Population structure and dynamics of the cassava green mite Mononychellus tanajoa (Bondar) and the predator Euseius ho (DeLeon) (Acari: Tetranychidae, Phytoseiidae)

Abstract

Population structure and dynamics of the cassava green mite Mononychellus tanajoa and the predator Euseius ho (Acari: Tetranychidae, Phytoseiidae). Cassava is attacked by several pests, among which the cassava green mite Mononychellus tanajoa. Predatory mites of the family Phytoseiidae are major natural enemies of pestmites and are naturally found inhabiting cassava plants in the field. We evaluated the temporal variation of the developmental stages of M. tanajoa and the most abundant predatory mite in cassava fields in the study region, the phytoseiid Euseius ho. Densities of all developmental stages of M. tanajoa were low during the rainy season, increasing over the cultivation cycle of cassava and peaking in the dry season. Overall, the larval stage of M. tanajoa presented the lowest densities throughout time. Densities of all developmental stages of E. ho were low and remained constant throughout the cultivation cycle of cassava. The number of eggs, nymphs and adults of M. tanajoa was higher in comparison to the larval stage whereas there were no differences in densities of the stages of E. ho. Densities of all developmental stages of M. tanajoa were negatively correlated with precipitation. Densities of the stages of egg, nymph and adult of M. tanajoa were positively related while the stage of larva was negatively related to temperature. We conclude that it is important to consider the population structure in studies of population dynamics of arthropods as each developmental stage experiences and responds uniquely to the local environment over time.

Keywords

• density
• environmental factors
• predatory mite
• smallholders