Juan Antonio Sanchez

This study evaluated the economic and environmental performance of three pear production systems in the Altiplano region of Murcia, Spain: conventional cultivation (CC), organic cultivation (EC), and organic cultivation with biological control (ECB). Life Cycle Costing (LCC) and Life Cycle Assessment (LCA) were combined to calculate and compare production costs, profitability, and environmental impacts derived from the systems. Pear cultivation required a high initial investment although its cost accounting is dominated by variable costs. Despite slightly higher unit production costs, the organic systems were more profitable due to higher market prices. Environmentally, EC and ECB were less impactful than the conventional system in 8 of the 11 impact categories assessed. These results were mainly attributed to a lower use of fertilizer units, the use of organic fertilizers and pesticides instead of synthetic ones, and yields similar to those of the conventional system. In the CC system, synthetic fertilizer production was the main environmental hotspot, while in the organic systems the contributions were evenly distributed across different components. Compared with pear production in other Mediterranean areas, the three systems studied exhibited low greenhouse gas emissions (0.103–0.061 kg CO₂ eq kg⁻¹ of pears), mainly due to optimized fertilizer units, lower mechanization and similar yields to those reported in other areas. Overall, the results indicate that all three production systems are economically viable, profitable and with environmental performance in line with other studies. However, organic pear production, particularly when combined with biological control, is in this case the most profitable alternative and shows the most favorable environmental profile in the majority of the impact categories.

Bemisia tabaci is a major pest of open-field melons in Mediterranean regions. Combining several species of natural enemies can improve pest control but it can give undesirable results when the species engage in antagonistic interactions. This study evaluated the effectiveness of Deraeocoris serenus, Orius laevigatus, and Eretmocerus eremicus as biological control agents and the interactions among the species. This was assessed with the presence–absence of all three species combined in a full-factorial assay. Each microcosm consisted of a melon plant grown in a 5 L pot enclosed in fine mesh, with each of the eight treatments replicated four times. Whiteflies were counted on three leaves per plant, and natural enemies were counted on the whole plants over six weeks. Basal leaves were taken to the laboratory and observed for the emergence of parasitoids. All three natural enemies independently significantly reduced whitefly numbers. Deraeocoris serenus was the most effective biocontrol agent, achieving whitefly reductions of more than 100-fold compared to the control. In contrast, O. laevigatus and E. eremicus achieved reductions of approximately 2.4-fold and 3.6-fold, respectively. No additive or synergistic effects in whitefly control were observed when two or more natural enemies were combined. Deraeocoris serenus and O. laevigatus were found to engage in mutual antagonistic interactions, and these two predators also interfered with the parasitoid. In addition, E. eremicus was also found to interfere with D. serenus. Understanding such interactions is essential for optimizing the management of natural enemies and improving biological pest control.

Enhancing ground cover vegetation may favour biological pest control. This research aimed to test the effect of cover management on the abundance of natural enemies and pest control in pear orchards. Two types of cover management (i.e., sown/mown cover) were tested in an organic pear orchard during three years in southern Spain. The cover and pear trees were sampled periodically between April and June to estimate the abundance of arthropods. The abundance of all the groups of natural enemies, including ants, spiders, predatory thrips, hemipterans and four families of parasitoids, as well as phytophagous insects such as aphids and psyllids, was significantly higher in the vegetation of the sown than in the mown cover. The sown cover was found to significantly reduce the abundance of aphids on pear trees, while it had a neutral effect on Cacopsylla pyri. This reduction in aphid numbers could be mainly attributed to the increase in the abundance of spiders and predatory mirids on the trees with the sown cover. In contrast, the sown cover was found to significantly reduce the abundance of the ant Lasius grandis on pear trees in relation to the mown cover. Overall, the management of the cover had a stronger effect on the assemblage of arthropods on the understory vegetation than on pear trees. The increase of the abundance of natural enemies on pear trees with the sown cover could have been due to their movement from the cover and/or the reduction of harassment due to the lower ant activity.

