Kaolin particle films disrupt landing, settling behavior and feeding of Trioza erytrae on lemon plants.

BACKGROUND: The citrus greening disease or Huanglongbing (HLB) is the most devastating disease of citrus crops. Trioza erytreae is a vector of HLB. Since its introduction in Europe, the insect reached the northern region of Spain and the southern region of Portugal, threatening relevant citrus production areas. Limiting the spread of HLB vectors is mandatory to prevent this disease. In this work, we assessed the effect of kaolin, a white mineral clay, on the landing, settling behavior and feeding behavior of Trioza erytreae on lemon plants. RESULTS: After kaolin application, the number of plants on which the insect was found was significantly lower than on untreated plants in the laboratory and in the field. Moreover, there were significantly fewer T. erytreae and a shorter duration of phloem-related events on kaolin-treated than untreated plants. CONCLUSION: The use of kaolin could be a suitable and efficient tool for inclusion into integrated pest management programs or organic production to reduce populations of T. erytreae and subsequently limit the spread of HLB in citrus crops. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

A novel molecular diagnostic method for the gut content analysis of Philaenus DNA.

Philaenus spumarius is a vector of Xylella fastidiosa, one of the most dangerous plants pathogenic bacteria worldwide. There is currently no control measure against this pathogen. Thus, the development of vector control strategies, like generalist predators, such as spiders, could be essential to limit the spread of this vector-borne pathogen. In this study, a polymerase chain reaction (PCR)-based approach was developed to principally detect DNA of P. spumarius in the spider's gut. Accordingly, 20 primer pairs, targeting the mitochondrial cytochrome oxidase I (COI) and cytochrome b (cytB) genes, were tested for specificity, sensitivity, and efficiency in detecting P. spumarius DNA. Overall, two primer sets, targeting COI gene (COI_Ph71F/COI_Ph941R) and the cytB gene (cytB_Ph85F/cytB_Ph635R), showed the highest specificity and sensitivity, being able to amplify 870 pb and 550 bp fragments, respectively, with P. spumarius DNA concentrations 100-fold lower than that of the DNA of non-target species. Among these two primer sets, the cytB_Ph85F/cytB_Ph635R was able to detect P. spumarius in the spider Xysticus acerbus, reaching 50% detection success 82 h after feeding. The feasibility of this primer set to detect predation of P. spumarius by spiders was confirmed in the field, where 20% of the collected spiders presented positive amplifications.

A Model to Predict the Expansion of Trioza erytreae throughout the Iberian Peninsula Using a Pest Risk Analysis Approach.

Assessing the potential of spread of an introduced crop pest in a new country is crucial to anticipating its effects on crop production and deriving phytosanitary management toward reducing potential negative effects. Citrus production represents a key agricultural activity throughout the Mediterranean basin. The African citrus psyllid Trioza erytreae (del Guercio, 1918) (Hemiptera: Triozidae) is a natural vector of Candidatusliberibacter spp., the causal agent of the harmful disease huanglongbing (HLB) or "citrus greening disease". In continental Europe, T. erytreae was detected for the first time in northwestern Spain in 2014. Pest risk analysis (PRA) approaches, such as modeling, consider both time and space components to predict the potential distribution of pests in a given region. In this work, we aim to parameterize a model able to predict the expected spread of T. erytreae in the Iberian Peninsula using three types of PRA models. The kernel model with two hypothetical entry points accurately predicted the distribution of T. erytreae with respect to latitude. This model should be further refined and validated to support decision-makers in the adoption of timely and successful management and regulatory measures against the spread of T. erytreae to other citrus-producing areas in Europe.

A Guild-Based Protocol to Target Potential Natural Enemies of Philaenus spumarius (Hemiptera: Aphrophoridae), a Vector of Xylella fastidiosa (Xanthomonadaceae): A Case Study with Spiders in the Olive Grove.

