D3054: Spatial distribution and management of thrips (Thysanoptera) on eggplant using novel insecticides

Infestation of eggplant by thrips results in lower yields, and loss of foreign exchange due to its phytosanitary implications. Though thrips control most often relies on synthetic pesticides, effective control has not been achieved due to their physiological and thigmotactic attributes, aside their negative impact on the environment. This research sought to evaluate the efficacy of some novel less-risk insecticides to understand their influence on thrips’ spatial distribution, plant damage, phytotoxicity and, natural enemies in the Deciduous Forest and Coastal Savannah Agroecological Zones of Ghana for two cropping seasons. Eggplant seedlings transplanted onto field plots were sprayed with Pyrethrin (Agroblaster®), Mint + Coconut oil (Agroclean®), Acetamiprid + Indoxacarb (Viper®), Imidacloprid (Akape®), and Alpha-cypermethrin (Alphacep®) at a thrips threshold. Data were collected one day before application (1DBS) and at 3, 5, and 9 days after each application (3DAS, 5DAS, and 9DAS). The thrips population and damage were lower on treated plots than the control plots, and also in the Coastal Savannah than the Deciduous Forest Zone for all seasons. Different insecticide treatments had different efficacies for locations and seasons. Alphacep® was the best treatment at 3DAS, and Agroclean® and Agroblaster® were the best at 9DAS. Alphacep® reduced spiders' abundance and showed slight to strong phytotoxicity, whilst other insecticides did not affect natural enemies or plants. Adult thrips showed a high preference for flowers, whereas nymphs preferred the leaves, and the treatments significantly affected their spatial distribution. The importance of using novel insecticides as an integral component of thrips IPM is discussed.