Population dynamics of Aceria guerreronis and its natural enemies in coconut tree with and without application of pesticides

Abstract The coconut mite Aceria guerreronis Keifer is considered one of the most important pests of the coconut tree (Cocos nucifera L.), causing fruit malformation due to the appearance of cracks on the surface of the perianth below the bracts. This damage compromises fruit growth, reducing the production of solid and liquid albumen. The continuous use of chemical pesticides increases pest control costs, as in addition to being a practice highly harmful to the environment, it can also cause selection of resistant populations, as well as eliminate beneficial species. Therefore, the objective was to evaluate the population dynamics of A. guerreronis and its natural enemies, through the quantification of the most frequent and abundant predator species in two commercial areas of coconut plantation of the cultivar PB-121 (cross between Malaysian Yellow Dwarf x West African Giant). The study was conducted in Area 1 (with pesticide application), and Area 2 (without pesticide application - control) monthly from August 2018 to July 2019. Leaflets were collected (basal, median and apical part) from leaf 14 and fruits (bunches 4, 5, 6 and 7–4 to 6 months after inflorescence fertilization). In both areas, 933.580 mites were collected, 426,245 in Area 1 and 507.335 in Area 2, with emphasis on A. guerreronis (931.706 specimens – estimated value). Eriophid mites represented almost 100% of the specimens sampled, with high population density in periods with less precipitation. Among the predators, specimens belonging to the Phytoseiidae family were predominant, highlighting the species Amblydromalus zannouii Famah Sourassou, Amblyseius aerialis (Muma) and Amblyseius tamatavensis Blommers, present both in leaflets and in fruits, with the exception of A. zannouii, which was found only in leaflets.