Beyond Bites: Differential Role of Fall Armyworm Oral Secretions and Saliva in Modulating Sorghum Defenses.

Flavonoids are major plant secondary metabolites that provide defense against several insect pests. Previously, it has been shown that sorghum (Sorghum bicolor) flavonoids are required for providing resistance to fall armyworm (FAW; Spodoptera frugiperda), which is an important chewing insect pest on several crops. We demonstrate here the role of FAW oral cues in modulating sorghum flavonoid defenses. While feeding, chewing insects release two kinds of oral cues: oral secretions (OS)/regurgitant and saliva. Our results indicate that FAW OS induced the expression of genes related to flavonoid biosynthesis and total flavonoids, thereby enhancing sorghum's defense against FAW larvae. Conversely, FAW saliva suppressed the flavonoid-based defenses and promoted FAW caterpillar growth, independent of the FAW salivary component, glucose oxidase (GOX). Thus, we infer that different oral cues in FAW may have contrasting roles in altering sorghum defenses. These findings expand our understanding of the precise modes of action of caterpillar oral cues in modulating plant defenses and help in designing novel pest management strategies against FAW in this vital cereal crop. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Plant induced defenses that promote cannibalism reduce herbivory as effectively as highly pathogenic herbivore pathogens.

Plant induced defenses may benefit plants by increasing cannibalism among insect herbivores. However, the general efficacy of plant defenses that promote cannibalism remains unclear. Using a generalist Lepidopteran herbivore (Helicoverpa zea), we examined whether plant induced defenses in Solanum lycopersicum increased cannibalism among H. zea and whether defense-mediated cannibalism benefits both the plant and the cannibal. In a separate experiment, we also examined whether defense-mediated cannibalism has effects on H. zea herbivory that are comparable to the effects of pathogenic virus of H. zea (HzSNPV) and whether defense-mediated cannibalism modified pathogen efficacy. We found that both plant defenses and cannibalism decreased herbivory: H. zea consumed less plant material if plants were induced, if dead conspecifics were provided, or both. Cannibalism increased cannibal growth rate: cannibals effectively overcome the costs of plant defenses by eating conspecifics. Inoculating half of H. zea with virus strongly reduced caterpillar survival. Cannibalism occurred sooner among virus-inoculated groups of H. zea, and all caterpillars in virus-inoculated treatments died before the end of the 7-day experiment. Although the rise in mortality caused by HzSNPV occurred more rapidly than the rise in mortality due to defense-mediated cannibalism, overall H. zea mortality at the end of the experiment was equal among virus-inoculated and induced-defense groups. Defense-mediated cannibalism and viral inoculation equally reduced herbivory on S. lycopersicum. Our results provide evidence that defense-mediated increases in cannibalism can be as effective as other forms of classic herbivore population regulation, and that both viral pathogens and defense-induced cannibalism can have significant benefits for plants.

Exploring the Volatiles Released from Roots of Wild and Domesticated Tomato Plants under Insect Attack.

Plants produce volatile organic compounds that are important in communication and defense. While studies have largely focused on volatiles emitted from aboveground plant parts upon exposure to biotic or abiotic stresses, volatile emissions from roots upon aboveground stress are less studied. Here, we investigated if tomato plants under insect herbivore attack exhibited a different root volatilome than non-stressed plants, and whether this was influenced by the plant's genetic background. To this end, we analyzed one domesticated and one wild tomato species, i.e., Solanum lycopersicum cv Moneymaker and Solanum pimpinellifolium, respectively, exposed to leaf herbivory by the insect Spodoptera exigua. Root volatiles were trapped with two sorbent materials, HiSorb and PDMS, at 24 h after exposure to insect stress. Our results revealed that differences in root volatilome were species-, stress-, and material-dependent. Upon leaf herbivory, the domesticated and wild tomato species showed different root volatile profiles. The wild species presented the largest change in root volatile compounds with an overall reduction in monoterpene emission under stress. Similarly, the domesticated species presented a slight reduction in monoterpene emission and an increased production of fatty-acid-derived volatiles under stress. Volatile profiles differed between the two sorbent materials, and both were required to obtain a more comprehensive characterization of the root volatilome. Collectively, these results provide a strong basis to further unravel the impact of herbivory stress on systemic volatile emissions.

