<p>Economic thresholds based on quantitative associations between yield reduction and pest density are key to optimizing the use of pest control inputs in agricultural systems. However, for insect pests that do not cause direct damage to produce or verifiable injury to plants, such associations are hard to determine. The greenhouse whitefly is a limiting pest of greenhouse and open-field tomato, mostly due to damage that results from honeydew deposition on which sooty molds grow, affecting produce market value. Since greenhouse whitefly populations grow quickly, growers overreact by applying broad-spectrum insecticides on a regular basis, without considering the marginal benefits of doing so. Here, we assessed greenhouse whitefly population growth patterns and their relationship with sooty mold incidence in commercial tomato greenhouses and developed a decision-support strategy based on a low-cost trapping method which is both efficient and easy to use. We found that there is a three-week delay between greenhouse whitefly population counts and the resulting sooty mold incidence. Because yield reduction due to sooty mold incidence is context-dependent and hard to quantify, our approach relies on growers’ input to determine the maximum level of sooty mold incidence that they are willing to tolerate at harvest. We present a novel approach to translating grower‑defined tolerance thresholds into actionable, evidence‑based decision thresholds for greenhouse whitefly management. Our approach overcomes a main restriction for the use of economic thresholds for pest management in systems where damage is difficult to quantify, by combining observational evidence with growers’ experience and preferences.</p>