Unsuitable Host Plant Research Articles

Host-plant adaptation in xylophagous insect-microbiome systems: Contributionsof longicorns and gut symbionts revealed by parallel metatranscriptome

Adaptation to host plants is of great significance in the ecology of xylophagous insects. The specific adaptation to woody tissues is made possible through microbial symbionts. We investigated the potential roles of detoxification, lignocellulose degradation, and nutrient supplementation of Monochamus saltuarius and its gut symbionts in host plant adaptation using metatranscriptome. The gut microbial community structure of M.saltuarius that fed on the two plant species were found to be different. Plant compound detoxification and lignocellulose degradation genes have been identified in both beetles and gut symbionts. Most differentially expressed genes associated with host plant adaptations were up-regulated in larvae fed on the less suitable host (Pinus tabuliformis) compared to larvae fed on the suitable host (Pinus koraiensis). Our findings indicated that M.saltuarius and its gut microbes respond to plant secondary substances through systematic transcriptome responses, allowing them to adapt to unsuitable host plants.

Laboratory evaluation of leguminous plants for the development and reproduction of the bean bug Riptortus pedestris (Hemiptera: Alydidae)

AbstractRiptortus pedestris is one of the most destructive pests of leguminous crops in East Asia. In this study, we assessed the effect of different leguminous plant species, including soybean, wild soybean, white kidney bean, runner bean, pea, cowpea, adzuki bean, mung bean, faba bean, and lentil vetch, on the development and reproduction of R. pedestris. We found that leguminous plant species significantly affect the developmental duration and survivability of the nymphs, adult longevity, and oviposition and fecundity in R. pedestris. The nymphs completed their development on all of these plants. The developmental duration of nymphs was the shortest (16.24 ± 0.57 days) on soybean and the longest (31.33 ± 1.76 days) on faba bean. The rates of survival of nymphs on soybean and pea were 93.2% and 93.0%, respectively. Female adults survived the longest on soybean (64.67 ± 6.64 days) and the shortest (13.27 ± 3.67 days) on white kidney bean. The fecundity on faba bean (decorticated pods) (143.0 ± 28.04 eggs) and soybean (116.63 ± 12.76 eggs) was higher than those on other plants. The age‐specific life table revealed that the population trend index values were all >1 except on wild soybean and faba bean, and the highest was on soybean (30.36), followed by pea (21.0). Soybean and pea were identified as the most suitable hosts for R. pedestris because of their shorter developmental duration, higher survivability, longevity and fecundity and greater population trend index on these hosts, while wild soybean and faba bean were relatively unsuitable host plants.

Population Development, Fecundity, and Flight of Spodoptera frugiperda (Lepidoptera: Noctuidae) Reared on Three Green Manure Crops: Implications For an Ecologically Based Pest Management Approach in China.

The fall armyworm, Spodoptera frugiperda (Smith), is an invasive pest of cereal crops that now inhabits southern China year-round. Cultivation of crops unsuitable as host plants has been an effective pest management strategy for some insect pests, but the effects of green manure crops on S. frugiperda have not been investigated. An age-stage two-sex life table and tethered flight performance of S. frugiperda reared on different green manure species were obtained, and a population dynamics model established. Developmental durations of stages, survival rates, and fecundities of S. frugiperda differed significantly depending on host plant. Larvae fed Astragalus sinicus L. did not complete development. Although some larvae fed Vicia villosa Roth and Vicia sativa L. completed development, generation time was significantly prolonged, egg production was halved, and net reproductive rate decreased to 31% and 3% of those reared on corn, respectively. Survival rates of early-instars fed V. villosa and V. sativa were significantly lower than those fed corn. Population dynamics projections over 90 d showed the number of generations of S. frugiperda fed on V. villosa and V. sativa was reduced compared to those reared on corn. Flight performance of S. frugiperda reared on V. villosa decreased significantly compared to corn. Our results show that the three green manure species are unsuitable host plants for S. frugiperda. Therefore, reduction of corn production in southern China through rotation with these green manure crops may be a feasible method of ecological management of this major corn pest in China.

