Root Feeding Research Articles

Disentangling the influence of water limitation and simultaneous above and belowground herbivory on plant tolerance and resistance to stress

Abstract Plants face multiple biotic and abiotic stressors simultaneously. Many species can tolerate and resist stress, but countermeasures differ between roots and leaves. Since herbivores and environmental conditions modulate costs and benefits of plant defence traits, stress responses are context‐dependent. We examined whole‐plant tolerance and resistance responses to individual and combined effects of above and belowground herbivory under variable water conditions. We manipulated water availability and access by two common herbivores (Spodoptera exigua caterpillars and Meloidogyne incognita nematodes) to Solanum lycocarpum. Plants were either watered based on historical regional averages or the 30% reduction predicted by IPCC studies. Herbivory treatments included isolated above (AG) and belowground (BG) attacks, simultaneous (AGBG) attacks and no‐herbivory controls. We then parameterized generalized linear mixed‐effects models with data on plant survival, leaf and root biomass accumulation, root complexity and terpenoid concentration. Foliar herbivory increased terpenoid concentrations in roots relative to no‐herbivory plants under control water but decreased concentrations in both roots and leaves under drought. Similarly, root feeders increased concentrations of terpenoids in leaves under control water but decreased concentrations only in roots under drought. Plants challenged with AGBG herbivory had greater whole‐plant biomass (i.e. tolerance) and lower total concentrations of defensive compounds (i.e. resistance) than plants exposed to no‐herbivore controls, regardless of water conditions. Importantly, the capacity of plants to grow or produce terpenoids changes when herbivory level is considered. In plants exposed to AGBG herbivory, greater nematode infection was related to decreases in whole‐plant biomass and marginal increases in total terpenoid concentration. Ultimately, accounting only for individual AG and BG responses would have led to different conclusions and underestimated the magnitude of S. lycocarpum's compensatory responses. A ‘whole‐plant’ approach revealed that belowground herbivory is the primary driver of tolerance in plants surviving moderate water stress. Synthesis. Whole‐plant responses to stress in variable environments are complex, and their comprehensive understanding requires accounting for belowground herbivores and root responses.

Woody encroachment in grassland elicits complex changes in the functional structure of above‐ and belowground biota

AbstractWoody plant encroachment affects dry grasslands globally. To predict changes in biodiversity and ecosystem processes, it is important to understand how this process affects the functional composition of grassland organism groups. In this context, seminatural wooded meadows represent a form of experimental manipulation—where open grassland and woody patches co‐occur in homogeneous environmental conditions due to human management decisions—which provides an opportunity to address the effect of woody plant encroachment on vegetation and soil biota. We used environmental DNA metabarcoding to address variation in plant, soil fungal, and soil animal communities in parallel. We also addressed functional groups of fungi—animal and plant pathogens, saprotrophs, decomposers, arbuscular mycorrhizal, ectomycorrhizal, endophytic, and other symbiotrophic fungi—and of soil animals—fungivores, bacterivores, litter feeders, root feeders, macro plant feeders, algal/lichen feeders, predators, and parasites. Co‐variation between communities was detected from aboveground vegetation plots and metabarcoding of soil DNA, in terms of estimated richness and compositional patterns. Differences between open and wooded patches were most pronounced among plants and symbiotic fungi, whereas soil animals exhibited less marked differences. For most organisms, mean richness, as well as total richness per habitat type, was higher in open than wooded patches, but ectomycorrhizal fungi exhibited the opposite pattern. The functional structure of the soil biotic community, as characterized by the proportion of DNA sequences attributed to different functional groups, differed significantly between open and wooded grassland patches, with symbiotic fungi (arbuscular mycorrhizal, ectomycorrhizal, and other symbiotrophic [mostly orchid mycorrhizal] fungi) contributing most to the difference. This study supports the notion that a soil DNA‐based metabarcoding approach can provide insights into the diversity and composition of multiple taxonomic groups in natural ecosystems. It also provides a first demonstration of the complex changes to the functional structure of the belowground community that accompany woody plant encroachment in grasslands.

