Biocontrol in practice in Canadian floricultural greenhouses

The environment inside Canadian prairie greenhouses differs from greenhouses built in other northern latitude locations in terms of lighting, temperature, humidity, and photoperiod. Since the performance of biocontrol agents depends upon several interactive environmental variables, their effectiveness to control pests in a particular crop growing under certain climatic conditions does not directly translate to another crop or location. So, we analyzed research trials assessing the efficacy and compatibility of various biocontrol agents (Amblyseius cucumeris, Amblyseius cucumeris, Phytoseiulus persimilis, Encarsia formosa, Aphidius colemani, Aphidius ervi, and Steinernema feltiae) on key pests (Western flower thrips, two-spotted spider mites, greenhouse whiteflies, and aphids) of spring bedding plants grown in a commercial floricultural greenhouse. Were analyzed several compatible combinations of biocontrol agents and observed a significant reduction in pest densities and plant damage symptoms as compared to untreated control plants. The results demonstrate that P. persimilis controlled two-spotted spider mites successfully in calibrachoa crop. The combination of Amblyseius cucumeris and S. feltiae resulted in significantly better control of Western flower thrips than the use of Amblyseius cucumeris alone in sweet potato vine plants. The application of E. formosa and Amblyseius cucumeris individually reduced greenhouse whiteflies on calibrachoa plants as compared to control, but their combination performed better resulting in a significantly lower number of whiteflies on plants. Another combination of Aphidius colemani and Aphidius ervi controlled green peach aphids and foxglove aphids effectively on the pansy crop. The biocontrol agents were effective for managing a variety of pests in a commercial greenhouse setting.

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.

Infection of the Western Flower Thrips, Frankliniella occidentalis, by the Insect Pathogenic Fungus Beauveria bassiana

The western flower thrips, Frankliniella occidentalis, is an aggressive agricultural insect pest causing significant damage to a wide range of fruit, vegetable, and ornamental crops. Beauveria bassiana is a broad-host-range entomopathogenic fungus capable of infecting and killing F. occidentalis. Infection of thrips by B. bassiana strain BbYT12 using a concentration of 1 × 108 conidia/mL resulted in 81.48% mortality in adults in 6 d (LT50 = 90 ± 15.1 h). Scanning electron microscopy of the infection process revealed preferential adhesion and germination of fungal spores to inter-segmental folds or grooves on the insect body surface with penetrating germlings and extended hyphae visualized during the initial stages of infection (6–24 h). Histological analyses showed the appearance of in vivo hyphal bodies in sagittal sections and the fat body as early as 24 h post-infection. Within 72 h, hyphal bodies and hyphae could be found throughout the infected organism including in the midgut, Malphigian tubules, alimentary canal, ovarioles (in females), and an extended hyphal network could be seen on insect cadavers (>72 h post-infection). Real-time RT-PCR analyses of the expression of select genes implicated in virulence including the Pr1 protease, beauvericin synthase, involved in the production of the secondary metabolite beauvericin, two cytochrome P450 monooxygenases implicated in cuticular hydrocarbon degradation, two multidrug efflux proteins, a perilipin involved in lipid storage, and the Hog1 MAP kinase and protein kinase A signaling factors revealed discrete patterns of infection-time dependent expression. These data provide basic insights into the process of B. bassiana infection of F. occidentalis.

Study on the Visual Response of Frankliniella occidentalis to Ultra Violet-Visible Spectroscopy with Different Wavelength Ranges

To understand the visual sensitivity of western flower thrips to 350–450 nm light, we examined thrips selective response effect and the effect of white light on thrips visual response effect. The results showed that the visual selection response to Ultra Violet (UV) light at 360–365 nm, the approach sensitivity to 380–385 nm light with 6000 lx was respectively the best (15.59, 7.26%), while under light energy, both of them to 360–365 nm light with 60 mW/cm2 were the best (20.04, 11.13%). Under contrast white light, the most sensitive UV spectra of thrips respectively caused by illumination, light energy was 380–385, 360–365 nm, and white light enhanced thrips visual response effect to UV light, which further increased by the increasing intensity, showing that under illumination, the visual response effect to 380–385 nm light with 6000 lx was the best (51.21,69.78%), while that to 360–365 nm light with 60 mW/cm2 were the best (43.98, 65.68%), originated from the different intensity spread by light energy and illumination. These results indicate that the change of photo-stimulus intensity property can regulated thrips visual sensitivity to enhance the phototactic effect.