Poplar protease inhibitor expression differs in an herbivore specific manner.

BACKGROUND: Protease inhibitors are defense proteins widely distributed in the plant kingdom. By reducing the activity of digestive enzymes in insect guts, they reduce the availability of nutrients and thus impair the growth and development of the attacking herbivore. One well-characterized class of protease inhibitors are Kunitz-type trypsin inhibitors (KTIs), which have been described in various plant species, including Populus spp. Long-lived woody perennials like poplar trees encounter a huge diversity of herbivores, but the specificity of tree defenses towards different herbivore species is hardly studied. We therefore aimed to investigate the induction of KTIs in black poplar (P. nigra) leaves upon herbivory by three different chewing herbivores, Lymantria dispar and Amata mogadorensis caterpillars, and Phratora vulgatissima beetles. RESULTS: We identified and generated full-length cDNA sequences of 17 KTIs that are upregulated upon herbivory in black poplar leaves, and analyzed the expression patterns of the eight most up-regulated KTIs via qRT-PCR. We found that beetles elicited higher transcriptional induction of KTIs than caterpillars, and that both caterpillar species induced similar KTI expression levels. Furthermore, KTI expression strongly correlated with the trypsin-inhibiting activity in the herbivore-damaged leaves, but was not dependent on damage severity, i.e. leaf area loss, for most of the genes. CONCLUSIONS: We conclude that the induction of KTIs in black poplar is controlled at the transcriptional level in a threshold-based manner and is strongly influenced by the species identity of the herbivore. However, the underlying molecular mechanisms and ecological consequences of these patterns remain to be investigated.

Silencing an E3 Ubiquitin Ligase Gene OsJMJ715 Enhances the Resistance of Rice to a Piercing-Sucking Herbivore by Activating ABA and JA Signaling Pathways.

The RING-type E3 ubiquitin ligases play an important role in plant growth, development, and defense responses to abiotic stresses and pathogens. However, their roles in the resistance of plants to herbivorous insects remain largely unknown. In this study, we isolated the rice gene OsJMJ715, which encodes a RING-domain containing protein, and investigated its role in rice resistance to brown planthopper (BPH, Nilaparvata lugens). OsJMJ715 is a nucleus-localized E3 ligase whose mRNA levels were upregulated by the infestation of gravid BPH females, mechanical wounding, and treatment with JA or ABA. Silencing OsJMJ715 enhanced BPH-elicited levels of ABA, JA, and JA-Ile as well as the amount of callose deposition in plants, which in turn increased the resistance of rice to BPH by reducing the feeding of BPH and the hatching rate of BPH eggs. These findings suggest that OsJMJ715 negative regulates the BPH-induced biosynthesis of ABA, JA, and JA-Ile and that BPH benefits by enhancing the expression of OsJMJ715.

Phytochemistry-mediated disruption of ant-aphid interactions by root-feeding nematodes.

