Sap-sucking Pests Research Articles

An integrative strategy used by the aphid Uroleucon formosanum to counter host sesquiterpene lactone defense: Insights from combined genomic and transcriptomic analysis.

Insect herbivores adapt and develop strategies to counteract plant chemical defenses. The aphid Uroleucon formosanum is a serious sap-sucking pest that infests lettuces containing toxic sesquiterpene lactones (STLs). Herein, we employed a combination of genome sequencing and RNA-seq transcriptome profiling to understand the mechanisms underlying phytotoxin tolerance in U.formosanum. We generated the first chromosome-level genome assembly for U.formosanum, with a total size of 453.26Mb and a scaffold N50 of 33.22Mb. Comparative genomic analyses revealed an enrichment of signals for positive selection and gene family expansion in immune-related pathways. Specifically, the expanded set of heat shock protein70 (HSP70) genes showed upregulation after treatment with lactucin, suggesting that they may play a role in the immune response against STLs. The expression of takeout-like genes and cuticle-associated genes was also significantly increased in the lactucin-treated samples. Additionally, 53 cytochrome P450 monooxygenase, 30 carboxylesterase, 19 glutathione S-transferase, 32 uridine diphosphate glycosyltransferase and 63 ATP-binding cassette (ABC) transporter genes were identified in the U.formosanum genome. CYP4C1, CYP6A13 and 7 ABC genes were strongly upregulated in response to lactucin treatment, indicating the involvement of detoxifying enzymes in the tolerance of U.formosanum to STLs. Our findings suggest that the cuticle barrier, immune response and enzyme-mediated metabolic detoxification jointly enhance the tolerance of U.formosanum to phytotoxins and promote its adaptation to host plants. This study presents a valuable genomic resource and provides insights into insect adaptation to plant chemical challenges and future technological developments for pest management.

Side effects of semi-synthetic insecticide spinetoram on the whitefly parasitoid Encarsia formosa.

Insecticide risk assessment for biological control agents is essential for implementing integrated pest management (IPM) programs. Spinetoram is a naturally derived insecticide used to control a variety of agricultural sap-sucking insect pests, and Encarsia formosa Gahan (Hymenoptera: Aphelinidae) plays a key role in the biocontrol of greenhouse whiteflies. Despite its presumed safe ecotoxicological profile, the side effects of spinetoram on E. formosa are partially unknown, especially at sublethal doses. In the laboratory, we estimated the lethal concentrations (LC) of spinetoram on E. formosa by topical exposure of pupae and 48 h residual contact exposure of emerged adults. Afterwards, we assessed the impact of spinetoram LCs on the life history traits (juvenile development, adult longevity, parasitism, adult emergence) and population growth parameter (the instantaneous rate of increase, ri) of the parasitoid. Probit analysis allowed the estimation of LC10 = 0.10 mg/L, LC50 = 0.56 mg/L, and LC90 = 3.28 mg/L. Spinetoram at LC10 had no impact on the observed parameters of E. formosa. Conversely, spinetoram at LC50 and LC90 significantly reduced adult longevity by 19.2% and 40.6%, total parasitism by 33.4% and 38.7%, and total adult emergence by 29.6% and 39.1%, respectively. Also, the ri of E. formosa was significantly affected by spinetoram LC50 and LC90 with a reduction of 8.17 and 29.83%, respectively. Our results suggested that spinetoram significantly threatens the effectiveness of E. formosa when applied at the field recommended rate. However, further validation of spinetoram under greenhouse conditions is required for a comprehensive risk assessment for E. formosa in IPM programs. © 2024 Society of Chemical Industry.

