Herbivorous Pests Research Articles

Soil conservation practices for insect pest management in highly disturbed agroecosystems – a review

AbstractDecline in soil health is a serious worldwide problem that decreases complexity and stability of agricultural ecosystems, commonly making them more prone to outbreaks of herbivorous insect pests. Potato (Solanum tuberosumL., Solanaceae) and onion (Allium cepaL., Amaryllidaceae) production is currently characterized by high soil disturbance and heavy reliance on synthetic inputs, including insecticides. Evidence suggests that adopting soil conservation techniques often (but not always) increases mortality and decreases reproductive output for the major insect pests of these important vegetable crops. Known mechanisms responsible for such an effect include increases in density and activity of natural enemy populations, enhanced plant defenses, and modified physical characteristics of respective agricultural habitats. However, most research efforts focused on mulches and organic soil amendments, with additional research needed on elucidating effects and their mechanisms for conservation tillage, cover crops, and arbuscular mycorrhizae.

Whorl-stage maize provides a microclimate refuge for predatory ladybeetles

Ladybeetles are voracious predators and contribute to the in-field suppression of herbivorous pests, yet are especially vulnerable to variable climatic conditions. In this study, we surveyed the temporal dynamics of ladybeetles on maize plants (Zea mays L.) at different phenological stages within experimental plots (2010–2014) and commercial fields (2013–2014). Ladybeetle adults attained high abundance on whorl-stage maize, despite a relative scarcity of prey items (e.g., aphids, insect eggs). Field work in 2015 further revealed how ladybeetle abundance on whorl-stage maize was higher than on adjacent cotton plants – with > 88% of ladybeetle adults occurring within the maize whorl. Whorl-inhabiting adults were the most abundant at 12:00, when air temperature was the highest; abundance levels dropped at 6:00, 18:00 and 24:00 with declining ambient temperature. Within maize whorls, average temperature was 3.9 °C lower and presence of free water 50.1% higher than under ambient conditions. Hence, whorl-stage maize plants offer suitable micro-climatic conditions for foraging ladybeetles and could act as a refuge during seasonally hot or dry conditions in agro-ecosystems. Our work offers novel information on how crop diversification (i.e., addition of maize strips) can benefit in-field abundance and activity patterns of ladybeetles, and thereby eventually promote conservation biological control in agro-ecosystems of northern China.

Anti-insect activity of a partially purified protein derived from the entomopathogenic fungus Lecanicillium lecanii (Zimmermann) and its putative role in a tomato defense mechanism against green peach aphid

Many biotrophic and necrotrophic fungi synthesize proteins that may elicit induced plant resistance against different herbivore pests. This in-vitro study elucidates the sub-lethal effect of a partially-purified protein derived from the entomopathogenic fungus Lecanicillium lecanii (Zimmerman) (Hypocreales: Clavicipitaceae) against green peach aphid Myzus persicae (Sulzer) (Hemiptera: Aphididae), an economically important pest of many solanaceous crops including tomato. Bioassays were conducted to determine the impact of different concentrations of protein (i.e. 0.018, 0.036 and 0.054 µM) on the survival and fecundity of M. persicae on tomato (Lycopersicon esculentum) plants. Moreover, the potential role of this exogenous protein in the plant defense mechanism was assessed by expression analyses of key genes associated with salicylic acid (SA) and jasmonic acid (JA) pathways using RT-qPCR. The results indicated a significant negative effect of all protein concentrations on the survivorship and fecundity of M. persicae. The highest concentration (0.054 µM) resulted in lowest survival (46%) of aphids at 7th day post-treatment, while two other concentrations (0.036 and 0.018 µM) resulted in 61 and 71% survival rate, respectively. Similarly, lowest and highest mean fecundity rates were recorded for the highest protein concentration and the control (1.5 and 2.4 nymphs day−1 female−1), respectively. Moreover, L. lecanii-derived protein strongly upregulated the SA associated genes PR1, BGL2 and PAL, and moderately upregulated the JA associated genes LOX, AOS and AOC in protein-treated tomato plants compared to the control plants. These findings demonstrate the systemic resistance induced in tomato plants against M. persicae by the exogenous application of partially-purified protein extracted from L. lecanii, suggesting its further purification and characterization as a novel biological pest management tool against aphids and other phloem-feeding insect pests.

