Reduced Egg Hatch Research Articles

The SA-WRKY70-PR-Callose Axis Mediates Plant Defense Against Whitefly Eggs.

The molecular mechanisms of plant responses to phytophagous insect eggs are poorly understood, despite their importance in insect-plant interactions. This study investigates the plant defense mechanisms triggered by the eggs of whitefly Bemisia tabaci, a globally significant agricultural pest. A transcriptome comparison of tobacco plants with and without eggs revealed that whitefly eggs may activate the response of defense-related genes, including those involved in the salicylic acid (SA) signaling pathway. SA levels are induced by eggs, resulting in a reduction in egg hatching, which suggests that SA plays a key role in plant resistance to whitefly eggs. Employing Agrobacterium-mediated transient expression, virus-induced gene silencing assays, DNA-protein interaction studies, and bioassays, we elucidate the regulatory mechanisms involved. Pathogenesis-related proteins NtPR1-L1 and NtPR5-L2, downstream of the SA pathway, also affect whitefly egg hatching. The SA-regulated transcription factor NtWRKY70a directly binds to the NtPR1-L1 promoter, enhancing its expression. Moreover, NtPR1-L1 promotes callose deposition, which may impede the eggs' access to water and nutrients. This study establishes the SA-WRKY70-PR-callose axis as a key mechanism linking plant responses and defenses against whitefly eggs, providing new insights into the molecular interactions between plants and insect eggs.

Pleiotropic effects of Ebony on pigmentation and development in the Asian multi-coloured ladybird beetle, Harmonia axyridis (Coleoptera: Coccinellidae).

Melanin plays a pivotal role in insect body pigmentation, significantly contributing to their adaptation to diverse biotic and abiotic environmental challenges. Several genes involved in insect melanin synthesis showed pleiotropic effects on insect development and reproduction. Among these, the N-β-alanyl dopamine synthetase gene (Ebony) is integral to the pigmentation process. However, the full spectrum of its pleiotropic impacts is not yet thoroughly understood. In this study, we identified and characterised the HaEbony gene in the Asian multi-coloured ladybird beetle (Harmonia axyridis) and found that HaEbony gene is a conserved gene within the Coleoptera order. We aimed to further explore the multiple roles of HaEbony in the physiology and behaviour in H. axyridis. The CRISPR/Cas9 system was applied to generate multiple HaEbony knockout allele (HaEbony+/-), showing nucleotide deletion in the G0 and G1 generations. Remarkably, the resultant HaEbony+/- mutants consistently displayed darker pigmentation than their wild-type counterparts across larval, pupal and adult stages. Furthermore, these HaEbony+/- individuals (G0) demonstrated an enhanced predatory efficiency, evidenced by a higher number of aphids consumed compared to the wild type. A significant finding was the reduced egg hatchability in both G0 and G1 generations of the HaEbony+/- group, highlighting a potential reproductive fitness cost associated with HaEbony deficiency. In conclusion, our study not only sheds light on the multifaceted roles of HaEbony in H. axyridis but also highlights the potential of employing CRISPR/Cas9-targeted modifications of the Ebony gene. Such genetic interventions could enhance the environmental adaptability and predatory efficacy of ladybirds, presenting a novel strategy in biological control application.

Exploring nematicidal biomolecules from Xenorhabdus nematophila as a novel source for Meloidogyne incognita management

Attempts were made to evaluate the purified bioactive compounds of Xenorhabdus nematophila against Meloidogyne incognita. In order to extract the purified compounds, a solid-supported liquid-liquid extraction system with a flow rate (1 mL/min) was used to purify bioactive molecules. Compounds were individually collected concentrated and evaluated against M. incognita. Among 25 fractions the L19 fraction, exhibited 98% inhibition in egg hatching and mortality of juveniles. The biomolecules were identified through Liquid Chromatography- Mass Spectroscopy (LC-MS) technique. To decipher the mode of action of compounds, molecular docking studies were performed with potential protein targets such as acetylcholinesterase, β-1,4-endoglucanase, glutathione S-transferase-1, cytochrome c oxidase, G-protein coupled receptor and Fatty acid and retinol-binding proteins of M. incognita. The results revealed that among eight compounds from the L19 fraction, malonate and pidopidon exhibited greater binding affinity towards the selected protein targets of M. incognita. In vitro studies with malonate and pidopidon against M. incognita showcased a 99% reduction in egg hatching and juvenile mortality. Moreover, greenhouse experiments revealed that malonate compounds not only reduced 94% of the M. incognita population but also enhanced the plant growth parameters in tomato by 60%. Hence the present study stands novel in exploiting the nematicidal compounds from X. nematophila giving limelight to explore pidopidon and malonate as novel nematicidal compounds for the management of M. incognita.

