Mari Carmen Asensio‐S.‐Manzanera

Biological control using parasitoids is a key strategy for managing psyllid pests in horticultural crops. This study investigated the parasitoid complex associated with Bactericera tremblayi and Bactericera trigonica, two economically important psyllid pests of leek and carrot, respectively, in Castile and León (Spain). Nymphs of both psyllid species were collected and reared to assess parasitism; emerging parasitoids were identified morphologically and by DNA barcoding. A total of 969 parasitized nymphs were collected, from which 291 parasitoids emerged, including Tamarixia pronomus, Tamarixia tremblayi, Syrphophagus herbidus, Syrphophagus cf. taeniatus, Cheiloneurus sp. and Encyrtidae sp. Tamarixia pronomus is reported here for the first time as parasitoids of B. tremblayi while T. tremblayi, S. herbidus, and S. cf. taeniatus are newly recorded as parasitoids of B. trigonica. Moreover, the two Syrphophagus species represent the first records of this genus for Spain. The COI barcode sequences were generated for T. pronomus, T. tremblayi and S. cf. taeniatus. The parasitism rate of S. herbidus on B. trigonica reached a maximum of 23.18%. No significant differences in parasitism by Tamarixia species were observed between the two Bactericera hosts. Maximum parasitism rates recorded were 32.43% for T. pronomus on B. trigonica, and approximately 11–12% for T. tremblayi on both host species. Total parasitism of B. tremblayi in leek crops reached up to 70%, whereas parasitism of B. trigonica in carrot remained generally low and poorly synchronized with pest population dynamics. These results highlight a diverse parasitoid complex with substantial natural control of B. tremblayi and variable but lower impact on B. trigonica, underscoring the relevance of habitat and temporal factors for conservation biological control in these agroecosystems.

Plants of the Lamiaceae family are widely used for the extraction of essential oils, and this industry generates a large number of solid residues as by-products, which contain non-volatile valuable compounds. The aim of this work was to identify and quantify the phenolic compounds present in these solid residues from different important Spanish species of Lamiaceae to characterize and valorize them. Forty-seven phenolic compounds were identified by HPLC-DAD-MS and quantified by HPLC-DAD. Different concentrations and types of phenolic compounds were found between the solid residues. The Rosmarinus officinalis extracts showed the highest total phenolic content due to their high phenolic terpene concentrations. The Thymus mastichina extracts were characterized by kaempferol and flavanones, and some flavones were derived from luteolin and apigenin. Finally, the sample Lavandula and Salvia lavandulifolia extracts presented the lowest content of most phenolic compounds, with the exception of some phenolic acids, such as danshensu, salvianolic acid A, and glucosides of hydroxycinnamic acids. Therefore, this work provides information on the quantification of a large number of phenolic compounds using a simple, sensitive, reproducible, and accurate methodology. In addition, the results indicate that these solid residues still contain important amounts of different polyphenols, which are antioxidants and can be used in different industries.

Bactericera tremblayi (Wagner, 1961) (Hemiptera: Triozidae), the onion and leek psyllid, belongs to the Bactericera nigricornis Förster complex, along with B. trigonica and B. nigricornis. In contrast to the other two species, there has been a notable absence of studies examining the distribution and seasonal occurrence of B. tremblayi, despite its association with significant issues in leek crops. Surveys were conducted between 2017 and 2020 in the main leek-growing area of Castile and Leon (Spain). An extensive survey encompassing 29 distinct plots was monitored with sweep nets and visual inspection, counting plants with immature forms at three times in the crop cycle. Additionally, a total of seven seasonal monitoring surveys were conducted in the same area of study. Plots were monitored every ten days, employing three distinct sampling methods including horizontal green tile water traps, sweep nets, and visual inspection, counting the juvenile stages by plant. The results revealed that B. tremblayi predominated as the primary species of jumping plant-lice in leek crops throughout the entire crop cycle. To date, there exists no documented incidence of pathogenic agents within symptomatic leeks. Consequently, the manifestation of severe symptoms is highly likely to be a direct consequence of the feeding activity of the onion psyllid. Populations of B. tremblayi were present in leek crops from May–July to harvest (September–November). Adults were captured in horizontal green water traps several days before they were found in sweep net samples, making the former effective in capturing early immigrant individuals. The maximum peaks of B. tremblayi were observed at the end of the crop cycle, particularly during late-season cycles characterized by lower mean temperatures. During observations made in a controlled environment, temperature exerted a significant influence on the developmental time of all stages of B. tremblayi. The complete development from egg to adult occurred within a temperature range of 15 to 25 °C. At 30 °C, the survival of eggs and N1 nymphs was limited and B. tremblayi did not complete its developmental cycle. The optimum temperature for the development of B. tremblayi provided by the models used was close to 24 °C with the application of Briere, Taylor, and Lactin models and around 21 °C with the SSI model. These results provided a good adjustment in predicting the survival patterns of B. tremblayi under the studied environmental conditions.

