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- Development of multiple transgenic CRISPR/Cas9 methods for genome editing
in the fall armyworm, Spodoptera frugiperda-
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Abstract: Abstract The use of CRISPR/Cas9 system in model insects has facilitated functional genomics studies. However, this system has not been applied to many pest insects. Here, we report on the establishment of multiple transgenic CRISPR/Cas9-based genome editing methods in a global agricultural pest, the fall armyworm (FAW), Spodoptera frugiperda. To identify fluorescent proteins suitable for screening for transgenic FAW, nine transgenic lines expressing genes coding for fluorescent proteins under the control of different promoters were produced and evaluated. The enhanced green fluorescent protein and a red fluorescent protein, tdTomato genes driven by the hr5ie1 promoter were found to be suitable for the identification of transgenic FAW. Multiple lines of transgenic FAW expressing Cas9 were generated and microinjection of sgRNAs into the embryos of these lines failed to induce target gene knockout. To overcome this problem, sgRNAs were expressed in FAW using U6-sgRNA and U6-tRNA-sgRNA systems, U6-tRNA-sgRNA system was found to be more efficient than U6-sgRNA system. Expression of Cas9 and sgRNAs in the same transgenic animal or in two separate strains followed by crossing them to bring Cas9 and sgRNA together resulted in an efficient knockout of target genes. The multiple transgenic CRISPR/Cas9-based genome editing methods developed provide invaluable tools for gene editing and functional genomics studies in this global pest and other lepidopteran pests.
PubDate: 2022-07-30
- Biological control in a changing climate: plant-mediated impact of
elevated CO2 concentration on Lobesia botrana eggs and egg parasitism by
Trichogramma cacoeciae-
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Abstract: Abstract Climate change can affect biological pest control by altering trophic interactions. Elevated carbon dioxide (CO2) concentrations can reduce host plant quality and, in turn, alter herbivore and natural enemy preference and performance. Using the Geisenheim VineyardFACE (free-air carbon dioxide enrichment) facility, we studied plant- and herbivore-mediated bottom-up effects of elevated CO2 concentration on the European grapevine moth, Lobesia botrana, and the parasitoid Trichogramma cacoeciae. Grapevine inflorescences of two cultivars cultivated at ambient or elevated CO2 (aCO2 and eCO2: 400 and 480 ppm) in the VineyardFACE were incorporated into L. botrana artificial diet. Eggs laid by the respective adults were parasitized by T. cacoeciae. Egg size and emergence rate of L. botrana as well as parasitism rate, parasitoid emergence rate and egg size preference of T. cacoeciae were evaluated. We observed an indirect grapevine cultivar-dependent bottom-up effect of CO2 on both herbivore and egg parasitoid. Compared to aCO2, eCO2 resulted in larger host eggs and higher parasitism rates regarding Riesling-feeding but not regarding Cabernet Sauvignon-feeding L. botrana larvae. Parasitoid emergence rate was higher when L. botrana had fed on Riesling compared to Cabernet Sauvignon-diet. Egg size preference depended on the host’s diet: T. cacoeciae preferred larger L. botrana eggs when the larvae had fed on grapevine-containing diet but not when they fed on standard artificial diet. Our results highlight the importance of the host’s diet for the parasitoid’s preference and performance. They furthermore suggest that the future efficiency of L. botrana-biocontrol by T. cacoeciae will not decrease under elevated CO2 concentrations.