Plants link interactions between aboveground and belowground organisms. Herbivore-induced changes in plant chemistry are hypothesized to impact entire food webs by changing the strength of trophic cascades. Yet, few studies have explored how belowground herbivores affect the behaviors of generalist predators, nor how such changes may act through diverse changes to the plant metabolome. Using a factorial experiment, we tested whether herbivory by root-knot nematodes (Meloidogyne incognita) affected the aboveground interaction among milkweed plants (Asclepias fascicularis or Asclepias speciosa), oleander aphids (Aphis nerii), and aphid-tending ants (Linepithema humile). We quantified the behaviors of aphid-tending ants, and we measured the effects of herbivore treatments on aphid densities and on phytochemistry. Unexpectedly, ants tended aphids primarily on the leaves of uninfected plants, whereas ants tended aphids primarily at the base of the stem of nematode-infected plants. In nematode-infected plants, aphids excreted more sugar per capita in their ant-attracting honeydew. Additionally, although plant chemistry was species-specific, nematode infection generally decreased the richness of plant secondary metabolites while acting as a protein sink in the roots. Path analysis indicated that the ants' behavioral change was driven in part by indirect effects of nematodes acting through changes in plant chemistry. We conclude that belowground herbivores can affect the behaviors of aboveground generalist ant predators by multiple paths, including changes in phytochemistry, which may affect the attractiveness of aphid honeydew rewards.

Asymmetry in Herbivore Effector Responses: Caterpillar Frass Effectors Reduce Performance of a Subsequent Herbivore.

Multiple species of phytophagous insects may co-occur on a plant and while plants can defend themselves from insect herbivory, plant responses to damage by different species and feeding guilds of insects may be asymmetric. Plants can trigger specific responses to elicitors/effectors in insect secretions altering herbivore performance. Recently, maize chitinases present in fall armyworm (FAW, Spodoptera frugiperda) frass were shown to act as effectors suppressing caterpillar-induced defenses in maize while increasing caterpillar performance. We investigated the effect of frass chitinase-mediated suppression of herbivore defenses in maize on the performance and preference of a subsequent insect herbivore from a different feeding guild, corn leaf aphid (Rhopalosiphum maidis). Aphid performance was highest on plants with FAW damage without frass chitinases compared to damaged plants with frass chitinases or undamaged plants. Plant exposure to frass chitinases post FAW damage also altered the production of herbivore-induced volatile compounds compared to damaged, buffer-treated plants. However, aphid preference to damaged, frass chitinase-treated plants was not different from damaged, buffer-treated plants or undamaged plants. This study suggests that frass effector-mediated alteration of plant defenses affects insect herbivores asymmetrically; while it enhances the performance of caterpillars, it suppresses the performance of subsequent herbivores from a different feeding guild.

Site-dependent induction of jasmonic acid-associated chemical defenses against western flower thrips in Chrysanthemum.

MAIN CONCLUSION: Local and systemic induction of JA-associated chemical defenses and resistance to western flower thrips in Chrysanthemum are spatially variable and dependent on the site of the JA application. Plants have evolved numerous inducible defense traits to resist or tolerate herbivory, which can be activated locally at the site of the damage, or systemically through the whole plant. Here we investigated how activation of local and systemic chemical responses upon exogenous application of the phytohormone jasmonic acid (JA) varies along the plant canopy in Chrysanthemum, and how these responses correlate with resistance to thrips. Our results showed that JA application reduced thrips damage per plant when applied to all the plant leaves or when locally applied to apical leaves, but not when only basal leaves were locally treated. Local application of JA to apical leaves resulted in a strong reduction in thrips damage in new leaves developed after the JA application. Yet, activation of a JA-associated defensive protein marker, polyphenol oxidase, was only locally induced. Untargeted metabolomic analysis further showed that JA increased the concentrations of sugars, phenylpropanoids, flavonoids and some amino acids in locally induced basal and apical leaves. However, local application of JA to basal leaves marginally affected the metabolomic profiles of systemic non-treated apical leaves, and vice versa. Our results suggest that JA-mediated activation of systemic chemical defense responses is spatially variable and depends on the site of the application of the hormone in Chrysanthemum.

Chemically induced plasticity in early life history of Palaemon argentinus: are chemical alarm cues conserved within palaemonid shrimps?

