Table C.1.
Factors potentially influencing DFR
| Application regime |
|---|
| Application rate |
| Frequency of the treatment |
| Application volume (high, low) |
| Physico‐chemical properties of the chemical: |
| Photolysis, hydrolysis |
| Mode of action (e.g. cellular uptake via hydrophobic diffusion across living cell membranes) |
| Volatility, persistence |
| Properties of the formulation: |
| Components of the formulation (adjuvants, carriers, surfactants, efficacy improvers, etc.) can influence the solubility, deposition, surface retention and penetration of the active ingredient through the cuticular layer |
| Adsorption/binding to the plant surface |
| Impact of formulants on atomisation, droplet formation, transport and target impingement |
| Form of the a.s. particles; particulate vs. emulsion or solution |
| Application techniques: |
| Spraying equipment (e.g. knapsack sprayer, knapsack mist blower, high‐pressure spray gun) |
| Moving direction during application for handheld equipment |
| Size of droplets and droplets dispersion |
| Droplet properties (diameter, impact velocity, adhesion energy, etc.) |
| Weather/cultivation conditions: |
| Post‐application irrigation, rain |
| Wind erosion, droplet abrasion |
| Temperature |
| Humidity of the air (influencing co‐distillation) |
| Crop specific factors: |
| Structure of the leaves |
| Density of plant foliage (canopy) |
| Plant height |
| For greenhouses: |
| Set up of the greenhouse (orientation, structure, isolation and construction material) |
| Structural design (glass, fiberglass, polyvinyl sheeting, rigid acrylic, walls and ceilings) allows for different degrees of light transmission |
| Ventilation systems vary greatly (passive ventilation to mechanical ventilation) |
| Heating system |
| Temperature and humidity (high humidity is assumed to enhance pesticide penetration into the leaf by favouring stomatal opening and by slowing the drying of spray deposits allowing more time for absorption) |
| Some general conditions for validity of DFR studies: |
|
No rain events during the study Replicate samples should be collected on more than 1 day Residue should be dislodged from leaf surfaces with a detergent solution, Application should be at or near the maximum stated on the product label Study performed under climate conditions typical for the crop’s growing season |
| Evaluation of predicted DFR values: |
| Different models can be applied, pending better fit (log‐linear versus log‐quadratic) |
| Inclusion/exclusion of Day 0 DFR values in the calculation of dissipation, pending variability of data |
| Use of biased/non‐biased backtransformations |