The olive grove is a key landscape across the Mediterranean basin. This agroecosystem is threatened by Xylella fastidiosa, the causal agent of the olive tree quick decline syndrome, Philaenus spumarius being the main vector. A way to limit pest populations relies on the use of biological control agents such as arthropods. Among them, spiders are generalist predators with different hunting strategies that feed mostly on insects and can contribute to limit pests. In this work, field and laboratory data were used to provide a protocol aiming to facilitate the selection of species of spiders among different guilds that could represent potential natural enemies of P. spumarius. Sampling of spiders was conducted in olive groves in northeastern Portugal. Two species, namely the orb-weaver Araniella cucurbitina and the ambusher Synema globosum, were selected according to the dominant guilds of spiders inhabiting the olive crop. We tested the differences of potential predatory efficiency using classical functional response tests with P. spumarius as prey. A type-II functional response was found for A. cucurbitina, whereas a type-I response was found for S. globosum. This difference uncovers a different potential efficiency among the two species as natural enemies of P. spumarius with relevant implications at high prey density in the field. A conceptual workflow to follow the fieldwork and selection of species for further work (i.e., laboratory assays) is provided and discussed. Standardized methods regarding the assessment of the suitability and efficiency of potential natural enemies are essential for the integration of results at different geographical extents and crops. Selecting functional counterparts such as different species of predators occurring at different locations that use the same prey (e.g., a pest) in the same way (e.g., hunting strategy) would facilitate developing biological control schemes.

Farmland biodiversity and agricultural management on 237 farms in 13 European and two African regions.

Farmland is a major land cover type in Europe and Africa and provides habitat for numerous species. The severe decline in farmland biodiversity of the last decades has been attributed to changes in farming practices, and organic and low-input farming are assumed to mitigate detrimental effects of agricultural intensification on biodiversity. Since the farm enterprise is the primary unit of agricultural decision making, management-related effects at the field scale need to be assessed at the farm level. Therefore, in this study, data were collected on habitat characteristics, vascular plant, earthworm, spider, and bee communities and on the corresponding agricultural management in 237 farms in 13 European and two African regions. In 15 environmental and agricultural homogeneous regions, 6-20 farms with the same farm type (e.g., arable crops, grassland, or specific permanent crops) were selected. If available, an equal number of organic and non-organic farms were randomly selected. Alternatively, farms were sampled along a gradient of management intensity. For all selected farms, the entire farmed area was mapped, which resulted in total in the mapping of 11 338 units attributed to 194 standardized habitat types, provided together with additional descriptors. On each farm, one site per available habitat type was randomly selected for species diversity investigations. Species were sampled on 2115 sites and identified to the species level by expert taxonomists. Species lists and abundance estimates are provided for each site and sampling date (one date for plants and earthworms, three dates for spiders and bees). In addition, farmers provided information about their management practices in face-to-face interviews following a standardized questionnaire. Farm management indicators for each farm are available (e.g., nitrogen input, pesticide applications, or energy input). Analyses revealed a positive effect of unproductive areas and a negative effect of intensive management on biodiversity. Communities of the four taxonomic groups strongly differed in their response to habitat characteristics, agricultural management, and regional circumstances. The data has potential for further insights into interactions of farmland biodiversity and agricultural management at site, farm, and regional scale.

Effects of kaolin particle films on the life span of an orb-weaver spider.

Araniella cucurbitina (Araneae: Araneidae) is a widespread orb-weaver spider commonly found in agroecosystems. Mineral particle films such as kaolin, due to their protective or anti-feeding action, can represent an alternative to pesticides, especially in organic farming systems, but little is known about its effects on A. cucurbitina. Therefore, we tested the effect of kaolin sprays on the life span of A. cucurbitina under laboratory conditions. Four treatments were tested encompassing different exposure routes. Thus, kaolin sprays were applied on (i) the surface, (ii) the prey (fly), (iii) the spider and (iv) both spider & prey. A control group was tested with water in each treatment. Results showed that sprays of kaolin significantly affected the survival of A. curcubitina when applications were done on the surface and on both spider & prey registering a reduction of 48% and 56%, respectively. Spiders in control obtained higher probability of reaching alive at the end of the assay than those treated with kaolin. Differences observed can be explained by the feeding behavior of the species and may depend on the consumption of the web by the spider and the ratio spider/fly for body size.