‘Candidatus Liberibacter solanacearum’ (CaLsol), the etiological agent of potato zebra chip (ZC), is transmitted to potato plants by the psyllid Bactericera cockerelli (Šulc, 1909) in North and Central America and New Zealand. The risk of the dispersion of ZC in Spain depends on the presence of an efficient vector. This work studies the presence and abundance of ZC symptoms and CaLsol in potato plants, as well as the presence and abundance of psyllid species associated with potato crops in the main producing areas in Spain. Eighty-eight plots were surveyed punctually to detect ZC symptoms and psyllid species in the main potato-producing areas. Furthermore, fourteen potato plots were surveyed by different sampling methods during the cropping season to detect psyllid species from 2016 to 2018. Very few symptomatic and CaLsol-positive plants were detected in Mainland Spain, and any positive plant was detected in the Canary Islands. Most of the adult psyllids captured were identified as Bactericera nigricornis (Foerster, 1848), and some of them as Bactericera trigonica, but no B. cockerelli was detected. B. nigricornis was found widely distributed in the northern half of the Iberian Peninsula; however, this psyllid does not seem sufficient to pose a threat to potato production, due to the scarce number of specimens and because the frequency of B. nigricornis specimens that were CaLsol+ was very low.

Liberibacter is a bacterial group causing different diseases and disorders in plants. Among liberibacters, Candidatus Liberibacter solanaceraum (CLso) produces disorders in several species mainly within Apiaceae and Solanaceae families. CLso isolates are usually grouped in defined haplotypes according to single nucleotide polymorphisms in genes associated with ribosomal elements. In order to characterize more precisely isolates of CLso identified in potato in Spain, a Multilocus Sequence Analysis (MLSA) was applied. This methodology was validated by a complete analysis of ten housekeeping genes that showed an absence of positive selection and a nearly neutral mechanism for their evolution. Most of the analysis performed with single housekeeping genes, as well as MLSA, grouped together isolates of CLso detected in potato crops in Spain within the haplotype E, undistinguishable from those infecting carrots, parsnips or celery. Moreover, the information from these housekeeping genes was used to estimate the evolutionary divergence among the different CLso by using the concatenated sequences of the genes assayed. Data obtained on the divergence among CLso haplotypes support the hypothesis of evolutionary events connected with different hosts, in different geographic areas, and possibly associated with different vectors. Our results demonstrate the absence in Spain of CLso isolates molecularly classified as haplotypes A and B, traditionally considered causal agents of zebra chip in potato, as well as the uncertain possibility of the present haplotype to produce major disease outbreaks in potato that may depend on many factors that should be further evaluated in future works.

To achieve a detailed chemical characterization and to find the changes in the composition the volatiles of Lavandula latifolia, Salvia lavandulifolia and Thymus mastichina were analyzed through GC-FID/MS and a total of 47, 48 and 48 compounds were identified, respectively. 1,8-cineol+limonene was the main compound in the three species. Three extracting methodologies were used: hydrodistillation (HD), microdistillation (MD) and dichloromethane extraction (EX). The amount of volatile compounds was affected by the kind of method used and by the kind of species analyzed, thus, S. lavandulifolia produced a higher amount of volatiles with the EX and T. mastichina with MD. HD showed significantly lower amount of volatiles for the three species. With HD and MD a higher amount of β-pinene was obtained. MD produced a higher proportion of 1,8-cineol+limonene. Canonical discrimination function was done using the two most predictable compounds to distinguish among techniques revealing the method used for each species.