Publications by authors named "Marcel Dicke"

223 Publications

SLI1 confers broad-spectrum resistance to phloem-feeding insects.

Plant Cell Environ 2021 Apr 10. Epub 2021 Apr 10.

Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands.

Resistance (R) genes usually compete in a coevolutionary arms race with reciprocal effectors to confer strain-specific resistance to pathogens or herbivorous insects. Here, we investigate the specificity of SLI1, a recently identified R gene in Arabidopsis that encodes a small heat shock-like protein involved in resistance to Myzus persicae aphids. In a panel with several aphid and whitefly species, SLI1 compromised reproductive rates of three species: the tobacco aphid M. persicae nicotianae, the cabbage aphid Brevicoryne brassicae and the cabbage whitefly Aleyrodes proletella. Electrical penetration graph recording of aphid behaviour, revealed shorter salivations and a 3-to-5-fold increase in phloem feeding on sli1 loss-of-function plants. The mustard aphid Lipaphis erysimi and Bemisia tabaci whitefly were not affected by SLI1. Unlike the other two aphid species, L. erysimi exhibited repetitive salivations preceding successful phloem feeding, indicating a role of salivary effectors in overcoming SLI1-mediated resistance. Microscopic characterization showed that SLI1 proteins localize in the sieve tubes of virtually all above- and below-ground tissues and co-localize with the aphid stylet tip after penetration of the sieve element plasma membrane. These observations reveal an unconventional R gene that escapes the paradigm of strain specificity and confers broad-spectrum quantitative resistance to phloem-feeding insects.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/pce.14064DOI Listing
April 2021

Relative contributions of egg-associated and substrate-associated microorganisms to black soldier fly larval performance and microbiota.

FEMS Microbiol Ecol 2021 04;97(5)

Laboratory of Entomology, Plant Sciences Group, Wageningen University & Research, PO Box 16, 6700 AA Wageningen, The Netherlands.

Larvae of the black soldier fly (BSF) can be used to convert organic waste into insect biomass for animal feed. In this process, they interact with microorganisms originating from the substrate, the insect and the environment. The substrate is the main determinant of the larval gut microbiota composition, but inoculation of the substrate with egg-associated bacteria can improve larval performance. We aimed to quantify the relative importance of substrate-associated and egg-associated microorganisms in BSF larval performance, bacterial abundance and bacterial community composition, when larvae were fed with chicken feed or chicken manure. For this, we inactivated substrate-associated microorganisms by autoclaving, or disinfected BSF eggs. Larval survival, weight and proportion of prepupae were determined on day 15. We collected substrate and larval samples on days 0 and 15 and performed 16S rRNA gene-targeted qPCR and amplicon sequencing. In both chicken feed and chicken manure, egg disinfection did not cause any difference in larval performance or overall microbiota composition. In contrast, in chicken manure, substrate-associated microorganisms increased larval biomass and sterilizing the substrate caused major shifts in microbiota. Thus, substrate-associated microorganisms impact not only larval microbiota but also larval performance, whereas egg-associated microorganisms have a minor role in the densities present.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/femsec/fiab054DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8044291PMC
April 2021

Multiple Attack to Inflorescences of an Annual Plant Does Not Interfere with the Attraction of Parasitoids and Pollinators.

J Chem Ecol 2021 Feb 28;47(2):175-191. Epub 2021 Jan 28.

Laboratory of Entomology, Wageningen University, Droevendaalsesteeg 1, Radix building, Wageningen, 6708PB, The Netherlands.

Plants in the flowering stage need to ensure reproduction by protecting themselves from attack and by preserving interactions with mutualist pollinators. When different plant mutualists are using the same type of cues, such as volatile compounds, attraction of parasitoids and pollinators may trade off. To explore this, we compared volatile emission of Brassica nigra plants in response to single or dual attack on their inflorescences. Additionally, we recorded flower visitation by pollinators and the attraction of parasitoids in the greenhouse and/or field. Brassica nigra were exposed in the flowering stage to one or two of the following three attackers: Brevicoryne brassicae aphids, Pieris brassicae caterpillars, and Xanthomonas campestris pv. raphani bacteria. We found that single attack by caterpillars, and dual attack by caterpillars plus aphids, induced the strongest changes in plant volatile emission. The caterpillars' parasitoid C. glomerata did not exhibit preference for plants exposed to caterpillars only vs. plants exposed to caterpillars plus aphids or plus bacteria. However, the composition of the pollinator community associated with flowers of B. nigra was affected by plant exposure to the attackers, but the total number of pollinators visiting the plants did not change upon attack. We conclude that, when B. nigra were exposed to single or dual attack on their inflorescences, the plants maintained interactions with natural enemies of the insect attackers and with pollinators. We discuss how chemical diversity may contribute to plant resilience upon attack.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s10886-020-01239-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7904547PMC
February 2021

Insect species richness affects plant responses to multi-herbivore attack.

New Phytol 2021 Jan 23. Epub 2021 Jan 23.

Laboratory of Entomology, Wageningen University and Research Centre, Droevendaalsesteeg 1, Wageningen, 6708PB, the Netherlands.