PubDate: 2022-07-27
- Enhanced biocontrol services in artificially selected strains of Orius
laevigatus-
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Abstract: Abstract Augmentative biological control in protected crops relies mainly on omnivorous predators. Their performance as biological control agents (BCA) depends on several characteristics of the species, which in turn may differ among strains within a species. We have recently reported the achievement of two Orius laevigatus (Hemiptera: Anthocoridae) strains showing a significant larger body size or better fitness when feeding on pollen, two characteristics having a key impact on field performance. However, selection towards a specific trait might result in trade-offs, such as reduced predation capacity, which may impair control efficiency. Therefore, the predation capacity of these selected populations was tested in laboratory as a first step prior to its field use. Functional response to different densities of Frankliniella occidentalis (Thysanoptera: Thripidae) (adults and larvae) and Myzus persicae (Hemiptera: Aphididae) (nymphs) were studied in the large-sized and pollen-tolerant O. laevigatus strains in comparison with commercial and wild populations. A type-II functional response was observed regardless of the population. Body size was significantly related to thrips but not to aphid predation. The large-sized strain showed a superior predation capacity, both on thrips larvae and especially on adult thrips, although not on aphids. Therefore, the larger body size of the selected strain may increase its effectiveness as BCA of thrips. Regarding the pollen-tolerant strain, no trade-offs were observed in predation rates on adults or larvae of thrips, but it showed higher predation capacity on aphid nymphs, suggesting an expanded prey range. Implications of such enhanced biocontrol services on crop protection are also discussed.
PubDate: 2022-07-24
- Species-specific effects of ethanol concentration on host colonization by
four common species of ambrosia beetles-
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Abstract: Abstract Ambrosia beetles (Coleoptera; Curculionidae; Scolytinae and Platypodinae) can cause severe damage to trees growing in plant nurseries, orchards and natural forests. Ethanol is emitted by stressed trees and represents an important cue used by ambrosia beetles to locate suitable hosts to infest. Ethanol also favors the growth of ambrosia beetles’ nutritional fungal symbionts and suppresses the growth of antagonistic fungi. An optimal concentration of ethanol in host tissues might maximize fungal growth and offspring production, but it is unclear if this optimal concentration varies among ambrosia beetle species. To investigate this mechanism, we injected five different concentrations of aqueous ethanol solution (5%, 25%, 50%, 75% and 90%) into the stems of container-grown oak trees, Quercus robur L. Modified Falcon tube chambers were used to confine four species of field-collected ambrosia beetles to the injected stems, namely, Anisandrus dispar, Xyleborinus saxesenii, Xylosandrus germanus, and Xylosandrus crassiusculus. Incidence of boring, ejected sawdust, gallery development, and offspring production were then quantified. The incidence of boring generally increased with increasing ethanol concentration for all four Scolytinae species tested. Ejected sawdust and offspring production increased with increasing ethanol concentration up to 90% for A. dispar and X. saxesenii; by contrast, an increasing trend up to 75% ethanol followed by a decrease at 90% ethanol was associated with X. germanus and X. crassiusculus. Our study highlights the key role of ethanol for ambrosia beetles, and showed that the optimal concentration maximizing colonization and offspring production can vary among species.
PubDate: 2022-07-22
- Verbena × hybrida and Scaevola aemula flowers provide nutrients for
the reproduction of Nesidiocoris tenuis used for biological pest control
in greenhouses-
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Abstract: Abstract Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae) is a zoophytophagous mirid that can also feed on the plants upon which its prey lives. It is a generalist predator feeding on whiteflies, thrips, aphids, and other pests. The use of alternative plants as banker plants is recommended to aid the establishment of released natural enemies in greenhouses. If N. tenuis populations reproduce only on banker plants, the use of alternative hosts or prey to rear N. tenuis will be unnecessary, which makes the banker plant system easier to manage. Verbena × hybrida Voss (Lamiales: Verbenaceae) cv. Tapien and Scaevola aemula R. Br. (Asterales: Goodeniaceae) are recommended banker plants in Japan. This study examined the development, survival, and oviposition of N. tenuis on these two plant species in the laboratory, with and without flowers. N. tenuis performed similarly on both plants. The intrinsic rate of increase was slightly higher on Verbena × hybrida than S. aemula. The sugars in water samples collected from flowers of both plant species were analyzed using high-performance liquid chromatography. Fructose and glucose were detected in Verbena × hybrida, while fructose, glucose, and sucrose were detected in S. aemula. The total amount of sugars per ten flowers was much higher in Verbena × hybrida. These sugars, possibly derived from floral nectars, are considered as nutrients promoting the reproduction of N. tenuis, in addition to pollen. Verbena × hybrida and S. aemula both facilitate N. tenuis reproduction and can be used as banker plants.
