Adaptation of spray dosage in stone‐fruit orchards on the basis of tree row volume

The tree row volume (TRV) model was adapted for use in stone‐fruit orchards. The number of leaves, leaf area and TRV were determined in apricot, peach, cherry and plum orchards in France and Switzerland. The number of leaves per tree ranged from 2500 to 25900, and TRV values ranged from 5400 to 28600 m 3 ha −1 . Trees were sprayed with a fluorescent tracer, according to TRV, in order to determine the quantity and distribution of tracer deposition in the crown of the trees. For large trees with TRV values above 15000 m 3 ha −1 , tracer deposits on leaves were lower in the upper half of the crown than in the lower half. The TRV formula developed for pome‐fruit trees was accordingly used for spraying stone‐fruit trees, but with a 15% increase in spray volume for large trees. Under these conditions, disease control was efficient, and residues of difenoconazole, penconazole and dithianon were below the maximum residue limit. The TRV method was thus found to allow adaptation of spray dosage and volume to the volume of the trees, on condition that sprayers are carefully calibrated and adjusted for each orchard. The TRV concept can be applied to a wide range of pome and stone‐fruit orchards and can help to harmonize registration protocols for fungicides and insecticides.