Sublethal Effect of Six Insecticides on Predatory Activity and Survival of Coccinella Septempunctata (Coleoptera: Coccinellidae) Following Contact with Contaminated Prey and Residues

Coccinella septempunctata L. is a dominant predator of herbivorous pest insects (e.g. aphids) in various crops in Pakistan. A series of bioassays were conducted to determine the sublethal and residual activities of six insecticides, which are commonly used in canola crop (Brassica napus L.) in Pakistan on adult and fourth instar larvae of Coccinella septempunctata L. in laboratory conditions. We measured the mortality, uncoordination and consumption rate of coccinellid beetle to identify the products with comparatively low toxicity or short duration effects. Six insecticides (imidacloprid, thiamethoxam, profenophos, chlorpyriphos, lambda-cyhalothrin and cypermethrin) were used to treat aphids and arenas at sublethal concentration (LC30). Compared to control treatment, increased mortality and knockdown effects were observed following contact with residues and prey treated with all insecticides. While predatory efficiency of both adult and larval stages of C. septempunctata was significantly decreased after treatments. However, significantly lower mortality and high prey consumption were observed after treatment with imidacloprid and thiamethoxam (neonicotinoids) compared to other four insecticides. Results of choice and no-choice tests using field doses and ½ field doses also confirmed the significant difference in consumption of prey between imidacloprid, thiamethoxam and other four chemicals. Larvae and adult of C. septempunctata preferentially consumed untreated aphids than treated aphids with ½ and maximum field dose over the 5 h experimental period. This study provides information to guide canola growers in their selection of insecticides.

Toxicity and Oxidative Stress Induced in Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae) Treated with Some Insecticides

Integrated pest management of herbivorous pests relies on combining bio-insecticides and chemical insecticides for a satisfactory population control. The present study focused on evaluating the comparative toxicity of five insecticides, with different modes of action, against third and fifth instar larvae of Spodoptera littoralis and their influence on extent of oxidative stress in insect via detecting vitamin C content as well as measuring the activity of phenol oxidase (PO), catalase (CAT), peroxidase (POX), glutathione-S-transferase (GST) antioxidant enzymes compared to control. The results revealed that emamectin benzoate and indoxacarb were the most potent insecticides among the selected insecticides, based on their respective LC50 values. Thiacloprid, indoxacarb and emamectin benzoate significantly reduced Vitamin C content. Almost all treatments significantly increased PO activity. Only emamectin benzoate and Bacillus thuringiensis significantly induced POX activity. Indoxacarb and emamectin benzoate increased CAT activity in both instar larvae, whereas thiacloprid and indoxacarb decreased GST activity. In conclusion, emamectin benzoate and indoxacarb were the most potent insecticides. Activity of oxidative stress biomarkers upon insecticidal pressure has showed variable response.

Plant composition changes in a small-scale community have a large effect on the performance of an economically important grassland pest

BackgroundThe grasshopper Oedaleus asiaticus Bey-Bienko (Acrididae: Oedipodinae) is a dominant and economically important pest that is widely distributed across the Mongolian plateau. This herbivore pest causes major damage to the grassland of the Inner Mongolian steppe in China. The population dynamics of herbivore pests is affected by grassland management practices (e.g., mowing and heavy livestock grazing) that alter plant community structures and stoichiometric characteristics. For example, O. asiaticus outbreak is closely associated with plant preference changes caused by nitrogen loss from heavy livestock grazing. However, the manner by which small-scale variation in vegetation affects grasshopper performance and promotes outbreak is poorly characterized. To address this question, we investigated the relationship between small-scale (1 m2) vegetation variability and measures of O. asiaticus performance associated with plant stoichiometric characteristics.ResultsWe found that food preferences of O. asiaticus varied significantly, but maintained a specific dietary structure for different plant compositions. Notably, small-scale changes in plant community composition significantly affected grasshopper food preference and body size. Partial least-square modeling indicated that plant proportion and biomass affected grasshopper body size and density. We found that this effect differed between sexes. Specifically, female body mass positively correlated with the proportion of Stipa krylovii grass, whereas male mass positively correlated with the proportion of Artemisia frigida grass. Further analyses indicated that grasshopper performance is closely associated with plant stoichiometric traits that might be responsible for the pest’s plague.ConclusionsThis study provides valuable information for managing grasshoppers using rational grassland management practices.