Genetic Variability and Heritability of Horticultural Traits, Impact on Susceptibility to Two Sap-Sucking Pests and Efficacy of Beauveria Bassiana and Lemongrass Oil as Biocontrol Agents in Six Inbred Lines of Summer Squash

Genetic Variability and Heritability of Horticultural Traits, Impact on Susceptibility to Two Sap-Sucking Pests and Efficacy of Beauveria Bassiana and Lemongrass Oil as Biocontrol Agents in Six Inbred Lines of Summer Squash

Transgenic cotton expressing Allium sativum leaf agglutinin exhibits resistance to whiteflies and aphids without negative effects on ladybugs

Cotton (Gossypium hirsutum L.) is of great economic importance as a cultivated crop in many parts of the world. In addition to being a pillar of the textile industry, cotton and its byproducts are used for livestock feed, seed oil, and other products. Bacillus thuringiensis crystal toxin (Bt) expression in cotton provides effective protection against chewing insects but does not defend plants from piercing/sucking insect pests. With the aim to create transgenic plants with resistance against piercing/sucking pests, we used Agrobacterium-mediated genetic transformation of cotton cultivar Coker 312 to express the Allium sativum leaf agglutinin (ASLA) gene from the phloem-specific rolC promoter. The ASLA transgene was stably inherited and showed Mendelian segregation in the T1 generation. Transgenic lines, expressing the ASLA gene, showed explicit resistance against major sap-sucking pests. Green peach aphid (Myzus persicae Sulzer) choice assays showed that 75% of aphids preferred untransformed cotton plants relative to those expressing the ASLA gene. In detached leaf bioassays, plants expressing ASLA caused 82% aphid mortality and 44–53% reduction in fecundity. Clip cage bioassays with whiteflies (Bemisia tabaci Gennadius) showed 74–82% mortality and 44–60% decrease in fecundity due to ASLA gene expression. In whole plant bioassays, whiteflies showed 77% mortality and a 54% decrease in fecundity on ASLA transgenics. Importantly, we did not observe a negative effect of the ASLA gene on ladybugs (Coccinella septempunctata) that consumed these whiteflies. Together, our findings demonstrate the potential of ASLA-transgenic cotton for providing protection against two devastating insect pests, whiteflies and aphids. The ASLA-transgenic cotton appears promising for direct commercial cultivation besides serving as a potential genetic resource in recombination breeding.

Design the fusion double-strand RNAs to control two global sap-sucking pests

RNA interference (RNAi) is an effective pest management strategy through silencing the crucial genes in target organisms. However, the effectiveness of targeting a single gene is often limited by the silencing efficiency due to tissue or developmental stage-specific gene expression. Moreover, multiple pests often infest the same crop simultaneously under current ecological conditions. Therefore, a combined strategy of “targeting multiple genes” and “controlling multiple pests” is expected to yield better management results. In this study, homologous genes from two globally sap-sucking pests, the peach aphid (Myzus persicae) and the whitefly (Bemisia tabaci), were screened on a genome-wide scale. Subsequently, RNAi bioassays showed silencing the genes (MpAbd-A, MpH3, MpRpL27a, and MpScr) exhibited high mortalities in both species, which were further selected for designing fusion dsRNAs. These fusion dsRNAs resulted in higher mortalities in both pests than single gene silencing and posed a minimal off-target risk to the predator ladybeetle (Propylaea japonica) based on the sequence analysis. Finally, the tobacco plants expressing the fusion dsRNAs through virus-induced gene silencing (VIGS) technology enhanced the resistance to both pests. In conclusion, this study proposes a novel RNAi-based approach for managing two sap-sucking pests simultaneously.

Hormetic effect induced by Beauveria bassiana in Myzus persicae.

Myzus persicae, a serious sap-sucking pest of a large variety of host plants in agriculture, is traditionally controlled using chemical insecticides but there isinterestin using biopesticides as restrictions are increasingly placed on the use of broad-spectrum pesticides. Here, we show that in Petri dish experiments, high concentrations of the fungal entomopathogen Beauveria bassiana led to rapid mortality of M. persicae, although at a low concentration (1 × 104 conidia mL-1) there is a hormetic effect in which survival and fecundity are enhanced. Hormetic effects persisted across a generation with reduced development time and increased fecundity in the offspring of M. persicae exposed to B. bassiana. The whole-plant experiment points to a hormetic effect being detected in two out of three tested lines. The impact of these effects might also depend on whether M. persicae was transinfected with the endosymbiont Rickettsiella viridis, which decreases fecundity and survival compared with aphids lacking this endosymbiont. This fecundity cost was ameliorated in the generation following exposure to the entomopathogen. Although B. bassiana is effective in controlling M. persicae especially at higher spore concentrations, utilization of this entomopathogen requires careful consideration of hormetic effects at lower spore concentrations, and further research to optimize its application for sustainable agriculture is recommended. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Thiamethoxam-Induced Intergenerational Sublethal Effects on the Life History and Feeding Behavior of Rhopalosiphum padi