'The Garlic Gambit': an alternative strategy for controlling vine weevil (Otiorhynchus sulcatus F.; Coleoptera: Curculionidae).

Plant protection products derived from plant material are proposed to be a sustainable alternative to conventional synthetic chemical pesticides. This study determines the efficacy of a commercially available bioinsecticide based on garlic (Allium sativum L.; Asparagales: Amaryllidaceae) extract against vine weevil (Otiorhynchus sulcatus F.; Coleoptera: Curculionidae) eggs and larvae in contact, fumigation and a combination of contact and fumigation bioassays under laboratory conditions. Results showed that garlic significantly reduced egg hatch rate compared to the control group when applied as a fumigant. Similarly, the egg hatch rate was reduced compared to the control group when garlic was applied as combined contact and fumigant applications. No effect was observed when the garlic product was applied as a contact application. The bioinsecticide significantly reduced larval survival when either contact or fumigant applications were used. A combined contact and fumigant effect was shown also when vine weevil eggs were exposed to the bioinsecticide for 30 days in plastic containers containing growing media. The number of larvae recovered after this period was significantly reduced compared to the control group. This study demonstrates the potential of garlic-based bioinsecticides, such as Pitcher GR, for vine weevil control. Further studies are, however, needed to determine the efficacy of such bioinsecticides under field conditions and investigate how these products can be most effectively used as a part of a wider vine weevil integrated pest management program.

Efficacy of plant-based products and nonconventional pesticides for the management of tropical bed bug.

Insecticide resistance is widespread in global bed bug populations. Both common bed bugs and tropical bed bugs are pyrethroid-resistant among most field populations. Plant-based products and nonconventional pesticides offer minimal-risk strategies for managing bed bug resistance, but this strategy has yet to be formally evaluated in Cimex hemipterus (F.) (Hemiptera: Cimicidae). Here, several commercial plant-based formulations (Cedarcide, EcoRaider (also known as EcoVenger), EcoSMART, and Bio-D), a novel product, Provecta, and a pyrethroid insecticide, Pesguard FG161 were tested against pyrethroid-susceptible and resistant strains of C. hemipterus using direct spray, residual exposure, and egg dipping assays. Direct spray treatments outperform residual applications against all tested bed bug strains. Cedarcide exhibits the highest consistency in eliminating bed bugs, followed by EcoRaider, EcoSMART, and Provecta that outperform Bio-D and Pesguard FG161. In comparison to Pesguard FG161, all plant-based insecticide products and Provecta showed higher efficacy against pyrethroid-resistant strains. Although effective, product efficacy varies in terms of speed. Cedarcide kills all bed bugs within 1 min after spraying; however, other products can take up to 9 days to achieve 100% mortality. The efficacy of all products was reduced when evaluated on fabric surface (42%-65% mortality). Cedarcide and EcoRaider reduced egg hatchability by 37%-73% and 47%-70%, respectively. This study suggests that certain plant-based insecticides and an unconventional insecticide can serve as alternative direct spray treatments for managing tropical bed bugs, though their residual effects are limited.