Analysis of tebuconazole residues in coconut water, kernel and leaves using LC–MS/MS

A method was validated for determining tebuconazole residues in coconut water, kernel and leaves using Liquid chromatography-Mass spectrometry/Mass spectrometry (LC–MS/MS) with electro spray ionization in positive ion mode. Samples were extracted with acetonitrile and subsequent clean-up was done using dispersive solid phase extraction. Recovery ranged between 70 and 114.39 % and the RSD was between 0.64 and 10.24 %. Root feeding studies with tebuconazole @ 5 and 10 mL/100 mL of water/tree revealed the presence of tebuconazole residues in coconut leaves until three days after treatment but dissipated to below quantifiable limit on 5th day at single dose while the residues went below quantifiable limit after 10 days at double the dose. Residues were below quantifiable limit in coconut water and kernel until three days. Data obtained from the study were used for estimating the risks associated with the exposures to tebuconazole residues in coconut.

ROLE OF ROOT FEEDING IN MODERN TECHNOLOGY OF CULTIVATING GRAIN CORN

The article presents the results of studying the impact of foliar fertilization with Ekolist Mono Zinc microfertilizer on the complex of economically valuable traits and productivity of maize hybrids of different maturity groups. The research has been conducted for studying the dependence of the timing of foliar fertilization on the level of productivity of corn. Field research was established during 2019-2020 in the research field of the Department of Plant Breeding, Breeding and Bioenergy Crops of SE "Kordelivske" IC NAANU Vinnytsia National Agrarian University. The soil of the experimental site - dark gray is characterized by the following agrochemical parameters: humus content - 3.27%, nitrogen supply (by the method of Cornfield) low - 116 mg / kg of soil, mobile phosphorus compounds (by Chyrykov method) average - 95 mg / kg of soil , and high potassium - 137 mg / kg of soil, pH - 6.5. A two-factor experiment with corn was established by the method of split plots. The study was performed in quadruplicate. The sown area of the plot is 50 m2, the accounting area is 25 m2. Observations and crop accounting were performed according to generally accepted methods. Studies have shown that the largest increase in plant height (11-18 cm) and the height of attachment of cobs was observed in variants with two foliar feeding of corn with microfertilizer Ecolist Mono Zinc. Application of Ekolist Mono Zinc microfertilizer in the phase of 5-7 and 10-12 corn leaves provides the highest value of cob length: DKS 2971 (FAO 200) - 22.0 cm, DKS 3476 (FAO 260) - 25.2 cm and DKS 3511 330) - 26.0 cm, increases the weight of 1000 grains by 7.5-12.4%, protein content by 0.07-0.15%, reduces the fat content by 0.01-0.20% compared with the control. The highest value of yield of the studied maize hybrids was obtained by double application of microfertilizer Ecolist Mono Zinc in the phase of 5-7 and 10-12 leaves of corn, and on average for two years it was: DKS 2971 (FAO 200) - 7.5 t / ha, DKS 3476 (FAO 260) - 9.8 t / ha and DKS 3511 (FAO 330) - 10.4 t / ha, while the control yield was 6.6; 8.8 and 9.0 t / ha, respectively. Taking into consideration the results of the analysis of economic indicators of cultivation of maize hybrid DKS 3511 (FAO 330), the highest value of gross production per 1 ha - 41.44 thousand UAH / ha - was obtained on the option with double application of microfertilizer Ecolist Mono Zinc in phase 5-7 and 10-12 leaves of corn, the lowest cost of grain is set - 156.5 UAH / c. The final indicator of economic efficiency - the level of profitability - was the highest and amounted to 254.5%. Thus, foliar fertilization increases the yield of maize hybrids of different maturity groups, improves the quality of grain in terms of chemical composition and optimizes the value of economically valuable traits.