Thiamethoxam, a second-generation neonicotinoid insecticide is widely used for controlling sap-sucking insect pests including Rhopalosiphum padi. The current study aimed to investigate the life-history parameters and feeding behavior of R. padi following treatments with sublethal concentrations of thiamethoxam. The lethal concentration 50 (LC50) value of thiamethoxam against adult R. padi was 11.458 mg L−1 after 48 h exposure. The sublethal concentrations of thiamethoxam (LC5 and LC10) significantly decreased the adult longevity, fecundity, and reproductive days in the directly exposed aphids (F0 generation). In the progeny R. padi (F1), the developmental durations and total prereproductive period (TPRP) were decreased while the adult longevity, fecundity, and reproductive days (RPd) were increased at both thiamethoxam concentrations. The demographic parameters including the net reproductive rate (R0), intrinsic rate of increase (r), and finite rate of increase (λ) were prolonged only at the LC5 of thiamethoxam. The EPG results indicated that the sublethal concentrations of thiamethoxam increases the total duration of non-probing (Np) while reducing the total duration of E2 in directly exposed aphids (F0). Interestingly, the E2 were significantly increased in the progeny generation (F1) descending from previously exposed parental aphids (F0). Overall, this study showed that thiamethoxam exhibited high toxicity against directly exposed individuals (F0), while inducing intergenerational hormetic effects on the progeny generation (F1) of R. padi. These findings provided crucial details about thiamethoxam-induced hormetic effects that might be useful in managing resurgences of this key pest.

Moderate nitrogen application facilitates Bt cotton growth and suppresses population expansion of aphids (Aphis gossypii) by altering plant physiological characteristics.

Excessive application of nitrogen fertilizer in cotton field causes soil and water pollution as well as significant increase of aphid population. Reasonable fertilization is an important approach to improve agricultural production efficiency and reduce agriculture-derived pollutions. This study was aimed to explore the effects of nitrogen fertilizer on the Bt cotton physiological characteristics and the growth and development of A. gossypii, a sap-sucking cotton pest. Five different levels of Ca(NO3)2 (0.0 g/kg, 0.3 g/kg, 0.9 g/kg, 2.7 g/kg and 8.1 g/kg) were applied into vermiculite as nitrogen fertilizer in order to explore the effects of nitrogen fertilizer on the growth and development of Bt cotton and aphids. The results showed that the medium level of nitrogen fertilizer (0.9 g/kg) effectively facilitated the growth of Bt cotton plant and suppressed the population expansion of aphids, whereas high and extremely high nitrogen application (2.7 and 8.1 g/kg) significantly increased the population size of aphids. Both high and low nitrogen application benefited aphid growth in multiple aspects such as prolonging nymph period and adult lifespan, enhancing fecundity, and improving adult survival rate by elevating soluble sugar content in host Bt cotton plants. Cotton leaf Bt toxin content in medium nitrogen group (0.9 g/kg) was significantly higher than that in high (2.7 and 8.1 g/kg) and low (0.3 g/kg) nitrogen groups, but Bt toxin content in aphids was very low in all the nitrogen treatment groups, suggesting that medium level (0.9 g/kg) might be the optimal nitrogen fertilizer treatment level for promoting cotton seedling growth and inhibiting aphids. Overall, this study provides insight into trophic interaction among nitrogen fertilizer levels, Bt cotton, and cotton aphid, and reveals the multiple effects of nitrogen fertilizer levels on growth and development of cotton and aphids. Our findings will contribute to the optimization of the integrated management of Bt cotton and cotton aphids under nitrogen fertilization.

