Search Results (88)

Tetranychus urticae is a highly destructive, polyphagous mite that has developed resistance to multiple acaricides, necessitating the evaluation of new compounds. Isocycloseram is a novel insecticide with potential to control this mite; the effects of its sublethal concentrations are still uninvestigated. In this study, an age-stage, two-sex life table model was used to evaluate the sublethal effects of isocycloseram concentrations (LC₁₀ and LC₃₀) on population growth, reproduction, and development of the two-spotted spider mite. The results showed that the LC₁₀ and LC₃₀ values were 0.012 mg/L and 0.022 mg/L, respectively. Sublethal concentrations of LC₁₀ significantly affected population growth by reducing fertility, while LC₃₀ significantly prolonged the immature stage and reduced average fecundity by 37%. With the LC₃₀ treatment, the net reproductive rate R₀ decreased by 43%, and the intrinsic rate of increase r decreased significantly, from 0.152 day⁻¹ to 0.117 day⁻¹. The doubling time DT was extended by 30%, from 4.55 days to 5.92 days. This study covers the importance of life table analysis for investigating sublethal effects and for ensuring that, when isocycloseram is incorporated into integrated pest management, both its direct toxicity and its effects on population dynamics are considered. Full article

The two-spotted spider mite, Tetranychus urticae, poses significant agricultural challenges due to its rapid population growth and high capacity for developing chemical resistance. This study evaluated the acaricidal activity of bacterial strain TAM1, isolated from naturally deceased mites in Taiwan. In bioassays, TAM1 caused over 90% adult mite mortality within 48 h. Infected mites showed symptoms of body darkening and deformation of the ventral abdominal crest lines. Enzymatic analysis confirmed significant chitinase and gelatinase activities. Whole genome sequence of TAM1 was acquired with a 5,066,903 bp circular chromosome (CP120954) and a 164,574 bp circular plasmid (CP120955). Refined functional profiling identified a sophisticated enzymatic arsenal including core chitin-active families (GH18, GH20, AA10) and 157 proteases, with a high prevalence of metallopeptidases that correlate with the detected gelatinase activities. Secretome analysis predicted 42 extracytoplasmic proteases primarily utilizing the Sec-dependent pathway, while the presence of multiple CBM50 modules suggests a potential for targeted substrate anchoring. These genomic insights provide a plausible molecular basis for the observed enzymatic potential and the localized ultrastructural disruption of the T. urticae cuticle. The alignment between phenotypic observations, microscopic evidence, enzymatic activities, and genomic data suggests that TAM1 utilizes synergistic, multi-target mechanisms to exert its acaricidal effects. Based on analyses of whole-genome sequence and 16S rRNA gene sequence, TAM1 was tentatively designated as a strain of Kosakonia sacchari. The bacterial strain reported here represents a promising microbial agent for integrated pest management (IPM) programs. Full article

Chemical pesticides are indispensable for protecting crops from pests and supporting a stable food supply; however, their environmental impacts have raised growing concerns. This has driven efforts to develop alternative, lower-impact pesticides and technologies for sustainable agriculture. Vinegar, a natural and eco-friendly option, has been used to protect plants from pests and diseases. Here, we investigated the effects of acetic acid, the main component of vinegar, on host selection by spider mites using a common bean (Phaseolus vulgaris)-two-spotted spider mite (Tetranychus urticae) system. The results indicated that spider mites avoided acetic acid-treated plants, with plant volatiles influencing their preference. Volatile organic compound (VOC) analysis revealed that acetic acid treatment altered VOC composition. Although changes in the levels of compounds such as (E)-2-hexenal and 1-octen-3-one contributed to this shift, individual testing showed that unrealistically high concentrations were required to repel spider mites. This suggests that the effect of acetic acid treatment is not primarily due to the induction of specific VOCs, but rather to an overall alteration of VOC composition. These findings highlight the potential of vinegar as an eco-friendly pest management strategy, although further studies are needed to evaluate its long-term efficacy and impact on crop protection under field conditions. Full article

