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Abstract: The banana weevil, Cosmopolites sordidus (Germar), is an important pest of bananas. Predatory ants are increasingly being viewed as possible biological control agents of this pest because they are capable of entering banana plants and soil in search of prey. We studied ant predation on banana weevil in Uganda in crop residues and live plants in both laboratory and field experiments. Field studies with live plants used chemical ant exclusion in some plots and ant enhancement via colony transfer in others to measure effects of Pheidole sp. 2 and Odontomachus troglodytes Santschi on plant damage and densities of immature banana weevils. In crop residues, an important pest breeding site, twice as many larvae were removed from ant-enhanced plots as in control plots. In young (2 month) potted suckers held in shade houses, ant ability to reduce densities of banana weevil life stages varied with the weevil inoculation rate. At the lowest density (2 female weevils per pot), densities of eggs, larvae, and pupae were reduced by ants. At higher rates there was no effect. In older suckers (5–11 months) grown in larger containers, banana weevil densities were not affected by ants, but damage levels were reduced. In a field trial lasting a full crop cycle (30 months), we found that the ants tested reduced the density of banana weevil eggs in suckers during the crop, but did not affect larval densities in the sampled suckers. However, most larvae occur in the main banana plants, rather than associated suckers. Nevertheless, levels of damage in mature plants at harvest did not differ between Amdro-treated and ant-enhanced plots, suggesting the ant species studied were not able to provide economic control of banana weevil under our test conditions. [Copyright &y& Elsevier]

Abstract: A survey of ant composition and relative abundance was conducted in farmers’ fields in the banana growing areas of Uganda in 2003 to assess the effects of farming practices on ant species composition in banana fields. This survey was done to identify potentially important predators of the banana weevil, Cosmopolites sordidus (Germar). Work was repeated in both one wet and one dry season at all locations. We sampled at 39 farms in four regions and found 55 species of ants in pitfall traps and 24 species in fish and honey baits. When banana weevil larvae were exposed as baits, 11 ant species were attracted, of which Pheidole sp. 1, Pheidole sp. 2, Pheidole sp. 3, Paratrechina sp. 1, and Lepisiota sp. 1 were the most abundant. Seventeen ant species were found in pseudostems and 34 in corms of live banana plants and residues of harvested plants. High species richness and abundance especially inside plants and residues, suggest that ants are important foragers in banana plantations. Seven of the ant species found in plants demonstrated significant ability to remove banana weevil eggs artificially inserted in corms. Two species, Odontomachus troglodytes Santschi and Pheidole sp. 2, were able to remove eggs from naturally infested corms. O. troglodytes removed 33–68% of the eggs in naturally infested corms, while Pheidole sp. 2 removed 38–60% of such eggs. The attraction of O. troglodytes and Pheidole sp. 2 to banana weevil-infested plant pieces, their close association with banana plants and residues, and their ability to extract artificially and naturally introduced banana weevil eggs from plant tissue suggest that these two species may have significant potential to consume weevil immature stages in plants and residues. [Copyright &y& Elsevier]

Abstract: Beauveria bassiana is considered a virulent pathogen against the banana weevil Cosmopolites sordidus. However, current field application techniques for effective control against this pest remain a limitation and an alternative method for effective field application needs to be investigated. Three screenhouse experiments were conducted to determine the ability of B. bassiana to form an endophytic relationship with tissue culture banana (Musa spp.) plants and to evaluate the plants for possible harmful effects resulting from this relationship. Three Ugandan strains of B. bassiana (G41, S204 and WA) were applied by dipping the roots and rhizome in a conidial suspension, by injecting a conidial suspension into the plant rhizome and by growing the plants in sterile soil mixed with B. bassiana-colonized rice substrate. Four weeks after inoculation, plant growth parameters were determined and plant tissue colonization assessed through re-isolation of B. bassiana. All B. bassiana strains were able to colonize banana plant roots, rhizomes and pseudostem bases. Dipping plants in a conidial suspension achieved the highest colonization with no negative effect on plant growth or survival. Beauveria bassiana strain G41 was the best colonizer (up to 68%, 79% and 41% in roots, rhizome and pseudostem base, respectively) when plants were dipped. This study demonstrated that, depending on strain and inoculation method, B. bassiana can form an endophytic relationship with tissue culture banana plants, causing no harmful effects and might provide an alternative method for biological control of C. sordidus. [Copyright &y& Elsevier]

Abstract: The banana weevil, Cosmopolites sordidus (Germar), is an important pest of highland banana and plantain in Africa. It exists in low densities in its presumed area of origin in Southeast Asia. This suggests the possible existence of effective co-evolved natural enemies that might be useful in a classical biological program against the pest in Africa. Surveys on banana weevil and its natural enemies were undertaken in Indonesia, in 2000 and 2001. Banana weevil incidence was found to be low, 0.6–1.7 adults per trap in West Sumatra and 0.2–0.4 in West Java. Plant damage indices were below 2.2%, a level that would be considered unimportant in Uganda. We collected and reared 25,980 eggs and 3671 larvae, but no parasitism was detected. Phorids (Megaselia sp.) and drosophilids were recovered from larval rearings, but most likely were scavengers. A complex of predators was detected, the most important of which was the histerid Plaesius javanus Erichson. In laboratory tests, adults and larvae of P. javanus attacked 75–88 and 38–53% of banana weevil larvae and pupae, respectively, that had been inserted in plant pieces. In separate tests, P. javanus larvae entered banana weevil tunnels in corms and attacked 70% of the banana weevil larvae in them. Predatory ants, including species of Myrmicinae, Ponerinae, Formicinae, and Dolichoderinae, were found associated with banana plants and residues. Adults of Myopopone castanea Smith (Ponerinae) were directly observed attacking banana weevil larvae in crop residues. [Copyright &y& Elsevier]