Plants are often attacked by multiple insect herbivores. How plants deal with an increasing richness of attackers from a single or multiple feeding guilds is poorly understood. We subjected black mustard (Brassica nigra) plants to 51 treatments representing attack by an increasing species richness (one, two or four species) of either phloem feeders, leaf chewers, or a mix of both feeding guilds when keeping total density of attackers constant and studied how this affects plant resistance to subsequent attack by caterpillars of the diamondback moth (Plutella xylostella). Increased richness in phloem-feeding attackers compromised resistance to P. xylostella. By contrast, leaf chewers induced a stronger resistance to subsequent attack by caterpillars of P. xylostella while species richness did not play a significant role for chewing herbivore induced responses. Attack by a mix of herbivores from different feeding guilds resulted in plant resistance similar to resistance levels of plants that were not previously exposed to herbivory. We conclude that B. nigra plants channel their defence responses stronger towards a feeding-guild specific response when under multi-species attack by herbivores of the same feeding guild, but integrate responses when simultaneously confronted with a mix of herbivores from different feeding guilds.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/nph.17228DOI Listing
January 2021

Parasitic wasps avoid ant-protected hemipteran hosts via the detection of ant cuticular hydrocarbons.

Proc Biol Sci 2021 01 6;288(1942):20201684. Epub 2021 Jan 6.

Instituto Valenciano de Investigaciones Agrarias, Plant Protection and Biotechnology Research Center, Moncada, Spain.

One of the most studied and best-known mutualistic relationships between insects is that between ants and phloem-feeding insects. Ants feed on honeydew excreted by phloem-feeding insects and, in exchange, attack the phloem feeders' natural enemies, including parasitic wasps. However, parasitic wasps are under selection to exploit information on hazards and avoid them. Here, we tested whether parasitic wasps detect the previous presence of ants attending colonies of phloem feeders. Behavioural assays demonstrate that wasps left colonies previously attended by ants more frequently than control colonies. This behaviour has a potential cost for the parasitic wasp as females inserted their ovipositor in fewer hosts per colony. In a further bioassay, wasps spent less time on papers impregnated with extracts of the ant cues than on control papers. Gas chromatography coupled with mass spectrometry analyses demonstrated that ants left a blend of cuticular hydrocarbons when they attended colonies of phloem feeders. These cuticular hydrocarbons are deposited passively when ants search for food. Overall, these results suggest, for the first time, that parasitic wasps of honeydew producers detect the previous presence of mutualistic ants through contact infochemicals. We anticipate such interactions to be widespread and to have implications in numerous ecosystems, as phloem feeders are usually tended by ants.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1098/rspb.2020.1684DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7892424PMC
January 2021

IPM-recommended insecticides harm beneficial insects through contaminated honeydew.

Environ Pollut 2020 Dec 8;267:115581. Epub 2020 Sep 8.

Instituto Valenciano de Investigaciones Agrarias (IVIA), Centro de Protección Vegetal y Biotecnología, Unidad Mixta Gestión Biotecnológica de Plagas UV-IVIA, Carretera CV-315, Km 10,7, 46113, Moncada, Spain.

The use of some systemic insecticides has been banned in Europe because they are toxic to beneficial insects when these feed on nectar. A recent study shows that systemic insecticides can also kill beneficial insects when they feed on honeydew. Honeydew is the sugar-rich excretion of hemipterans and is the most abundant carbohydrate source for beneficial insects such as pollinators and biological control agents in agroecosystems. Here, we investigated whether the toxicity of contaminated honeydew depends on i) the hemipteran species that excretes the honeydew; ii) the active ingredient, and iii) the beneficial insect that feeds on it. HPLC-MS/MS analyses demonstrated that the systemic insecticides pymetrozine and flonicamid, which are commonly used in Integrated Pest Management programs, were present in honeydew excreted by the mealybug Planococcus citri. However, only pymetrozine was detected in honeydew excreted by the whitefly Aleurothixus floccosus. Toxicological studies demonstrated that honeydew excreted by mealybugs feeding on trees treated either with flonicamid or pymetrozine increased the mortality of the hoverfly Sphaerophoria rueppellii, but did not affect the parasitic wasp Anagyrusvladimiri. Honeydew contaminated with flonicamid was more toxic for the hoverfly than that contaminated with pymetrozine. Collectively, our data demonstrate that systemic insecticides commonly used in IPM programs can contaminate honeydew and kill beneficial insects that feed on it, with their toxicity being dependent on the active ingredient and hemipteran species that excretes the honeydew.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.envpol.2020.115581DOI Listing
December 2020

Exploiting the chemical ecology of mosquito oviposition behavior in mosquito surveillance and control: a review.

J Vector Ecol 2020 12;45(2):155-179

Laboratory of Entomology, Wageningen University and Research, P.O. Box 16, 6700 AA, Wageningen, The Netherlands.

Vector control is an important component of the interventions aimed at mosquito-borne disease control. Current and future mosquito control strategies are likely to rely largely on the understanding of the behavior of the vector, by exploiting mosquito biology and behavior, while using cost-effective, carefully timed larvicidal and high-impact, low-volume adulticidal applications. Here we review the knowledge on the ecology of mosquito oviposition behavior with emphasis on the potential role of infochemicals in surveillance and control of mosquito-borne diseases. A search of PubMed, Embase, Web of Science, Global Health Archive, and Google Scholar databases was conducted using the keywords mosquito, infochemical, pheromone, kairomone, allomone, synomone, apneumone, attractant, host-seeking, and oviposition. Articles in English from 1974 to 2019 were reviewed to gain comprehensive understanding of current knowledge on infochemicals in mosquito resource-searching behavior. Oviposition of many mosquito species is mediated by infochemicals that comprise pheromones, kairomones, synomones, allomones, and apneumones. The novel putative infochemicals that mediate oviposition in the mosquito subfamilies Anophelinae and Culicinae were identified. The role of infochemicals in surveillance and control of these and other mosquito tribes is discussed with respect to origin of the chemical cues and how these affect gravid mosquitoes. Oviposition attractants and deterrents can potentially be used for manipulation of mosquito behavior by making protected resources unsuitable for mosquitoes (push) while luring them towards attractive sources (pull). In this review, strategies of targeting breeding sites with environmentally friendly larvicides with the aim to develop appropriate trap-and-kill techniques are discussed.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/jvec.12387DOI Listing
December 2020

Volatiles from soil-borne fungi affect directional growth of roots.

