Journal of Pest Science最新文献

The corn leafhopper, Dalbulus maidis (Hemiptera, Cicadellidae), is an important pest of maize in Latin America, transmitting plant pathogens that impact grain production. Recently, mycopesticides have been considered as an alternative for the biological control of D. maidis populations, but there is controversy surrounding the efficacy of these products. We assessed the susceptibility of D. maidis to invertebrate-pathogenic fungi and, for the first time, investigated the protective role of the protein-lipid coat of brochosomes on the insect integument as a barrier against infections. Adult mortality was lower than 35% seven days after exposure to maize plants sprayed with water + surfactant-based conidia suspensions of 31 fungal strains from three different genera (Beauveria, Cordyceps and Metarhizium). Direct application of conidia suspensions on adults did not increase significantly the mortality rates when compared to adults exposed to contaminated surfaces. Conidia in water + surfactant readily adhered and germinated on detached forewings of D. maidis from which brochosomes were removed, but wings coated with this protein-lipid layer repelled droplets. Dry conidia easily adhered to brochosome-coated wings and their germination was not affected, although the methodical self-cleaning behavior of the adults effectively dislodged most conidia (either in suspensions or as a dry powder) from insect’s body after treatment. In conclusion, brochosomes and self-cleaning together efficiently prevent adhesion of conidia to D. maidis cuticle, serving as important barriers against fungal invasion and decreasing insect mortality. Our study highlights the importance of combining mycopesticides with effective adjuvants in spray applications to enhance infection rates and successfully control D. maidis populations.

Plants face an array of insect herbivores and have evolved complex defense approaches against various insect feeding strategies. However, little is known about how plants respond to successive attacks by herbivores with different feeding modes and coordinate their diverse defense mechanisms. In this study, we unveil that inducible jasmonic acid (JA) accumulation in response to leaf-chewing insects augments plant resistance and repellence to sequential leaf-chewing insect (caterpillar) and phloem-feeding insect (whitefly) infestations. Conversely, constitutive and whitefly inducible salicylic acid (SA) accumulation exclusively bolsters defense against later-stage whitefly invasion. Through assessments of herbivore performance and preferences on wild-type, JA-deficient, and SA-deficient plants, we show that JA/SA levels regulate plant resistance to both initial and sequential herbivores. Notably, JA or SA accumulation due to caterpillar or whitefly attacks does not substantially affect constitutive levels of the other compound, despite their antagonistic crosstalk. Furthermore, exogenous JA application in tobacco elicits efficient defense against successive caterpillar and whitefly assaults, surpassing SA's efficacy, albeit with associated growth penalties. Our discoveries demonstrate that plants can tailor their defense strategies against initial and sequential insects with different feeding modes. This customized defense is facilitated by JA/SA responses and their intricate cross-talk while taking account of the growth-defense trade-off.

Moutan Cortex essential oil (MCEO) is considered to be a promising botanical insecticide. However, like most oils, MECO has several limitations, including instability and poor solubility. Nanoencapsulation technology is an excellent strategy for stabilizing essential oils because of its controlled release, enhanced efficacy, and strengthened biological activity. The present study investigated the acaricidal efficacy of pure MCEO and its encapsulated nanoemulsion (NE) and mesoporous silica nanoparticles (MSNs) against the house dust mite Dermatophagoides farinae using contact bioassays, fumigant bioassays, repellent bioassays, and the observation of toxic symptoms. MCEO-MSNs obtained in the study successfully encapsulated MCEO with an encapsulation efficiency of 63.83%. The acaricidal mortality experiments revealed that MCEO-NE and MCEO-MSN showed more significant toxicity against D. farinae than did pure MCEO. The nanomaterials showed better larvicidal and nymphicidal activities than pure MCEO at a high concentration (12-h LC₉₀). Notably, the repellent effect experiment showed that MCEO-NE and MCEO-MSN had long-term and stable repellent effects on D. farinae, indicating the sustained release and persistence of the nanomaterials. More toxicity symptoms were observed in the IM-type group than in the KD-type group, suggesting that the MCEO nanoparticles have adverse effects on the respiratory system. Nanomaterials and MCEO promoted superoxide dismutase (SOD) activity and inhibited acetylcholinesterase (AChE) activity in D. farinae. In addition, the binding sites of paeonol to SOD and AChE were found through molecular docking. These findings demonstrate the potential of MCEO as a biological acaricide, which merits further investigation.