Control of two insect pests by expression of a mismatch corrected double-stranded RNA in plants.

RNA interference (RNAi) has emerged as an efficient technology for pest control by silencing the essential genes of targeted insects. Owing to its nucleotide sequence-guided working mechanism, RNAi has a high degree of species-specificity without impacts on non-target organisms. However, as plants are inevitably under threat by two or more insect pests in nature, the species-specific mode of RNAi-based technology restricts its wide application for pest control. In this study, we artificially designed an intermediate dsRNA (iACT) targeting two β-Actin (ACT) genes of sap-sucking pests Bemisia tabaci and Myzus persicae by mutual correction of their mismatches. When expressing hairpin iACT (hpiACT) from tobacco nuclear genome, transgenic plants are well protected from both B. tabaci and M. persicae, either individually or simultaneously, as evidenced by reduced fecundity and suppressed ACT gene expression, whereas expression of hpRNA targeting BtACT or MpACT in transgenic tobacco plants could only confer specific resistance to either B. tabaci or M. persicae, respectively. In sum, our data provide a novel proof-of-concept that two different insect species could be simultaneously controlled by artificial synthesis of dsRNA with sequence optimization, which expands the range of transgenic RNAi methods for crop protection.

Fusion dsRNA designs incorporating multiple target sequences can enhance the aphid control capacity of an RNAi-based strategy.

RNA interference (RNAi) is the sequence-dependent suppression of gene expression by double-stranded RNA (dsRNA). This is a promising strategy for the control of insect pests because dsRNA can be rationally designed to maximize efficacy and biosafety, the latter by using sequences that are found in target pests but are safe for non-target insects. However, this has yet to be optimized in aphids, destructive sap-sucking pests that also transmit plant viruses. We used the green peach aphid (Myzus persicae) as a case study to optimize the efficiency of RNAi by applying a novel fusion dsRNA design. Comparative transcriptomics revealed a number of genes that are induced in feeding aphids, and eight candidate genes were chosen as RNAi targets. To improve RNAi efficiency, our fusion dsRNA design approach combined optimal gene fragments (highly conserved in several aphid species but with less homology in beneficial insects such as the predator ladybeetle Propylea japonica) from three candidate genes. We compared this RNAi-based biological control approach with conventional chemical control using imidacloprid. We found that the fusion dsRNA strategy inhibited the aphid population to a significantly greater extent than single-target RNAi and did not affect ladybeetle fitness, allowing an additive effect between RNAi and natural predation, whereas imidacloprid was harmful to aphids and ladybeetles. Our fusion dsRNA design approach enhances the ability of RNAi to control aphids without harming natural predators. © 2024 Society of Chemical Industry.

Juniper mealybug Planococcus vovae (Nasonov, 1908) (Hemiptera: Pseudococcidae) – a new dangerous pest of Cupressaceae in the Donbass and Cis-Azov region

In August 2022, during phytopathological surveys in the city of Taganrog, focal occurrences of the juniper mealybug, Planococcus vovae (Nasonov, 1908) (Hemiptera: Pseudococcidae), were registered for the first time. In 2023, the species had been recorded in urban plantings of Donetsk and Mariupol. The following introduced species, commonly utilized in urban landscaping within the steppe zone, were observed as host plants for the mealybug: Thuja occidentalis L., Juniperus communis L., J . chinensis L., J . scopulorum Sarg., and others. The biology of Planococcus vovae in the steppe zone remains unstudied; it is presumed that at least two generations may develop within a year. The juniper mealybug has the capacity to trigger outbreaks of mass reproduction and is deemed one of the most detrimental sap-sucking pests of Cupressaceae. The penetration ofP. vovae into the steppe zone presents an ominous prognosis for the phytosanitary conditions of urban green spaces. Presently, a complex comprising 13 species of specialized phytophages has emerged on Cupressaceae in the Donbass region, among which P. vovae could potentially emerge as a principal pest. Plants weakened by mealybug feeding become susceptible to aggressive xylophagous pests such as Lamprodila festiva (Linnaeus, 1767) and Phloeosinus aubei (Perris, 1855). Establishing phytosanitary monitoring systems and implementing a set of protective measures will inevitably elevate the costs associated with maintaining urban plantings. Given that the primary vector of invasion by specialized Cupressaceae phytophagous species is the inadvertent introduction through infected plants, it is paramount to conduct thorough inspections and impose quarantines on planting materials. Additionally, curtailing the volume of imports can be achieved through the development of regional nurseries.