The Impact of Root-Derived Resources on Forest Soil Invertebrates Depends on Body Size and Trophic Position

Forest soil food webs have been assumed to be fueled substantially by root-derived resources. However, until today the flux of root-derived resources into soil animals has been investigated virtually exclusively using isotope labeling experiments, whereas studies on the consequences of disrupting the flux of root-derived resources into the soil animal food web are scarce. We here investigated the importance of root-derived resources for a wide range of soil animals by interrupting the resource flux into the soil of different forest types in Central Europe using a trenching experiment. We recorded the abundance of soil animal taxa varying in body size (micro-, meso-, and macrofauna) 1 and 3 years after root trenching, and quantified changes in biomass, species composition, and trophic shift using stable isotopes and NLFA analysis. Among the microfauna groups studied (trophic groups of Nematoda) only the abundance of plant feeding nematodes showed a trend in being decreased by -58% due to root trenching. Major soil mesofauna groups, including Collembola and Oribatida, suffered to a similar extent from root trenching with their abundance and biomass being reduced by about 30–40%. The soil macrofauna groups studied (Diplopoda, Isopoda, Chilopoda, Araneae, Coleoptera) generally were only little affected by root trenching suggesting that they rely less on root-derived resources than micro- and in particular mesofauna. Notably, the community structure of micro-, meso-, and macrofauna was not affected by root trenching. Further, we observed trophic shifts only in 2 out of 10 investigated species with the shifts generally being only minor. The results indicate that soil animal communities are markedly resilient to deprivation of root-derived resources suggesting that links to root-derived resources are non-specific. However, this resilience appears to vary with body size, with mesofauna including both decomposers as well as predators being more sensitive to the deprivation of root-derived resources than microfauna (except for root feeders) and macrofauna. Overall, this suggests that body size constrains the channeling of energy through soil food webs, with root-derived resources in temperate forests being channeled predominantly via soil taxa of intermediate size, i.e., mesofauna.

Tolerance in Maize Landraces to Diabrotica speciosa (Coleoptera: Chrysomelidae) Larvae and Its Relationship to Plant Pigments, Compatible Osmolytes, and Vigor.

The rootworm Diabrotica speciosa (Germar) is native to South America and causes severe economic losses to several crops due to root feeding and disease spread. In maize (Zea mays L.), losses in production come from larval rootworm attack on plant roots resulting in plant health problems, including stalk lodging. More options for controlling this pest are needed to create well balanced, integrated pest management programs for farmers in this region. Natural sources of tolerance in maize genotypes are important for maize breeding programs, and this study investigated the expression of tolerance in several Brazilian maize landraces to D. speciosa. Plant vigor and compounds associated with plant health, including chlorophylls, carotenoids, glycine betaine, and proline were assessed for each landrace. Five landraces and one maize cultivar were selected based on their levels of antibiosis-resistance to D. speciosa that were determined in a prior screening. The percent reduction in plant growth was used as the measure of tolerance. The landrace Azteca was classified as tolerant to D. speciosa larval feeding, displaying less reduction in plant matter despite having lower plant vigor. This landrace also had higher amounts of chlorophyl and carotenoid pigments, suggesting a positive correlation between tolerance to D. speciosa and higher contents of these photosynthetic pigments. The compatible osmolytes glycine betaine and proline do not seem to be associated with tolerance in maize landraces to D. speciosa larvae. Landrace Azteca seems promising for plant breeding, and repeated field studies are needed to confirm its suitability in maize integrated pest management.

Assessment of Farmer’s Perception on Pesticide Usage Pattern and Knowledge on Pest Management in Amaranthus in Coimbatore District

Amaranthus is a protein rich grain that is commonly cultivated as a leafy vegetable. Insect pests (63.2%), marketing (22.4%) and weather parameters (14.4%) acted as the major constraints in amaranthus production. Among the constraints, infestation by numerous insect pests that feed on different plant parts such as stem, leaves, flowers and seeds had greater negative impact on amaranthus production. A total number of 92 insect pests from 11 different orders have been documented in cultivated amaranthus. Among them, the leaf webber, Hymenia recurvalis Fab. (Crambidae : Lepidoptera) and stem weevil, Hypolixus truncatulus (Curculionidae: Coleoptera) were considered as major threat to the farmers. Leaf webber, H. recurvalis caused the maximum damage through webbing and defoliation up to 8.8%. Stem weevil, H. truncatulus resulted in 12.6% damage, while, the damage was up to 7.3% due to white grub, the root feeder. Almost all the amaranthus farmers relied on chemical pesticides for the management of insect pests of amaranthus. A field survey on pesticide usage pattern in amaranthus was undertaken in three amaranthus growing blocks of Coimbatore district viz., Sultanpet, Karamadai and Thondamuthur. Most of the farmers (73.3 %) used chlorantraniliprole for managing the insect pests infesting amaranthus. Around 66 per cent of the farmers used organic pesticide (Exodus) as an alternate next to chlorantraniliprole. Percentage of farmers using imidacloprid, flubendiamide, panchakavya and jeevamrutham for crop protection represent 53.3, 33.3 and 13.3 per cent, respectively.