PubDate: 2022-07-21
- Increasing plant diversity does not always enhance the efficacy of
omnivorous mirids as biocontrol agents-
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Abstract: Abstract The plant matrix influences the performance of omnivorous mirids as biocontrol agents and increasing plant diversity has been hypothesised to enhance pest control. This research aimed to determine the effect of using calabash, Lagenaria siceraria, as a companion plant on the population dynamics and whitefly control efficacy of Dicyphus argensis in tomato greenhouses. The response of D. argensis was also compared with that of Nesidiocoris tenuis. Four treatments were assayed in a complete randomised block design with three replicates each: (1) Bemisia tabaci, (2) B. tabaci + D. argensis, (3) B. tabaci + D. argensis + calabash and (4) B. tabaci + N. tenuis. Calabash harboured high populations of D. argensis, but its abundance on tomato plants was significantly lower in the presence of calabash than in its absence, and in both treatments, it reached lower numbers than N. tenuis. Dicyphus argensis reduced the whitefly density on tomato plants relative to the compartments with no mirids, but the whitefly density was higher in the presence of companion plants, and N. tenuis was more effective in reducing whitefly populations. Calabash served as a host for the multiplication of whitefly and increased the pest density on tomato. In this research, increasing plant diversity in crops did not enhance pest control because: (1) the aggregation of D. argensis in calabash reduced its abundance in tomato plants; (2) the pest populations multiplied. This contrasts with the diversity hypothesis and confirms the importance of the plant context for predatory dicyphines.
PubDate: 2022-07-21
- Correction: Essential oils from two aromatic plants repel the tobacco
whitefly Bemisia tabaci-
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PubDate: 2022-07-20
- A chitin synthase mutation confers widespread resistance to buprofezin, a
chitin synthesis inhibitor, in the brown planthopper, Nilaparvata lugens-
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Abstract: Abstract Development of insecticide resistance in insect populations is a major challenge to sustainable agriculture and food security worldwide. Buprofezin, one of the commonly used chitin synthesis inhibitors, has severely declined its control efficacy against the brown planthopper (BPH, Nilaparvata lugens), a devastating rice insect species. To date, however, mechanism of buprofezin resistance in target pests remains elusive. We conducted a long-term (25 years from 1996 to 2020) and large geographical scale (11 provinces and cities in China) resistance monitoring program for buprofezin in BPH, a notorious pest of rice crop in East and Southeast Asia. BPH rapidly developed resistance with > 1,000-fold resistance being detected in nearly all the field populations after 2015. Using the bulk segregant mapping method, we uncovered a novel mutation (G932C) in chs1 gene encoding chitin synthase 1 from a near isogeneic buprofezin-resistant (> 10,000-fold) strain harboring recessive, monogenic resistance. Using CRISPR/Cas9-based genome-modified Drosophila melanogaster possessing the same mutation as a model, we found that the G932C mutation was not only responsible for buprofezin resistance but also conferred a cross-resistance to cyromazine, an insect molting disruptor, on which the mode of action is largely unknown. Taken together, our study for the first time revealed the molecular mechanism conferring buprofezin resistance in BPH and implicated that cyromazine also targets chitin biosynthesis to confer its toxicity.
PubDate: 2022-07-16
- Fitness of Frankliniella occidentalis and Bemisia tabaci on three plant
species pre-inoculated by Orius sauteri-
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Abstract: Abstract Exploring the interactions between host plants, herbivores, and natural enemies is an important experimental approach for enhancing biological control. Induced plant defense responses following infestation by herbivores enable plants to minimize damage. Orius sauteri (Poppius), an important generalist predator, has been widely used as a biological control agent for suppressing many agricultural pests on agronomic and horticultural crops. Because this predator oviposits and feeds on plant tissue, in this work we hypothesized that these behaviors can induce defenses that modulate the subsequent pest attack. For this, we explored the fitness parameters of two key pests, the western flower thrips Frankliniella occidentalis (Pergande) and the tobacco whitefly Bemisia tabaci (Gennadius), on three different O. sauteri-pre-inoculated plant species, tomato, cucumber, and cowpea when compared to non-pre-inoculated plants. Pre-inoculation of O. sauteri on these three plant species decreased the performance of both herbivore pests but to differing degrees. The survival of F. occidentalis on tomato and B. tabaci on cowpea was significantly reduced on O. sauteri-pre-inoculated plants compared to non-inoculated plants. The reproduction of B. tabaci on tomato, cucumber, and cowpea was decreased in varying degrees by the pre-release of O. sauteri, whereas in the case of F. occidentalis the reproduction was only reduced on tomato and cucumber pre-inoculated plants. These results further enhance our knowledge of ecological relationships between natural enemies and herbivores and provide the context for the early release of natural enemies to control pests.