Farmer perception, knowledge and management of the scale insect pest complex infesting crops and trees in Coastal Kenya

Scale insects and mealybugs (Hemiptera: Sternorrhyncha: Coccomorpha) are serious plant sap-sucking pests affecting a wide range of cultivated crops and tree species. The insects are highly diverse and can have devastating effects on yields due to lack of farmer awareness and inappropriate management practices. Recent alien mealybug invasions in Kenya include among others, papaya mealybug (Paracoccus marginatus), a highly invasive pest that is spreading quickly. Farmer experience with diverse crop pests can support development of a successful pest management strategy and contribute to reduced impacts on both crop yields and agro-biodiversity. This socio-economic survey was carried out in three coastal counties of Kenya (Mombasa, Kilifi and Kwale) to establish the impact of scale insect and mealybug pests on farmer livelihoods and to document the perception, knowledge and management practices used by smallholder farmers. Data from oral interviews using ODK were administered to respondents and analysed using Excel and GENSTAT. It emerged that 26% of the respondents were familiar with scale insects and 51% with mealybugs, respectively. Of these, 78.13 % and 94% acknowledged having encountered scale insects and mealybugs, respectively, on their farms. The farmers confirmed that scale insect pests affected a high diversity of crops and trees. About 56% of the respondents used pesticides to control the pests while 25% did not apply any management strategy. The remaining 19% practiced cultural control methods such as field sanitation and intercropping with less susceptible crops. Pesticides were reported to be moderately effective (41-70%) at controlling scale insects and mealybugs. Other management options reported by farmers included farm hygiene, the use of high-pressure water jets, and applications of ash and bio-pesticides such as home-made neem extract. Based on the findings, it is recommended that capacity building for farmers and input providers be undertaken to enhance the knowledge of scale insect and mealybug pest biology, symptoms of crop and tree attack, host ranges and management practices. Additonally, training on the use of low-risk pest control products and innovative control methods should be undertaken to reduce the impact of the pest on crop production and agro-biodiversity. Keywords: Farmer knowledge, management, mealybugs, scale insects and socio-economic survey.

Evaluation of Toxicity Effect of different Insecticides against Camponotus Compressus.

Carpenter ant species play a significant ecological role and are widely prevalent. Ants contribute to safeguarding plants from sap-sucking pest insects through natural biological control mechanisms. The current study was conducted to collect ants from Block B farms at Muhammad Nawaz Sharif University of Agriculture, Multan (MNSUAM), Pakistan. In current study, various insecticides (such as Imidacloprid, Fipronil, Methoxyfenozide, Emamectin benzoate, and Flubendiamide) were formulated at different concentrations (including 160, 80, 40, 20, 10, 5, and 0 ppm) for evaluation against carpenter ants. Notably, Fipronil and emamectin benzoate exhibited heightened toxicity, even at lower doses of 5 ppm and 10 ppm, resulting in the mortality of nearly all worker ants within 24 hours. In contrast, Imidacloprid displayed no distinct preference, as most worker ants remained alive even after 72 hours. These findings indicate that Fipronil and emamectin benzoate may serve as effective active ingredients for controlling carpenter ants. The data was meticulously recorded and subjected to rigorous statistical analysis using specialized software.