STARCH CONTENT IN CORN GRAIN DEPENDING ON ROOT FEEDING

The article presents the results of researching the impact of foliar fertilization with microfertilizers Ecolist Mono Zinc and Rostok Corn, plant growth regulator Vimpel and bacterial preparation Biomag on the complex of economically valuable traits and productivity of maize hybrids of different maturity groups (early ripening group: Kharkiv 195 MV, (FAO 190), DKS 2960 (FAO 250), DKS 2949 (FAO 190), DKS 2971 (FAO 200), middle-early: DKS 3472 (FAO 270), DKS 3420 (FAO 280), Pereyaslavsky 230 SV (FAO 230), DKS 3871 (FAO 280) and medium-ripe: DK 391 (FAO 320), DK 440 (FAO 350), DKS 4964 (FAO 390), DK 315 (FAO 310)). The dependence of foliar fertilization usage and the starch content in corn grain is generalized. One-time foliar feeding provided a starch content increase by 0.1-0.5%, double feeding - by 0.85-1.30%. The yield of starch was in hybrids DK 391 - 8,748 t / ha, DK 440 - 8,821 t / ha, DKS 4964 - 9,559 t / ha, DK 315 - 9,314 t / ha with a single feeding and with a double feeding it was significantly higher - 9,220 t / ha, - 9,384 t / ha, 10,142 t / ha, 9,993 t / ha, accordingly. The highest yield of starch in all hybrids was provided by double application of microfertilizer Ecolist Mono Zinc (8,983-10,595 t / ha) and Rostok corn (8,721-10,597 t / ha), the increase in starch yield with the use of these fertilizers was 0.5-1.8 t / ha, relative to control (water supply). It is established that in dry years with high temperatures (2012) there is a decrease in starch content, regardless of the studied vegetation factors and cultivation technology. Foliar fertilization contributed to an increase in the starch content of the grain (by 0.1-0.46% in 2011-2013) compared to the control (without foliar fertilization). The highest starch content in the grain of the studied maize hybrids (70.92-76.72% and 71.45-76.72%) was provided by foliar fertilization with microfertilizers Ecolist Mono Zinc and Rostock corn. A decrease in the starch content was observed during crop treatment with the plant growth regulator Vimpel in the phase of 5-7 corn leaves on hybrids DKS 3420 by 0.36%, Pereyaslavsky 230SV by 0.11% and DKS 3871 by 0.5%, respectively.

Bioturbation by endogeic earthworms facilitates entomopathogenic nematode movement toward herbivore-damaged maize roots

Entomopathogenic nematodes (EPNs) have been extensively studied as potential biological control agents against root-feeding crop pests. Maize roots under rootworm attack have been shown to release volatile organic compounds, such as (E)-β-caryophyllene (Eβc) that guide EPNs toward the damaging larvae. As yet, it is unknown how belowground ecosystems engineers, such as earthworms, affect the biological control capacity of EPNs by altering the root Eβc-mediated tritrophic interactions. We here asked whether and how, the presence of endogeic earthworms affects the ability of EPNs to find root-feeding larvae of the beetle Diabrotica balteata. First, we performed a field mesocosm experiment with two diverse cropping systems, and revealed that the presence of earthworms increased the EPN infection potential of larvae near maize roots. Subsequently, using climate-controlled, olfactometer-based bioassays, we confirmed that EPNs response to Eβc alone (released from dispensers) was two-fold higher in earthworm-worked soil than in earthworm-free soil. Together our results indicate that endogeic earthworms, through burrowing and casting activities, not only change soil properties in a way that improves soil fertility but may also enhance the biocontrol potential of EPNs against root feeding pests. For an ecologically-sound pest reduction in crop fields, we advocate agricultural practices that favour earthworm community structure and diversity.