Plant Cell Environ 2021 01 30;44(1):339-345. Epub 2020 Sep 30.

Department of Microbial Ecology, Netherlands Institute of Ecology, Wageningen, The Netherlands.

Volatiles play major roles in mediating ecological interactions between soil (micro)organisms and plants. It is well-established that microbial volatiles can increase root biomass and lateral root formation. To date, however, it is unknown whether microbial volatiles can affect directional root growth. Here, we present a novel method to study belowground volatile-mediated interactions. As proof-of-concept, we designed a root Y-tube olfactometer, and tested the effects of volatiles from four different soil-borne fungi on directional growth of Brassica rapa roots in soil. Subsequently, we compared the fungal volatile organic compounds (VOCs) previously profiled with Gas Chromatography-Mass Spectrometry (GC-MS). Using our newly designed setup, we show that directional root growth in soil is differentially affected by fungal volatiles. Roots grew more frequently toward volatiles from the root pathogen Rhizoctonia solani, whereas volatiles from the other three saprophytic fungi did not impact directional root growth. GC-MS profiling showed that six VOCs were exclusively emitted by R. solani. These findings verify that this novel method is suitable to unravel the intriguing chemical cross-talk between roots and soil-borne fungi and its impact on root growth.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/pce.13890DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7821104PMC
January 2021

Genome-Wide Analysis Reveals Transcription Factors Regulated by Spider-Mite Feeding in Cucumber ().

Plants (Basel) 2020 Aug 11;9(8). Epub 2020 Aug 11.

Laboratory of Plant Physiology, Wageningen University and Research, 6708 PB Wageningen, The Netherlands.

To gain insight into the regulatory networks that underlie the induced defense in cucumber against spider mites, genes encoding transcription factors (TFs) were identified in the cucumber () genome and their regulation by two-spotted spider mite () herbivory was analyzed using RNA-seq. Of the total 1212 annotated TF genes in the cucumber genome, 119 were differentially regulated upon spider-mite herbivory during a period of 3 days. These TF genes belong to different categories but the , , and families had the highest relative numbers of differentially expressed genes. Correlation analysis of the expression of TF genes with defense-associated genes during herbivory and pathogen infestation, and in different organs resulted in the putative identification of regulators of herbivore-induced terpenoid and green-leaf-volatile biosynthesis. Analysis of the -acting regulatory elements (CAREs) present in the promoter regions of the genes responsive to spider-mite feeding revealed potential TF regulators. This study describes the TF genes in cucumber that are potentially involved in the regulation of induced defense against herbivory by spider mites.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/plants9081014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7465836PMC
August 2020

Next-generation biological control: the need for integrating genetics and genomics.

Biol Rev Camb Philos Soc 2020 12 14;95(6):1838-1854. Epub 2020 Aug 14.

Laboratory of Entomology, Wageningen University & Research, Droevendaalsesteeg 1, 6708 PB, Wageningen, The Netherlands.

Biological control is widely successful at controlling pests, but effective biocontrol agents are now more difficult to import from countries of origin due to more restrictive international trade laws (the Nagoya Protocol). Coupled with increasing demand, the efficacy of existing and new biocontrol agents needs to be improved with genetic and genomic approaches. Although they have been underutilised in the past, application of genetic and genomic techniques is becoming more feasible from both technological and economic perspectives. We review current methods and provide a framework for using them. First, it is necessary to identify which biocontrol trait to select and in what direction. Next, the genes or markers linked to these traits need be determined, including how to implement this information into a selective breeding program. Choosing a trait can be assisted by modelling to account for the proper agro-ecological context, and by knowing which traits have sufficiently high heritability values. We provide guidelines for designing genomic strategies in biocontrol programs, which depend on the organism, budget, and desired objective. Genomic approaches start with genome sequencing and assembly. We provide a guide for deciding the most successful sequencing strategy for biocontrol agents. Gene discovery involves quantitative trait loci analyses, transcriptomic and proteomic studies, and gene editing. Improving biocontrol practices includes marker-assisted selection, genomic selection and microbiome manipulation of biocontrol agents, and monitoring for genetic variation during rearing and post-release. We conclude by identifying the most promising applications of genetic and genomic methods to improve biological control efficacy.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/brv.12641DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7689903PMC
December 2020

Insights in the Global Genetics and Gut Microbiome of Black Soldier Fly, : Implications for Animal Feed Safety Control.

Front Microbiol 2020 7;11:1538. Epub 2020 Jul 7.

Plant Health Theme, International Centre of Insect Physiology and Ecology, Nairobi, Kenya.