Semi-supervised learning with convolutional neural networks for UAV images automatic recognition

The annotation of large datasets is an issue whose challenge increases as the number of labeled samples available to train the classifier reduces in comparison to the amount of unlabeled data. In this context, semi-supervised learning methods aim at discovering and propagating labels to unsupervised samples, such that their correct labeling can improve the classification performance. Our proposal makes use of semi-supervised methodologies to classify an unlabeled training set that is used to train a Convolution Neural Network using different training strategies. The proposed approach is experimentally validated for soybean leaf and herbivorous pest identification using images captured by Unmanned Aerial Vehicles and can support specialists and farmers in the pest control management in soybean fields, especially when they have a limited amount of labeled samples.

Levels and times of artificial defoliation on performance of second cycle cassava

The information on behavior of crop linked to defoliation is essential to determine the management of herbivore pests. The aim of this study was to evaluate the performance of cassava as a function of the time and level of defoliation applied in the second cycle of cultivation, that is, after the first year of cultivation in which the crop was naturally submitted to the physiological rest period, caused by low temperatures and pluviometric precipitation typical of the southern Brazilian region. We used a randomized block design in factorial 5 x 5.in which 5 levels of defoliation (0, 25, 50, 75 or 100% of defoliation) were applied at 5 different times of 45, 90, 135, 180, or 225 days after sprouting (DAS) of the stems. The following variables were measured: plant height, stem diameter, number of roots per plant, root mass and amount of starch in the roots. The means were submitted to the F test at 5% of probability and analyzed by the regression test using the Sisvar software. Plant height and diameter were inversely proportional to the degree of defoliation when subjected to treatments, especially when subjected to 100% defoliation at 90 DAS. For the root mass, the more drastic defoliation treatments (100 %), when applied at 132 DAS, led to a low production, whereas only the defoliation levels induced a meaningful reduction in the deposition of starch in roots, showing a linear effect and decreasing according to the increase in defoliation. It can be concluded that defoliation between 90 and 135 DAS at the more drastic levels resulted in a greater root mass loss, regardless of the time of defoliation, caused the greatest losses in the amount of starch, therefore, it is recommended to the producer to control this pest before the 90 days of sprouting of the stems at the beginning of the defoliation.

Potential of cow dung as insect herbivore repellent on Cowpea (<i>Vigna unguiculata</i>)

This study examined the potential of using cow dung as a repellent of herbivore pest on cowpea (Vigna unguiculata) and the work was carried out in the botanical and zoological garden of the University of Lagos, Akoka, Lagos, Nigeria. Four accessions of cowpea were grown in the soil samples collected from the Botanical and Zoological garden of the University of Lagos. The experiment was arranged in a randomized block design with three replicates to monitor the potential of using cow dung as a repellent of herbivore pest on cowpea for a period of six weeks. The data collected was analyzed using ANOVA. The results showed that cow dung treatments did not have significant effect at (P> 0.05) in repelling the insect of cowpeas. However, the plants treated with high concentrations of cow dung attracted significantly (P<0.05) higher number of insect pests and as the days of the application of the treatments increases, the number of leaves damaged by the insects increases. This study therefore recommends that a further study should be carried out using some other different plants species at different locations and under different environmental conditions. Keywords: Cow dung, cowpea, insect repellent

The 'Botanical Triad': The Presence of Insectary Plants Enhances Natural Enemy Abundance on Trap Crop Plants in an Organic Cabbage Agro-Ecosystem.

