BACKGROUND: In this study, field and greenhouse experiments were done with spray application of the insecticides acetamiprid, indoxacarb, deltamethrin, λ-cyhalothrin, spinosad, chlorantraniliprole on pepper and tomato plants. Results were interpreted with numerical modeling. RESULTS: Observed fruit concentration dynamics could be described overall well by modeling. After application, concentrations decreased in pepper and (slower) in tomato fruits (lower degradation and dissipation for tomato). Chemical input to individual above-ground compartments (fruit, leaf, stem, soil), arising from spray, was among the unknowns and hence estimated. Input to fruits was estimated 1-13% and 1-17% of the total applied amount
input to stem, leaf and/or soil 0-13% and 0-26% (pepper and tomato). Input showed high variation across compounds, with considerable uncertainty due to a partly low sensitivity of stem/leaf/soil input to fruit concentrations. The pathway stem-fruit was relevant for all compounds except λ-cyhalothrin (pepper, tomato) and deltamethrin (tomato). The pathways soil-root-stem-fruit and leaf-stem-fruit (phloem) were only sensitive for acetamiprid and chlorantraniliprole. CONCLUSION: The dynamic model approach, implementing the appearance and growth of individual fruits, was after calibration successful in describing insecticide fate in pepper and tomato plants. Special consideration was given to dynamic modelling of plant growth and connected xylem and phloem flow. The dynamic approach was superior to assuming constant plant mass and transpiration, where growth dilution is described by rate constants. Information on the time-window of experiments within the vegetation period and on the number and appearance of individual fruits is important for adequately describing growth and thus chemical fate within plants. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.