Maize terpene synthase 1 impacts insect behavior via the production of monoterpene volatiles β-myrcene and linalool

Plant-derived volatiles are important mediators of plant-insect interactions as they can provide cues for host location and quality, or act as direct or indirect defense molecules. The volatiles produced by Zea mays (maize) include a range of terpenes, likely produced by several of the terpene synthases (TPS) present in maize. Determining the roles of specific terpene volatiles and individual TPSs in maize-insect interactions is challenging due to the promiscuous nature of TPSs in vitro and their potential for functional redundancy. In this study, we used metabolite GWAS of a sweetcorn diversity panel infested with Spodoptera frugiperda (fall armyworm) to identify genetic correlations between TPSs and individual volatiles. This analysis revealed a correlation between maize terpene synthase 1 (ZmTPS1) and emission of the monoterpene volatiles linalool and β-myrcene. Electroantennogram assays showed gravid S. frugiperda could detect both linalool and β-myrcene. Quantification of headspace volatiles in a maize tps1 loss-of-function mutant confirmed that ZmTPS1 is an important contributor to linalool and β-myrcene emission in maize. Furthermore, pairwise choice assays between tps1 mutant and wild-type plants showed that ZmTPS1, and by extension its volatile products, aid host location in the chewing insect S. frugiperda, yet repel the sap-sucking pest, Rhopalosiphum maidis (corn leaf aphid). On the other hand, ZmTPS1 had no impact on indirect defense via the recruitment of the parasitoid Cotesia marginiventris. ZmTPS1 is therefore an important mediator of the interactions between maize and its insect pests.

Egg-associated secretions from the brown planthopper (Nilaparvata lugens) activate rice immune responses.

The brown planthopper (BPH, Nilaparvata lugens) is a notorious sap-sucking insect pest that damages rice (Oryza sativa) plants throughout Asia. During BPH feeding, saliva enters rice plant tissues, whereas during oviposition egg-associated secretions (EAS) are deposited in damaged plant tissue. Dynamic changes in rice to planthopper salivary effectors have been widely reported. However, the effects of EAS from planthopper on rice immunity remains largely unexplored. In this study, we found that both infestation of rice by gravid BPH female adults and treatment with the EAS elicited a strong and rapid accumulation of jasmonic acid (JA), JA-isoleucine, and hydrogen peroxide in rice. EAS enhanced plant defenses not only in rice but also in tobacco, and these impaired the performance of BPH on rice, as well as the performance of aphids and whiteflies on tobacco. High-throughput proteome sequencing of EAS led to 110 proteins being identified and 53 proteins with 2 or more unique peptides being detected. Some proteins from BPH EAS were also found in the salivary proteome from herbivores, suggesting potential evolutionary conservation of effector functions across feeding and oviposition; however, others were only identified in EAS, and these are likely specifically related to oviposition. These findings point to novel proteins affecting interactions between planthoppers and rice during oviposition, providing an additional source of information for effector studies.

Identification of novel associations of candidate marker genes with resistance to onion-fusarium basal rot interaction pathosystem

We evaluated the selected populations of eighteen open-pollinated short-day onion genotypes for FBR-Fusarium basal rot (Fusarium oxysporum f. sp. cepae-FOC) susceptibility; population genetic variation via ISSR marker; and transcriptome analysis using qRT-PCR with six novel selected marker genes: R1, R5, RGA29, lectin, LOX, and Osmotin, at tree time post inoculation (wpi). Screening for resistance showed the average severity between 4.7 and 88.9%; of which, the lowest one was in ‘Saba’ and ‘Saba – HS (6.7 and 4.7%, respectively). ISSR analysis recorded 226 amplified bands, of which 160 bands showed polymorphism, of which ISSR1 and ISSR10 primers showed the best performance. We also found that following inoculation with FOC could regulate defense-related marker genes; R1, PR5, Lectin, LOX, Osmotin, and RGA29 in resistant onion “Saba” and ‘Saba’-HS in comparison to susceptible and controls, non-inoculated ones ranging from 1.23 to 6.99 -fold significantly. Surprisingly, marker genes; Lectin, LOX, and Osmotin were also expressed to FOC simultaneous, though basically are resistance to other biotic and abiotic stress: Lectin to Rhizoctonia solani, Aphid, and major sap-sucking pests; LOX to root-knot and cyst nematode, Heterodera glycines; Osmotin to drought stredd, and oxidative burst in plants. This indicates the double, and or multiple roles of our selected marker genes covering two or more functions at a time. The findings introduce newly resistant onion genotypes, and also can be used in management programs to reduce damages caused by FOC disease. Cumulatively, the transcriptome-data provide novel-insights into the response of onions for improving onion-breeding to FOC.