Redundancy in microbiota-mediated suppression of the soybean cyst nematode

BackgroundSoybean cyst nematodes (SCN) as animal parasites of plants are not usually interested in killing the host but are rather focused on completing their life cycle to increase population, resulting in substantial yield losses. Remarkably, some agricultural soils after long-term crop monoculture show a significant decline in SCN densities and suppress disease in a sustainable and viable manner. However, relatively little is known about the microbes and mechanisms operating against SCN in such disease-suppressive soils.ResultsGreenhouse experiments showed that suppressive soils (S) collected from two provinces of China and transplantation soils (CS, created by mixing 10% S with 90% conducive soils) suppressed SCN. However, SCN suppressiveness was partially lost or completely abolished when S soils were treated with heat (80 °C) and formalin. Bacterial community analysis revealed that the specific suppression in S and CS was mainly associated with the bacterial phylum Bacteroidetes, specifically due to the enrichment of Chitinophaga spp. and Dyadobacter sp., in the cysts. SCN cysts colonized by Chitinophaga spp. showed dramatically reduced egg hatching, with unrecognizable internal body organization of juveniles inside the eggshell due to chitinase activity. Whereas, Dyadobacter sp. cells attached to the surface coat of J2s increased soybean resistance against SCN by triggering the expression of defence-associated genes. The disease-suppressive potential of these bacteria was validated by inoculating them into conducive soil. The Dyadobacter strain alone or in combination with Chitinophaga strains significantly decreased egg densities after one growing cycle of soybeans. In contrast, Chitinophaga strains alone required more than one growing cycle to significantly reduce SCN egg hatching and population density.ConclusionThis study revealed how soybean monoculture for decades induced microbiota homeostasis, leading to the formation of SCN-suppressive soil. The high relative abundance of antagonistic bacteria in the cyst suppressed the SCN population both directly and indirectly. Because uncontrolled proliferation will likely lead to quick demise due to host population collapse, obligate parasites like SCN may have evolved to modulate virulence/proliferation to balance these conflicting needs.BVs6NXuQzznnTv7j41Q5n6Video

Impact of age on the reproductive output of Hermetia illucens (Diptera: Stratiomyidae).

The current study examined the impact of adult black soldier fly (Hermetia illucens (L.)), age on reproductive output. Four treatments consisting of an equal sex ratio of the following combinations were used: 2-day-old males with 2-day-old females (YMYF); 6-day-old males with 2-day-old females (OMYF); 2-day-old males with 6-day-old females (YMOF); 6-day-old males with 6-day-old females (OMOF). Adult age was a significant factor for the overall number of mating events observed, with YMYF having 2.2× more than YMOF and 2.7× more than OMOF. Time was a significant factor in the number of mating events observed, with 97.8% observed on days 2-6. Age was not a significant factor for the total number of oviposition events, but the inclusion of time as a factor was significant, with 91.5% of all events occurring on days 2-6. Treatment and trial significantly interacted with egg production. This response can be attributed to treatments containing old females, which had a 50% variation in egg output across trials. Treatments containing young females were consistent in terms of egg production. As anticipated, due to oviposition events, 94.8% of total eggs were oviposited on days 2-6. Fecundity and egg hatch were also significantly impacted by female age, with a 50% reduction in both cases across trials occurring in old females. Young females paired with old males had a 20% reduction in egg hatch, but this difference was not statistically significant.

Green synthesis of Malvastrum coromandelianum fabricated AgNPs: Anti-dengue and mosquitocidal studies

In the field of nanobiotechnology, tools from nanotechnology are created and used to investigate biological phenomena. Nanoparticles, for instance, can act as sensors, probes, or delivery systems for biomolecules in cellular systems. This study investigates the anti-dengue effectiveness of silver nanoparticles mediated by Malvastrum coromandelianum against the dengue virus and its vector, Aedes aegypti. The methanol extract of M. coromandelianum leaves contains various compounds, including proteins, carbohydrates, alkaloids, flavonoids, phenols, tannins, triterpenoids, and steroids. M. coromandelianum leaves were used as a reducing and capping agent for the creation of silver nanoparticles (AgNPs). The LC50 values for M. coromandelianum leaf extract against Ae. aegypti larvae to pupa in mosquitocidal experiments ranged from 263.059 ppm (Larva I) to 530.291 ppm (pupa). AgNPs produced by M. coromandelianum had LC50 values between 22.268 ppm for larva I and 39.416 ppm for pupa. Adult Ae. aegypti rats exposed to M. coromandelianum leaf-based coils died at rates 63 and 67 % higher than the permethrin-based positive control. In ovicidal experiments, a treatment with 500 ppm of M. coromandelianum extract and 40 ppm of AgNPs resulted in a 100 % reduction in egg hatchability. The research suggests that M. coromandelianum may serve as a suitable replacement for developing bio-formulated mosquitocidal abilities against vector control techniques. In-vitro experiments show that AgNPs have an antiviral effect on vero cells infected with DEN-2. Molecular docking was used in in-silico studies to identify potential interactions between the bioactive components in M. coromandelianum leaf extract and the viral NS5 protein. Propiophenone was found to be the best ligand, displaying a high affinity for the NS5 protein and a binding energy of 4.38 kcal/mol.

