Season- and fruit age-dependent population dynamics of Aceria guerreronis and its associated predatory mite Neoseiulus paspalivorus on coconut in Benin

The coconut mite Aceria guerreronis Keifer resides beneath the perianth of coconut fruits where it feeds on the tender meristematic tissue. A. guerreronis is one of the most important coconut pests but knowledge of its population dynamics is scant. We quantified seasonal and fruit age-related population fluctuations of A. guerreronis and its predator Neoseiulus paspalivorus DeLeon in Benin. N. paspalivorus was the most common and abundant beneath the bracts compared with other predators, which were very scarce and were largely found outside the bracts. Both percent fruit occupation and abundance of A. guerreronis and N. paspalivorus varied across sampling months as well as among coconut plantations and fruit age classes. Both parameters peaked in the middle of the rainy season and at the end of the dry season. Fruit age at which A. guerreronis and N. paspalivorus started to colonize the fruits was 0.9 and 1.2 months, respectively. The two species reached their peak abundance (1512 A. guerreronis and 2.3 N. paspalivorus per fruit) on 3 months-old fruits. Peak percent fruit occupation by A. guerreronis (∼70%) occurred after 4.3 months, which was ∼0.7 months earlier than that by N. paspalivorus (∼22%). Difficulties encountered by the predators in accessing the area beneath the perianth on the very young fruits allowed A. guerreronis a head-start in population build-up leading to strongly diverging population curves as a function of fruit age (higher population increase compared to N. paspalivorus). Protecting the very young fruits from A. guerreronis colonization should be a key issue for developing successful control strategies of this pest.