Many agricultural landscapes offer few resources for maintaining natural enemy populations and floral plantings have frequently been adopted to enhance biological pest control in crops. However, restored margins may harbour both pests and natural enemies. The aim was to compare the abundance of pests and natural enemies in three types of margins (unmanaged, sown herbaceous floral strips and shrubby hedgerows) as well as in adjacent melon fields. Besides, yield was compared among melon fields as way of testing the effect of the type of margin on biocontrol. The research was carried out during 2 years in twelve melon fields from four different locations in southern Spain. Arthropods were sampled periodically in margins and melon fields by visual inspections and Berlese extraction. Hedgerow and floral strips hosted higher numbers of both pests and predators than unmanaged margins. Besides, hedgerows had a similar or higher number of natural enemies than floral strips but lower number of pests. In just a few occasions, the type of margin had a significant effect on the abundance of pests and natural enemies in melon fields, but rarely there was consistency between the two growing seasons. No differences were found in yield. We hypothesised that the lack of association in the abundances of pests and natural enemies between margins and melon fields could be attributed to the overriding effects of the landscape and/or the internal population dynamics of arthropods in melon fields. Overall, shrubby hedgerows are more recommended than herbaceous floral strips.

Intensive agriculture has a strong impact on the structure of arthropod communities in soil. Sown covers can contribute to their conservation, especially for generalist predators such as spiders and predatory beetles. The aim of this research was to assess the effect of cover crop management on the abundance and diversity of ground-dwelling arthropods. For this purpose, a three-year experiment was conducted in a pear orchard that was divided into three blocks with two plots each: one with a sown cover of mixed plants from different families, including Boraginaceae, Asteraceae, Apiaceae, Brassicaceae, and Fabaceae, and the other with no cover, in which any spontaneous plants were periodically removed without using herbicides. The abundance of ground-dwelling arthropods was sampled using pitfall traps. The sown cover increased the overall richness of arthropods. Additionally, spiders from the families Lycosidae and Linyphiidae, as well as beetles from the families Carabidae and Staphylinidae, were more abundant in the sown cover. Conversely, detritivores such as collembolans and beetles from the family Tenebrionidae were less abundant in the cover. The abundance of ants was not affected by the type of cover. The sown cover increased the diversity of arthropods in the crop, as well as the abundance of generalist predators.

The ability to locate suitable food resources affects fitness in animals. Therefore, movements are necessary to optimize foraging in habitats where food is distributed in patches of different qualities. The aim of this work was to investigate the dispersal and distribution of females and males of the omnivorous mirid D. hesperus in mesocosms composed by food patches of different values in terms of fitness. In agreement with the Marginal Value Theorem (MVT) and the Ideal Free Distribution (IFD), individuals were expected to aggregate in the highest quality patches. Besides, the proportion of individuals in patches was predicted to be proportional to fitness, and interference among individuals was expected to rise as the density of individuals increased. Emigration rates were predicted to be higher for low- than for high-quality patches, while the opposite was predicted for immigration. Three types of habitats each with different combinations of food resources were tested: (1) habitat including patches of tomato plants with no-prey, and patches infested with either mite or whitefly; (2) with no-prey and whitefly; (3) with no-prey and mites. Each type of habitat was set up in a tomato greenhouse compartment and replicated four times. Individuals were tracked by mark-recapture methods using luminous paintings. The number of females and males in whitefly patches was significantly higher than in mite and no-prey patches, but a significant interaction sex*habitat and sex*patch was found. In habitats with only one type of prey, D. hesperus adults fitted the IFD, while in mixed prey habitats their distribution diverged from IFD. Interference was found to be significant, with female fitness decreasing as their density increased. Emigration rates were significantly lower for whitefly patches with a significant interaction patch*sex; the opposite was found for immigration. This research shows that it is unlikely that D. hesperus forage according to the omniscient principle of IFD and MVT; in contrast, it strongly suggests that it uses some simple rules to make decisions about inter-patch movement, and emigration from habitats and patches.