Morphological features of the cuticle of hatching eggs of chickens and turkeys subjected to pre-incubation treatment

Improving the productivity of poultry, especially egg crosses, depends on the quality of the bioceramic calcite (CaCO3) layers and surface glycoprotein film of the egg (cuticle). These are the barriers that control the flow of gases and water vapor. Any disruptions in the transport process can lead to a significant reduction in egg hatchability. It has been proven that treatment of chicken and turkey eggs with acid solutions (acetic acid or hydrochloric acid) and sodium hypochlorite prior to hatching has increased egg hatchability compared to the control. In view of this, the aim of this study was to investigate the protective structures of incubation eggs of chickens and turkeys using non-destructive electron microscopic methods and computer processing of digital images of the cuticle coatings of these eggs for reliable prediction of the degree of increase in gas permeability of the cuticle-shell system due to the destructive effect of various chemicals, including disinfectants, for pre-hatching egg treatment. In the experiments, hatching eggs of Leghorn White hens (n = 90) 15–20 weeks of laying and Broad Breasted White turkeys (n = 80) were used. The antimicrobial agents used in the experiments were a 0.6% solution (0.08 mol/L) of sodium hypochlorite, a 2.5% solution (0.4 mol/L) of acetic acid, and a 5.0% solution (1.40 mol/L) of hydrochloric acid. Using the computer analysis of digital electron microscopic images of the egg surface with the software packages Visilog and FemtoScan Online, it was experimentally proved that the destructive effect of these substances on the cuticle-shell system increases in the range of sodium hypochlorite < hydrochloric acid < acetic acid, which positively correlates with the gas permeability of hatching eggs of chickens and turkeys and the egg hatchability index. The presence of fundamentally different morphological features and correlations of the cuticle of chicken and turkey eggs in response to the action of acids and oxidants used for pre-hatching treatment was shown. The digital markers of the cuticle-shell system state, obtained from analytical programs of digital images, have been established, which makes it possible to reliably predict the indicators of increasing the hatchability of chicken and turkey eggs under the conditions of using certain chemicals. The prospect of further research is to study the effect of modern complex antimicrobial agents on the hatchability of poultry eggs of different species.

Field tests of egg and larval release methods of biological control agents (Archanara neurica, Lenisa geminipuncta) for introduced Phragmites australis australis (Cav.) trin. Ex Steud

Field releases of the stem-boring moths Archanara neurica and Lenisa geminipuncta (Lepidoptera: Noctuidae) as classical biological control agents for introduced Phragmites australis australis (Cav.) Trin. ex Steud. began in Canada during 2019. Since then, we have developed and tested release methods for eggs and larvae of both agents. Experiments here include comparisons of: (1) egg survival from exposed “egg card” and protected “egg cup” release methods to assess the risk of agent predation and test mitigation strategies; (2) performance of egg cups overwintered at the release site and those placed shortly before emergence in spring to test for any potential phenological asynchrony between biological control agents and the target weed; and (3) effectiveness of egg cup and larval-inoculated stem releases at a large geographic scale across 15 field sites in southern Ontario. Egg card releases experienced high egg loss likely due to predation (∼90 % of eggs), but egg cups were successful at reducing these losses to near zero. Releasing eggs in cups during the spring made it easier to place releases near phenologically synchronized microsites, minimized the risk of damage to the egg cups, and avoided a 16 % reduction in egg hatch likely associated with desiccation. Both larval-inoculated stems and egg cups produced highly encouraging feeding damage in the first season of release, with 7.7-fold higher damage from stem larvae compared to egg cups. Overall, we recommend a combination of larval-inoculated stems and spring egg cups for the primary release strategies of A. neurica and L. geminipuncta as biological control agents of introduced Phragmites. Both methods offer protection from predation and varying degrees of control over phenological mismatches. The release of larval-inoculated stems is a more labour-intensive but highly effective method in terms of initial feeding damage whereas egg cups are a more efficient mass-release method than stems with a lower amount of initial feeding damage per agent released.