Differential effects of the rhizobacterium Pseudomonas simiae on above‐ and belowground chewing insect herbivores

AbstractPlant growth‐promoting rhizobacteria (PGPR) can enhance plant growth and defence. Via plant‐mediated effects, PGPR have been reported to impact the performance of generalist leaf‐chewing insects either negatively or positively. However, only a few insect species, mainly feeding on aboveground tissues, have thus far been investigated. Here, we investigated how addition of rhizobacteria to the soil in which cabbage plants are growing affects the performance of three chewing insect herbivores, two leaf chewers and one root feeder. In a greenhouse experiment, we grew white cabbage (Brassica oleracea) plants in soil supplemented with and without the rhizobacterium Pseudomonas simiae WCS417r. We investigated the consequences for three important insect pests of Brassica species, larvae of the cabbage moth Mamestra brassicae, the diamondback moth Plutella xylostella, or the cabbage root fly Delia radicum after 5 weeks of plant growth. We recorded aboveground plant biomass, insect biomass, plant defence marker gene expression levels and plant defence‐related hormone concentrations. Rhizobacterial inoculation increased aboveground plant biomass in non‐infested plants but not in infested plants. Rhizobacterial inoculation affected insect performance differently: on PGPR‐inoculated plants biomass of Plutella xylostella was lower, while biomass of Delia radicum was higher than on control plants. However, no effect was found on Mamestra brassicae biomass. Rhizobacterial inoculation increased the expression of the defence marker gene LOX2 in P. xylostella‐infested plants and MYC2 in M. brassicae‐infested plants. Transcription levels of the plant defence marker gene PAL1 showed upregulation between inoculated and non‐inoculated insect‐free plants. Levels of the phytohormones jasmonic acid, salicylic acid and abscisic acid were similar in inoculated and non‐inoculated plants. We conclude that rhizobacterial inoculation has potential to be applied in the protection of cabbage crops against the diamondback moth whereas this does not apply to reducing damage caused by the cabbage moth or cabbage root fly.

Evaluation of oil dispersion formulation of nematophagus fungus, Pochonia chlamydosporia against root-knot nematode, Meloidogyne incognita in cucumber

Abstract Root-knot nematode, Meloidogyne incognita is considered as one of the major non-insect pests of crops. The management of these root feeders becomes highly challenging due to a strong host-parasitic relationship. Pochonia chlamydosporia is a nematophagus fungus that colonizes eggs of nematodes. This study aimed to test the efficacy of P. chlamydosporia (NAIMCC-SF0039) against M. incognita. An oil dispersion formulation of P. chlamydosporia was prepared using emulsifiers and vegetable oil. This formulation had a shelf-life of 90 days (3.3 × 108 CFU/mL) at room temperature (28 ± 1 °C). The inhibitory effect of oil formulation was tested against M. incognita by inoculating it on the egg mass. We found that colonization of the gelatinous matrix occurred on the third day of inoculation followed by complete egg parasitization on the seventh day. A greenhouse trial was laid out to evaluate the biocontrol potential of P. chlamydosporia in cucumber (Cucumis sativus). The results showed that the application of talc formulation of P. chlamydosporia at the rate of 1 kg per acre during planting, followed by delivery of 1 L of oil dispersion formulation through drip lines at 30-day intervals caused the highest reduction of nematode infestation. This treatment recorded 67.9 and 57.5% reduction in egg masses and soil nematode population respectively than that of control.