Complexity and local specificity of the virome associated with tospovirus-transmitting thrips species.

Frankliniella occidentalis (western flower thrips=WFT) and Thrips tabaci (onion thrips=OT) are insect species that greatly impact horticultural crops through direct damage and their efficient vectoring of tomato spotted wilt virus and iris yellow spot virus. In this study we collected thrips of these species from 12 field populations in various regions in Italy. We also included one field population of Neohydatothrips variabilis (soybean thrips=ST) from the U.S.A. Total RNAseq from high-throughput sequencing (HTS) was used to assemble the virome and then we assigned putative viral contigs to each thrips sample by qRT-PCR. Excluding plant and fungal viruses, we were able to identify 61 viral segments, corresponding to 41 viruses: 14 were assigned to WFT, 17 to OT, one from ST and 9 viruses could not be assigned to any species based on our stringent criteria. All these viruses are putative representative of new species (with only the exception of a sobemo-like virus that is 100% identical to a virus recently characterized in ST) and some belong to new higher-ranking taxa. These additions to the viral phylogeny suggest previously undescribed evolutionary niches. Most of the Baltimore’s classes of RNA viruses were present (positive- and minus- strand and dsRNA viruses), but only one DNA virus was identified in our collection. Repeated sampling in a subset of locations in 2019 and 2020 and further virus characterization in a subset of four thrips populations maintained in laboratory allowed us to provide evidence of a locally persistent thrips core virome that characterizes each population. IMPORTANCE Harnessing the insect microbiome can result in new approaches to contain their populations or the damage they cause vectoring viruses of medical, veterinary, or agricultural importance. Persistent insect viruses are a neglected component of their microbiota. Here for the first time, we characterize the virome associated with the two model systems for tospovirus-transmitting thrips species, of utmost importance for the direct and indirect damage they cause to a number of different crops. The thrips virome here characterized includes several novel viruses, that in some cases reveal previously undescribed clades. More importantly, some of the viruses we describe are part of a core virome that is specific and consistently present in distinct geographical locations monitored over the years, hinting at a possible mutualistic symbiotic relationship with their host.

Morphological and Chemical Factors Related to Western Flower Thrips Resistance in the Ornamental Gladiolus

Understanding the mechanisms involved in host plant resistance opens the way for improved resistance breeding programs by using the traits involved as markers. Pest management is a major problem in cultivation of ornamentals. Gladiolus (Gladiolus hybridus L.) is an economically important ornamental in the Netherlands. Gladiolus is especially sensitive to attack by western flower thrips (Frankliniella occidentalis (Pergande) (Thysanoptera:Thripidae)). The objective of this study was, therefore, to investigate morphological and chemical markers for resistance breeding to western flower thrips in Gladiolus varieties. We measured thrips damage of 14 Gladiolus varieties in a whole-plant thrips bioassay and related this to morphological traits with a focus on papillae density. Moreover, we studied chemical host plant resistance to using an eco-metabolomic approach comparing the 1H NMR profiles of thrips resistant and susceptible varieties representing a broad range of papillae densities. Thrips damage varied strongly among varieties: the most susceptible variety showed 130 times more damage than the most resistant one. Varieties with low thrips damage had shorter mesophylls and epidermal cells, as well as a higher density of epicuticular papillae. All three traits related to thrips damage were highly correlated with each other. We observed a number of metabolites related to resistance against thrips: two unidentified triterpenoid saponins and the amino acids alanine and threonine. All these compounds were highly correlated amongst each other as well as to the density of papillae. These correlations suggest that papillae are involved in resistance to thrips by producing and/or storing compounds causing thrips resistance. Although it is not possible to distinguish the individual effects of morphological and chemical traits statistically, our results show that papillae density is an easy marker in Gladiolus-breeding programs targeted at increased resistance to thrips.