Two-spotted Spider Mite, Tetranychus urticae Control on Okra by Portulaca oleracea Extract and Cyperus rotundus Oil

The study determined the effect of alcoholic extract of common purslane, Portulaca oleracea, Java grass, and Cyperus rotundus oil in controlling the two-spotted spider mite on okra plants. The results of laboratory experiments showed the efficiency of purslane alcoholic extract was highly toxic to adult mites, but its effect was limited on eggs. In contrast, Cyperus oil was highly effective against mite eggs and adults. Cyperus oil gave the highest mortality of 86.94%, with significant differences from the purslane extract, where 68.61% mortality was observed and differed significantly from the control treatment. An increase in mortality increased with concentration, and the highest mortality of 95.83% was achieved at 5%, compared to the mortality of 59.58% at 1% treatment. The ovicidal activity was significant after the C. rotundus oil treatment compared to the purslane extract application. Cyperus oil reduced egg hatching by 42.50%. However, purslane extract did not affect the hatching significantly (91.70% hatching) and was not significantly different from the control. In general, the hatching rate decreased with increasing concentration of Cyperus oil and was only 40% at the 5% treatment compared to 60 and 96.70% at 1% treatment and controls, respectively.. KEYWORDS :Biological control, Cyperus rotundus, Insecticidal, Ovicidal, Portulaca oleracea, Tetranychus urticae

Safety of Nicarbazin in Raptors in Relation to Pigeon Eradication Programs

he anticoccidial drug nicarbazin, mixed at a concentration of 800 mg/kg with corn kernels, is marked as Ovistop® and R-12® for the fertility control of pigeons. Nicarbazin is considered “practically non-toxic” when fed to birds and mammals, and the only potential adverse effect in non-target birds is a reduction in egg hatchability.

Nematicidal activity of <i>Ageratum conyzoides</i> leaf extract against root-knot nematode (<i>Meloidogyne javanica</i>) on eggplant in Jalingo, Nigeria

Devastation of crops by pests is exacerbated by human activities but nature provides remedies that are environmentally friendly. This study was carried out to evaluate the activity of A. conyzoides leaf extract against Meloidogyne javanica on eggplant in Jalingo, Nigeria. Three concentrations (crude extract, 5 ml and 10 ml dilutions) of extract of Ageratum conyzoides as well as control (no application) were applied on juveniles and eggs of M. javanica in petri dishes in the laboratory in 2018 and 10 ml of the same extract was applied into holes at the base of eggplants transplanted into a nematode-infested field in 2018 and 2019. Result of the juvenile mortality test showed that the extract treatments caused the mortality of M. javanica juveniles with crudes extract being highest at 90.3%. Results of the egg hatch inhibition test also showed the extract treatments significantly reduced egg hatch compared to control with crude extract having the highest inhibition of 85.5%. Field experiment in both years indicated that the extract treatments recorded significantly (P˂0.05) better result than control in all parameters in both years. There was reduced root galling and nematode reproduction and by extension final nematode population with attendant high yield in extract-treated plants. It is therefore concluded that A. conyzoides has the potential for use as a bio-pesticide against M. javanica.

Comparative biological activity of abamectin formulations on root-knot nematodes (Meloidogyne spp.) infecting cucumber plants: in vivo and in vitro

The root-knot nematodes (Meloidogyne spp.) are considered one of the most destructive diseases in the world. In Egypt, farmers primarily rely on chemical nematicides, which have become costly to control. Currently, abamectin is a bio-based pesticide used as an alternative tool against Meloidogyne spp. on cucumber plants (Cucumis sativus L.). During the current research, four tested abamectin formulations were DIVA (1.8% EW), RIOMECTIN (5% ME), AGRIMEC GOLD (8.4% SC) and ZORO (3.6% EC) compared with two reference nematicides namely, CROP NEMA (5% CS) and TERVIGO (2% SC). The main results showed that, in vitro study elucidated that the most effective formulations of abamectin as a larvicidal were EW with LC50 value of 21.66 µg ml−1. However, in the egg hatching test, the formulations of abamectin SC (2%) and EW were the most effective in reducing egg hatching, with LC50 values of 12.83 and 13.57 µg ml−1. The calculated relative potency values showed diversity depending on the two referenced nematicides. On the other hand, in vivo study, the results indicated that, all tested formulations of abamectin recorded general mean reductions in root galls (23.05–75.23%), egg masses (14.46–65.63%). Moreover, the total population density declined by 39.24–87.08%. Furthermore, the influence of abamectin formulations, in the presence of root-knot nematodes, on the growth of cucumber plants parameters, such as root dry weight, root length, root radius, root surface area, shoot dry weight and shoot height, as well as the content of macro-elements (N, P and K) exhibited varying levels of response.