Most aquatic animals use infochemicals from both conspecifics and heterospecifics to assess local predation risks and enhance predator detection. Released substances from injured conspecifics and other species (chemical alarm cues) are reliable cues to indicate an imminent danger in a specific habitat and often mediate the development of inducible defenses. Amphibian and fish embryos have been shown to acquire this information while at the embryonic stage of development, in relation to the developing nervous system and sensory development. With the exception of Daphnia, there is no information on chemically mediated responses to alarm cues in embryos of any crustacean groups. Therefore, we tested whether embryo exposure to chemical cues simulating predation on conspecifics or heterospecifics (closely related, non-coexisting species), or a mixture of both, alters embryonic developmental time, size and morphology of the first larval instar in Palaemon argentinus (Crustacea: Decapoda). Embryonic exposure to chemical alarm cues from conspecifics shortened the embryonic developmental time and elicited larger larvae with a longer rostrum. Rostrum length of the first larval instar changed independently of their size, thus elongated rostra can be considered a defensive feature. Embryonic developmental time was not altered by chemical alarm cues from either heterospecifics or the mixed cues treatment; however, exposure to these cues resulted in larger larvae compared with the control group. Chemically induced morphological plasticity in larvae in response to alarm cues from con- and heterospecifics suggests that such cues are conserved in palaemonids shrimps, providing embryos with an innate recognition of heterospecific alarm cues as predicted by the phylogenetic relatedness hypothesis.

Drought-Mediated Changes in Tree Physiological Processes Weaken Tree Defenses to Bark Beetle Attack.

Interactions between water stress and induced defenses and their role in tree mortality due to bark beetles are poorly understood. We performed a factorial experiment on 48 mature ponderosa pines (Pinus ponderosa) in northern Arizona over three years that manipulated a) tree water stress by cutting roots and removing snow; b) bark beetle attacks by using pheromone lures; and c) phloem exposure to biota vectored by bark beetles by inoculating with dead beetles. Tree responses included resin flow from stem wounds, phloem composition of mono- and sesqui-terpenes, xylem water potential, leaf gas exchange, and survival. Phloem contained 21 mono- and sesqui-terpenes, which were dominated by (+)-α-pinene, (-)-limonene, and δ-3-carene. Bark beetle attacks (mostly Dendroctonus brevicomis) and biota carried by beetles induced a general increase in concentration of phloem mono- and sesqui-terpenes, whereas water stress did not. Bark beetle attacks induced an increase in resin flow for unstressed trees but not water-stressed trees. Mortality was highest for beetle-attacked water-stressed trees. Death of beetle-attacked trees was preceded by low resin flow, symptoms of water stress (low xylem water potential, leaf gas exchange), and an ephemeral increase in concentrations of mono- and sesqui-terpenes compared to surviving trees. These results show a) that ponderosa pine can undergo induction of both resin flow and phloem terpenes in response to bark beetle attack, and that the former is more constrained by water stress; b) experimental evidence that water stress predisposes ponderosa pines to mortality from bark beetles.

Phytohormones in Fall Armyworm Saliva Modulate Defense Responses in Plants.

Insect herbivory induces plant defense responses that are often modulated by components in insect saliva, oral secretions or regurgitant, frass, or oviposition fluids. These secretions contain proteins and small molecules that act as elicitors or effectors of plant defenses. Several non-protein elicitors have been identified from insect oral secretions, whereas studies of insect saliva have focused mainly on protein identification. Yet, insect saliva may also contain non-protein molecules that could activate defense responses in plants. The goal of this study was to identify non-protein plant defense elicitors present in insect saliva. We used the fall armyworm (FAW), Spodoptera frugiperda and its host plants tomato, maize, and rice as a model system. We tested the effect of protein-digested saliva or non-protein components on herbivore-induced defense responses in maize, rice and tomato. We identified phytohormones in FAW saliva using high performance liquid chromatography coupled with mass spectrometry. The results of this study show that non-protein components in FAW saliva modulated defense responses in different plant species. The saliva of this insect contains benzoic acid, and the phytohormones jasmonic acid, salicylic acid, and abscisic acid at concentrations of <5 ng per µl of saliva. Plant treatment with similar phytohormone quantities detected in FAW saliva upregulated the expression of a maize proteinase inhibitor gene in maize, and down-regulated late herbivore-induced defenses in tomato plants. We conclude that FAW saliva is a complex fluid that, in addition to known enzymatic plant defense elicitors, contains phytohormones and other small molecules.