Habitat manipulation through the incorporation of non-crop plants such as trap crops (to lure pests away from the cash crop) and insectary plants (to provide resources for natural enemies) into agro-ecosystems is an ecological approach to pest management. In a field-scale study, we quantified the effects of integrating the use of trap crops with insectary plants as a novel method to control pest herbivores in an organic cabbage agro-ecosystem. We hypothesized that pests would be concentrated in the trap crop habitat and suppressed by insectary-subsidized natural enemies in situ. We documented arthropod abundance (both adults and immature stages) associated with (1) two insectary plant species (sweet alyssum, Lobularia maritima, and buckwheat, Fagopyrum esculentum) either alone or in combination; (2) a trap crop mixture of mighty mustard (Brassica juncea), red Russian kale (Brassica oleracea var. acephala), and glossy collards (Brassica oleracea var. italica), and (3) cabbage cash crop (Brassica oleracea var. capitata). Trap crops were more attractive to pests than the cash crop. On a per-plant basis, densities of the herbivores Evergestis rimosalis, Trichoplusia ni, and Plutella xylostella were 154, 37, and 161× greater on the kale trap crop than on the cabbage cash crop, and 54, 18, and 89× greater on the collards trap crop than on the cash crop. Insectary plants contributed to the consumption of pests that aggregated on the trap crop. Parasitism of E. rimosalis by the braconid wasp Cotesia orobenae was significantly increased, and the abundance of eggs and larvae of the predatory coccinellid beetle Coleomegilla maculata was greater on the trap crop in the presence of insectary plants compared to trap crops that lacked insectary plants. The ‘Botanical Triad’ of cash crop, trap crop, and insectary plants represents a new type of agro-ecosystem manipulation that integrates ecosystem service providers (e.g., predators and parasitoids) within the cropping system.

The Parasitic Wasp, Cotesia congregata (Say), Consists of Two Incipient Species Isolated by Asymmetric Reproductive Incompatibility and Hybrid Inability to Overcome Host Defenses

Parasitic wasps are highly diverse and play a major role in suppression of herbivorous insect pest populations. Several previously identified species of parasitic wasps have been found to be complexes of cryptic species resulting from adaptations to specific hosts or host foodplants. Cotesia congregata (Say) (Hymenoptera: Braconidae), which has long served as a model system for host-parasitoid interactions, can be used for investigating the process of diversification among sympatric populations that differ in host and host foodplant usage. Two incipient species of C. congregata have been identified in the USA mid-Atlantic region, “MsT wasps” originate from Manduca sexta (L.) (Lepidoptera: Sphingidae) on tobacco and “CcC wasps” originate from Ceratomia catalpae (Boisduval) (Lepidoptera: Sphingidae) on catalpa. Both wasp sources can develop in either host species. Hybrids resulting from MsT♂xCcC♀ crosses are fertile, whereas hybrids from CcC♂xMsT♀ crosses are typically sterile. In this study, we compared relative expression in vivo of seven C. congregata bracovirus (CcBV) genes among MsT and CcC parental and hybrid crosses. Also, we established hybrid crosses between MsT and CcC wasps and four additional host foodplant sources of C. congregata. Patterns of relative expression in vivo of MsT and CcC CcBV genes differed; a few were not expressed in hosts parasitized by CcC wasps. Overall, relative expression of CcBV genes from MsT and CcC wasps did not differ with respect to the host species parasitized. Low or absent expression of CcBV genes was found in hosts parasitized by sterile hybrids. For the most part, the other four host-foodplant wasp sources were reproductively compatible with either MsT or CcC wasps and hybrid crosses with the alternative wasp source were asymmetrically sterile. Crosses involving CcC males or MsT females produced sterile hybrids that lacked mature ovaries. Cumulatively, results indicate that C. congregata is composed of two sympatric incipient species that can utilize multiple host species rather than several host-associated races or cryptic species.

Weaver Ants Provide Ecosystem Services to Tropical Tree Crops

Generalist predators bring a complex mix of beneficial and harmful effects to agroecosystems. When these predators feed on herbivorous pests, biological control is improved with the potential to increase crop yield. However, generalists often feed on predators, pollinators, and plants, which might worsen pest outbreaks and reduce fruit set. For example, weaver ants (Oecophylla smaragdina) are major predators of several key, economically-damaging pest insects of tropical fruit and nut crops. Yet the ants also attack other predatory arthropods and important pollinators, while tending trophobiont honeydew producers like mealybugs (Pseudococcidae) that are themselves pests. Finally, ants will supplement their diet with sugars from floral and extra floral nectaries, a form of plant feeding that presumably carries a physiological cost to the plant. Here, across previously-published experimental studies that compared treatments where ants were present vs. excluded, we summarize the effects of weaver ants on beneficial and pest insects and tree-crop productivity. Our quantitative review revealed nearly ubiquitous benefits of Oecophylla ants for tropical agriculture. Treatments with ants present generally showed lower pest densities and damage from pest insects in the families Coreidae, Miridae, Pentatomidae, and Tephritidae. Pest reduction was seen on cacao (Theobroma cacao), cashew (Anacardium occidentale), and mango (Mangifera indica) trees. The single exception to these pest reductions occurred when ants facilitated the population growth of mealybugs and other honeydew producers. In general, we found that Oecophylla ants provided the valuable ecosystem service of natural pest control to a diversity of tropical tree crops. Despite the potential for the ants to harm other predators or pollinators, evidence for these ecosystem disservices was rare and other beneficial insects co-exist well with this group of ants. Our findings bolster the general finding that ant species that tend herbivores who are not themselves pests can provide broad-reaching benefits to plant productivity. More generally, our findings are consistent with the many cases where non-pest prey bolster densities of polyphagous predators with bene fits for biological control despite some degree of plant feeding by the predators.

