising plant anchorage, reducing yield, and shortening plantation life. Yield losses in bananas and plantains may exceed 50%. Available technologies for the management of the pest include cultural control, biological control, and chemical control. These methods may be costly, labor intensive, or ecologically unsustainable. Such effects, together with developed pesticide resistance, have led to various efforts searching for sustainable alternatives. To achieve this, there is a need to understand the biology of the pest and the currently available management options which includes use of cultural practices, resistant banana varieties, biological and microbial control, pheromone trapping and chemical and botanical insecticides. This article reviews the research status concerning C. sordidus biology, distribution, management options, including current innovations such as genome editing, and suggests future research directions for the management of the pest. Research findings suggest that no single control strategy will provide complete control. The integration of appropriate conventional C. sordidus management options with genetic engineering and other ecologically friendly methods such as use of botanicals and infochemicals will manage the pest and sustainably increase banana production.