The utilization of the black soldier fly (BSF) L. for recycling organic waste into high-quality protein and fat biomass for animal feeds has gained momentum worldwide. However, information on the genetic diversity and environmental implications on safety of the larvae is limited. This study delineates genetic variability and unravels gut microbiome complex of wild-collected and domesticated BSF populations from six continents using mitochondrial gene and 16S metagenomics. All sequences generated from the study linked to accessions KM967419.1, FJ794355.1, FJ794361.1, FJ794367.1, KC192965.1, and KY817115.1 from GenBank. Phylogenetic analyses of the sequences generated from the study and rooted by GenBank accessions of Fabricius and Macquart separated all samples into three branches, with and being closely related. Genetic distances between samples from the study and GenBank accessions of ranged between 0.0091 and 0.0407 while and samples clearly separated from all by distances of 0.1745 and 0.1903, respectively. Genetic distance matrix was used to generate a principal coordinate plot that further confirmed the phylogenetic clustering. Haplotype network map demonstrated that Australia, United States 1 (Rhode Island), United States 2 (Colorado), Kenya, and China shared a haplotype, while Uganda shared a haplotype with GenBank accession KC192965 BSF from United States. All other samples analyzed had individual haplotypes. Out of 481,695 reads analyzed from 16S metagenomics, four bacterial families (Enterobactereaceae, Dysgonomonadaceae, Wohlfahrtiimonadaceae, and Enterococcaceae) were most abundant in the BSF samples. Alpha-diversity, as assessed by Shannon index, showed that the Kenyan and Thailand populations had the highest and lowest microbe diversity, respectively; while microbial diversity assessed through Bray Curtis distance showed United States 3 (Maysville) and Netherlands populations to be the most dissimilar. Our findings on genetic diversity revealed slight phylogeographic variation between BSF populations across the globe. The 16S data depicted larval gut bacterial families with economically important genera that might pose health risks to both animals and humans. This study recommends pre-treatment of feedstocks and postharvest measures of the harvested BSF larvae to minimize risk of pathogen contamination along the insect-based feed value chain.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fmicb.2020.01538DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7381391PMC
July 2020

Insects for peace.

Curr Opin Insect Sci 2020 08 2;40:85-93. Epub 2020 Jun 2.

Laboratory of Entomology, Wageningen University, PO Box 16, 6700 AA Wageningen, The Netherlands. Electronic address:

Insects such as the black soldier fly (BSF) are a nutritious feed component for livestock with high protein levels. BSF can be reared on a wide range of organic residual streams. This allows for local production within a circular agriculture, decoupling livestock production from import of expensive feed components, such as fishmeal or soymeal. Rearing of BSF can be done by smallholder farmers, thus contributing to their livelihood, economic sustainability and social status. Smallholder farmers contribute importantly to food security, which is a prerequisite for a stable society. In armed conflicts, smallholder farmers are usually the first to suffer. In countries recovering from conflict, agricultural development should focus on restoring food production by smallholder farmers, improving their socio-economic position, thereby contributing to sustainable development goals 2 (zero hunger) and 16 (peace and justice). Here, we focus on these SDGs with an example of reintegration of ex-combatants as smallholder insect producers in post-conflict Colombia.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.cois.2020.05.011DOI Listing
August 2020

Correction to: Transcriptional and metabolite analysis reveal a shift in direct and indirect defences in response to spider‑mite infestation in cucumber (Cucumis sativus).

Plant Mol Biol 2020 07;103(4-5):507-509

Laboratory of Plant Physiology, Wageningen University and Research, Wageningen, The Netherlands.

In the above mentioned publication, part of Fig. 1b was distorted (48 h after TSSM Infestation). The original article has been corrected and the proper version of Fig. 1 is also published here.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s11103-020-01009-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7645467PMC
July 2020

Transcriptional and metabolite analysis reveal a shift in direct and indirect defences in response to spider-mite infestation in cucumber (Cucumis sativus).

Plant Mol Biol 2020 Jul 18;103(4-5):489-505. Epub 2020 Apr 18.

Laboratory of Plant Physiology, Wageningen University and Research, Wageningen, The Netherlands.

Key Message: Cucumber plants adapt their transcriptome and metabolome as result of spider mite infestation with opposite consequences for direct and indirect defences in two genotypes. Plants respond to arthropod attack with the rearrangement of their transcriptome which lead to subsequent phenotypic changes in the plants' metabolome. Here, we analysed transcriptomic and metabolite responses of two cucumber (Cucumis sativus) genotypes to chelicerate spider mites (Tetranychus urticae) during the first 3 days of infestation. Genes associated with the metabolism of jasmonates, phenylpropanoids, terpenoids and L-phenylalanine were most strongly upregulated. Also, genes involved in the biosynthesis of precursors for indirect defence-related terpenoids were upregulated while those involved in the biosynthesis of direct defence-related cucurbitacin C were downregulated. Consistent with the observed transcriptional changes, terpenoid emission increased and cucurbitacin C content decreased during early spider-mite herbivory. To further study the regulatory network that underlies induced defence to spider mites, differentially expressed genes that encode transcription factors (TFs) were analysed. Correlation analysis of the expression of TF genes with metabolism-associated genes resulted in putative identification of regulators of herbivore-induced terpenoid, green-leaf volatiles and cucurbitacin biosynthesis. Our data provide a global image of the transcriptional changes in cucumber leaves in response to spider-mite herbivory and that of metabolites that are potentially involved in the regulation of induced direct and indirect defences against spider-mite herbivory.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s11103-020-01005-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7299927PMC
July 2020

Smallholder farmers' knowledge and willingness to pay for insect-based feeds in Kenya.

PLoS One 2020 25;15(3):e0230552. Epub 2020 Mar 25.

International Centre of Insect Physiology and Ecology (icipe), Nairobi, Kenya.

Edible insects are increasingly being considered as sustainable alternatives to fish and soybean meals in animal feed because of their high nutritional quality and environmental benefits. However, successful introduction of a new product to the market depends on the target user's acceptance. Thus, evaluating the potential demand of insect-based feeds would provide relevant information for policy development. The present study assessed farmers' knowledge on edible insects as feed, their acceptance of integrating insect meals in animal feeds and willingness to pay (WTP) for insect-based feed (IBF) using a contingent valuation method. A household survey was conducted among 957 randomly selected farmers including: 409 poultry, 241 fish and 307 pig farmers in four counties in Kenya. Results of the study reveal that over 70 and 80% of poultry and fish farmers, respectively, are aware that insects can be used as a feed ingredient. In addition, over 60 and 75% of poultry and fish farmers, respectively, consider insects as a good component of feed. Poultry, pig and fish farmers interviewed accepted and showed willingness to pay for IBF. Regression analysis indicated that age, gender, education, marital status, distance to feed trader, awareness of insects as feed, attitude towards insects, acceptance of insect species, availability of agricultural inputs, use of commercial feeds, availability of training and market information had a significant influence on the WTP for IBF. Therefore, increased extension services to educate famers on the nutritional benefits of insect meals in animal feeds and existing market opportunities are expected to improve farmers' attitude towards utilization and consequently enhance WTP for IBF, which in return would significantly reduce the existing pressure on conventional fishmeal feed resources. Our findings provide the first insights into the market opportunities of including insect meals in the animal feed value chain in Kenya.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0230552PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7094868PMC
June 2020

Plant responses to butterfly oviposition partly explain preference-performance relationships on different brassicaceous species.