Asatone and Isoasatone A Against Spodoptera litura Fab. by Acting on Cytochrome P450 Monoxygenases and Glutathione Transferases.

Asatone and isoasatone A from Asarum ichangense Cheng were determined to be defensive compounds to some insects in a previous investigation. However, the anti-insect activity mechanisms to caterpillar are still unclear. The compounds asatone and isoasatone A from A. ichangense were induced by Spodoptera litura. The anti-insect activity of asatone and isoasatone A to S. litura was further tested by weight growth rate of the insect through a diet experiment. Isoasatone A showed a more significant inhibitory effect on S. litura than asatone on the second day. The concentration of asatone was higher than isoasatone A in the second instar larvae of S. litura after 12 h on the feeding test diet. Both compounds caused mid-gut structural deformation and tissue decay as determined by mid-gut histopathology of S. litura. Furthermore, some detoxification enzyme activity were measured by relative expression levels of genes using a qPCR detecting system. Asatone inhibited the gene expression of the cytochrome P450 monooxygenases (P450s) CYP6AB14. Isoasatone A inhibited the relative expression levels of CYP321B1, CYP321A7, CYP6B47, CYP6AB14, and CYP9A39. Asatone increased the relative gene expression of the glutathione transferases (GSTs) SIGSTe1 and SIGSTo1, in contrast, isoasatone A decreased the relative gene expression of SIGSTe1 by about 33 fold. Neither compound showed an effect on acetylcholinesterase SIAce1 and SIAce2. The mechanism of anti-insect activity by both compounds could be explained by the inhibition of enzymes P450s and GSTs. The results provide new insights into the function of unique secondary metabolites asatone and isoasatone A in genus Asarum, and a new understanding of why A. ichangense is largely free of insect pests.

Intergenerational environmental effects: functional signals in offspring transcriptomes and metabolomes after parental jasmonic acid treatment in apomictic dandelion.

Parental environments can influence offspring traits. However, the magnitude of the impact of parental environments on offspring molecular phenotypes is poorly understood. Here, we test the direct effects and intergenerational effects of jasmonic acid (JA) treatment, which is involved in herbivory-induced defense signaling, on transcriptomes and metabolomes in apomictic common dandelion (Taraxacum officinale). In a full factorial crossed design with parental and offspring JA and control treatments, we performed leaf RNA-seq gene expression analysis, LC-MS metabolomics and total phenolics assays in offspring plants. Expression analysis, leveraged by a de novo assembled transcriptome, revealed an induced response to JA exposure that is consistent with known JA effects. The intergenerational effect of treatment was considerable: 307 of 858 detected JA-responsive transcripts were affected by parental JA treatment. In terms of the numbers of metabolites affected, the magnitude of the chemical response to parental JA exposure was c. 10% of the direct JA treatment response. Transcriptome and metabolome analyses both identified the phosphatidylinositol signaling pathway as a target of intergenerational JA effects. Our results highlight that parental environments can have substantial effects in offspring generations. Transcriptome and metabolome assays provide a basis for zooming in on the potential mechanisms of inherited JA effects.

Plants eavesdrop on cues produced by snails and induce costly defenses that affect insect herbivores.