Comparison of life‐history traits and oviposition preferences of Tuta absoluta for 12 common tomato varieties in Burkina Faso

AbstractThe South American tomato pinworm, Tuta absoluta Meyrick (Lepidoptera: Gelechiidae), is an economically important insect pest of tomatoes. Since its discovery in Burkina Faso in 2016, the use of synthetic insecticides was favored, with many cases of treatment failure. To explore alternative control methods, we conducted a screening of the 12 main tomato varieties produced in the country to test two hypotheses: (i) Some tomato varieties are less likely to attract gravid females and be used as oviposition site; (ii) Some varieties are unsuitable host plants as they allow slower development and lead to higher mortality. The varieties tested include RomaVF, KanonF1, Cobra 26 F1, FBT1, FBT2, FBT3, RaissaF1, JampacktF1, Mongal, Rio Grande, Tropimech, and Petomech. T. absoluta fitness was largely impacted by the tomato variety, especially egg incubation time and larval and pupal stage durations. As a result, the total T. absoluta life cycle was slower on Cobra 26 F1 and Kanon F1 (24.6 ± 1.8 and 25.8 ± 3.3 days, respectively) and faster on FBT1 and Rio grande (22.6 ± 3.0 and 22.8 ± 2.6 days, respectively). None of the varieties impacted the adult lifespan. All varieties were accepted as hosts by gravid females during multiple‐choice oviposition assays. The number of eggs laid per female was statistically similar among the varieties. We conclude that two varieties, Kanon F1 and Cobra 26 F1, have better abilities to slow T. absoluta development, limiting the number of generations while increasing the probability that natural enemies find and kill their prey.

Fundamental host range of Lophodiplosis indentata (Diptera: Cecidomyiidae), the last proposed biological control agent for Melaleuca quinquenervia (Myrtaceae) in Florida

ABSTRACT Melaleuca quinquenervia (hereafter melaleuca) was until recently one of the worst ecological invaders in Florida. Introduced for horticulture and levee stabilisation during the early twentieth century, melaleuca spread to cover vast areas of the largest freshwater wetlands ecosystem in North America, The Everglades. From 1997 until 2008, four insects and an associated nematode were approved and released for control of melaleuca, three of which are known to have established. Biological control is frequently a slow and incremental process, but with the integration of complimentary control methods (e.g. chemical and mechanical removal), melaleuca infestations are a fraction of their former range. These few persistent infestations are facilitated by conditions that prevent one species, Oxyops vitiosa, the melaleuca snout weevil, from completing its life cycle, which prompted the testing of and application to release Lophodiplosis indentata (Diptera: Cecidomyiidae). This leaf gall forming midge feeds within pea-shaped growths distributed throughout the canopy. No-choice host range tests suggest that L. indentata will occasionally oviposit on unsuitable host plants, but gall induction and formation is only accomplished on M. quinquenervia. A petition for the release of L. indentata was recommended by TAG in May 2020. [word count: 181]

Growth performance and transcriptomic response of Calliptamus abbreviatus Ikonn (Orthoptera: Acrididae) to suitable and unsuitable host plant species

The growth of herbivorous insects is influenced by their host plants, which is underpinned by genetic regulations. We studied the growth performance of the grasshopper Calliptamus abbreviatus Ikonn when it fed on a suitable host plant, Artemisia frigida (Asteraceae) and unsuitable host plant, Stipa krylovii (Poaceae) in a two-year feeding trial. Additionally, the underlying transcriptomic response was also measured using RNA-seq. When C. abbreviatus fed on S. krylovii, it had a significantly reduced growth rate and large variation in its gene expression profiles. A total of 106 genes were significantly up-regulated and mainly enriched in stress resistance-related KEGG pathways. Another 161 genes were significantly down-regulated and were mainly associated with development regulation-, cuticle biosynthesis-, and nutrition metabolism-related pathways. A total of 18 candidate genes were verified by RT-qPCR and were consistent with the transcriptomic results. Stress resistance was significantly induced in grasshopper when C. abbreviatus fed on the unsuitable host. However, the capacity for cuticle biosynthesis or nutrition metabolism significantly declined. The negative effects which S. krylovii had on the grasshopper’s growth performance and gene expression indicate that this plant species was a stressor compared to A. frigida. This study enhances the knowledge on the underlying molecular mechanisms involved in plant–herbivore insect co-evolution.

Previous herbivory alerts conspecific gravid sawflies to avoid unsuitable host plants.

