Rational application of pesticides by properly adjusting the amount of product to the actual needs and specific conditions for application is a key factor for sustainable plant protection. However, current plant protection product (PPP) labels registered for citrus in EU are usually expressed as concentration (%; rate/hl) and/or as the maximum dose of product per unit of ground surface, without taking into account those conditions. In this work, the fundamentals of a support tool, called CitrusVol, developed to recommend mix volume rates in PPP applications in citrus orchards using airblast sprayers, are presented. This tool takes into consideration crop characteristics (geometry, leaf area density), pests, and product and application efficiency, and it is based on scientific data obtained previously regarding the minimum deposit required to achieve maximum efficacy, efficiency of airblast sprayers in citrus orchards, and characterization of the crop. The use of this tool in several commercial orchards allowed a reduction of the volume rate and the PPPs used in comparison with the commonly used by farmers of between 11% and 74%, with an average of 31%, without affecting the efficacy. CitrusVol is freely available on a website and in an app for smartphones.

Pruning is one of the most manpower-consuming agricultural operations in citrus production. Mechanical pruning can help to reduce pruning time and costs. In order to obtain the knowledge of its effects on the important orange variety “Navel Foyos”, several pruning strategies that include manual pruning and various intensities of mechanical pruning were tested for three years. The results showed that in “Navel Foyos” oranges, the mechanical pruning strategies did not affect the yield nor the size of the fruit in comparison with manual pruning. In conclusion, mechanical strategies are a potential alternative to manual pruning because they reduce the time necessary to prune and the pruning costs, thereby maintaining or even increasing the yield.

Pesticides in three-dimensional (3D) crops are usually applied sidewise, so the vertical component must be considered for adjusting the applications. For this, different approaches have been proposed. Leaf Wall Area (LWA) was selected to express the minimum dose to be used in efficacy field trials for plant protection product (PPP) authorization in northern areas of Europe, where 3D crops are grown as narrow wall-forming structures. However, southern European areas also managed 3D crops as wide walls or globular crops with non-negligible canopy width. Therefore, a Tree Row Volume (TRV) model is thought to be more appropriate for dose expression. Furthermore, efficacy evaluations for pesticide authorization are usually carried out with manual sprayers in young plantations with medium-sized trees. However, growers normally apply PPP with air-blast sprayers in plantations of different tree sizes. The objective of this study was to determine which dose expression is more suitable in citrus orchards, as well as to analyze, in turn, the influence of the sprayer. The results demonstrated that TRV was the most appropriate for dose expression. Knapsacks and air-blast sprayers distributed the spray on the canopy in different ways, and the size of the vegetation influenced the differences between them. Moreover, knapsack sprayers produced higher ground losses, and air-blast sprayers produced higher potential drift.

The optimization of the water volume used to apply pesticides with airblast sprayers is key to reducing water footprint, costs, operational time and drift of pesticides. This study evaluated a new tool (CitrusVol) that adjusts the spray volume to the characteristics of the vegetation and the pesticide used to control the two-spotted spider mite Tetranychus urticae in clementine trees. This mite is one of the main citrus pests because it damages fruit before harvest. For this aim, a total of 20 applications against T. urticae were evaluated during two consecutive years in seven commercial orchards. In these orchards, we evaluated: (i) the distribution of the spray in tree canopies, (ii) pest density before and after the treatment, and (iii) fruit damage at harvest when conventional volumes and volumes adjusted with CitrusVol were applied. On average, CitrusVol reduced 36% the water volume used to control T. urticae in the 20 applications. This reduction in the spray volume involved a decrease in the coverage in some parts of the canopy. However, T. urticae density and fruit damage at harvest were similar in trees treated with the adjusted volume calculated with CitrusVol and the volume used by the owners of the orchard. Therefore, the spray volume recommended by CitrusVol is adequate to control T. urticae in clementines.

Pruning is one of the most expensive tasks in citrus production, and its mechanization could increase the productivity and competitiveness of citrus farms. The effect of mechanical pruning on yield depends on the variety, crop condition, and location; among other factors. The ‘Clemenules’ mandarin variety is one of the most important ones; therefore, the aim of this work was to study the effects of twelve pruning strategies on ‘Clemenules’ yield over four years, and to conduct an economic analysis. These strategies included fully manual pruning, annual alternation of mechanical/manual pruning, mechanical pruning with manual follow-up, and fully mechanical pruning with different types of cuttings. The results showed that pruning strategies affected the yield and fruit size in some years of the study but not when the four years overall are considered. Strategies that annually alternated mechanical pruning with manual pruning had higher yields than the fully mechanical approaches, and similar yields to the manual and control (no pruning) strategies. Furthermore, although the mechanical pruning costs per hectare were as minimum two times less than those with manual pruning, higher net value was achieved with the manual pruning approach followed by alternate annual mechanical/manual pruning. In conclusion, after four years of study, the pruning strategy with the best global results for ‘Clemenules’ mandarin was that which involved annually alternating mechanical (topping and one-sided hedging) and manual pruning. This strategy allows maintaining regular tree dimensions without dry branches inside.