Direct and indirect effects of two endophytic entomopathogenic fungi on survival and feeding behaviour of meadow spittlebug Philaenus spumarius

The most effective way to contain spread of the plant pathogen Xylella fastidiosa in Europe is to manage populations of its main insect vector, Philaenus spumarius L. (Hemiptera: Aphrophoridae). The action of some entomopathogenic endophytic fungi (EEF) on insect pests, directly through contact or indirectly by internal colonization of host plant tissues, may offer an excellent control option within integrated pest management (IPM) programmes. This study evaluated the impact of two EEF strains as control agents of P. spumarius (Metarhizium brunneum strain EAMa 01/58-Su and Beauveria bassiana strain EABb 01/33-Su [Hypocreales: Clavicipitaceae and Cordycipitaceae, respectively]); both strains were known to be excellent control agents of many other serious chewing and sap-sucking agricultural pests. First, the pathogenicity of strains applied directly to P. spumarius adults was evaluated, resulting in 50.0% and 32.0% mortality and a mean survival time of 4.7 and 6.2 days for M. brunneum and B. bassiana, respectively. Furthermore, colonization of Sonchus oleraceus by EEFs was observed after both soil and foliar applications. Greatest colonization (91.0%) was observed in plants treated with foliar applications of M. brunneum. Based on these results, we evaluated the feeding behaviour of P. spumarius on S. oleraceus plants previously colonized by M. brunneum using the ‘Electrical Penetration Graph’ technique. P. spumarius fed in a similar way on EEF-colonized and non-colonized S. oleraceus plants, with the exception that insects feeding on colonized plants reached xylem vessels faster than insects feeding on non-colonized plants. In addition, significantly higher mortality of P. spumarius was observed when feeding on plants treated by M. brunneum compared with the control. The duration of xylem ingestion events indicates that P. spumarius preferred to feed on basal leaves of the plant compared with apical leaves. Our results indicate strong potential for strain EAMa 01/58-Su of M. brunneum to be used as part of an X. fastidiosa IPM programme.

An efficient mutagenesis system to improve the propamocarb tolerance in Lecanicillium lecanii (Zimmermann) Zare & Gams.

Lecanicillium lecanii (Zimmermann) Zare & Gams is used as an effective biopesticide for the control of sap-sucking insect pests on agricultural crops. However, low fungicide tolerance limits its large-scale field application. To improve the propamocarb tolerance in L. lecanii, a composite mutagenesis system was established by using UV-light (U), N-Methyl-N'-nitro-N-nitrosoguanidine (NTG) (N) and N+ ion-beam (I). The permutation type of three agents was a consecutive mutagenesis treatment (I/N/U) after an intermittent treatment (U + N + I). The "U" mutagenesis was performed at 254 nm for 60 s and at a distance of 45 cm under a 20 W germicidal lamp, the "N" mutagenesis was performed at a concentration of 1.0 mg/mL NTG for 60 min, and the "I" mutagenesis was performed by low energy N+ ion-beam using a dose of 10 × 1013 ions/cm2 at 30 keV. This composite mutagenesis system was recorded as the "U + N + I + I/N/U," and then the mutagenesis efficiency in improving propamocarb tolerance was assessed by analyzing changes of mutants in the propamocarb sensitivity, mitotic stability, mycelial growth speed on plates or in liquid, sporulation on plates or aphids, conidial germination, 50% lethal concentration (LC50) and 50% lethal time (LT50) to aphids, lipid constituent and cell membrane permeability and control against aphids in the presence or absence of propamocarb. Compared to the wild-type isolate with a 50% effective concentration (EC50) value of 503.6 μg/mL propamocarb, the Ll-IC-UNI produced by the "U + N + I + I/N/U" had the highest EC50 value of 3576.4 μg/mL and a tolerance ratio of 7.1. The mutant was mitotically stable in 20-passage cultivation and did not show any unfavorable changes in growth and virulence indicators. The mutant showed the highest ability to resist or avoid the damaging effects of propamocarb as reflected by the alternations of lipid constituents and membrane permeability. The interval time for applying fungal agent was significantly shortened in this mutant after spraying a field recommended dose of 550 μg/mL propamocarb. In conclude, the "U + N + I + I/N/U" composite mutagenesis mode was efficient and useful to improve the propamocarb-tolerance of L. lecanii and the obtained Ll-IC-UNI could have commercial potential for field application.