Turfgrass Cultivar Diversity Provides Associational Resistance in the Absence of Pest Resistant Cultivars.

Turfgrasses are ubiquitous in urban landscapes and can provide numerous ecosystem services. However, most warm season turfgrasses are produced, planted, and maintained as cultivar monocultures, which may predispose them to herbivore attack and reduce the services lawns provide. Though rarely done, host plant resistance can be used as a strategy to reduce herbivory and preserve beneficial services. Increasing turfgrass cultivar diversity may provide similar or greater benefits through associational resistance, whereas conserving desirable maintenance and aesthetic traits. However, no studies have examined this in warm season turfgrasses. To address this, we evaluated host plant resistance to fall armyworm (Spodoptera frugiperda [J.E. Smith] [Lepidoptera: Noctuidae]) in commercially available cultivars of St. Augustinegrass (Stenotaphrum secundatum [(Walt.) Kuntz] [Lepidoptera: Noctuidae]) and then investigated if the resistance or susceptibility of St. secundatum cultivars carried over in mixed cultivar plantings. Through a no-choice experiment and a limited-choice experiment, we detected no host plant resistance in monocultures of St. secundatum cultivars. However, we did find that as cultivar diversity increased, female Sp. frugiperda larval weight and herbivory decreased. Additionally, choice tests indicated that larvae prefer less diverse stands of St. secundatum cultivars. Interestingly, our results suggest that in the absence of host plant resistance, warm season turfgrass cultivar diversity may reduce herbivore pest fitness and damage. These results demonstrate that warm season turfgrass cultivar diversity may be a viable integrated pest management tool that warrants further investigation.

Contribution of predation to the biological control of a key herbivorous pest in citrus agroecosystems

Biological control has traditionally simplified the view of trophic relationships between herbivorous pests and their natural enemies in agriculture. The success or failure of this pest management strategy is still mainly attributed to the ability of a few key natural enemies to suppress the pest density. For example, successful regulation of the California red scale (Aonidiella aurantii), a key citrus pest, is generally credited to specific parasitoids of the Aphytis genus. Currently, research is revealing how herbivore regulation in agroecosystems can be alternatively achieved with a greater number of trophic associations within the system. The goals of the present study were as follows: i) to unravel species-specific trophic links between A.aurantii and its natural enemies in citrus agroecosystems, and ii) to assess their contribution to control of A.aurantii. Predation and parasitism of this herbivorous pest were assessed through exclusion experiments. Species-specific trophic links between this herbivorous pest and its natural enemies were studied using gut-content analysis of field-collected predators employing prey-specific DNA molecular markers. Relative predation rates of the species involved in A.aurantii regulation were estimated. Predation was found to be the main biotic component of A.aurantii mortality, causing reductions of more than 75% in recently settled cohorts. Aonidiella aurantii DNA was detected in the digestive system of 11 species of predators. Generalist and stenophagous predators, mainly associated with other citrus pests such as aphids, proved to be the most important biological control agents of this pest. Complex trophic relationships, such as apparent competition between two key citrus pests, were revealed. The present study highlights the role of predation as biotic mortality factor of key pests in perennial agroecosystems, wherein it is a rich complex of indigenous or naturalized generalist predators that are primarily responsible for this mortality. The results herein presented may therefore offer another perspective on the biological control of one of the key world-wide citrus pests, at least in those regions where specific parasitoids are not able to successfully regulate the scale populations.