Spodoptera frugiperda is a newly invasive pest in China, often sharing the same feeding niche with native S. exigua. To clarify the competitive displacement, colonization and potential threat to crops by S. frugiperda, the cannibalism and predation behavior, feeding preferences, development and reproduction of both species under laboratory conditions, as well as the population dynamics and damage to maize plants in the field, were studied. Results found that food scarcity intensified interspecific predation between S. frugiperda and S. exigua, but the survival rate of 4th instar S. frugiperda was not significantly influenced (> 93%; P > 0.05). Although S. frugiperda exhibited less aggressive behaviors, its cannibalism coefficient and attack intensity were significantly higher than those of S. exigua (P < 0.05). Moreover, S. frugiperda showed a higher feeding preference for mechanically lethal insects when the maize leaf supply was insufficient. Additionally, a combined diet of maize leaves and lethal insects significantly increased their pupal weight and fecundity (P < 0.05). Field trials showed that when S. frugiperda and S. exigua co-occurred, the population of S. frugiperda at mature stage was similar to that after the intraspecific treatment, and seriously damaged maize plants. These results suggested that interspecific predation by S. frugiperda on S. exigua not only conferred an obvious advantage, but may also promote its development and reproduction, and facilitated its colonization in the invaded area. Our results provide an understanding of the rapid colonization mechanisms of S. frugiperda and will assist development of integrated management strategies.

Tomato chlorosis virus (ToCV) causes widespread infections in tomatoes globally, rapidly spreading in China is closely associated with the dominant whitefly, Bemisia tabaci (Gennadius) Mediterranean (MED). Viruliferous whiteflies have been reported to have shown preference for healthy tomato plants and thus greatly facilitate the spread of this virus. However, the mechanism underlying the change in the host selection behavior is yet unknown. We studied the effects of ToCV infection on the volatile emissions of tomato plants to determine the main volatiles associated with host selectivity by B. tabaci MED. Gas chromatography mass spectrometry (GC-MS) analyses revealed that ToCV infection significantly altered concentrations of 11 volatile compounds. Notably, the attractive p-ethylacetophenone, decreased, while the repellent butylated hydroxytoluene increased. RT-qPCR showed significant expression changes in 10 odorant binding protein (OBP) genes and 11 chemosensory protein (CSP) genes in viruliferous whiteflies compared to non-viruliferous whiteflies. RNA interference indicated that silencing OBP-17 or CSP-1 triggered a strong repellent response from B. tabaci toward tomatoes. Furthermore, OBP-17 expression rose notably with p-ethylacetophenone exposure, with both OBP-17 and CSP-1 exhibiting strong binding affinity for this compound, having dissociation constants of K_{D OBP-17} = 17.24 µmol/L and K_{D CSP-1} = 15.02 µmol/L, respectively. In conclusion, our study revealed dual effects of ToCV on its vectoring whitefly as well as its host plant, which together facilitate the spread of the virus. This novel insight into the epidemiological mechanisms of insect-vectored plant viruses may help to develop new strategies to control these exceedingly important agricultural pests.

The fall armyworm, Spodoptera frugiperda, is a polyphagous pest in the Americas and a target of Bt crops. A study from 2011-2013 demonstrated practical resistance of S. frugiperda to Cry1F maize in the southeastern coastal region of the U.S. In this study, diet-overlay and leaf tissue bioassays were conducted to determine the susceptibility to four common Bt proteins in maize (Cry1F, Cry1A.105, Cry2Ab2, and Vip3Aa) in 23 S. frugiperda populations collected during 2021-2022 from seven southern U.S. states, including nine populations from the southeastern coastal region. In the diet-overlay bioassays with Cry1F, 22 populations were equally or more susceptible than a susceptible reference, with a single population showing an increased susceptibility ratio (LC₅₀ of field population/LC₅₀ of the susceptible strain) of 1.97. Susceptibility ratios of the 23 populations ranged from <0.15 to 4.67 for Cry1A.105 and <0.12 to 5.04 for Vip3Aa. Three populations exhibited an LC₅₀ >tenfold greater than the susceptible strain to Cry2Ab2. Altogether, the study did not provide evidence of practical resistance in S. frugiperda to the four Bt proteins. Instead, the results show that the recently collected populations were susceptible to Cry1F, Cry1A.105, and Vip3Aa. The Bt susceptibility was consistent across geographical locations and host plants. Results from the leaf tissue assays confirmed the findings of the diet-overlay bioassays. The reversed Cry1F susceptibility in S. frugiperda identified in this study represents the first case of documented practical resistance reverting to susceptible status in Bt crop-insect systems and thus has important implications for resistance management.