Although induced defenses are widespread in plants, the degree to which plants respond to herbivore kairomones (incidental chemicals that herbivores produce independent of herbivory), the costs and benefits of responding to cues of herbivory risk, and the ecological consequences of induced defenses remain unclear. We demonstrate that undamaged tomatoes, Solanum lycopersicum, induce defenses in response to a kairomone (locomotion mucus) of snail herbivores (Helix aspersa). Induced defense had significant costs and benefits for plants: plants exposed to snail mucus or a standard defense elicitor (methyl jasmonate, MeJA) exhibited slower growth, but also experienced less herbivory by an insect herbivore (Spodoptera exigua). We also find that kairomones from molluscan herbivores lead to deleterious effects on insect herbivores mediated through changes in plant defense, i.e., mucus-induced defenses of Solanum lycopersicum-reduced growth of S. exigua. These results suggest that incidental cues of widespread generalist herbivores might be a mechanism creating variation in plant growth, plant defense, and biotic interactions.

Inducible phenotypic plasticity in plants regulates aquatic ecosystem functioning.

Differences among individuals within species affect community and ecosystem processes in many systems, and may rival the importance of differences between species. Intraspecific variation consists of both plastic and genetic components that are regulated by different processes and operate on different time scales. Therefore, probing which mechanisms can affect traits sufficiently strongly to affect ecosystem processes is fundamental to understanding the consequences of individual variation. We find that a dominant deciduous tree of Pacific Northwest riparian ecosystems, red alder, exhibits strong and synergistic responses to nutrient resources and herbivory stress. These induced responses, which include shifting nutrient and plant secondary metabolite composition, have cascading effects on aquatic ecosystem function. Defense responses suppress leaf litter decomposition in small streams, thus altering the rate of energy capture for one of the most abundant terrestrial carbon sources entering aquatic systems. We find that alder responses to herbivory stress largely depend on availability of soil nutrients, with modification of the highly cytotoxic diarylheptanoid group of secondary metabolites being favored in nutrient-poor environments and modification of the typically dose-dependent ellagitannins being favored in nutrient-rich environments. Importantly, these findings identify traits for herbivore resistance in alder trees and demonstrate that plastic responses occurring within a species and over short time scales substantially alter a key function of an adjacent ecosystem. Furthermore, demonstrating plasticity among alder secondary metabolites lends insight into this system, in which decomposer communities are known to adjust to the secondary chemistry of local alder trees to facilitate rapid decomposition of locally derived leaf litter.

Does Cohistory Constrain Information Use? Evidence for Generalized Risk Assessment in Nonnative Prey.

Though prey use a variety of information sources to assess predation risk, evolutionary cohistory with a predator could constrain information use, and nonnative prey might fail to recognize risk from a novel predator. Nonnative prey might instead use generalized risk assessment, relying on general alarm signals from injured conspecifics rather than cues from predators. I tested the influence of shared predator-prey history on information use, comparing responses among three native and four nonnative prey species to chemical cues from a native predator and cues from injured conspecific prey. Nonnative prey demonstrated information generalism: (1) responding stronger to alarm cues released by injured conspecific prey than to cues from predators and (2) responding similarly to alarm cues as to cues from predators consuming injured conspecific prey. By contrast, for native prey, multiple information sources were required to elicit the greatest defense. The influence of other sources of chemical information was not predicted by cohistory with the predator: only one nonnative snail responded to the predator; digestion was important for only two native species; the identity of injured prey was important for all prey; and predator and prey cues contributed additively to prey response. Information generalism, hypothesized to be costly in coevolved interactions, could facilitate invasions as a driver of or response to introduction to novel habitats.

Herbivory-induced jasmonates constrain plant sugar accumulation and growth by antagonizing gibberellin signaling and not by promoting secondary metabolite production.