Sex-dependent effects of biosynthesized nanoparticles on stored bean pests and their non-target parasitoid

The efficacy of green nanotechnology in biological control remains uncertain because of a lack of knowledge of side-effects on natural enemies and sex-dependent effects on target and non-target organisms. To address this issue, we exposed stored bean pest beetles, Callosobruchus chinensis and C. maculatus (Chrysomelidae: Bruchinae), the former infected by endosymbiont Wolbachia, and their non-target parasitoid wasp Anisopteromalus calandrae (Pteromalidae) to six types of fungus-synthesized nanoparticles (NPs): silver (AgNPs), selenium (SeNPs), silicon dioxide (SiO2NPs), copper oxide (CuONPs), titanium dioxide (TiO2NPs) and zinc oxide (ZnONPs). The nanoparticles were applied directly to the adults or indirectly via azuki beans, which served as the oviposition medium for female beetles and the sole resource for beetle larvae.Susceptibility to the nanoparticles varied across species and between sexes. SeNPs decreased the longevity of female A. calandrae, while both SeNPs and AgNPs decreased the longevity of female C. maculatus. Surprisingly, ZnONPs increased the adult longevity of C. chinensis, and SeNPs extended the longevity of male C. maculatus. When the bean surface was treated, SeNPs significantly reduced the fecundity and egg hatchability of C. maculatus, resulting in 35% reduction in emerged adults, while SiO2NPs reduced egg hatchability in both beetle species. Interestingly, none of the nanoparticles negatively impacted C. chinensis adults, likely due to the high abundance of the endosymbiont Wolbachia at this life stage. Overall, our results suggest that biosynthesized SeNPs have potential as an effective alternative insecticide for controlling C. maculatus in storage. However, the nanoparticles can increase the fitness of Wolbachia-infected pests, and also affect biocontrol agents like A. calandrae.

Is UV-C light compatible with biological control of twospotted spider mite?

Biological control agents such as predatory mites, Neoseiulus cucumeris Oudemans, Amblyseius swirskii Athias-Henriot, and Phytoseiulus persimilis Athias-Henriot are effective in the management of a cosmopolitan crop pest, Tetranychus urticae Koch. Studies have shown that physical control by ultraviolet B (UV-B, 280–315 nm) light applications can control T. urticae by reducing egg hatch. However, to have a successful biological control program, the compatibility with other crop management strategies such as use of UV light needs to be determined. Therefore, the objectives of this study were to, 1) assess the impact of UV-C (200–280 nm) application on egg hatchability of biological control agents, A. swirskii, N. cucumeris, P. persimilis, and the pest T. urticae; 2) assess the impact of UV-C application on feeding efficiency of P. persimilis on T. urticae eggs; and 3) determine the LD50 and LD90 of adult female T. urticae to UV-C exposure. Results indicate that more eggs of A. swirskii survived when 200 J/m2 UV-C was used to control T. urticae, which suffered higher egg loss from the same UV-C dose. Also, UV-C treatments of 200 and 350 J/m2 did not have a significant impact on predation by P. persimilis adult females on T. urticae eggs. Therefore, UV-C can be compatibly utilized along with biological control of T. urticae by timing the application before release of predators. After 24 h of application, the UV-C LD50 for T. urticae adults was 8,839.35 J/m2 and the LD90 was 12,352.91 J/m2. After 48 h of application, the LD50 was 7,449.81 J/m2 and the LD90 was 9,621.83 J/m2. These UV-C doses are not feasible for T. urticae adult suppression, but biological control agents can play a crucial role with effective predation on T. urticae adults.

Control of Globodera pallida Using Sinapis alba or 4-Hydroxybenzyl Alcohol with the Trap Crop Solanum sisymbriifolium or the Biofumigant Brassica juncea Seed Meal Extract.

The pale cyst nematode Globodera pallida is a highly specialized, economically important pest for potato production. The specialized hatching requirements, ability to adapt, and the loss of effective control strategies such as methyl bromide fumigation increase the challenge to eradicate G. pallida in Idaho. Without a suitable host, this nematode can remain dormant as encysted eggs in soil for up to 20 years. In this study, we first demonstrated that Sinapis alba seed meal extract (SME) or 4-hydroxybenzyl alcohol (HBA), under laboratory and greenhouse conditions, enhances G. pallida egg hatch rate when exposed to potato root diffusate (PRD). This hatch rate enhancement in the presence of PRD is speculated to be due to an increase in egg-shell permeability. We then tested the efficacy of (i) Solanum sisymbriifolium following prior treatment with S. alba SME (0 and 4.48 t/ha) or HBA (0 and 0.12 t/ha) and (ii) Brassica juncea SME (0, 0.14, 0.56, and 1.12 t/ha) following HBA treatment (0 and 4.48 t/ha) on egg viability, hatch rate, and reproduction of G. pallida encysted eggs. S. sisymbriifolium alone reduced the number of encysted eggs compared to the nontreated control by up to 67%, indicating that this trap crop triggered G. pallida eggs to hatch. When combined with S. alba SME or HBA, S. sisymbriifolium significantly reduced egg count, hatch rate, and viability more than S. sisymbriifolium alone. The combination of S. sisymbriifolium with HBA or S. alba SME eliminated G. pallida reproduction on the susceptible potato. All the tested rates of B. juncea SME alone or with HBA reduced egg hatch rate, viability, and reproduction compared to the nontreated control. Combining HBA and B. juncea SME further significantly reduced egg hatch rate, viability, and reproduction than those rates of B. juncea SME alone.