The willow sawfly, Nematus oligospilus (Förster), is a pest in Salix commercial forests and has been reported worldwide. Female adults must recognize a suitable host plant to oviposit, since her offspring lack the ability to move to another host. We evaluated the effect of conspecific herbivory on the oviposition choices of N. oligospilus females by providing damaged (DP) and undamaged (UP) plants of Salix humboldtiana, a native willow from South America, as oviposition substrates. Local and systemic effects were studied. For the local treatment, a twig from the DP with damaged leaves was contrasted to a twig from a UP in dual choice experiments. For systemic treatment, a twig from the DP with intact leaves was contrasted to a twig from a UP. We estimated the use of olfactory and contact cues by comparing volatile emission of DP and UP, and by analysing the behaviour of the females during host recognition after landing on the leaf surface. In the context of the preference-performance hypothesis (PPH), we also tested if oviposition site selection maximizes offspring fitness by evaluating neonate hatching, larval performance and survival of larvae that were born and bred on either DP or UP. Our results demonstrate that previous conspecific herbivory on S. humboldtiana has a dramatic impact on female oviposition choices and offspring performance of the sawfly N. oligospilus. Females showed a marked preference for laying eggs on UP of S. humboldtiana. This preference was found for both local and systemic treatments. Volatile emission was quantitatively changed after conspecific damage suggesting that it could be related to N. oligospilus avoidance. In the dual choice preference experiments, the analysis of the behaviour of the females once landing on the leaf surface suggested the use of contact cues triggering egg laying on leaves from UP and avoidance of leaves from DP. Furthermore, 48 h of previous conspecific feeding was sufficient to dramatically impair neonate hatching, as well as larval development and survival, suggesting a rapid and effective reaction of the induced resistance mechanisms of the tree. In agreement with the PPH, these results support the idea that decisions made by colonizing females may result in optimal outcomes for their offspring in a barely studied insect model, and also opens the opportunity for studying tree-induced defences in the unexplored South American willow S. humboldtiana.

Host plant specificity and feeding preferences of Morpho epistrophus argentinus (Lepidoptera: Nymphalidae) larvae in coastal woodlands of Argentina

The selection of suitable host plants for larval development is critical for most herbivorous insects. In this study, we examined host plant preferences of larvae of the Epistrophus white morpho butterfly, Morpho epistrophus argentinus (H. Fruhstorfer), a specialized butterfly that oviposits on a few plant species. In many species, the selection of host plant species for larvae development is under the control of ovipositing females and the role of larvae in host selection is minimal. Through field observations, we characterized larval host plant use in coastal woodland patches of its southernmost distribution range at eastern Buenos Aires, Argentina. All sampled M.e. argentinus larvaegroups (n = 40) were found on Scutia buxifolia trees, although the number of larval groups did not correlate with cover of this plant at patch scale. To further examine host plant preferences we performed translocation experiments and feeding choice assays. M.e. argentinus larvae translocated to unsuitable host plants had a shorter residence time than those translocated to suitable (i.e. control) hosts. Choice assays also indicated strong feeding preferences of wild larvae for S. buxifolia leaves. Our results highlight the high degree of host specificity of this butterfly, and reveal that host preference of growing larvae matches that of ovipositing females.

Potential of Melia azedarach L. (Meliaceae) as a Host Plant for Halyomorpha halys (Stål) (Hemiptera: Pentatomidae)

Currently, the invasive brown marmorated stink bug, Halyomorpha halys (Stal) (Hemiptera: Pentatomidae), is considered an agricultural and nuisance pest in Georgia. The invasive chinaberry tree, Melia azedarach L. (Meliaceae), commonly grows in dense thickets along roadsides, and in woodlands adjacent to agricultural crops across the southeastern USA. Thus, the objective of this study was to determine the potential of M. azedarach to serve as a host plant of H. halys by examining mortality and feeding of first and second instars on M. azedarach leaves vs. carrot (i.e., a control diet), and documenting presence of H. halys on M. azedarach in woodlands at 2 locations in Georgia where this stink bug has become established. Over all sampling dates and locations, the number of H. halys in chinaberry was very low (0.1 per tree), and only 3 late instars and 1 adult were observed feeding on M. azedarach at 1 field site late in the season. Percentage feeding by second instars of H. halys was lower for individuals given M. azedarach leaves vs. those provided with carrot, most likely indicating that compounds in M. azedarach have an antifeeding effect. In fact, mortality for second instars on M. azedarach leaves was very high, and thus we conclude that M. azedarach is an unsuitable host plant for H. halys.