PubDate: 2022-07-16
- Cowpea aphid resistance in cowpea line CB77 functions primarily through
antibiosis and eliminates phytotoxic symptoms of aphid feeding-
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Abstract: Abstract Cowpea (Vigna unguiculata) is one of the most important crops in semiarid areas of the world, where it thrives in hot, dry conditions. While cowpea is able to withstand abiotic stresses, it suffers serious losses from biotic antagonists, including infestation by the cowpea aphid (Aphis craccivora). Cowpea aphid infestations are highly destructive, especially on young plants. However, it is unclear whether cowpea aphid damage is the result of aphids having phytotoxic effects on their hosts, or simple density effects. To better understand cowpea aphid damage and the potential for resistance traits to mitigate aphid impacts, we evaluated phenotypic changes in cowpea in response to variable aphid densities and systemic versus local infestations. Low aphid densities induced leaf distortions and pseudogalling, suggesting that cowpea aphids are phytotoxic to cowpea. Resistance to the cowpea aphid has been previously identified in an African cowpea germplasm, and near isogenic lines (NILs) containing resistance quantitative trait loci (QTL) were generated in the California blackeye cultivar background. Using a series of performance assays, we determined that resistance conferred by the two QTL counteracts aphid phytotoxicity and severely limits aphid growth and fecundity. Using choice assays, a preference by cowpea aphids for the susceptible NIL was observed. Electrical penetration graph analysis revealed that the resistance phenotype includes weak surface level deterrence and strong phloem-based resistance that manifests during the sap ingestion phase. Our study provides evidence of phytotoxic traits in A. craccivora while identifying a viable means of counteracting aphid damage and reproductive potential through resistance.
PubDate: 2022-07-14
- Modeling fall armyworm resistance in Bt-maize areas during crop and
off-seasons-
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Abstract: Abstract Entomologists have often used computational modeling to study the dynamics of insects in agricultural landscapes. Recently, important issues such as the movement of adults and immatures associated with insect resistance to GMO (genetically modified organism) crops have been addressed using computational models. We developed an individual-based model using the cellular automata approach (CA) to investigate how an intercropping system composed of maize engineered with Bacillus thuringiensis (Bt) gene, refuge areas (non-Bt maize), and grasses combined with off-season periods might influence the evolution of resistance in Spodoptera frugiperda (Lepidoptera: Noctuidae), one of the leading agricultural pests targeted by GMOs. We designed the Bt and non-Bt plants in two different arrangements: (a) a seed mixture and (b) strips rows, adding grasses in areas adjacent to the field. We added the seasonal planting dynamics (crop season and off-season), to evaluate a total of six agricultural scenarios. We followed a crop calendar from the United States to create simulations close to agricultural practice. The results showed that the frequency of the resistance allele was strongly related to the landscape arrangements and their dynamics. Since the adult insects are mobile, the seed-mixture scenario increased the frequency of the resistance the most (95.86%), followed by strips (82.10%), without grass fields. The maize harvest made it possible to reduce the frequency of resistance allele below 1%. Based on our results, we can expect that the maintenance of pasture areas, for instance next to the corn crops, will act as a reservoir of susceptible insects during off-season periods.