Oecologia 2020 Feb 13;192(2):463-475. Epub 2020 Jan 13.

Laboratory of Entomology, Wageningen University, Wageningen, The Netherlands.

The preference-performance hypothesis (PPH) states that herbivorous female insects prefer to oviposit on those host plants that are best for their offspring. Yet, past attempts to show the adaptiveness of host selection decisions by herbivores often failed. Here, we tested the PPH by including often neglected oviposition-induced plant responses, and how they may affect both egg survival and larval weight. We used seven Brassicaceae species of which most are common hosts of two cabbage white butterfly species, the solitary Pieris rapae and gregarious P. brassicae. Brassicaceous species can respond to Pieris eggs with leaf necrosis, which can lower egg survival. Moreover, plant-mediated responses to eggs can affect larval performance. We show a positive correlation between P. brassicae preference and performance only when including the egg phase: 7-day-old caterpillars gained higher weight on those plant species which had received most eggs. Pieris eggs frequently induced necrosis in the tested plant species. Survival of clustered P. brassicae eggs was unaffected by the necrosis in most tested species and no relationship between P. brassicae egg survival and oviposition preference was found. Pieris rapae preferred to oviposit on plant species most frequently expressing necrosis although egg survival was lower on those plants. In contrast to the lower egg survival on plants expressing necrosis, larval biomass on these plants was higher than on plants without a necrosis. We conclude that egg survival is not a crucial factor for oviposition choices but rather egg-mediated responses affecting larval performance explained the preference-performance relationship of the two butterfly species.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00442-019-04590-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7002336PMC
February 2020

Foliar herbivory by caterpillars and aphids differentially affects phytohormonal signalling in roots and plant defence to a root herbivore.

Plant Cell Environ 2020 03 10;43(3):775-786. Epub 2020 Jan 10.

Laboratory of Entomology, Wageningen University and Research, Wageningen, The Netherlands.

Plant-mediated interactions are an important force in insect ecology. Through such interactions, herbivores feeding on leaves can affect root feeders. However, the mechanisms regulating the effects of above-ground herbivory on below-ground herbivores are poorly understood. Here, we investigated the performance of cabbage root fly larvae (Delia radicum) on cabbage plants (Brassica oleracea) previously exposed to above ground herbivores belonging to two feeding guilds: leaf chewing diamondback moth caterpillars (Plutella xylostella) or phloem-feeding cabbage aphids (Brevicoryne brassicae). Our study focusses on root-herbivore performance and defence signalling in primary roots by quantifying phytohormones and gene expression. We show that leaf herbivory by caterpillars, but not by aphids, strongly attenuates root herbivore performance. Above-ground herbivory causes changes in primary roots in terms of gene transcripts and metabolites involved in plant defence. Feeding by below-ground herbivores strongly induces the jasmonate pathway in primary roots. Caterpillars feeding on leaves cause a slight induction of the primary root jasmonate pathway and interact with plant defence signalling in response to root herbivores. In conclusion, feeding by a leaf chewer and a phloem feeder differentially affects root-herbivore performance, root-herbivore-induced phytohormonal signalling, and secondary metabolites.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/pce.13707DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7065167PMC
March 2020

Context-Dependence and the Development of Push-Pull Approaches for Integrated Management of .

Insects 2019 Dec 15;10(12). Epub 2019 Dec 15.

Groningen Institute of Evolutionary Life Sciences, University of Groningen, P.O. Box 11103, 9700 CC Groningen, The Netherlands.

Sustainable pest control requires a systems approach, based on a thorough ecological understanding of an agro-ecosystem. Such fundamental understanding provides a basis for developing strategies to manipulate the pest's behaviour, distribution, and population dynamics, to be employed for crop protection. This review focuses on the fundamental knowledge required for the development of an effective push-pull approach. Push-pull is a strategy to repel a pest from a crop, while attracting it toward an external location. It often relies on infochemicals (e.g., pheromones or allelochemicals) that are relevant in the ecology of the pest insect and can be exploited as lure or repellent. Importantly, responsiveness of insects to infochemicals is dependent on both the insect's internal physiological state and external environmental conditions. This context-dependency reflects the integration of cues from different sensory modalities, the effect of mating and/or feeding status, as well as diurnal or seasonal rhythms. Furthermore, when the costs of responding to an infochemical outweigh the benefits, resistance can rapidly evolve. Here, we argue that profound knowledge on context-dependence is important for the development and implementation of push-pull approaches. We illustrate this by discussing the relevant fundamental knowledge on the invasive pest species as an example.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/insects10120454DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6956413PMC
December 2019

Maternal effect determines drought resistance of eggs in the predatory mite Phytoseiulus persimilis.

Oecologia 2020 Jan 26;192(1):29-41. Epub 2019 Nov 26.

Laboratory of Entomology, Wageningen University, PO Box 16, 6700 AA, Wageningen, The Netherlands.