CanDarapsa myron(Lepidoptera: Sphingidae) Successfully Use the Invasive PlantAmpelopsis brevipedunculataas a Food Resource?

ABSTRACT. Although biological invasions are generally thought to negatively impact native fauna, native herbivores that can utilize invasive plants may benefit. The East Coast of the United States has been invaded by the vitaceous plant Ampelopsis brevipedunculata. The invaded range of A. brevipedunculata overlaps with that of the native Vitis labrusca, a closely-related species that is a host plant for the native moth Darapsa myron (Lepidoptera: Sphingidae). We reared D. myron larvae on either V. labrusca or A. brevipedunculata to assess whether development and survival differed on the two plant species. Larval growth and survival to pupation was only 5% on A. brevipedunculata compared to 30% on V. labrusca, suggesting that the invasive species is an unsuitable hostplant for D. myron.

Transcriptome analyses suggest a novel hypothesis for whitefly adaptation to tobacco

The adaptation of herbivorous insects to various host plants facilitates the spread and outbreak of many important invasive pests, however, the molecular mechanisms that underneath this process are poorly understood. In the past three decades, two species of the whitefly Bemisia tabaci complex, Middle East-Asia Minor 1 and Mediterranean, have invaded many countries. Their rapid and widespread invasions are partially due to their ability to infest a wide range of host plants. In this study, we determined the transcriptome and phenotypic changes of one Mediterranean whitefly population during its adaptation to tobacco, an unsuitable host plant. After several generations on tobacco, whiteflies showed increased survival and fecundity. High-throughput RNA sequencing showed that genes involved in muscle contraction and carbohydrate metabolism were significantly up-regulated after adaptation. Whiteflies reared on tobacco were further found to have increased body volume and muscle content and be trapped by tobacco trichomes in a lower frequency. On the other hand, gene expression in endosymbionts of whitefly did not change significantly after adaptation, which is consistent with the lack of cis-regulatory element on endosymbiont genomes. Over all, our data suggested that higher body volume and strengthened muscle might help whiteflies overcome physical barriers and survive on tobacco.

Host Plant Species Differentiation in a Polyphagous Moth: Olfaction is Enough

Polyphagous herbivorous insects need to discriminate suitable from unsuitable host plants in complex plant communities. While studies on the olfactory system of monophagous herbivores have revealed close adaptations to their host plant’s characteristic volatiles, such adaptive fine-tuning is not possible when a large diversity of plants is suitable. Instead, the available literature on polyphagous herbivore preferences suggests a higher level of plasticity, and a bias towards previously experienced plant species. It is therefore necessary to take into account the diversity of plant odors that polyphagous herbivores encounter in the wild in order to unravel the olfactory basis of their host plant choice behaviour. In this study we show that a polyphagous moth, Spodoptera littoralis, has the sensory ability to distinguish five host plant species using olfaction alone, this being a prerequisite to the ability to make a choice. We have used gas chromatography mass spectrometry (GC-MS) and gas chromatography electroantennographic detection (GC-EAD) in order to describe host plant odor profiles as perceived by S. littoralis. We find that each plant emits specific combinations and proportions of GC-EAD active volatiles, leading to statistically distinct profiles. In addition, at least four of these plants show GC-EAD active compound proportions that are conserved across individual plants, a characteristic that enables insects to act upon previous olfactory experiences during host plant choice. By identifying the volatiles involved in olfactory differentiation of alternative host plants by Spodoptera littoralis, we set the groundwork for deeper investigations of how olfactory perceptions translate into behaviour in polyphagous herbivores.

Digestive Physiology and Nutritional Responses of Autographa gamma (L.) (Lepidoptera: Noctuidae) on Different Sugar Beet Cultivars.