Plants respond to herbivory by reconfiguring hormonal networks, increasing secondary metabolite production and decreasing growth. Furthermore, some plants display a decrease in leaf energy reserves in the form of soluble sugars and starch, leading to the hypothesis that herbivory-induced secondary metabolite production and growth reduction may be linked through a carbohydrate-based resource trade-off. In order to test the above hypothesis, we measured leaf carbohydrates and plant growth in seven genetically engineered Nicotiana attenuata genotypes that are deficient in one or several major herbivore-induced, jasmonate-dependent defensive secondary metabolites and proteins. Furthermore, we manipulated gibberellin and jasmonate signaling, and quantified the impact of these phytohormones on secondary metabolite production, sugar accumulation and growth. Simulated herbivore attack by Manduca sexta specifically reduced leaf sugar concentrations and growth in a jasmonate-dependent manner. These effects were similar or even stronger in defenseless genotypes with intact jasmonate signaling. Gibberellin complementation rescued carbohydrate accumulation and growth in induced plants without impairing the induction of defensive secondary metabolites. These results are consistent with a hormonal antagonism model rather than a resource-cost model to explain the negative relationship between herbivory-induced defenses, leaf energy reserves and growth.

Nocturnal herbivore-induced plant volatiles attract the generalist predatory earwig Doru luteipes Scudder.

Numerous studies have demonstrated that entomophagous arthropods use herbivore-induced plant volatile (HIPV) blends to search for their prey or host. However, no study has yet focused on the response of nocturnal predators to volatile blends emitted by prey damaged plants. We investigated the olfactory behavioral responses of the night-active generalist predatory earwig Doru luteipes Scudder (Dermaptera: Forficulidae) to diurnal and nocturnal volatile blends emitted by maize plants (Zea mays) attacked by either a stem borer (Diatraea saccharalis) or a leaf-chewing caterpillar (Spodoptera frugiperda), both suitable lepidopteran prey. Additionally, we examined whether the earwig preferred odors emitted from short- or long-term damaged maize. We first determined the earwig diel foraging rhythm and confirmed that D. luteipes is a nocturnal predator. Olfactometer assays showed that during the day, although the earwigs were walking actively, they did not discriminate the volatiles of undamaged maize plants from those of herbivore damaged maize plants. In contrast, at night, earwigs preferred volatiles emitted by maize plants attacked by D. saccharalis or S. frugiperda over undamaged plants and short- over long-term damaged maize. Our GC-MS analysis revealed that short-term damaged nocturnal plant volatile blends were comprised mainly of fatty acid derivatives (i.e., green leaf volatiles), while the long-term damaged plant volatile blend contained mostly terpenoids. We also observed distinct volatile blend composition emitted by maize damaged by the different caterpillars. Our results showed that D. luteipes innately uses nocturnal herbivore-induced plant volatiles to search for prey. Moreover, the attraction of the earwig to short-term damaged plants is likely mediated by fatty acid derivatives.

Plant growth regulator-mediated anti-herbivore responses of cabbage (Brassica oleracea) against cabbage looper Trichoplusia ni Hübner (Lepidoptera: Noctuidae).

Plant elicitors can be biological or chemical-derived stimulators of jasmonic acid (JA) or salicylic acid (SA) pathways shown to prime the defenses in many crops. Examples of chemical elicitors of the JA and SA pathways include methyl-jasmonate and 1,2,3-benzothiadiazole-7-carbothioate (BTH or the commercial plant activator Actigard 50WG, respectively). The use of specific elicitors has been observed to affect the normal interaction between JA and SA pathways causing one to be upregulated and the other to be suppressed, often, but not always, at the expense of the plant's herbivore or pathogen defenses. The objective of this study was to determine whether insects feeding on Brassica crops might be negatively affected by SA inducible defenses combined with an inhibitor of detoxification and anti-oxidant enzymes that regulate the insect response to the plant's defenses. The relative growth rate of cabbage looper Trichoplusia ni Hübner (Lepidoptera: Noctuidae) fed induced cabbage Brassica oleraceae leaves with the inhibitor, quercetin, was significantly less than those fed control cabbage with and without the inhibitor. The reduced growth was related to the reduction of glutathione S-transferases (GSTs) by the combination of quercetin and increased levels of indole glucosinolates in the cabbage treated with BTH at 2.6× the recommended application rate. These findings may offer a novel combination of elicitor and synergist that can provide protection from plant disease and herbivores in cabbage and other Brassica crops.