The ability of an organism to adapt to short-term environmental changes within its lifetime is of fundamental importance. This adaptation may occur through phenotypic plasticity. Insects and mites, in particular, are sensitive to changes in temperature and humidity, especially during the juvenile stages. We studied the role of phenotypic plasticity in the adaptation of eggs to different relative humidity conditions, in the predatory mite Phytoseiulus persimilis, used worldwide as a biological control agent of the spider mite Tetranychus urticae. The biocontrol efficacy of P. persimilis decreases under dry conditions, partly because P. persimilis eggs are sensitive to drought. We exposed P. persimilis adult females from two different strains to constant and variable humidity regimes and evaluated the hatching rate of their eggs in dry conditions, as well as the survival and oviposition rates of these females. Whereas the eggs laid by P. persimilis females exposed to constant high humidity did not survive in dry conditions, females exposed to constant low humidity started laying drought-resistant eggs after 24 h of exposure. Survival and oviposition rates of the females were affected by humidity: females laid fewer eggs under constant low humidity and had a shorter lifespan under constant high and constant low humidity. The humidity regimes tested had similar effects across the two P. persimilis strains. Our results demonstrate that transgenerational phenotypic plasticity, called maternal effect, allows P. persimilis females to prepare their offspring for dry conditions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00442-019-04556-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6974492PMC
January 2020

Proximate mechanisms of drought resistance in Phytoseiulus persimilis eggs.

Exp Appl Acarol 2019 Dec 25;79(3-4):279-298. Epub 2019 Nov 25.

Laboratory of Entomology, Wageningen University, PO Box 16, 6700 AA, Wageningen, The Netherlands.

Under drought stress, Phytoseiulus persimilis females are able to lay drought-resistant eggs through an adaptive maternal effect. The mechanisms making these eggs drought resistant still remain to be investigated. For this purpose, we studied the physiological differences between drought-resistant and drought-sensitive eggs. We compared the volume and the surface-area-to-volume ratio (SA:V) of the eggs, their sex ratio, their chemical composition (by gas chromatography-mass spectrometry), their internal and external structure [by scanning electron microscope (SEM) and transmission electron microscope (TEM) images], and their developmental time. Our results show that drought-resistant and drought-sensitive eggs have a different chemical composition: drought-resistant eggs contain more compatible solutes (free amino acids and sugar alcohols) and saturated hydrocarbons than drought-sensitive eggs. This difference may contribute to reducing water loss in drought-resistant eggs. Moreover, drought-resistant eggs are on average 8.4% larger in volume, and have a 2.4% smaller SA:V than drought-sensitive eggs. This larger volume and smaller SA:V, probably the result of a higher water content, may make drought-resistant eggs less vulnerable to water loss. We did not find any difference in sex ratio, internal or external structure nor developmental time between drought-resistant and drought-sensitive eggs. These results mark the first step in the understanding of the strategies and the energetic costs involved in the production of drought-resistant eggs in P. persimilis females.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s10493-019-00442-9DOI Listing
December 2019

Cross-seasonal legacy effects of arthropod community on plant fitness in perennial plants.

J Ecol 2019 Sep 8;107(5):2451-2463. Epub 2019 Jul 8.

Laboratory of Entomology Wageningen University Wageningen The Netherlands.

In perennial plants, interactions with other community members during the vegetative growth phase may influence community assembly during subsequent reproductive years and may influence plant fitness. It is well-known that plant responses to herbivory affect community assembly within a growing season, but whether plant-herbivore interactions result in legacy effects on community assembly across seasons has received little attention. Moreover, whether plant-herbivore interactions during the vegetative growing season are important in predicting plant fitness directly or indirectly through legacy effects is poorly understood.Here, we tested whether plant-arthropod interactions in the vegetative growing season of perennial wild cabbage plants, , result in legacy effects in arthropod community assembly in the subsequent reproductive season and whether legacy effects have plant fitness consequences. We monitored the arthropod community on plants that had been induced with either aphids, caterpillars or no herbivores in a full-factorial design across 2 years. We quantified the plant traits 'height', 'number of leaves' and 'number of flowers' to understand mechanisms that may mediate legacy effects. We measured seed production in the second year to evaluate plant fitness consequences of legacy effects.Although we did not find community responses to the herbivory treatments, our data show that community composition in the first year leaves a legacy on community composition in a second year: predator community composition co-varied across years. Structural equation modelling analyses indicated that herbivore communities in the vegetative year correlated with plant performance traits that may have caused a legacy effect on especially predator community assembly in the subsequent reproductive year. Interestingly, the legacy of the herbivore community in the vegetative year predicted plant fitness better than the herbivore community that directly interacted with plants in the reproductive year. Thus, legacy effects of plant-herbivore interactions affect community assembly on perennial plants across growth seasons and these processes may affect plant reproductive success. We argue that plant-herbivore interactions in the vegetative phase as well as in the cross-seasonal legacy effects caused by plant responses to arthropod herbivory may be important in perennial plant trait evolution such as ontogenetic variation in growth and defence strategies.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/1365-2745.13231DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6774310PMC
September 2019

Microbial Symbionts of Parasitoids.

Annu Rev Entomol 2020 01 7;65:171-190. Epub 2019 Oct 7.