Belowground plant-plant signaling of root infection by nematodes

Communication between plants mediated by herbivore-induced volatile organic compounds has been extensively studied aboveground. However, the role of root herbivory in belowground plant-plant communication is much less understood. We here investigated whether root herbivores can trigger plant roots to emit warning signals to neighbouring plants that are not yet in direct contact with them.We used a split-root system and infected half of the roots of Agrostis stolonifera plants with root-knot nematodes (Meloidogyne minor) and left the other half uninfected. As a control, we grew plants without nematodes in separate pots. Leachates from each split-root soil compartment and from soils with control plants were applied to separate pots with A. stolonifera plants, of which biomass allocation and morphological traits were measured one month after leachate addition.Plants receiving leachates from the soil with the nematode-free roots of the nematode-infected plants showed a significantly larger total biomass, more root branches, and deeper rooting than plants receiving leachates from the soil with the nematode-infected roots or from soil with control plants. Plants were taller and the root/shoot ratio was higher in plants receiving leachates from soil with the nematode-free roots than in plants receiving leachates from soil with nematode-infected roots. Shoot tiller number was higher in plants receiving leachates from either root compartment of the nematode-infected plants than in plants receiving control leachates.Our results suggest that an overcompensation response was triggered by systemically induced root-derived compounds from nematode-free roots of a plant locally infected with root-feeding nematodes. Signals from directly attacked roots of the same nematode-infected plant only caused receiver plants to develop more shoot tillers, possibly for future stolon development to grow away from the infected area. This may indicate an anticipatory tolerance response to root feeders that are still distant and an additional generalized escape response to root feeding.

Banana defence responses to Cosmopolites sordidus feeding and methyl jasmonate application

AbstractEach year 25–75% of banana and plantain yields are lost because of rhizome damages caused by banana weevil (Cosmopolites sordidus) in growing regions of sub‐Saharan Africa. However, the specific plant defence response of the rhizome tissue in relation to the C. sordidus attack is unknown. Consequently, in this study, we evaluated whether plant defence substances in the rhizome are correlated with the degree of larval damage and whether applications of methyl jasmonate (MJ) elicit a greater induction of the plant defence potential against C. sordidus. Moreover, we attempted to reveal cellular modifications in response to the root feeding herbivore through histochemical staining. The banana cultivars “Km5” and “Mbwazirume” with tolerance and susceptibility to C. sordidus, respectively, were used in a pot experiment to evaluate percent rhizome damage, leaf chlorophyll content, total phenolic content (TPC), antioxidant capacity and cell morphology in response to C. sordidus attack and/or MJ applications compared to untreated control plants. We found that C. sordidus‐induced rhizome damage was 30% in the susceptible cultivar but less than 5% in the tolerant cultivar. The percent rhizome damage was not related to leaf chlorophyll content but showed a significant negative linear relationship to both TPC and antioxidant capacity. Larvae feeding induced a considerably greater increase of polyphenolic defence compounds in Km5 than in Mbwazirume; however, this response was opposite in the MJ treatment, suggesting that the phytohormone induced the susceptible plant to invest more into the synthesis of defence chemicals that in turn lead to reduced C. sordidus damage. Tissue staining demonstrated a greater deposition of lignin and suberin in C. sordidus challenged rhizome, presumably to seal off healthy tissue with a physical barrier from continued pest attack. It is concluded that MJ induces polyphenolics in susceptible Mbwazirume banana that reduced C. sordidus damage.

Sight unseen: Belowground feeding influences the distribution of an aboveground herbivore

AbstractPlants are under constant threat from insect herbivores that can consume all types of plant tissue, both aboveground and belowground. Because plants connect aboveground and belowground environments, they are uniquely positioned to mediate indirect herbivore interactions between the two ecosystems. The effects of this mediation may change over time with cascading consequences both aboveground and belowground. We used a system involving the larval belowground (BG) herbivore Diabrotica speciosa (Coleoptera: Chrysomelidae), corn, and the aphid aboveground (AG) herbivore Rhopalosiphum maidis to answer three questions: (1) What effects does belowground herbivory by D. speciosa have on feeding preferences and distributions of the aboveground R. maidis? (2) How do these preferences and distributions change over time? And (3) what are the longer term consequences for R. maidis populations? Adult alate aphids initially preferred corn seedlings with root feeding by D. speciosa, but preference declined over time driven by aphids leaving corn seedlings with root herbivory. Similarly, observations of aphid performance and colony growth indicated negative effects of root herbivory in contrast to previous studies. These results suggest that shifts in plant‐mediated aboveground–belowground interactions can have important consequences for long‐term distributions of aboveground herbivores.

