The whitefly is a prevalent pest in bean crops. Although it feeds on sap and can transmit phytopathogenic viruses, many farmers and existing literature do not fully acknowledge its potential harm to bean crops. To address this, it is crucial to quantify the Damage Index (DI), Economic Injury Level (EIL), and Economic Threshold (ET) to aid in decision-making and prevent economic losses. This study aimed to quantify the DI of whiteflies in a bean crop under field conditions. A bean plot was established with three treatments: Buffer Zone, Chemical Control, and No Control. Whitefly adults per leaflet were monitored every 14 days throughout the crop cycle. Yield per plant for each treatment was estimated and related to whitefly populations using linear regressions. The EIL and ET were calculated based on the region’s socioeconomic context. The estimated DI was 3.52 grams of dry beans per plant (47 kg per hectare) for each whitefly adult found per leaflet. Consequently, the EIL and ET were 14 and 8 adult whiteflies per leaflet, respectively. Whitefly populations can significantly reduce yields and result in economic losses for local farmers if not properly managed.