How plant composition in margins influences the assemblage of pests and predators and its effect on biocontrol in melon fields.

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.

The influence of altitude on the abundance and occurrence of species of the family Calliphoridae (Diptera) in corpses in a Mediterranean area.

A carcass is defined as a temporary resource that can support high levels of diversity compared to other resources. The level of diversity often depends on the environmental conditions in which the corpse is found. Calliphoridae (Diptera) are the most important necrophagous insects used in forensic investigations because this family is common, widespread, abundant, and usually the first to colonize a corpse. However, understanding the processes responsible for variation in calliphorid species abundance and richness along gradients in ecology remains a key challenge. In this study, we analyzed the influence of altitude on the abundance and diversity of Calliphoridae species in corpses at three different altitudes (400, 900, and 1500 m a.s.l.) in a mountainous area of southeastern Spain. The results revealed a gradient of decreasing abundance with increasing altitude. An altitudinal substitution of species was observed, with Chrysomya albiceps being found at the lowest altitude and Calliphora vicina at the highest altitude. Seasonal variation was also noted, with Ch. albiceps being the dominant species in the warmer months and C. vicina being the dominant species in winter. Our results confirm the importance of Calliphorids as seasonal, altitudinal, and environmental indicators, given the wide distribution and abundance of this family. This information is of great interest on the interpretation of data in forensic practice.

Effects of Managed and Unmanaged Floral Margins on Pollination Services and Production in Melon Crops.

Melon is among the most consumed fruits in the world, being a crop that depends almost entirely on insects for its reproduction, which is why it is especially sensitive to declining pollination services. Restoration and maintenance of hedgerows and agricultural borders around crops are generally carried out by sowing flowering herbaceous plants or establishing shrubby species; however, a cost-effective and lower-maintenance alternative for farmers could be as simple as allowing vegetation to regenerate naturally without any management actions. This work aimed to test the effects of three different types of margins (managed herbaceous, managed shrubby, and unmanaged herbaceous) on the overall abundance and richness of wild pollinators in melon crops. The work was performed in three localities in southern Spain over two years. Pollinators were monitored visually using 1 × 1 m sampling squares and pan traps within melon fields. Moreover, crop yield was estimated by measuring fruit weight and the number of seeds. In general, higher abundances of pollinators were observed in melon fields during the second year. In addition, the abundances of Syrphidae, Andrenidae, Apidae (excl. Apis mellifera), and pollinators other than bees, belonging to the orders Diptera, Coleoptera, Hymenoptera, and Lepidoptera, showed higher values in melon fields with shrubby margins than in fields with herbaceous margins (managed or unmanaged). However, no effect of floral margins on the yield of melon crops was found.

Life Cycle and Biometric Study of Hydrotaea capensis (Wiedemann, 1818) (Diptera, Muscidae), a Species of Forensic Interest.

One of the most important and perhaps most used applications of forensic entomology concerns the estimation of the minimum post-mortem interval (minPMI), defined as the time interval between death and the actual finding of a corpse. Some Diptera species are critical in these studies because they are the first ones capable of detecting and finding a corpse and are selectively attracted by its decomposing status. Thus, the knowledge of the micromorphology of their preimaginal stages and of their life cycles within a time frame constitutes solid indicators for estimating the minPMI. Hydrotaea capensis is a Muscidae of forensic interest usually considered as a late colonizer of corpses. It is widely distributed, living mainly in warm regions, and present in a wide variety of habitats. In this study, the H. capensis life cycle was studied at four constant temperatures, 18°, 20°, 25° and 30 °C, by recording the duration of its different developmental stages, including the length reached in each larval stage, as well as some biometric characteristics of the emerged adults. Significant differences were observed in the average time of development of most larval stages, with a longer duration at low temperatures, and in the length of each larval stage depending on the temperature, but, in this case, without a clear pattern. Moreover, significant differences were found in some alar features, pointing to them as a relevant indicator to be considered. The data provided will assist forensic entomologists to make more accurate minPMI estimations in cases where H. capensis is present.

Density thresholds and the incorporation of biocontrol into decision-making to enhance the control of Cacopsylla pyri in pear (cv. Ercolini) orchards.