The two-spotted spider mite, Tetranychus urticae Koch, is a major agricultural pest that causes economic losses in the cultivation of most crops worldwide. Pesticide resistance and the phase-out of many active pesticidal substances have accelerated research into alternative methods for pest management. The effects of light-emitting diodes (LEDs) on plants, as well as their potential use in pest management, have attracted the attention of researchers for the last 25 years. In this study, the repellent effects of UV-A, blue, and red LEDs on T. urticae were investigated using choice tests in laboratory conditions. The lethal effect of red LED light on adult individuals was determined by a no-choice test. Importantly, red LED caused 67.0 ± 4.5% (mean ± SE) mortality in adults in the no-choice test. Second, the UV-A LED clearly had a strong repellent effect on T. urticae in the choice tests. In the “UV-A vs. white LED” and “UV-A vs. darkness” choice tests, the egg-laying percentage in the UV-A part remained below 0.55%. Furthermore, UV-A also had a significant repellent effect on T. urticae larvae. In the choice tests, the larval ratio in the UV-A part was less than 5%. The results of laboratory experiments indicated that red and UV-A LEDs have significant lethal and repellent effects on T. urticae. Comprehensive investigations should be performed in greenhouses using different strategies to optimize how these potential effects can be used in pest management. Full article

The two-spotted spider mite, Tetranychus urticae Koch, is a major arthropod pest that causes substantial economic losses in strawberry and other crops worldwide. Its management often relies on intensive acaricide applications, which may negatively affect human health, the environment, and beneficial organisms. Biological control using predatory mites has been widely adopted under greenhouse conditions, and its success is influenced by several factors, particularly temperature, T. urticae population density, and predator release methods. During the 2023–2024 season, this study evaluated the effects of ambient greenhouse temperature on the population dynamics of T. urticae and on the efficacy of two phytoseiid predators, Phytoseiulus persimilis (Athias-Henriot) and Amblyseius swirskii (Athias-Henriot). The predators were released individually and in combination on strawberry plants. The efficacy of single and combined releases was assessed under three temperature ranges: 25–27 °C, 28–30 °C, and 30–32 °C. The results showed that the mean number of motile T. urticae per plant increased from 21.7 to 95.66, while the mean number per leaf increased from 2.33 to 6.05 during the experimental period. The mean greenhouse temperature ranged from 23.83 °C to 31.88 °C. Temperature was strongly and positively correlated with T. urticae population density, with higher temperatures generally accelerating development and population growth. Both predator species, whether released individually or in combination, significantly reduced T. urticae populations compared with untreated control plants. Amblyseius swirskii demonstrated greater efficacy than P. persimilis at temperatures above 28 °C. However, the combined release consistently achieved the highest level of mite suppression across all temperature ranges. Significantly greater population reduction was observed at approximately 25–26 °C compared with single-species releases, while maximum effectiveness occurred at temperatures above 28 °C. These findings indicate that the combined use of P. persimilis and A. swirskii represents an effective biological control strategy for managing T. urticae in greenhouse-grown strawberries, particularly under elevated and fluctuating temperature conditions. Full article

Hemp (Cannabis sativa L.) is an important crop, yet little is known about how herbivory and soil microbial communities interact to influence plant performance. In this study, two hemp cultivars, BaOx and Cherry Citrus, were grown under identical greenhouse conditions and exposed to naturally occurring background populations of the two-spotted spider mite (Tetranychus urticae). Plant traits were measured, and rhizosphere soil was sampled for 16S rRNA gene sequencing to compare bacterial community composition and diversity between cultivars. Spider mite injury was assessed using a standardized 0–5 visual damage scale commonly applied in integrated pest management studies. Although the cultivars did not differ significantly in growth traits, Cherry Citrus experienced significantly less spider mite damage than BaOx, suggesting greater tolerance or resistance to herbivory under shared conditions. Rhizosphere bacterial communities differed markedly between cultivars despite identical soil and environmental conditions. BaOx rhizospheres were enriched in Actinobacteria, including taxa associated with decomposition and antimicrobial compound production, whereas Cherry Citrus rhizospheres were enriched in Alphaproteobacteria, particularly nitrogen-cycling and root-associated taxa such as Rhizobium and Reyranella. Alpha diversity metrics did not differ between cultivars; however, beta diversity analyses revealed significant cultivar-level separation, particularly in phylogenetic community structure. Because herbivore pressure and microbial communities were not experimentally manipulated, this observational study identifies ecological associations rather than direct causal relationships. Nevertheless, the results demonstrate that hemp cultivar identity is associated with distinct rhizosphere microbiomes and differential susceptibility to spider mite damage. These findings highlight the potential for integrating cultivar selection and microbiome-informed strategies into sustainable pest management programs for hemp. Full article