Developing Wolbachia-based disease interventions for an extreme environment.

Aedes aegypti mosquitoes carrying self-spreading, virus-blocking Wolbachia bacteria are being deployed to suppress dengue transmission. However, there are challenges in applying this technology in extreme environments. We introduced two Wolbachia strains into Ae. aegypti from Saudi Arabia for a release program in the hot coastal city of Jeddah. Wolbachia reduced infection and dissemination of dengue virus (DENV2) in Saudi Arabian mosquitoes and showed complete maternal transmission and cytoplasmic incompatibility. Wolbachia reduced egg hatch under a range of environmental conditions, with the Wolbachia strains showing differential thermal stability. Wolbachia effects were similar across mosquito genetic backgrounds but we found evidence of local adaptation, with Saudi Arabian mosquitoes having lower egg viability but higher adult desiccation tolerance than Australian mosquitoes. Genetic background effects will influence Wolbachia invasion dynamics, reinforcing the need to use local genotypes for mosquito release programs, particularly in extreme environments like Jeddah. Our comprehensive characterization of Wolbachia strains provides a foundation for Wolbachia-based disease interventions in harsh climates.

Mating Competitiveness of Irradiated Lobesia botrana (Lepidoptera: Tortricidae) in Male-Only and Both Sex Release Strategies under Laboratory Cage Conditions

This laboratory study explored the concept of whether irradiated male-only releases are more or equally efficient as releases of both irradiated males and females in the context of using the sterile insect technique/inherited sterility (SIT/IS) for the management of the European grapevine moth Lobesia botrana. The current study examined the mating competitiveness of 150-Gy-treated L. botrana male and female moths or 150-Gy-treated male moths only, with untreated moths in laboratory cages. Our results showed that the release of both sexes significantly increased the competitiveness value (C) and the biological efficiency index (BE) as compared with male-only release, and this was independent of the male to untreated male ratio. Moreover, a single release of 150-Gy-treated and untreated males and females at a 1:1:10:10 ratio (untreated male:untreated female: treated male:treated female) significantly reduced egg hatch, and the number of first-generation offspring (F1) was small. The emergence of F2-moths per untreated F1 male and female moth was low, but these undesired fertile moths should be eliminated in order to achieve effective control. The results presented herein provide useful information on the impact of 150-Gy-treated male-only, versus releases of both treated males and females on untreated moths, which is essential to managing L. botrana populations with SIT/IS.

Efficacy of six essential oils for the management of Meloidogyne incognita in eggplant and their effect on the expression of plant defense genes

Hydrodistilled essential oils from six Egyptian plants were analyzed by gas chromatography/mass spectrometry (GC/MS). The essential oils were tested for their nematicidal activity against Meloidogyne incognita as well as their effect on the expression of defense genes of eggplant. Artemisia judaica oil (LC50 = 37.15 mg/L) had the highest toxicity against second-stage juveniles (J2), followed by Origanum vulgare and Callistemon viminalis oils. Likewise, A. judaica essential oil (IC50 = 15.68 mg/L) caused the greatest reduction in egg hatching and it was three times more active than oxamyl. In greenhouse experiment, the essential oils of A. judaica, O. vulgare and C. viminalis reduced gall and egg numbers per eggplant, and J2 numbers in soil at 500 and 1000 mg/L. Moreover, the essential oils improved the growth of eggplant and increased the expression of eggplant defense genes, chitinase, thaumatin-like proteins, and polyphenol oxidase, compared with control. The information obtained from this study suggests that the essential oils of A. judaica, O. vulgare and C. viminalis have a potential to be used for the management of M. incognita.