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.

Structure of the Assemblages of Spiders in Mediterranean Pear Orchards and the Effect of Intensity of Spraying.

Spiders are key predatory arthropods that are negatively affected by spraying pesticides in orchards. The aim of this research was to determine the structure of the community of spiders in pear orchards and the impact of the intensity of spraying. The study was carried out over three years in four pear orchards in southern Spain; two of them were conducted by ourselves with no or low-intensity spraying of insecticides, and two under the criteria of technicians (conventional). Spiders were sampled on pear trees by the beating method. The orchards hosted a rich community of spiders belonging to 13 different families and 51 genera. However, the genera Philodromus, Oxyopes, Cheiracanthium, Icius, and Neoscona accounted for 72% of the captures. Spiders were more abundant and had a higher richness of genera in the low-intensity spraying than in conventional orchards. Philodromidae, Salticidae, and Cheiracanthiidae experienced a significant population reduction in conventional orchards, while Araneidae, Linyphiidae, and Thomisidae were not significantly affected by the intensity of spraying. The wandering hunting mode could explain the negative impact on Philodromidae, Salticidae, and Cheiracanthiidae but does not explain the lack of effect on Oxyopidae and Thomisidae. No significant effect was found on any family of web builders.

The impact of ant mutualistic and antagonistic interactions on the population dynamics of sap-sucking hemipterans in pear orchards.

BACKGROUND: Ants are known to establish antagonistic and mutualistic interactions with honeydew-producing hemipterans, depending on the species involved and the ecological context. The aim of this work was to infer the role that such interactions play in the population dynamics of psyllids and aphids in pear orchards. Interactions were inferred from field data and periodical sampling along a 4-year study, and from interaction assays performed under controlled conditions. RESULTS: A decline in the abundance of the pear psyllid (Cacopsylla pyri L.), parallel to an increase in the abundance of aphids, was registered over 4 years. Ants were the dominant species, representing about 90% of the predators, followed by spiders and predatory hemipterans (namely Pilophorus gallicus Remane). Ant abundance increased over the 4 years, matching the population dynamics of aphids. Evidence of mutualistic and antagonistic interactions were found for ant-aphid and ant-psyllid, respectively: (i) ant-aphid abundances on pear trees were positively correlated, and ants reduced predation on aphids by generalist predators, and (ii) ant-psyllid abundances were negatively correlated, ants have a negative effect on the psyllid population growth rates, and ants were found to prey on the psyllid. CONCLUSIONS: Because of their high abundance in comparison with other predators and the mutualistic-antagonistic relationships with aphids-psyllids, ants are considered to be the principal force behind the decline of pear psyllid populations and the increase in aphid numbers. In summary, ants contribute positively to biological control by the suppresion of pests (i.e. the psyllid) which are more damaging than those they protect (i.e. aphids). © 2019 Society of Chemical Industry.

Cuticle hydrocarbons in saline aquatic beetles.

Hydrocarbons are the principal component of insect cuticle and play an important role in maintaining water balance. Cuticular impermeability could be an adaptative response to salinity and desiccation in aquatic insects; however, cuticular hydrocarbons have been poorly explored in this group and there are no previous data on saline species. We characterized cuticular hydrocarbons of adults and larvae of two saline aquatic beetles, namely Nebrioporus baeticus (Dytiscidae) and Enochrus jesusarribasi (Hydrophilidae), using a gas chromatograph coupled to a mass spectrometer. The CHC profile of adults of both species, characterized by a high abundance of branched alkanes and low of unsaturated alkenes, seems to be more similar to that of some terrestrial beetles (e.g., desert Tenebrionidae) compared with other aquatic Coleoptera (freshwater Dytiscidae). Adults of E. jesusarribasi had longer chain compounds than N. baeticus, in agreement with their higher resistance to salinity and desiccation. The more permeable cuticle of larvae was characterized by a lower diversity in compounds, shorter carbon chain length and a higher proportion of unsaturated hydrocarbons compared with that of the adults. These results suggest that osmotic stress on aquatic insects could exert a selection pressure on CHC profile similar to aridity in terrestrial species.