Root herbivory controls the effects of water availability on the partitioning between above‐ and below‐ground grass biomass

AbstractThe fraction of primary productivity allocated below‐ground accounts for a larger flow of carbon than above‐ground productivity in most grassland ecosystems. Here, we addressed the question of how root herbivory affects below‐ground allocation of a dominant shortgrass prairie grass in response to water availability. We predicted that high levels of root herbivory by nematodes, as seen under extreme drought in sub‐humid grasslands, would prevent the high allocation to root biomass normally expected in response to low water availability.We exposed blue gramaBouteloua gracilis, which accounts for most of the net primary productivity in the shortgrass steppe of the central and southern Great Plains, to three levels of water availability from extreme low to intermediate and extreme high crossed with a gradient of root­herbivore per cent abundance relative to the total nematode community in soil microcosms.As hypothesized, the effect of water availability on below‐ground biomass allocation was contingent on the proportion of root herbivores in the nematode community. The relationship between below‐ground biomass allocation and water availability was negative in the absence of root herbivory, but tended to reverse with increasing abundance of root feeders. Increasing abundance of root‐feeding nematodes prevented grasses from adjusting their allocation patterns towards root mass that would, in turn, increase water uptake under dry conditions. Therefore, below‐ground trophic interactions weakened plant responses and increased the negative effects of drought on plants.Our work suggests that plant responses to changes in precipitation result from complex interactions between the direct effect of precipitation and indirect effects through changes in the below‐ground trophic web. Such complex responses challenge current predictions of increasing plant biomass allocation below‐ground in water‐stressed grasslands, and deserve further investigation across ecosystems and in field conditions.A freePlain Language Summarycan be found within the Supporting Information of this article.

Can root traits predict communities of soil nematodes in restored northern prairies?

We examined how restoration affects the structure and function of grasslands belowground by relating changes in the morphology and architecture of root systems of dominant plants to the structure of soil food webs. We measured changes in root traits of dominant plants (Bouteloua gracilis and Pascopyrum smithii) and related them to the diversity and feeding structure of soil nematodes across a restoration chronosequence in a mixed-grass prairie in Grasslands National Park, Saskatchewan, Canada. Root architecture and morphology of dominant grasses changed with restoration, and soil food webs in recently restored prairies centred around resources provided by roots. In contrast, food webs in a native prairie centred around the decomposition of soil organic matter and plant litter. Our study demonstrates that changes in root traits following restoration can cascade through soil foodwebs, altering the function of restored prairies. Our study also highlights that the diversity and structure of soil nematodes can reflect changes in root traits of dominant plants. However, traits that generalize the whole root system may be insufficient to explain the causal relationship between root feeding nematodes and their resources.

Holistic approach to control Melolontha spp. in organic strawberry plantations

To achieve an effective reduction of the damage by root feeding grubs of Melolontha spp. in organic strawberry plantations, we have tested an approach targeting different stages of the insect’s biological cycle. Adult beetles were caught by using light traps or by manual shaking off trees associated to the monitoring of cockchafer swarm flights supported by forecasts models. Phytosanitary pre-crops and the application of biological control agents were tested against the larvae. The three predictive models utilized to forecast the period of emergence of the cockchafer were suitable to support the deployment of the light traps before the adults’ swarm flights. Traps positioned at 4-m height were more effective in attracting the beetles than those kept at 2-m height. Buckwheat in mixtures with either a mustard or leguminous species used as pre-crops was able to reduce the population of grubs, and considering also its capacity in solubilizing recalcitrant phosphorous sources should enter in a rotation with strawberry or any other crop susceptible to grubs damage. The distribution of two different strains of entomopathogenic fungi resulted in a reduction of the damage to plants due to the cockchafer grubs’ activity, even though the efficacy resulted to be dependent on environmental and agronomic factors, including the kind of formulation used. It is concluded that to assure a sufficient level of control of Melolontha spp. in organic strawberry plantations, it is necessary to integrate several methods that are targeting the different biological stages of the insect and are based on different kinds of practices.