PubDate: 2022-07-14
- Assessment of renewable compounds as biopesticides for Asian citrus
psyllid, Diaphorina citri (Kuwayama) (Hemiptera: Psyllidae).-
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Abstract: Abstract The Asian citrus psyllid (ACP), Diaphorina citri, Kuwayama (Hemiptera: Liviidae), is the vector of Candidatus Liberibacter asiaticus and Ca. Liberibacter americanus, both associated with Huanglongbing, the most destructive disease of citrus worldwide. ACP control mainly depends on the use of synthetic insecticides. However, the dependence on and overuse of synthetic insecticides can lead to insecticide resistance, adverse environmental effects. Due to this, as well as consumer demand for organic food and changing regulations, there is an urgent need to develop additional and more sustainable methods of control. Fatty acid-based and phenolic biopesticides derived from lignocellulosic biomass could be safe and inexpensive alternatives to synthetic insecticides. Thus, the objective of this work was to study the toxicity of two novel, naturally derived molecules—sucrose fatty acid ester (SFAE) and 2-methoxy-4-propylphenol (2M4P)—to ACP, and compare them with fenpropathrin and pyrethrum extract. Mortality of adult psyllids (3-7 days old) exposed to SFAE, 2M4P, the pyrethrum extract and fenpropathrin in topical application bioassays were compared at 1, 24 and 48 h post-treatment at different doses. Mortality of adults exposed to SFAE, 2M4P and the pyrethrum extract were also compared in whole plant assays under greenhouse conditions. In the topical bioassays all compounds worked rapidly against ACP, with the natural and synthetic pyrethroids showing significantly more toxicity than SFAE and 2M4P. Under greenhouse conditions, mortality caused by 2M4P was the highest, followed by the pyrethrum extract. Mortality caused by SFAE was not significantly different when compared to the control.
PubDate: 2022-07-14
- Fumigation activity of essential oils of Cinnamomum loureirii toward red
imported fire ant workers-
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Abstract: Synthetic pesticides used to control Solenopsis invicta Buren (Hymenoptera: Formicidae) can negatively affect human and environmental health due to non-target toxicity and long-lasting residues. Plant essential oils may have lower human health impacts and environmental toxicity. They can be an excellent source of pesticides because of their exceptional repellency and insecticidal properties. In this study, we used the fumigation method to study the insecticidal properties of essential oils from the bark and leaves of Cinnamomum loureirii Nees on S. invicta at different concentrations and fumigation time. The fumigation time with C. loureirii essential oils was positively correlated with the knockdown and mortality of S. invicta and negatively correlated with the grasping. The essential oils at 320 µg/cm3 had a noticeable fumigation effect. The insecticidal effect of the essential oils extracted from C. loureirii leaves was significantly stronger than that from the bark at effective concentrations. Cinnamyl acetate, an abundant component in leaf essential oils, plays a vital role in increasing the insecticidal effect of trans-cinnamaldehyde. The treatment of the mixed trans-cinnamaldehyde and cinnamyl acetate in a 2:1 ratio had the best insecticidal effect (at 50 and 25 µg/cm3, respectively) and more apparent electroantennogram change than the individual compounds. Essential oils caused disorganization and shedding of the antennae morphology and receptors that led to the death of S. invicta. This study provides a basis for developing and utilizing cinnamon leaf oil as a new environment-friendly insecticide resource to control S. invicta. Graphical abstract 
PubDate: 2022-07-14
- Comparison of the co-occurrence patterns of the gut microbial community
between Bt-susceptible and Bt-resistant strains of the rice stem borer,
Chilo suppressalis-
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Abstract: Bacillus thuringiensis (Bt), an effective entomopathogen, has been widely used for pest control. However, insect resistance risk threatens the sustainable utility of Bt products. Previous findings suggest the interactions between gut microbiota and the host probably influence the evolution of insect resistance. To understand how the microbiota affects the development of insect resistance and manage the resistance, we characterized the gut microbiota of Chilo suppressalis from five Bt-resistant or Bt-susceptible strains by 16S rRNA sequencing. The diversity, richness, and composition of gut microbial community were analyzed among these five strains by alpha and beta analyses. Gut microbiota diversity was significantly higher in Bt-resistant (BJ1Ab-R and FZ1Ca-R) than that in Bt-susceptible strains (BJ-S and FZ-S). A significantly higher abundance of the genus Enterococcus were found in BJ-S- and FZ-S-susceptible strains than that in BJ1Ab-R- and FZ1Ca-R-resistant strains. The genus Bifidobacterium significantly dominated in the FZ1Ca-R-resistant strain, compared with the other four strains. Moreover, the gut microbial community displayed significantly more complex cooccurrence patterns in Bt-resistant than in Bt-susceptible strains by network analysis. Furthermore, the BJ-S, FZ-S and FZ1Ca-R strains had significantly reduced larval mortalities in bioassays with Bt toxin after larval pretreatment with antibiotics to remove gut bacteria. This study suggests that the gut microbiota participates in regulating the Bt-induced killing mechanism in C. suppressalis, and provides insights into the impact of Bt selective pressure on microbiome composition and potential insect resistance induced by microbiome alterations. Graphical abstract 
PubDate: 2022-07-13
- Identifying cryptic species of Planococcus infesting vineyards to improve
control efforts-
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Abstract: Abstract Mealybugs (Hemiptera: Coccomorpha: Pseudococcidae) constitute important agricultural pests that often require control measures. Different mealybug taxa might, however, react differently to natural enemies and pesticides so that appropriate control measures against mealybugs rely heavily on the correct species identification. The mealybug Planococcus ficus (Signoret) is the most damaging scale insect infesting vineyards worldwide. Despite its economic impact, the taxonomic status of this mealybug species is still unclear, and recent studies suggest the possibility that P. ficus from eastern (i.e., Egypt) and western (i.e., France) Mediterranean regions may correspond in fact to two distinct species. The purpose of this work was to deepen our current knowledge of putative P. ficus from eastern Mediterranean using molecular tools and morphological analysis and test for the existence of cryptic species within P. ficus. Mealybug samples were collected from Egyptian vineyards to better characterize the genetic diversity and analyze the population structure of putative P. ficus along the eastern Mediterranean. We also estimated the phylogenetic relationships among the P. ficus complex haplotypes in different vineyard regions worldwide and analyzed the morphological characters of the different clades obtained. Morphological and molecular analyses confirmed the existence of two species: P. ficus (Signoret) s.str. and P. vitis (Niedielski), a species that was previously synonymized as P. ficus. These results have direct implications for pest management and could explain the lack of success in previous implementations of biological control programs against this pest in several vineyard regions.
PubDate: 2022-07-12
- Preference and plant damage caused by Nesidiocoris tenuis on twenty-one
commercial tomato cultivars-
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Abstract: Abstract The predatory bug Nesidiocoris tenuis (Hemiptera: Miridae) is the cornerstone of Integrated Pest Management (IPM) in greenhouse tomatoes in southern Europe. N. tenuis can also feed on the plant causing necrotic rings, flower abortion and punctured fruits. Thus, its role as biocontrol agent is controversial. Especially in Northern Europe, where N. tenuis has invaded recently, N. tenuis is considered a pest. Despite the importance of N. tenuis in Northern Europe, there is no information about the damage it may inflict on commercial tomato varieties. Thus, in this study, we evaluated the preference and plant damage caused by N. tenuis on twenty-one commercially available tomato cultivars. N. tenuis showed preference for certain tomato varieties. Higher N. tenuis populations on the plants resulted in more necrotic rings. A clearer distinction between the different tomato cultivars was the sensitivity for flower abortion. We observed that small fruit cultivars (cherry, plum) were more susceptible to suffering flower abortion compared to larger fruit-bearing cultivars (truss, beef) because of N. tenuis feeding. Interestingly, we identified tomato cultivars that supported high population densities of N. tenuis without suffering flower abortion. Analyses of plant nutrients suggest that the damage (percentage of necrotic rings) inflicted by N. tenuis was negatively associated with the amount of total sugars, sodium, chloride, sulphur and copper and positively associated with nutrients such as potassium, calcium, phosphorus and magnesium. The new insights provided herein about the interaction between N. tenuis and plant damage are relevant for growers, IPM consultants and plant breeders.