Digestive enzymatic activity and nutritional responses of Autographa gamma (L.) (Lepidoptera: Noctuidae), an important insect pest of sugar beet, on nine sugar beet cultivars (Peritra, Karolina, Paolita, Lenzier, Tiller, Ardabili, Persia, Rozier, and Dorothea) were studied. The highest proteolytic activity of fourth and fifth instar of A. gamma was in larvae fed on cultivar Persia. The highest amylolytic activity of fourth and fifth instar was observed in larvae fed on cultivars Rozier and Dorothea, respectively. The lowest proteolytic and amylolytic activities in fourth instar were observed on cultivar Tiller; whereas the lowest activities in fifth instar were detected on cultivars Karolina and Tiller, respectively. Larval weight in both larval instars (fourth and fifth) was the heaviest on cultivar Persia and the lightest on cultivar Karolina. Furthermore, weight gain of larvae was the highest on cultivar Persia and the lowest on cultivar Karolina. The results of this study suggest that cultivar Tiller was the most unsuitable host plant for feeding of A. gamma.

Prothoracicotropic hormone-producing neurosecretory neurons and antioxidative defense in midgut of Lymantria dispar in trophic stress

As a very invasive insect species, Lymantria dispar is adaptable and sensitive to a changing environment. In insects the neuroendocrine system first reacts to stress by production of prothoracicotropic neurohormones (PTTH) that control ecdysteroid synthesis (morphogenetic and stress hormones). In this article, we report changes in the L2' brain neurosecretory neurons that synthesize PTTH in L. dispar larvae after feeding on locust tree leaves (Robinia pseudoacacia), an unsuitable host plant. Groups of larvae (n = 20 per experimental group) were offered this in comparison with oak leaves (Quercus robur), a suitable control diet, for 3 days after molting into the fourth instar. L2' neurons and their nuclei were enlarged and the amount of neurosecretory product in the cytoplasm was increased (15.5%) after consumption of locust tree leaves in comparison to the control. Furthermore, activities of the following antioxidative defense components were estimated: superoxide dismutase (SOD), catalase (CAT), and amount of glutathione in the midgut. Higher SOD activity (13.85 ± 0.9 U/mg prot.) and glutathione amount (0.56 ± 0.06 mMGSH/g tissue) but unchanged CAT activity was found in the midgut of larvae offered locust tree leaves when compared to the control.

Larvae of Io Moth,Automeris io, On the Coral Bean,Erythrina herbacea, in Florida—the Limitations of Polyphagy

The coral bean, Erythrina herbacea, is reported as a new host for Automeris io in north-central Florida, based on a single batch of larvae found on this plant in nature and reared through on it in the laboratory. However, the consequent laboratory rearing showed a high cost associated with using this host plant. The mortality of young larvae of the F-2 generation reared on E. herbacea was very high (over 90%), and much higher than that of control larvae, which were reared on mature leaves of Quercus nigra (14–38%). The leaves of E. herbacea, known for their toxic alkaloids, were extracted with methanol, made into a water solution, applied on the mature leaves of Q. nigra, and fed to 1st instars of A. io. This produced no negative effect on the caterpillars. While the mature leaves of Q. nigra produced low mortality in young caterpillars, the young terminal leaves of this plant were as lethal to A. io as leaves of E. herbacea. Additionally, it was noted that rearing larvae on E. herbacea (a diet with a higher N2 content) led to faster larval development and smaller adult moths. The A. io larvae in this study developed during 63–100 days and underwent seven larval instars, which contradicts many popular accounts of the fifth instar being the final in A. io. Finally, Prunus angustifolia proved to be an unsuitable hostplant for A. io, as feeding on this species led to the arrested development of larvae and their eventual death.

Cloning and Functional Characterization of c-Jun NH2-Terminal Kinase from the Mediterranean Species of the Whitefly Bemisia tabaci Complex

c-Jun NH2-terminal kinase (JNK) signaling is a highly conserved pathway that controls gene transcription in response to a wide variety of biological and environmental stresses. In this study, a JNK from the invasive Mediterranean (MED) species of the whitefly Bemisia tabaci complex was cloned and characterized. The full-length JNK cDNA of MED consists of 1565 bp, with an 1176 bp open reading frame encoding 392 amino acids. Comparison of JNK amino acid sequences among different species showed that the sequences of JNKs are highly conserved. To reveal its biological function, the gene expression and functional activation of JNK were analyzed during various stress conditions. Quantitative RT-PCR analysis showed that the relative expression level of JNK remained hardly unchanged when the insects were transferred from cotton (a suitable host plant) to tobacco (an unsuitable host plant), infected with bacteria and treated with high and low temperatures. However, the mRNA level of JNK significantly increased when treated with fungal pathogens. Furthermore, we found that the amount of phosphorylated JNK increased significantly after fungal infection, while there is no obvious change for phosphorylated p38 and ERK. Our results indicate that the whitefly JNK plays an important role in whitefly’s immune responses to fungal infection.