Traits of the entomopathogenic nematode, Heterorhabditis bacteriophora (Hb-EG strain), for potential biocontrol in strawberry fields

Entomopathogenic nematodes (EPNs) can provide a substantial control, especially of the root feeding larval pests. The objective of the present study was to examine beneficial traits of an indigenous entomopathogenic nematode species, Heterorhabditis bacteriophora Poinar (Hb-EG strain), and to identify superior biocontrol candidates for suppression of the scarab beetle Temnorhynchus baal (Reiche & Saulcy) (Coleoptera: Scarabaeidae: Dynastinae) larvae as serious pests of strawberry in Egypt. The nematodes were applied to infect the greater wax moth, Galleria mellonella L. cadavers, to represent natural emergence from the host in laboratory and under field conditions. Its average yield was 49604 infective juveniles (IJs) per G. mellonella larva. Overall averages of nematode-induced mortality in G. mellonella larvae were (4.63, 3.12, and 1.92) at 4, 8, and 12 weeks, respectively, after continuous weekly baiting with 5 cadavers. Nematode capability for infection and reproduction ranged from 72 to 26% one to five months, respectively, after field inoculation of the infected larvae into the strawberry rhizosphere. The number of IJs, moved to the North of the rhizosphere, was significantly (P ≤ 0.05) less than that moved to the South or the East as reflected by the numbers of infected insects. The factors that may have a marked influence on EPN foraging behavior, persistence, and movement direction with implications for harnessing them as biological pest control agents were discussed.

Pest categorisation of Naupactus leucoloma.

The EFSA Panel on Plant Health performed a pest categorisation of Naupactus leucoloma Boheman (Coleoptera: Curculionidae) for the EU territory. N. leucoloma is a polyphagous pest reported to feed on 385 plant species; cultivated hosts include alfalfa, beans, brassicas, carrots, clover, onions, peas, potatoes and soft fruits. N. leucoloma is native to eastern South America. During the first half of the 20th century, it spreads to Australia, New Zealand, South Africa and the USA. In 2005, it was reported in the Azores where it occurs in the wild. In suitable conditions, N. leucoloma can develop from egg to adult in about 12 months with adults emerging during spring and summer. Outside of South America only females are known, they develop and lay eggs without fertilisation. Eggs are usually laid in the soil but can be laid on the stem or lower leaves of hosts. Larval root feeding causes damage to root surfaces leading to stunting and yield or quality losses. Larvae can tunnel inside potato tubers causing significant losses. Pupation takes place in the soil in spring and summer. Larvae and eggs that are laid late in the summer overwinter. Plants for planting and plant products, such as potatoes, provide potential pathways for entry into the EU. The suitable climate and the wide availability of host plants provide conditions to support the establishment of N. leucoloma in the EU. N. leucoloma is regulated in the EU by Commission Implementing Regulation 2019/2072 (Annex IIA). The import of soil or growing medium, from third countries other than Switzerland, is prohibited in the EU and therefore so far inhibited the entry of N. leucoloma larvae and pupae. All criteria assessed by EFSA for consideration either as a potential union quarantine pest or as a potential regulated non‐quarantine pest are met.

Identification of Novel Regulators of Plant Transpiration by Large-Scale Thermal Imaging Screening in Helianthus Annuus.

Plant adaptation to biotic and abiotic stresses is governed by a variety of factors, among which the regulation of stomatal aperture in response to water deficit or pathogens plays a crucial role. Identifying small molecules that regulate stomatal movement can therefore contribute to understanding the physiological basis by which plants adapt to their environment. Large-scale screening approaches that have been used to identify regulators of stomatal movement have potential limitations: some rely heavily on the abscisic acid (ABA) hormone signaling pathway, therefore excluding ABA-independent mechanisms, while others rely on the observation of indirect, long-term physiological effects such as plant growth and development. The screening method presented here allows the large-scale treatment of plants with a library of chemicals coupled with a direct quantification of their transpiration by thermal imaging. Since evaporation of water through transpiration results in leaf surface cooling, thermal imaging provides a non-invasive approach to investigate changes in stomatal conductance over time. In this protocol, Helianthus annuus seedlings are grown hydroponically and then treated by root feeding, in which the primary root is cut and dipped into the chemical being tested. Thermal imaging followed by statistical analysis of cotyledonary temperature changes over time allows for the identification of bioactive molecules modulating stomatal aperture. Our proof-of-concept experiments demonstrate that a chemical can be carried from the cut root to the cotyledon of the sunflower seedling within 10 minutes. In addition, when plants are treated with ABA as a positive control, an increase in leaf surface temperature can be detected within minutes. Our method thus allows the efficient and rapid identification of novel molecules regulating stomatal aperture.