Exotic urban trees conserve similar natural enemy communities to native congeners but have fewer pests.

Urban trees serve a critical conservation function by supporting arthropod and vertebrate communities but are often subject to arthropod pest infestations. Native trees are thought to support richer arthropod communities than exotic trees but may also be more susceptible to herbivorous pests. Exotic trees may be less susceptible to herbivores but provide less conservation value as a consequence. We tested the hypotheses that native species in Acer and Quercus would have more herbivorous pests than exotic congeners and different communities of arthropod natural enemies. The density of scale insects, common urban tree pests, was greatest on a native Acer and a native Quercus than exotic congeners in both years of our research (2012 and 2016) and sometimes reached damaging levels. However, differences in predator and parasitoid abundance, diversity, and communities were not consistent between native and exotic species in either genus and were generally similar. For example, in 2012 neither predator nor parasitoid abundance differed among native and exotic Acer congeners but in 2016 a native species, A. saccharum, had the least of both groups. A native, Q. phellos, had significantly more predators and parasitoids in 2012 than its native and exotic congeners but no differences in 2016. Parasitoid communities were significantly different among Acer species and Quercus species due in each case to greater abundance of a single family on one native tree species. These native and exotic tree species could help conserve arthropod natural enemies and achieve pest management goals.

Climate warming and plant biomechanical defences: Silicon addition contributes to herbivore suppression in a pasture grass

Abstract Plants, notably the Poaceae, often accumulate large amounts of silicon (Si) from the soil. Si has multiple functional roles, particularly for alleviating abiotic and biotic stresses (e.g., defence against herbivores). Recent evidence suggests that environmental change, including temperature changes, can diminish Si accumulation which could affect functions such as herbivore defence. Using a field warming experiment, we grew a pasture grass (Phalaris aquatica) that was either supplemented or untreated with Si (+Si and −Si, respectively) under ambient and elevated (+2.8°C above ambient) air temperatures. We quantified soil water, plant growth rates, Si accumulation, leaf biomechanical properties and in situ relative growth rates of a herbivorous global insect pest (Helicoverpa armigera). Si supplementation promoted shoot and root biomass by c. 48% and 61%, respectively under ambient temperatures, but these gains were not apparent under warmed conditions. Warmer temperatures reduced Si uptake by −Si plants by c. 17%, potentially due to the lower levels of soil water content in warmed plots. Si supplementation, however, increased Si accumulation in leaves by c. 24% in warmed plots restoring Si levels to those seen under ambient temperatures. Si supplementation enhanced biomechanical properties in the leaves, but this was only statistically significant under ambient temperatures; leaves of +Si plants required 42% more force to fracture and were 30% tougher at the midrib than leaves of −Si plants. The relative growth rates of H. armigera declined by 56% when feeding on +Si plants under ambient temperatures, and while Si supplementation caused a trend towards declining herbivore growth rates under warmer conditions, this was not statistically significant. We conclude that climate warming may mitigate the beneficial effects of Si on Phalaris aquatica in the short term, potentially by reducing Si uptake. While Si uptake can be restored with Si supplementation, Si‐enhanced biomechanical defences against a global pest may not be fully restored under warmer temperatures. A plain language summary is available for this article.

Generalist predator contributions to the control of Tetranychus urticae in strawberry crops documented by PCR-based gut content analysis.

The contribution of generalist insect predators to the control of the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), an herbivorous pest of many crops, is poorly understood. One of the common insect predators in strawberries is the generalist predatory bug Anthocoris nemorum L. (Hemiptera: Anthocoridae), which has the potential to contribute to the control of pest populations. The feeding of adult A. nemorum on T. urticae was assessed by sampling individuals from an organic strawberry field in Denmark, and using PCR gut content analysis to detect remains of T. urticae within their gut. In the lab, we assessed that the DNA half-life detectability was 21.5h. Significant numbers of field-collected A. nemorum tested positive for T. urticae prey DNA, with very high numbers in June (62.8%) and August (38.8%). This study presents conclusive evidence that the generalist predator A. nemorum can contribute to the decrease of T. urticae densities in strawberry fields, although the actual contribution in the present study is probably limited because predator populations were relatively low compared to T. urticae. The abundance of T. urticae did not increase significantly during the period of sampling, suggesting that a complex of natural enemies can achieve biological control of T. urticae in protected strawberries.

