Trade and transport of goods is widely accepted as a primary pathway for the introduction and dispersal of invasive species. However, understanding commodity flows remains a challenge owing to its complex nature, unavailability of quality data, and lack of systematic modeling methods. A robust network-based approach is proposed to model seasonal flow of agricultural produce and examine its role in pest spread. It is applied to study the spread of Tuta absoluta, a devastating pest of tomato in Nepal. Further, the long-term establishment potential of the pest and its economic impact on the country are assessed. Our analysis indicates that regional trade plays an important role in the spread of T. absoluta. The economic impact of this invasion could range from USD 17–25 million. The proposed approach is generic and particularly suited for data-poor scenarios. •Regional trade can impact the spread of pests which survive of agricultural commodities.•A structured network modeling approach can help study the dynamics of trade and its impact on pest spread even in data poor scenarios.•Case study with T. absoluta spread in Nepal indicates a strong role of trade in the way it has spread.•Spread forecasting and economic impact modeling estimate the total cost of invasion at USD 17–25 million.