Laboratory of Entomology, Wageningen University, 6700 AA Wageningen, The Netherlands; email:

Parasitoids depend on other insects for the development of their offspring. Their eggs are laid in or on a host insect that is consumed during juvenile development. Parasitoids harbor a diversity of microbial symbionts including viruses, bacteria, and fungi. In contrast to symbionts of herbivorous and hematophagous insects, parasitoid symbionts do not provide nutrients. Instead, they are involved in parasitoid reproduction, suppression of host immune responses, and manipulation of the behavior of herbivorous hosts. Moreover, recent research has shown that parasitoid symbionts such as polydnaviruses may also influence plant-mediated interactions among members of plant-associated communities at different trophic levels, such as herbivores, parasitoids, and hyperparasitoids. This implies that these symbionts have a much more extended phenotype than previously thought. This review focuses on the effects of parasitoid symbionts on direct and indirect species interactions and the consequences for community ecology.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1146/annurev-ento-011019-024939DOI Listing
January 2020

Leaf metabolic signatures induced by real and simulated herbivory in black mustard (Brassica nigra).

Metabolomics 2019 09 28;15(10):130. Epub 2019 Sep 28.

Department of Plant Physiology, Umeå University (Umeå Plant Science Centre), 90187, Umeå, Sweden.

Introduction: The oxylipin methyl jasmonate (MeJA) is a plant hormone active in response signalling and defence against herbivores. Although MeJA is applied experimentally to mimic herbivory and induce plant defences, its downstream effects on the plant metabolome are largely uncharacterized, especially in the context of primary growth and tissue-specificity of the response.

Objectives: We investigated the effects of MeJA-simulated and real caterpillar herbivory on the foliar metabolome of the wild plant Brassica nigra and monitored the herbivore-induced responses in relation to leaf ontogeny.

Methods: As single or multiple herbivory treatments, MeJA- and mock-sprayed plants were consecutively exposed to caterpillars or left untreated. Gas chromatography (GC) and liquid chromatography (LC) time-of-flight mass-spectrometry (TOF-MS) were combined to analyse foliar compounds, including central primary and specialized defensive plant metabolites.

Results: Plant responses were stronger in young leaves, which simultaneously induced higher chlorophyll levels. Both MeJA and caterpillar herbivory induced similar, but not identical, accumulation of tricarboxylic acids (TCAs), glucosinolates (GSLs) and phenylpropanoids (PPs), but only caterpillar feeding led to depletion of amino acids. MeJA followed by caterpillars caused higher induction of defence compounds, including a three-fold increase in the major defence compound allyl-GSL (sinigrin). When feeding on MeJA-treated plants, caterpillars gained less weight indicative of the reduced host-plant quality and enhanced resistance.

Conclusions: The metabolomics approach showed that plant responses induced by herbivory extend beyond the regulation of defence metabolism and are tightly modulated throughout leaf development. This leads to a new understanding of the plant metabolic potential that can be exploited for future plant protection strategies.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s11306-019-1592-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6765471PMC
September 2019

Effect of Dietary Replacement of Fishmeal by Insect Meal on Growth Performance, Blood Profiles and Economics of Growing Pigs in Kenya.

Animals (Basel) 2019 Sep 20;9(10). Epub 2019 Sep 20.

Laboratory of Entomology, Wageningen University & Research, 6700AA Wageningen, The Netherlands.

Pig production is one of the fastest growing livestock sectors. Development of this sector is hampered by rapidly increasing costs of fishmeal (FM), which is a common protein source in animal feeds. Here, we explored the potential of substituting FM with black soldier fly larval meal (BSFLM) on growth and blood parameters of pigs as well as economic aspects. At weaning, 40 hybrid pigs, i.e., crossbreeds of purebred Large White and Landrace were randomly assigned to five iso-nitrogenous and iso-energetic dietary treatments: Control (0% BSFLM and 100% FM (T0)), and FM replaced at 25% (T25), 50% (T50), 75% (T75) and 100% (T100) with BSFLM. Average daily feed intake (ADFI), average daily gain (ADG), body weight gain (BWG) and feed conversion ratio (FCR) were calculated for the whole trial. Hematological and serum biochemical parameters, the cost-benefit ratio (CBR) and return on investment (RoI) were evaluated. No significant effect of diet type was observed on feed intake and daily weight gain. Red or white blood cell indices did not differ among diets. Pigs fed T25, T75 and T100, had lower platelet counts compared to T0 and T50. Dietary inclusion of BSFLM did not affect blood total cholesterol, triglycerides, low-density lipoprotein and high-density lipoprotein. CBR and RoI were similar for the various diets. In conclusion, BSFLM is a suitable and cost-effective alternative to fishmeal in feed for growing pigs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/ani9100705DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6826664PMC
September 2019

Neonicotinoids in excretion product of phloem-feeding insects kill beneficial insects.

Proc Natl Acad Sci U S A 2019 08 5;116(34):16817-16822. Epub 2019 Aug 5.

Centro de Protección Vegetal y Biotecnología, Unidad Mixta Gestión Biotecnológica de Plagas, Instituto Valenciano de Investigaciones Agrarias, 46113 Moncada, Spain;

Pest control in agriculture is mainly based on the application of insecticides, which may impact nontarget beneficial organisms leading to undesirable ecological effects. Neonicotinoids are among the most widely used insecticides. However, they have important negative side effects, especially for pollinators and other beneficial insects feeding on nectar. Here, we identify a more accessible exposure route: Neonicotinoids reach and kill beneficial insects that feed on the most abundant carbohydrate source for insects in agroecosystems, honeydew. Honeydew is the excretion product of phloem-feeding hemipteran insects such as aphids, mealybugs, whiteflies, and psyllids. We allowed parasitic wasps and pollinating hoverflies to feed on honeydew from hemipterans feeding on trees treated with thiamethoxam or imidacloprid, the most commonly used neonicotinoids. LC-MS/MS analyses demonstrated that both neonicotinoids were present in honeydew. Honeydew with thiamethoxam was highly toxic to both species of beneficial insects, and honeydew with imidacloprid was moderately toxic to hoverflies. Collectively, our data provide strong evidence for honeydew as a route of insecticide exposure that may cause acute or chronic deleterious effects on nontarget organisms. This route should be considered in future environmental risk assessments of neonicotinoid applications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1073/pnas.1904298116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6708310PMC
August 2019

What makes a volatile organic compound a reliable indicator of insect herbivory?

