The Influence of Ecological Pest Management Practices on Pests and Natural Enemies Under a Cabbage–Garden Pea Rotational System in Central Kenya

Pest pressure is a major constraint on crop production in Sub-Saharan Africa, where smallholder farmers rely heavily on synthetic pesticides with potential environmental and health risks. Ecological pest management practices (EPMs) have been proposed as sustainable alternatives, although field-based evidence is limited. This study evaluated pest and natural-enemy responses to EPMs in a cabbage–garden pea rotation system over six years (2020–2025) in Central Kenya. Four treatments were assessed: homemade botanical extracts (Botanicals), coriander intercropping (Intercrop), botanical extracts combined with coriander intercropping (Botanicals + Intercrop), and a control. In cabbage, ecological treatments often recorded lower aphid and diamondback moth abundance and damage than the Control, although these patterns were not consistently significant. Aphid cumulative abundance ranged from an Area Under Disease Progress Curve (AUDPC) of 128.0 under the Control to 47.5 under Botanicals + Intercrop, while DBM abundance ranged from 68.5 to 20.0. In garden pea, aphid damage ranged from an AUDPC of 39.3 under Intercrop to 25.1 under Botanicals + Intercrop, while cutworm damage ranged from 56.3 under Botanicals to 14.8 under Intercrop. Significant treatment effects were detected for selected pest responses. Shannon diversity differed significantly among the treatments in both crop phases. As such, responses were pest- and season-specific rather than uniformly suppressive. These findings identify companion cropping and botanical applications as promising components of EPM within the treatments evaluated. Comparison with conventional pesticide-based or farmer-practice management is however required before recommendations for substitution or wider adoption can be made.