Ants are important because they damage agricultural equipment, including microirrigation systems. The aim of this research was to assess the efficiency of the incorporation of repellents in drip irrigation tubing as a method of protection against ant damage. Unlike previous studies, we tested a series of nontoxic compounds that are repellent to ants. First, we assessed their repellent effects on a local ant species via olfactometer trials. Then, the candidates showing the best results (cinnamon essential oil, p-anisaldehyde and ethyl anthranilate) were incorporated via compounding, injection and extrusion to polyethylene tubing to test their efficiency in the field. Field tests showed high damage levels in the control tubing containing no repellents, presumably caused by up to six different ant species (Cardiocondyla batesii, Plagiolepis pygmaea, P. schmitzii, Solenopsis sp., Tapinoma nigerrimum and Tetramorium semilaeve). In contrast, the pipes containing the three selected compounds remained almost intact, with the treatment including ethyl anthranilate showing no damage at all. These results suggest the strong repellent potential of the selected compounds, even when integrated into plastic, as well as the apparent success of the proposed methodology against the damage caused by ants. The diversity of damage-causing agents that exist in or above the soil strongly encourages further studies to determine the overall efficiency of repellents in protecting irrigation pipes.

BACKGROUND: Economic injury level (EIL) and economic threshold (ET) are customary tools for integrated pest management. Cacopsylla pyri L. is a major pest in pear orchards. The aim of this work was to establish EIL and ET for the optimization of the use of insecticides to control this psyllid, considering biocontrol and two spraying strategies (low‐toxicity versus broad spectrum chemicals). This research was conducted over 4 years in five commercial pear, cv. Ercolini, orchards in south‐eastern Spain.RESULTS: Psyllids and ant populations were followed using periodic sampling, and the russet on fruits was quantified. The effect of spray intensity and ant exclusion on psyllid abundance and yield were also tested: both had a significant effect on the cumulative number of C. pyri (CNP), yield and fruit weight. Yield was found to be negatively correlated with CNP. The russet index (RI) increased in a sigmoidal fashion as a function of CNP, being significantly higher with than without ant exclusion. The commercial categorization of fruits was explained satisfactorily as a function of CNP and the cumulative number of ants (CNA). The quantitative EIL was established at a CNP of 427.2 for spraying with paraffinic oil and 425.7 for abamectin. As for the cosmetic EIL, when CNA was zero, this EIL was 24.2, at a CNP of 16.6 for spraying with paraffinic oil or abamectin.CONCLUSIONS: The use of products of low toxicity, for the conservation of ants, is expected to increase ET and, thus, reduce the intensity of spraying. © 2021 Society of Chemical Industry.

BACKGROUND: Psyllids are principal pests of pear orchards. Pest control based on the intensive use of chemicals is facing difficulties and strategies with a low impact on natural enemies are considered as the most suitable for psyllid control. Ants have been reported as the main predators of Cacopsylla pyri (Hemiptera: Psyllidae) in the southern Mediterranean area. The aim of this work was to determine the contribution of ants to the reduction of the fruit damage caused by psyllids at different intensities of spraying. Five levels of spraying intensity and ant exclusion were tested in a pear orchard with three blocks of five plots each.RESULTS: The incidence of russet on fruits increased with the abundance of psyllids and with ant exclusion. In the absence of ants, the impact of russet increased progressively from the highest to lowest intensity of spraying. By contrast, when ants were present no significant differences were found between the lowest (two application of paraffinic oil) and the highest (six applications of abamectin plus paraffinic oil) spraying levels. In the presence of ants, the incidence of russet in the plots with three applications of paraffinic oil was similar to those with three or six applications of paraffinic oil plus abamectin).CONCLUSIONS: The importance of ants for the control of psyllids and the reduction of fruit damage is shown. Reduction in the frequency of spraying and the use of low toxic insecticides for natural enemies is presented as the most sustainable strategy for psyllid control in pear orchards. © 2020 Society of Chemical Industry