T6SS contributes to gut microbiome invasion and killing of an herbivorous pest insect by plant-beneficial Pseudomonas protegens.

Pseudomonas protegens are multi-talented plant-colonizing bacteria that suppress plant pathogens and stimulate plant defenses. In addition, they are capable of invading and killing agriculturally important plant pest insects that makes them promising candidates for biocontrol applications. Here we assessed the role of type VI secretion system (T6SS) components of type strain CHA0 during interaction with larvae of the cabbage pest Pieris brassicae. We show that the T6SS core apparatus and two VgrG modules, encompassing the respective T6SS spikes (VgrG1a and VgrG1b) and associated effectors (RhsA and Ghh1), contribute significantly to insect pathogenicity of P. protegens in oral infection assays but not when bacteria are injected directly into the hemolymph. Monitoring of the colonization levels of P. protegens in the gut, hemolymph, and excrements of the insect larvae revealed that the invader relies on T6SS and VgrG1a module function to promote hemocoel invasion. A 16S metagenomic analysis demonstrated that T6SS-supported invasion by P. protegens induces significant changes in the insect gut microbiome affecting notably Enterobacteriaceae, a dominant group of the commensal gut bacteria. Our study supports the concept that pathogens deploy T6SS-based strategies to disrupt the commensal microbiota in order to promote host colonization and pathogenesis.

Global disparity in public awareness of the biological control potential of invertebrates

Invertebrates make up over 95% of animal biodiversity on Earth and contribute to multiple ecosystem services (ES) in natural and human-dominated systems. One such service, biological control (BC) of herbivorous pests, is a core component of sustainable intensification of agriculture, yet its importance is routinely overlooked. Here we report a macro-scale, cross-cultural assessment of the public visibility (or ‘salience’) of BC invertebrates, using high-throughput analysis of large bodies of digitized text (i.e., ‘culturomics’). Using binomial scientific name frequency as proxy for visibility, we compared the extent to which a given species featured in webpages within either scientific media or the entire worldwide web, and in total search volume at varying spatial scale. For a set of 339 BC invertebrate species, scientific and internet coverage averaged 1020 and 1735 webpages, respectively. Substantial variability was recorded among BC taxa with Coleoptera, Hemiptera and Nematoda having comparatively high visibility. Online visibility exhibited large geographical variability ranging from France covering BC invertebrates on average in 1050 webpages versus Thailand or Indonesia on just 31–38. This work represents the first extensive use of culturomics to assess public visibility of insect-mediated ES. As BC uptake is dictated by stakeholders' access to (agro-ecological) information, our work identifies geographically-delineated areas that are differentially attuned to the concept of invertebrate BC, pinpoints opportunities for focusing education campaigns and awareness-raising, enables real-time tracking of BC public appeal, and informs public policy.

Evaluation of the resistance effect of QTLs derived from wild soybean (Glycine soja) to common cutworm (Spodoptera litura Fabricius).

Common cutworm (CCW) is a serious herbivorous insect pest of soybean. Previously, we conducted an antixenosis bioassay (measuring feeding preference) with CCW using recombinant inbred lines (RILs) derived from a cross between a wild soybean (Glycine soja) collected in Hiroshima prefecture (JP110755) and the leading cultivar, Fukuyutaka. The analysis revealed quantitative trait loci (QTLs) for antixenosis resistance, qRslx3 and qRslx4. In the present study we developed another RIL population using Fukuyutaka and a different G. soja, collected in Kumamoto prefecture (G406). An analysis revealed an antixenosis resistance QTL on chromosome 7, and the resistant allele of the QTL was derived from G406. The chromosomal position of the QTL was almost the same as that of CCW-2, a previously-reported antibiosis resistance QTL for CCW, detected in a F2 population derived from a cross between Fukuyutaka and a resistant cultivar Himeshirazu. These QTLs could be the same locus; however, G406 and Himeshirazu are likely to possess different alleles, because Himeshirazu allele exhibits no antixenosis effect. We expect that pyramiding of the resistance QTLs derived from G. soja will contribute to the development of CCW resistant cultivars.