Banker plants are non-crop plants that sustain populations of biological control agents prior to pest outbreaks, offering a preventive strategy within integrated pest management (IPM). Their benefits have primarily been attributed to top-down regulation via natural enemy-mediated pest suppression; however, their potential bottom-up effects remain largely unexplored. Here, we show that airborne cues emitted from banker plants infested with the zoophytophagous mirid bug Nesidiocoris tenuis altered the performance of the two-spotted spider mite Tetranychus urticae on neighboring tomato plants Solanum lycopersicum. Exposure to airborne cues from infested sesame Sesamum indicum significantly reduced mite fecundity, whereas those from tomato and spider flower Cleome hassleriana had no detectable effect, indicating that the induction of crop resistance is dependent on banker plant species. Moreover, T. urticae infestation of banker plants consistently suppressed mite oviposition on neighboring tomato plants across all banker plant species tested. These findings suggest that banker plants can exert previously unrecognized bottom-up effects by modulating crop resistance-related responses through airborne cues. Therefore, selecting banker plant species that emit effective airborne cues may strengthen crop protection and stabilize biological control performance in sustainable IPM strategies. Full article

Species sharing the same trophic level can interact not only through competition for resources but also through intraguild predation (IGP). Therefore, an important step toward implementing successful multiple predator releases in biological control strategies requires resolving how predators respond to the presence of heterogeneous competitors. This study examined the compatibility of two predatory mites, N. californicus and P. persimilis, which are both widely employed to suppress two-spotted spider mite populations in greenhouses and open fields. The experiments quantified the frequency and intensity of IGP across different developmental stages of these species on bean leaves, considering scenarios both with and without their shared prey being present. Additionally, a Y-tube olfactometer was employed to assess whether either predator avoided prey patches previously occupied by other heterospecifics, thereby providing insights into potential chemical cues that influence predator behavior. The results revealed that adult females of both predatory mite species predominantly targeted heterospecific eggs and larvae, whereas adults were largely avoided. In the absence of shared prey, N. californicus attacked 83% of the P. persimilis larvae and 37% of the eggs, whereas P. persimilis consumed 67% of the N. californicus eggs. The presence of shared prey reduced IGP risk by approximately 60%. Olfactometer assays revealed no significant avoidance of plants inhabited by heterospecifics at densities of 20 or 40 adults; both predators were similarly attracted to herbivore-induced volatiles. Generalized linear models indicated that host plant experience had a significant influence on the foraging response of N. californicus, whereas the effects of the feeding state weakened over time. Understanding predator foraging plasticity and responsiveness to chemical cues can help optimize biological control strategies in complex agroecosystems. Full article

The two-spotted spider mite, Tetranychus urticae Koch, is a major agricultural pest whose control is increasingly constrained by resistance to synthetic acaricides. This study evaluated the long-term field efficacy of three commercial entomopathogenic fungal (EPF) biopesticides—Velifer^® (Beauveria bassiana), Metab^® (B. bassiana + Metarhizium anisopliae), and Botanigard^® (B. bassiana)—against larval and protonymph stages of T. urticae on two host plants, Italian cypress (Cupressus sempervirens) and sweet orange (Citrus sinensis). Two foliar applications were conducted during the 2023 growing season (25 May and 25 July), and mite populations were monitored for 140 days after the final application. A randomized complete block design was used, and efficacy was calculated using the Henderson–Tilton formula. All EPF treatments significantly reduced mite populations compared with the untreated control throughout the monitoring period. Velifer consistently achieved the highest suppression of larval populations, particularly on C. sinensis, with efficacy comparable to the chemical standard. Botanigard showed more gradual but sustained population reduction over time, whereas Metab exhibited lower but stable efficacy in all cases. Treatment performance was strongly influenced by host plant species and mite developmental stage, with larvae consistently more susceptible than protonymphs. On C. sinensis, Velifer achieved the highest larval suppression (84.6%), comparable to the chemical standard abamectin, while Botanigard and Velifer were most effective on C. sempervirens. Survival analysis confirmed isolate- and host-dependent differences in hazard effects over time. These results demonstrate that EPF-based products can provide sustained, long-term suppression of T. urticae under field conditions, supporting their integration into integrated pest management programs. Full article

