Phthorimaea absoluta (Meyrick) is an invasive pest causing substantial losses in tomato production across Tanzania. This study assessed the efficacy and economic viability of Integrated Pest Management (IPM), conventional Farmers’ Practice (FP), and a control (CO) treatment in open-field tomato production over two cropping seasons in northern Tanzania. The IPM strategy combined plant extracts, microbial agents, and selective pesticides. Weekly monitoring of leaf and fruit infestation was conducted, alongside yield and profitability assessments. IPM significantly reduced leaf infestation compared to both the control and FP. The odds of obtaining unmarketable fruit were 92% lower under IPM than in the control. However, the effectiveness of IPM declined in season two, as indicated by increased odds of fruit non-marketability (OR = 2.076, p = 0.018) and weight loss (OR = 2.54, p = 0.005). Despite superior pest suppression and fruit quality, IPM did not surpass the control in profitability, which consistently yielded the highest benefit-cost ratio (BCR) and return on investment (ROI). These findings highlight the trade-offs between pest control efficacy and economic return, underscoring the need for threshold-based and seasonally adaptive IPM deployment in smallholder systems.