Impact of sublethal concentrations of flonicamid on key demographic parameters and feeding behavior of Schizaphis graminum.

Flonicamid is a novel systemic insecticide that efficiently controls sap-sucking insect pests. However, the impact of sublethal concentrations of flonicamid on key demographic parameters and the feeding behavior of greenbug, Schizaphis graminum has not yet been studied. In this study, we used the age stage, two-sex life table approach, and electrical penetration graphs (EPGs) to investigate the sublethal effects of flonicamid on the biological traits and feeding behavior of S. graminum. Bioassays showed that flonicamid possesses high toxicity to adult S. graminum with LC50 of 5.111 mg L-1 following 48 h exposure. Sublethal concentrations of flonicamid (LC5 and LC10) significantly decreased the longevity and fecundity of directly exposed parental aphids (F0), while the reproductive days were reduced only at LC10. The pre-adult stage and total pre-reproductive period (TPRP) increased in F1 individuals after exposure of F0 aphids to the sublethal concentrations of flonicamid. Furthermore, the adult longevity, fecundity and key demographic parameters (R0, r, and λ) were significantly reduced in progeny generation (F1). EPG recordings showed that the total duration of phloem sap ingestion and concurrent salivation (E2) decreased substantially in F0 and F1 aphids after exposure to LC5 and LC10 of flonicamid. Taken together, our results showed that the sublethal concentrations of flonicamid affect the demographic parameters and feeding behavior that ultimately suppress the population growth of S. graminum. This study provides in-depth information about the overall effects of flonicamid on S. graminum that might help to manage this key pest.

Evaluating pheromone dispenser density and longevity for San Jose scale mating disruption in apple orchards

San Jose scale (Comstockaspis perniciosus Comstock) (Hemiptera: Diaspididae) is a cryptic sap-sucking pest in temperate orchards. In recent years, San Jose scale has become more challenging to manage, in part due to the loss of registered insecticides and difficulty in timing insecticide applications with the appropriate life stage. For insects like San Jose scale whose sex pheromones are known, mating disruption presents a biorational alternative to insecticide use in orchards. In 2020 and 2021, we evaluated this approach for San Jose scale in on-farm trials in Michigan apple orchards. ISOMATE® twin-tube reservoir dispensers primed with San Jose scale mating pheromone were placed into small orchard plots with densities ranging from 62 to 926 per ha to determine optimum density for control. In both years, male capture using baited traps was significantly reduced in plots under mating disruption, suggesting competitive population suppression. Optimum density of dispensers was determined to be 247 per hectare. A separate comparison study of the ISOMATE® twin-tube and CIDETRAK® MESO pheromone dispensers showed comparable efficacy despite differing release rates between the two types of dispensers. However, higher rates did provide greater suppression during the lower population densities in the first generation. We suggest there is some flexibility with rate and dispenser types for efficacious control. We also provide updated information on the phenology of the male San Jose scale flight activity. These results provide evidence for the potential utility of pheromone mating disruption for managing San Jose scale in apple orchards and highlight focus for further optimization.