The Sterile Insect Technique (SIT) is a system based on the release of millions of sterile insects to prevent the reproduction of specific pest populations. However, to improve the efficacy of the SIT, sterile males must reach sexual maturity before being released to increase their probability of mating with wild females. Treatments with juvenile hormone (JH) analogs, such as pyriproxyfen (PPF), accelerate sexual maturity in sterile Anastrepha ludens (Loew) (Diptera: Tephritidae) males. We hypothesized that speeding up this life-history trait can affect male resistance to stressors such as chilling and starvation. In this study, we compared some quality control parameters of flies of two different strains, selected to resist desiccation (DR) and non-selected flies (NS), treated with PPF, and subsequently exposed to starvation and pre-release chilling periods. We used males that were treated with PPF after emergence. The results showed that, from 4 to 6 days of age, DR PPF-fed males mated less than NS PPF-fed males. DR and NS males obtained a similar number of copulations at 7 days of age. After chilling, survival was higher in DR than in NS males. In addition, NS males showed a slight advantage in number of copulations when they reached 5 days of age but not at 6 and 7 days of age. Chill-coma recovery time was longer in PPF-fed flies than in control flies. Moreover, PPF-fed flies obtained less copulations after exposure to chilling at 5 days of age compared to non-chilled flies. These results indicate that sexual maturity is accelerated in PPF-fed males, especially in NS flies. However, using PPF as a pre-release treatment for A. ludens results in a reduction in male quality, regardless of whether they are DR or NS.

Exotic natural enemies that are imported to control a target pest may attack non-target species or disrupt the performance of other natural enemies of the target that are already present. We evaluate possible interactions between three parasitoid species, the native Telenomus nizwaensis and the imported Trichogramma brassicae and Trichogramma evanescens, when presented with Deudorix livia host eggs under high-density laboratory conditions. Deudorix livia is a butterfly which is an economically damaging pest in the Omani pomegranate agro-ecosystem. Most (73.5% overall) of the observed parasitism was by T. nizwaensis. It performed best when presented with host eggs in the absence of either of the Trichogramma species. These imported species thus have some potential to disrupt suppression of the pest by the indigenous natural enemy under lower-density conditions in the field, and neither of them achieved high parasitism rates themselves (laboratory conditions: T. brassicae = 12.5%; T. evanescens = 18.5%; with no evidence for any parasitism of field-collected eggs). Future efforts in this agro-ecosystem would best be directed towards encouraging T. nizwaensis, rather than towards importation of Trichogramma. Screening for negative effects of natural enemies on the pest suppression provided by other natural enemies is recommended.

In this study, the objective was to develop a long-lasting mosquito repellent textile by synthesizing silk-based lavender oil microcapsules and applying them to cotton fabric. Lavender oil, derived from Lavandula angustifolia, was chosen as the plant-based material. The microcapsules’ morphology and the fabric’s surface were examined using optical and scanning electron microscopes. Dynamic light scattering was utilized to measure the capsule size and zeta potential. The mosquito repellent efficacy was evaluated through cage tests before and after multiple wash cycles and after exposure to different environments. A cytotoxicity assay was conducted on functionalized fabrics in order to assess their biocompatibility. Additionally, comfort properties such as breathability and water absorbency were assessed and compared to a control fabric. The results indicated that a higher concentration of lavender oil microcapsules (15 wt%) on the fabric exhibited excellent mosquito repellent efficacy (95.7%) prior to washing, which remained effective as 84.5% even after 40 washes. Furthermore, the functionalized fabric maintained its repellent properties following exposure to temperatures of 25 °C and 37 °C for 4 weeks. The cytotoxicity results indicated that the functionalized fabric exhibited non-toxic properties toward L929 cells, thereby confirming its favorable biocompatibility. This study successfully demonstrated the synthesis and application of silk-based lavender oil microcapsules on textiles, resulting in highly durable mosquito repellent fabrics effective against Aedes aegypti mosquitoes. These findings highlight the potential of this eco-friendly approach for developing effective and long-lasting mosquito repellent textiles.

While symbiont infections in invertebrates are widespread, their role in protecting hosts against natural enemies and chemical insecticides remains incompletely understood. Our study investigates the protective effects of Arsenophonus and Wolbachia, either individually or in co-infection, on Nilaparvata lugens against chemical insecticides. Our findings reveal that both Arsenophonus and Wolbachia confer protection against chemical insecticides, including triflumezopyrim, nitenpyram, and dinotefuran. However, these symbionts do not show protective effects against pymetrozine. Wolbachia infection leads to the up-regulation of the glutathione S-transferase (GST) gene GSTm2 and the P450 gene CYP6AY1. Uniquely, co-infection results in the up-regulation of the P450 gene CYP18A1. Furthermore, the stability of the co-infection is not constant, with its frequency decreasing from 93.3 to 73.1% over a nine-generation passage, while single infections remain consistently high (> 95%). Our study suggests that Wolbachia and Arsenophonus, both individually and in co-infection, provide protection against two commonly used chemical insecticides in N. lugens.