The banana weevil borer, Cosmopolites sordidus
Germar (Coleoptera: Curculionidae), is a nocturnal pest and larvae tunnel into banana rhizomes. Infestation and damage are assessed mainly by pseudostem trapping of adults, and the determination of coefficient of infestation. Deficiencies of these methods were identified and field experiments and destructive sampling of bananas carried out to answer some of the questions raised.
Variations in trapping conditions, such as trap length, placement, duration of trapping, and soil moisture conditions significantly influenced weevil catches in pseudostem traps. The relationship between external rhizome tunneling, indexed as percent Coefficient of Infestation (PCI), and internal rhizome damage by C. sordidus
varied among the banana types and with the parameters used to quantify damage. There was also a poor correlation between weevil trap catches and rhizome damage.
For trap to be statistically comparable, trap size and trapping conditions should be defined and standardized. Proper use of the PCI requires that correlations between external tunneling and internal rhizome damage be established for a given banana type of cultivar.