Determination of economic injury levels and quantification of yield losses caused by Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) on okra in Indonesian lowland production systems 

Abstract:

A recent field survey across five Indonesian provinces revealed that cotton mealybug infestation severity on okra had escalated by 240% between 2018 and 2023, yet the economic thresholds governing management decision-making for this pest remained undefined for tropical Southeast Asian conditions. This research established the economic injury level (EIL) and economic threshold (ET) for Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) on okra (Abelmoschus esculentus L.) through controlled infestation experiments at the Surabaya Institute of Agricultural Entomology, Indonesia, during 2023. Seven infestation levels (0, 5, 10, 20, 40, 80, and 160 mealybugs per plant) were established on okra cultivar Genie at the four-leaf stage in a completely randomized design with eight replications. Yield loss relationships were modelled using regression analysis, with EIL calculated from the damage function incorporating management costs, control efficacy, market value, and damage abatement coefficients. Results demonstrated a highly significant linear-plateau yield loss function (R² = 0.94), with yield declining at a rate of 0.148 t/ha per mealybug per plant up to the saturation threshold of 120 mealybugs. The calculated EIL was 8.4 mealybugs per plant, with the corresponding ET set at 5.6 mealybugs per plant (67% of EIL). At the EIL population, yield loss amounted to 18.4% relative to uninfested controls. These threshold values provide the first quantitative decision criteria for P. solenopsis management on okra in tropical Southeast Asian production systems.