PubDate: 2022-07-09
- Vibrational calling signals improve the efficacy of pheromone traps to
capture the brown marmorated stink bug-
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Abstract: Abstract Halyomorpha halys (Stål, 1855), the brown marmorated stink bug (BMSB), is an invasive species that has become a key agricultural pest in its invaded range. Commercial traps available for BMSB monitoring rely on male produced aggregation pheromones as lure, with two possible shortcomings: trap spillover and low detection precision. In this study, we assessed if vibrational signals can increase the attractiveness of pheromone traps by testing the optimized vibration-based lure (Female Song 2, FS2) associated with a specifically designed trap (i.e., the vibrotrap). We evaluated the efficacy of this bimodal trap (i.e., pheromones + vibrations) on females, males and nymphs in controlled conditions (greenhouse) and in the field, in two sites at the margin of two commercial vineyards. In the field, bimodal vibrotraps were compared to three unimodal (i.e., only pheromone) trap types. Both experiments showed that the vibrotrap is highly attractive for BMSB, and the optimized FS2 signal significantly improved its effectiveness. Even though FS2 was selected to target males, the number of trapped females increased as well. Overall, the presented findings show a feasible improvement to future commercial BMSB traps through the synergic use of semiophysicals and semiochemicals. Further research is needed to evaluate the effectiveness of vibrotraps for both early detection and mass trapping.
PubDate: 2022-07-08
- Correction to: Artificial heat waves induce species-specific plastic
responses on reproduction of two spider mite predators-
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PubDate: 2022-07-07
- Sorghum and maize flavonoids are detrimental to growth and survival of
fall armyworm Spodoptera frugiperda-
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Abstract: Abstract Fall armyworm (FAW) Spodoptera frugiperda (J.E. Smith) is becoming an invasive pest globally, and it causes significant yield losses in sorghum (Sorghum bicolor (L.) Moench) and maize (Zea mays L.). In this study, we demonstrated that sorghum and maize flavonoids affect survival of FAW larvae. Larvae reared on an artificial diet supplemented with sorghum flavonoids showed significant mortality and decreased body weight. When sprayed on leaves of susceptible maize lines, flavonoid extract effectively reduced the growth and increased the mortality of FAW larvae. As FAW is a major pest of maize, we further investigated the larval mortality when reared on maize lines overproducing flavonoids compared to their near-isogenic wild-type lines. The detached leaf assays showed significantly high mortality of larvae that were fed on flavonoid producer lines compared to wild type. The peritrophic membrane that protects the midgut was severely damaged in larvae fed on leaves of flavonoid producer lines compared to wild type. The effectiveness of the flavonoids as feeding deterrents by endogenous expression and exogenous application demonstrates the eco-friendly potential for the management of FAW larvae.
PubDate: 2022-07-07
- Fitness consequences of oviposition choice by an herbivorous insect on a
host plant colonized by an endophytic entomopathogenic fungus-
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Abstract: Abstract Several species of entomopathogenic fungi (EPF), often considered as bioinsecticides, are able to colonize and establish a symbiotic relationship with plants as endophytes. Recent studies have demonstrated that insects feeding on endophytically colonized plants could have reduced survival. These newly emerging, but not yet fully understood, ecological roles suggest the possibility that EPF may affect preferences and performance of herbivorous insects. However, such plant-mediated effects and underlying mechanisms are largely unexplored. Here, we examined that the endophytic EPF, Beauveria bassiana, could affect oviposition selection and offspring fitness of Asian corn borer, Ostrinia furnacalis on maize, Zea mays. We observed that O. furnacalis females preferred to lay eggs on B. bassiana-inoculated maize plants. This was attributed to the changes in plant volatile profiles upon endophytic colonization by B. bassiana. Of these plant volatiles, we observed increased amounts of insect-preferred compounds, 2-ethyl-1-hexanol and 3-hexen-1-ol, and decreased amounts of non-preferred compounds β-caryophyllene, naphthalene and α-pinene. This finding suggests that B. bassiana-induced plant volatiles could modulate the interactions between plants and insects. However, fewer O. furnacalis larvae, pupae, and adults survived on the B. bassiana-colonized maize plants and this was correlated with lower plant nitrogen content in these plants. These results indicated that oviposition selection of O. furnacalis did not reflect the maximization of offspring fitness following maize inoculation with B. bassiana. We suggest that EPF-inoculated maize causes a detrimental attraction for O. furnacalis, which should be considered for potential application of “trap plants” when incorporating endophytic EPF within integrated pest management programs.
PubDate: 2022-06-29
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