Plant Cell Environ 2019 12 18;42(12):3308-3325. Epub 2019 Aug 18.

Laboratory of Entomology, Department of Plant Sciences, Wageningen University, 6708PB, Wageningen, The Netherlands.

Plants that are subject to insect herbivory emit a blend of so-called herbivore-induced plant volatiles (HIPVs), of which only a few serve as cues for the carnivorous enemies to locate their host. We lack understanding which HIPVs are reliable indicators of insect herbivory. Here, we take a modelling approach to elucidate which physicochemical and physiological properties contribute to the information value of a HIPV. A leaf-level HIPV synthesis and emission model is developed and parameterized to poplar. Next, HIPV concentrations within the canopy are inferred as a function of dispersion, transport and chemical degradation of the compounds. We show that the ability of HIPVs to reveal herbivory varies from almost perfect to no better than chance and interacts with canopy conditions. Model predictions matched well with leaf-emission measurements and field and laboratory assays. The chemical class a compound belongs to predicted the signalling ability of a compound only to a minor extent, whereas compound characteristics such as its reaction rate with atmospheric oxidants, biosynthesis rate upon herbivory and volatility were much more important predictors. This study shows the power of merging fields of plant-insect interactions and atmospheric chemistry research to increase our understanding of the ecological significance of HIPVs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/pce.13624DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6972585PMC
December 2019

Ecology of Plastic Flowers.

Trends Plant Sci 2019 08 13;24(8):725-740. Epub 2019 Jun 13.

Laboratory of Entomology, Wageningen University, PO Box 16, 6700 AA Wageningen, The Netherlands.

Plant phenotypic plasticity in response to herbivore attack includes changes in flower traits. Such herbivore-induced changes in flower traits have consequences for interactions with flower visitors. We synthesize here current knowledge on the specificity of herbivore-induced changes in flower traits, the underlying molecular mechanisms, and the ecological consequences for flower-associated communities. Herbivore-induced changes in flower traits seem to be largely herbivore species-specific. The extensive plasticity observed in flowers influences a highly connected web of interactions within the flower-associated community. We argue that the adaptive value of herbivore-induced plant responses and flower plasticity can be fully understood only from a community perspective rather than from pairwise interactions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.tplants.2019.04.007DOI Listing
August 2019

Volatiles of pathogenic and non-pathogenic soil-borne fungi affect plant development and resistance to insects.

Oecologia 2019 Jul 15;190(3):589-604. Epub 2019 Jun 15.

Laboratory of Entomology, Wageningen University and Research, Wageningen, The Netherlands.

Plants are ubiquitously exposed to a wide diversity of (micro)organisms, including mutualists and antagonists. Prior to direct contact, plants can perceive microbial organic and inorganic volatile compounds (hereafter: volatiles) from a distance that, in turn, may affect plant development and resistance. To date, however, the specificity of plant responses to volatiles emitted by pathogenic and non-pathogenic fungi and the ecological consequences of such responses remain largely elusive. We investigated whether Arabidopsis thaliana plants can differentiate between volatiles of pathogenic and non-pathogenic soil-borne fungi. We profiled volatile organic compounds (VOCs) and measured CO emission of 11 fungi. We assessed the main effects of fungal volatiles on plant development and insect resistance. Despite distinct differences in VOC profiles between the pathogenic and non-pathogenic fungi, plants did not discriminate, based on plant phenotypic responses, between pathogenic and non-pathogenic fungi. Overall, plant growth was promoted and flowering was accelerated upon exposure to fungal volatiles, irrespectively of fungal CO emission levels. In addition, plants became significantly more susceptible to a generalist insect leaf-chewing herbivore upon exposure to the volatiles of some of the fungi, demonstrating that a prior fungal volatile exposure can negatively affect plant resistance. These data indicate that plant development and resistance can be modulated in response to exposure to fungal volatiles.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00442-019-04433-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6647456PMC
July 2019

Defense of pyrethrum flowers: repelling herbivores and recruiting carnivores by producing aphid alarm pheromone.

New Phytol 2019 08 31;223(3):1607-1620. Epub 2019 May 31.

Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, 430070, China.

(E)-β-Farnesene (EβF) is the predominant constituent of the alarm pheromone of most aphid pest species. Moreover, natural enemies of aphids use EβF to locate their aphid prey. Some plant species emit EβF, potentially as a defense against aphids, but field demonstrations are lacking. Here, we present field and laboratory studies of flower defense showing that ladybird beetles are predominantly attracted to young stage-2 pyrethrum flowers that emitted the highest and purest levels of EβF. By contrast, aphids were repelled by EβF emitted by S2 pyrethrum flowers. Although peach aphids can adapt to pyrethrum plants in the laboratory, aphids were not recorded in the field. Pyrethrum's (E)-β-farnesene synthase (EbFS) gene is strongly expressed in inner cortex tissue surrounding the vascular system of the aphid-preferred flower receptacle and peduncle, leading to elongated cells filled with EβF. Aphids that probe these tissues during settlement encounter and ingest plant EβF, as evidenced by the release in honeydew. These EβF concentrations in honeydew induce aphid alarm responses, suggesting an extra layer of this defense. Collectively, our data elucidate a defensive mimicry in pyrethrum flowers: the developmentally regulated and tissue-specific EβF accumulation and emission both prevents attack by aphids and recruits aphid predators as bodyguards.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/nph.15869DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6772172PMC
August 2019