Population dynamics of banana aphid

Quantitative knowledge of the relative impact of factors that affect a species’ population dynamics is necessary for its conservation or control. The banana aphid, Pentalonia nigronervosa, is a pantropical species that infests bananas and plantains wherever they are grown. The aphid is also the principal vector of banana bunchy top virus, the causal agent of the devastating banana bunchy top disease. Knowledge of the aphid’s population ecology, particularly the relative impact of principal factors affecting its population dynamics, is scant and fragmented. We conducted a multi-year, multi-factor study in an agroecology representative of a relatively large area of Central Africa where low-input production of bananas and plantains is practiced. Overall, population dynamics of the pantropical banana aphid - unlike numerous temperate aphid species - appear to be driven not by rainfall but by complex interactions among temperature, relative humidity, host plant genotypes and aphid-associated ants and predatory arthropods. Vegetation ground cover did not affect overall banana aphid abundance on any of four widely grown Musa genotypes, but reduced aphid immigration in vegetation-diversified plots during the first year, but that did not translate into differences in aphid abundance. Ants and predators cycled with aphids but all declined from the highest to the lowest peak in the first and third year, respectively. No parasitoids and entomopathogens were found in association with the aphid. Path analysis uncovered a set of complex interactions in which rainfall had little or no effect on aphid populations, while the effects of temperature and relative humidity on aphids were largely indirect - through their effects on ants and predatory arthropods. Ant-aphid association remained strong and relatively unchanged, regardless of the presence of predators, while an already weak predator-aphid association was relaxed by the presence of ants, but only in vegetation-diversified plots. The insights provided by the present study contrast with those on aphid species from temperate climates and will serve to guide the management of the banana aphid and banana bunchy top disease that threaten bananas and plantains across much of the old-world tropics.