Effects of diversifying the planting period of maize on herbivorous and their natural enemies

Knowledge of the specific insect densities during crop development is necessary to perform appropriate measures for the control of insect pests and to minimize yield losses. In a previous study, both spatial and temporal approaches were adopted to analyse the influence of landscape structure and field variables on herbivore and predatory insects on maize. Both types of variables influenced insect abundance, but the highest effect was found with maize phenology. Given that the field planting date could modulate the influence produced by the structure of the landscape on herbivores and predatory insects, analyses of population dynamics must be performed at both the local and landscape levels. The anterior prompted us to study these aspects in the two common planting periods (early and late) in northern Spain. The present study tests the hypothesis that the period of maize planting could have a higher effect than phenology or interannual variation on the abundance of natural enemies and herbivores on maize. Our results showed that only the abundances of other herbivore thrips and Syrphidae were significantly different between the two planting periods. Moreover, we found significant effects of planting period when we performed yearly analysis in 2015 for Coccinellidae and Chrysopidae and in 2016 and 2017 for Aeolothrips sp. Most of the taxa had abundance peaks in earlier growth stages, which are related to pollination (before or during), while only Stethorus punctillum and Syrphidae increased later in the season. Furthermore, Frankliniella occidentalis, aphids, Syrphidae and Coccinellidae registered higher abundances in fields sown in the late planting period than in the rest of the insect species. The results of the present study highlight the effects of sowing dates on insect dynamics in maize.

Alfa and beta diversity of thrips (Thysanoptera) and biological control agents in chrysanthemum flowers (Chrysanthemum sp.) of two ecoregions in Jujuy province, Argentina

The objectives of this study are to identify thrips and their biological controllers, to analyze their abundance in three flower opening stages stages of chrysanthemum crops, and to determine alpha and beta diversity in two ecoregions of Jujuy province (Argentina). The study was carried out in the Chaco ecoregion (ECH) in October and November 2016, and in the Prepuna ecoregion (EP) in February and March 2018. On each date, six replicates of five flowers were excised in the stages: flower bud , semi-open flower and open flower. Diversity profiles and rank-abundance curves were built, and Jaccard's coefficient of similarity was applied. The diversity profiles showed significant differences in thrips communities. In the ECH, 15 thrips species were identified; the dominant and permanent species were Microcephalothrips abdominalis (Crawford) and Frankliniella occidentalis (Pergande). Five species were recorded in the EP, although Frankliniella gemina Bagnall and Thrips tabaci Lindeman on their own represented 78% of the total abundance. In the ECH, 20 entomophagous species/morphospecies were recognized, and 19 in the EP; antocorids were dominant in both ecoregions. The thrips and the entomophagous communities of chrysanthemum flowers were different (34%) between the ecoregions studied.

First report of the predatory mite Amblyseius tamatavensis Blommers, 1974 (Acari: Phytoseiidae) in Peru, and a key for the separation of the Amblyseius species reported so far from that country

Phytoseiidae (Acari: Mesostigmata) is an important family of predatory mites, with some species being commercialized as biological control agents for the control of phytophagous mites and small insects. In Peru, 65 species of this family have been recorded so far, with Amblyseius being the most diverse genus, with 11 species. The aim of this study is to report for the first time the presence of Amblyseius tamatavensis Blommers, 1974 in Peru. In South America, this species has so far been reported only in Brazil and Venezuela. In Peru, A. tamatavensis was found on orange plants [Citrus sinensis (L.) Osbeck] in the district of Pangoa, department of Júnin. In the laboratory, collected specimens were observed to feed on Phyllocoptruta oleivora (Ashmed, 1879) (Acari: Eriophyidae) and Frankliniella occidentalis (Pergande, 1895) (Thysanoptera: Thripidae). Studies to verify the potential of this species as a biological control agent for pests occurring in Peru should be conducted. A key to the Amblyseius species recorded in Peru is presented.

Integration of transcriptomics and network analysis reveals co-expressed genes in Frankliniella occidentalis larval guts that respond to tomato spotted wilt virus infection

Background The gut is the first barrier to infection by viruses that are internally borne and transmitted persistently by arthropod vectors to plant and animal hosts. Tomato spotted wilt virus (TSWV), a plant-pathogenic virus, is transmitted exclusively by thrips vectors in a circulative-propagative manner. Frankliniella occidentalis (western flower thrips), the principal thrips vector of TSWV, is transmission-competent only if the virus is acquired by young larvae. To begin to understand the larval gut response to TSWV infection and accumulation, a genome-assisted, transcriptomic analysis of F. occidentalis gut tissues of first (early L1) and second (early L2 and late L2) instar larvae was conducted using RNA-Seq to identify differentially-expressed transcripts (DETs) in response to TSWV compared to non-exposed cohorts. Results The larval gut responded in a developmental stage-dependent manner, with the majority of DETs (71%) associated with the early L1 stage at a time when virus infection is limited to the midgut epithelium. Provisional annotations of these DETs inferred roles in digestion and absorption, insect innate immunity, and detoxification. Weighted gene co-expression network analysis using all assembled transcripts of the gut transcriptome revealed eight gene modules that distinguish larval development. Intra-module interaction network analysis of the three most DET-enriched modules revealed ten central hub genes. Droplet digital PCR-expression analyses of select network hub and connecting genes revealed temporal changes in gut expression during and post exposure to TSWV. Conclusions These findings expand our understanding of the developmentally-mediated interaction between thrips vectors and orthotospoviruses, and provide opportunities for probing pathways for biomarkers of thrips vector competence.