Induced resistance in plants is a promising strategy for pest management, helping to reduce dependence on synthetic pesticides. However, no study has yet examined the interaction between Tetranychus urticae and Aronia melanocarpa, including host acceptance, performance, and antioxidant defence mechanisms. In this study, host acceptance of T. urticae was evaluated using two A. melanocarpa ecotypes: a non-cultivar (AMe) and the cultivated variety ‘Galicjanka’ (AGe). Leaf morphological traits (trichome density and length) and key life-history parameters of the mite (fecundity, egg development time, and larval duration) were assessed. Mite feeding effects on oxidative stress markers (hydrogen peroxide—H₂O₂; thiobarbituric acid reactive substances—TBARS) and antioxidant enzyme activity (guaiacol peroxidase—GPX ascorbate peroxidase—APX) were analysed by ecotype and infestation duration. Results showed low fecundity and prolonged development, indicating that neither ecotype is a preferred host for T. urticae. Ecotype-dependent differences in acceptance and mite performance suggest that variation in trichome density and biochemical traits may influence susceptibility. Baseline differences in H₂O₂ and TBARS imply a role in constitutive resistance, while their induction, accompanied by increased GPX and APX activity, highlights oxidative stress and antioxidant defences as key components of A. melanocarpa responses to mite attack. Full article

The growing resistance of Tetranychus urticae to chemical pesticides highlights the need for alternative solutions for its sustainable control. To develop botanical acaricides and reduce the usage of chemical pesticides, this study assessed the acaricidal activity of AB extract and its combinations with four commercial insecticides: imidacloprid (IMI), acetamiprid (ACE), thiamethoxam (TMX), and bifenthrin (BF). Results showed that the AB extract suppressed detoxification enzymes and downregulated their corresponding genes in T. urticae. Bioassays identified hyoscyamine and genistein as key bioactive compounds. Field trials revealed that treatments with AB + IMI, AB + TMX, and AB + BF significantly enhanced the corrected efficacy against T. urticae compared with AB treatment, with the highest corrected efficacy observed for AB + BF. Notably, the AB + BF treatment did not influence the stability of the natural enemy community, as indicated by the characteristic indices of the natural enemy community, which suggests that the integration of AB extract with BF may represent a sustainable pest management strategy. Therefore, the AB extract represents an environmentally benign alternative to chemical pesticides for the sustainable control of T. urticae. Full article

The two-spotted spider mite, Tetranychus urticae, is a global pest with increasing resistance to conventional acaricides, prompting the search for sustainable alternatives. Essential oils (EOs) are promising botanical biocides due to ecological safety and multitarget action. We evaluated lethal and sublethal effects of EOs from Alpinia zerumbet and Mesosphaerum suaveolens against T. urticae. Oils were obtained by hydrodistillation and characterized by GC–MS (major constituents: A. zerumbet—1,8-cineole 14.05%, sabinene 12.6%; M. suaveolens—β-sabinene (predominant), spathulenol 12.28%, 1,8-cineole 11.01%). In adult bioassays, M. suaveolens was more toxic (LC₅₀ = 4.24 µL mL⁻¹), whereas A. zerumbet showed LC₅₀ = 8.74 and LC₉₀ = 46.24 µL mL⁻¹. In ovicidal assays at LC₉₀, egg viability declined to 2% with A. zerumbet versus 57% with M. suaveolens. Repellency at sublethal concentrations (LC₂₀–LC₃₀) was high for both oils (≥75%) and exceeded 90% for M. suaveolens. Both oils suppressed population growth (instantaneous rate r_i reduced from 0.5848 in the control to 0.4746–0.5155 under treatments). PCA confirmed lethal concentration and repellency as the main discriminators among treatments. These data demonstrate the multitarget potential of A. zerumbet and M. suaveolens EOs as botanical acaricides for sustainable management of T. urticae. Full article

