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 25 900, and TRV values ranged from 5400 to 28 600 m3 ha-'. 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 15 000 m3 ha-', 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.
The tree row volume model is a method for adapting dosage and spray volumes to tree crops. The method can potentially facilitate the comparison of field efficacy trials and can contribute to fanners’effective and rational use of plant protection products. It has been developed and applied in pome fruit but not yet in stone fruit. Stone‐fruit orchards vary considerably in tree size, tree shape and distance between tree rows. Based on 700 detailed measurements of stone‐fruit trees in south‐eastern France, in southern Germany and in Switzerland, a multiple linear regression was computed that allows the calculation of tree row volume from the height and maximum width of the tree crown, and the distance between tree rows. Seasonal increases of tree row volumes in stone‐fruit orchards were most pronounced in May and June, and the increase was usually greater in young orchards than in older ones.
A survey concerning registration of plant protection products was carried out in 41 EPPO member countries. Twenty six countries responded and results are summarized in three groups. Various models are discussed which seek to adapt product dosage to the crowns of fruit-tree crops. The tree row volume model (TRV) is favoured by the authors since it can adequately cope with the wide variability of orchards encountered across Europe. It is suggested that experimenters who carry out registration field trials should measure the height and width of the tree crowns and the distance between the tree rows to facilitate comparison of registration trials including residue data.
For an efficient use of pesticides, targeted against diseases and pests which attack green plant parts and fruit, a certain amount of active ingredient must be deposited per unit leaf area of the target plant. Measurements in commercial berry crops in various parts of Switzerland over the last 3 years have shown that the leaf area of strawberries, raspberries, blackberries and red currants increase by a factor of 8-12 from the early stages of growth till fruit maturing (Figure 1). This marked increase in leaf area implies that the dosage of the products would need to follow, for practical reasons, a stepwise increase approximately matching the increase of the leaf area. This concept of adapting the product dosage to the growing leaf area of a given crop coupled to the application of the product with a well-calibrated sprayer properly adjusted to reach all parts of the leaf canopy of the specific crop can be termed Crop Adapted Spraying (CAS). Commonly labels on crop protection products only state a certain amount of product in kilograms or litres to be used per hectare. It is left to the grower whether and how to adapt the dosage of the product to the growing crop. Onfarm observations have shown clearly that most growers are uncertain about what amount of product in which volume of water they should use at a given growth stage. Often products are grossly under-or overdosed, and spray equipment is not or is poorly calibrated and adjusted to the specific crop. Thus our primary goal for developing CAS in berry crops was to provide growers with a guideline on how to use fungicides, insecticides and acaricides more efficiently and economically.
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