Oviposition dynamics and larval development of Helicoverpa armigera on a highly preferred unsuitable host plant, Solanum viarum

AbstractOogenesis and oviposition dynamics of female moths of tomato fruitworm, Helicoverpa armigera Hübner (Lepidoptera: Noctuidae), were compared in a monoculture of tomato (Solanum lycopersicum L.) and in mixtures with a highly preferred but unsuitable host plant, Solanum viarum Dunal. Female H. armigera provided with S. viarum laid many more eggs than those provided with tomato, both in choice and no‐choice experiments. Gravid female moths did not display any preference for oviposition neither between young or old plants of S. viarum or tomato, nor between young and old leaves of S. viarum. Larval mortality and larval developmental period significantly increased, with subsequent reduction in pupal weight, when H. armigera larvae fed on S. viarum leaves compared to a meridic diet. Oviposition of female moths significantly increased in tomato in the presence of S. viarum volatiles. However, in screen cages with an increasing percentage of S. viarum as a trap crop, the number of eggs laid on tomato as the main crop was the same. The results of this study are discussed in light of the possibility of using S. viarum as a ‘dead‐end’ trap crop.

Analysis of correlation structure in Lymantria dispar L. larvae from locally adapted populations

The influence of allelochemical stress and population origin on the patterns of phenotypic and genetic correlations among life history traits and digestive enzyme activities were investigated in larvae of the gypsy moth (Lymantria dispar L.; Lepidoptera: Lymantriidae). Thirty-two full-sib families from oak (suitable host plant, Quercus population), and twenty-six full-sib families from locust-tree (unsuitable host plant, Robinia population) forests were reared on an artificial diet, with or without a 5% tannic acid supplement. Comparison of correlation matrices revealed significant similarity between the two populations in the structure of phenotypic and genetic correlations of life history traits and of digestive enzyme activities. The patterns of correlations of the examined traits, within each of the two locally adapted populations and in the presence of allelochemical stress, remained stabile despite the different selection pressures that mold these traits.

Biogenic amines in protocerebral A2 neurosecretory neurons of Lymantria dispar L. (Lepidoptera:Lymantriidae): Response to trophic stress

The number, morphometric parameters and amount of aminergic neurosecretory product of protocerebral A2 neurosecretory neurons were investigated in the fifth instar of Lymantria dispar caterpillars, following a suitable or unsuitable trophic regime. Caterpillars originated from two populations (Quercus rubra or Robinia pseudoacacia forest) and were differently adapted to trophic stress, i.e. feeding on locust tree leaves - unsuitable host plant. The number of neurosecretory neurons was higher in the caterpillars originated from Robinia population than in Quercus population, regardless of feeding. A2 neurosecretory neurons, nuclei and their nucleoli were larger in caterpillars fed with unsuitable leaves in both populations. There was more aminergic product in the A2 neurosecretory neurons of the caterpillars fed with unsuitable leaves independently of population origin.

The effects of tannic acid on the fitness-related traits of Lymantria dispar L. larvae

In this study we investigated the effects of tannic acid on fitness-related traits in gypsy moth larvae from two differently adapted populations. Thirty two full-sib families from oak (suitable host plant, Quercus population), and twenty six full-sib families from locust-tree (unsuitable host plant, Robinia population) forests were reared on artificial diets with or without a 5% tannic acid supplement. Tannic acid shortened the duration of larval development till the 4th instar in the Robinia population, and decreased the mass of larvae from both Quercus and Robinia populations. Local adaptation was not recorded for any of the examined traits. In general, regardless of population origin, genetic variation (broad-sense heritability) was higher in larvae fed on the diet containing tannic acid than in larvae fed on the control diet. Variability of phenotypic plasticity was significant for the examined traits, except for larval duration traits in Quercus larvae, pointing to the potential of gypsy moth larvae from both populations for the evolution of adaptive plastic responses to new environmental conditions and the presence of stressors. Genetic correlations between the environments were positive and significantly different from ?one? and accordingly, do not represent constraint for the evolution of plasticity.