Hemp (Cannabis sativa L.) cultivation in the United States has expanded rapidly over the past decade. Due to federal and state regulations, only a limited number of studies have examined the chemical options available for controlling pests on C. sativa. In the U.S., two of the most important species of arthropod pests affecting C. sativa are the beet leafhopper Circulifer tenellus Baker (Hemiptera: Cicadellidae) and the two-spotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae). This study evaluated the effects of four biopesticides, Chromobacterium subtsugae, Burkholderia spp., Chenopodium ambrosioides, and azadirachtin, under greenhouse conditions against C. tenellus adults and nymphs and T. urticae adults. Biopesticides were applied to foliage using a calibrated hand sprayer. To evaluate the biopesticides’ potency, C. tenellus adults, nymphs, and mites were released 1 h after treatment; to evaluate the residual efficacy, they were released 7 days after treatment (DAT). In both experiments, C. tenellus adults, nymphs, and mites were counted 1, 3, and 7 days after release. Our results indicate that Burkholderia spp. exhibited the highest efficacy against C. tenellus adults at 7 DAT, whereas C. ambrosioides and azadirachtin caused the greatest nymphal mortality at 1 and 3 DAT, respectively. Our results show that Burkholderia spp. had the greatest potency against C. tenellus adults 7 DAT, while C. ambrosioides and azadirachtin highly affect the mortality of nymphs at 1 and 3 DAT, respectively. Treatments with C. subtsugae and C. ambrosioides showed high potency against T. urticae. Finally, C. subtsugae showed the lowest residual effect against the mite pest. The data presented in this article will add to the arsenal of information to improve the current management strategies used against these two hemp pests. Full article

The two-spotted spider mite (Tetranychus urticae Koch) (Acari: Tetranychidae) is one of the most widespread and destructive phytophagous mite species, occurring across all climatic zones worldwide. Currently, the control of spider mites in crop protection relies primarily on chemical acaricides. However, the selection of resistant populations to their active ingredients is reducing their efficacy. The aim of the present study was to assess the susceptibility of T. urticae to a native isolate of entomopathogenic nematodes, Steinernema feltiae Filipjev ZWO21, under laboratory conditions. The experiment was conducted using Petri dishes, each containing 22–28 adult T. urticae. Infective juveniles (IJs) of the nematodes were then applied at a dose of 8000 IJs per dish (±300 IJs per mite). Petri dishes with mites treated with nematodes were placed in a Sanyo incubation chamber at 25 °C and 60% relative humidity. After three days, dead mites were collected from the Petri dishes and dissected, and mortality was subsequently determined. The present study confirmed that the S. feltiae ZWO21 isolate exhibited considerable potential for the biological control of T. urticae, causing 37.5–83.3% (mean 57.0%) mortality in this pest species. Although this result indicates a moderate efficacy when nematodes are applied alone, it also underscores the relevance of further research into their integration with other control strategies, including acaricides, within integrated pest management (IPM) programmes. Full article

The two-spotted spider mite, Tetranychus urticae, is one of the polyphagous pests of several crops and forestry, resistant to numerous conventional chemicals. Due to the negative side effects of harmful chemical pesticides, such as environmental pollution, and risks to human health, the introduction of effective and low-risk alternatives is essential. The promising pesticidal effects of essential oils (EOs) isolated from Artemisia annua have been documented in recent studies. In the present study, the acaricidal effects of an A. annua EO, along with its two dominant monoterpenoids, 1,8-cineole and camphor, were investigated against adults of T. urticae. Artemisia annua EO, 1,8-cineole, and camphor, with 24 h-LC₅₀ values of 0.289, 0.533, and 0.64 µL/L air, respectively, had significant toxicity by fumigation against T. urticae adults. Along with lethality, A. annua EO and monoterpenoids had significant inhibitory effects on the activity of detoxifying enzymes, including α- and β-esterases, glutathione S-transferases, and cytochrome P-450 monooxygenase. According to the findings of the present study, A. annua EO and its two dominant monoterpenoids, 1,8-cineole and camphor, with significant toxicity and inhibitory effects on detoxifying enzymes, can be introduced as available, effective, and eco-friendly acaricides in the management of T. urticae. Full article