Tetranychus evansi (Tetranychidae) spider mites now a major solanaceous crop pest in Côte d'Ivoire.

Abstract

The West African market gardening sector has been plagued in recent decades by phytophagous mite damage to solanaceous crops. Recent studies in Benin and Burkina Faso have confirmed West African outbreaks of red spider mites (Tetranychus evansi), a novel mite species native to South America, which has now virtually replaced local species. This study aimed to identify the different mite species infesting solanaceous crops in Côte d'Ivoire, while assessing their abundance and mapping their distributions. Tomato, eggplant and African eggplant crops were sampled along a north-south transect. Structured interviews were conducted to gather information on the crop protection practices. We confirmed the presence of the invasive species, Tetranychus evansi, with higher densities noted in the north, where the hot dry climatic conditions were suitable for its development. Local Tetranychus urticae and Polyphagotarsonemus latus species were not very abundant. The highest spider mite diversity was observed in the Abidjan area, where two new species of the T. urticae group were found. Very few Phytoseiidae predatory mites were present, even in plots that had barely been treated or not at all. Five species were identified: Neoseiulus barkeri, Neoseiulus teke, Amblyseius swirskii, Amblyseius tamatavensis, and Paraphytoseius horrifer. These predatory phytoseiid species seemed unable to control T. evansi populations. According to farmers, abamectin was the only pesticide effective for controlling these pests. To reduce the chemical control intensity, biological control based on the introduction and dissemination of a specific predatory mite such as Phytoseiulus longipes could be considered on a national and regional scale.