Tomato hybrids with complex resistance for ground greenhouses

На фоне усиливающейся инфекционной нагрузки на культуру томата, обусловленной появлением новых болезней и новых физиологических рас традиционных патогенов, возрастает значение создания и использования в производстве гетерозисных гибридов с комплексной устойчивостью. Возрастает вредоносность новых насекомых-вредителей культуры томата. По вредоносности выходят на первое место томатная минирующая моль (Tuta absoluta) и западный цветочный трипс (Frankliniella occidentalis), который помимо нанесения прямого ущерба культуре выступает как переносчик вирусных заболеваний, в том числе вируса бронзовости (TSVW). Начатая селекционная программа на полевую устойчивость томата к трипсу позволила в 2020–2021 годах выделить восемь источников устойчивости среди образцов различных товарных групп. В результате двадцатилетней селекции созданы коммерческие гибриды с различным набором генов устойчивости. В задачи современной селекции входят этапы оценки и отбора селекционного материала на наличие генов устойчивости в генотипах методами ПЦР-диагностики, а также контроль устойчивости путем испытания материала в условиях инфекционных фонов или искусственного заражения. Важный этап – контроль товарных партий семян на присутствие генов устойчивости. Результаты ПЦР-анализа коммерческих гибридов на четыре гена устойчивости в сочетании с испытанием полевой устойчивости к кладоспориозу на сильном многолетнем инфекционном фоне приведены в табличной форме. Результаты показывают, что практически во всех товарных группах есть гибриды с устойчивостью к кладоспориозу, фузариозному увяданию, вирусу томатной мозаики (ВТоМ) и галловой нематоде. Также была обнаружена относительная устойчивость к фитофторозу у гибрида F1Изящный (Ph2\Ph2). Сегодня проводится работа по расширению числа генов для ПЦР-анализа селекционного материала. Under conditions of the increasing infectious load on the tomato crop due to the emergence of new diseases and new physiological races of traditional pathogens, the importance of creating and growing heterotic hybrids with complex resistance is increasing. The harmfulness of new insect pests of tomato culture is also increasing. In terms of harmfulness, the tomato mining moth (Tuta absoluta) and the western flower thrips (Frankliniella occidentalis) take the first place, which, in addition to causing direct damage to the culture, is a carrier of viral diseases, including Tomato spotted wilt virus. The started breeding program for the field resistance of tomato to thrips made it possible for the period 2020–2021 to identify 8 sources of resistance among the samples of various commodity groups. As a result of 20 years of selection, commercial hybrids with different sets of resistance genes have been created. The goals of modern breeding include breeding material assessment and selection for the presence of resistance genes in genotypes by PCR diagnostics method, as well as control of resistance by testing the material under infectious backgrounds or artificial infection inoculation. Another important step is the control of commercial seed lots for the presence of resistance genes. The results of PCR analysis of commercial hybrids for 4 resistance genes in combination with the test of field resistance to Cladosporium fulvum under condition of strong long-term infectious background are given in tabular form. These results show that in almost all product groups there are hybrids with resistance to ToMV, in combination with other resistances, including the relative resistance to late blight in the F1 Iziyaschniy (Ph2\Ph2) hybrid. Currently, the progress is being made towards expanding the number of genes for PCR analysis of breeding material.

Developing a Phototactic Electrostatic Insect Trap Targeting Whiteflies, Leafminers, and Thrips in Greenhouses

Our aim was to develop an electrostatic apparatus to lure and capture silverleaf whiteflies (Bemisia tabaci), vegetable leafminers (Liriomyza sativae), and western flower thrips (Frankliniella occidentalis) that invade tomato greenhouses. A double-charged dipolar electric field producer (DD-EFP) was constructed by filling water in two identical transparent soft polyvinyl chloride tubes arrayed in parallel with fixed separation, and then, inserting the probes of grounded negative and positive voltage generators into the water of the two tubes to generate negatively and positively charged waters, respectively. These charged waters electrified the outer surfaces of the opposite tubes via dielectric polarization. An electric field formed between the oppositely charged tubes. To lure these phototactic insects, the water was colored yellow using watercolor paste, then introduced into the transparent insulator tubes to construct the yellow-colored DD-EFP. This apparatus lured insects in a manner similar to commercially available yellow sticky traps. The yellow-colored DD-EFP was easily placed as a movable upright screen along the plants, such that invading pests were preferentially attracted to the trap before reaching the plants. Furthermore, pests settling on the plants were attracted to the apparatus, which used a plant-tapping method to drive them off the plants. Our study provided an experimental basis for developing an electrostatic device to attract and capture insects that enter greenhouses.

Ovicidal activity of spirotetramat and its effect on hatching, development and formation of Frankliniella occidentalis egg

Frankliniella occidentalis (Pergande) has become an important vegetable pest worldwide because of its economic damage to crop production. However, it is difficult to control due to its unique living habits. In this study, the eggs of F. occidentalis were used as the target to explore the ovicidal activity of spirotetramat on the thrips and its effect on hatching, development and formation. After the treatment of spirotetramat, the LC50 value descreased with increased egg age using egg dipping method, and showed the same trend as the leaf dipping method verified on living plants. Through ultra-depth-of-field microscopy, scanning electron microscopy and transmission electron microscopy, the egg shell and internal structures of F. occidentalis eggs were studied. Spirotetramat can destroy the egg shells of F. occidentalis, resulting in shrinkage of the egg surface, sunken pores, egg deformities, egg shell rupture and other phenomena. This allows spirotetramat to enter the egg and destroy the egg structure, making the egg internal structure flocculent, fuzzy and unevenly distributed, which affects embryonic development and causes the nymphs to die before hatching. Therefore, the prevention and control of F. occidentalis using spirotetramat before damage is caused to crops should have a better effect.

Rapid Detection of Tomato Spotted Wilt Virus With Cas13a in Tomato and Frankliniella occidentalis

Graphical AbstractSchematic of CRISPR/Cas13-based virus detection.