Threshold-based pest management for smallholder rice farmers in Ghana: a symptom-driven approach

Introduction The rice production system is evolving toward intensive and extensive monoculture, resulting in frequent and severe insect pest outbreaks that are met with excessive insecticide use. The current study evaluated a threshold-based integrated pest management (IPM) strategy tailored for smallholder rice systems in the forest belt in Ghana. Methods Field experiments were conducted across three locations using a split-plot design with two rice varieties (CRI-Agra and CRI-Enapa) as main plots and three management practices as sub-plots: Farmer Practice (FP), Good Agronomic Practices + Threshold-Based Pest Management (TBPM), and Good Agronomic Practices only (GAP). Pest populations and crop damage were monitored weekly. Interventions were triggered using simplified, symptom-based thresholds: 2–4% deadheart, leaf lacerations and leaf cut. Data were analyzed using Analysis of Variance (ANOVA) and regression. Results and discussion Results showed that TBPM significantly reduced stem borers, rice leaf beetles and caseworm densities up to 75%, 64%, and 80%, and associated damages up to 85%, 77% and 73%, respectively, compared to FP and GAP (60%, 64%, 57% and 38%, 37%, 33% respectively). Similar trends were observed for densities of leafhoppers and rice sucking bugs. The systemic-contact insecticide mixture (acetamiprid + abamectin) used in IPM outperformed the contact insecticide (chlorpyrifos) used by farmers, particularly against concealed pests (stem borers and caseworm). TBPM achieved the highest yields (7.33–10.11 t/ha) and benefit-cost ratios (BCR: 11.42–16.13), while FP yielded the lowest (1.045–1.835 t/ha, BCR: 0.40–1.45). Strong correlations between pest density and damage symptoms (R² = 0.36–0.92) validated the use of visual thresholds. The lowest R 2 (0.36 and 0.48) was recorded for the stem borers-deadheart, indicating the possible higher incidence of moth stem borers, which were shy of being captured by the sweep net. In conclusion, TBPM proved to be an effective and economically viable strategy capable of reducing insecticide use while improving yields and farm profitability. The sampling method needs further modification to make it farmer-friendly to enhance adoption.