Improving pesticide uptake modeling and management in potatoes: A simple and approximate phloem-adjusted model.

To evaluate the impact of the phloem flux on the pesticide uptake process in potatoes, this study developed a phloem-adjusted model based on the classic model that focuses mainly on the diffusion process. To achieve high-throughput simulations, we introduced an approximate method to convert the phloem flux transport process into a simple specific uptake rate of pesticides. In comparison to the classic model (non-phloem model), the phloem-adjusted model generated higher pesticide concentrations and bioconcentration factors (BCFs) in potatoes, owing to the additional pesticide uptake route introduced to the adjusted model. However, the simulation, which was conducted for 740 pesticides, indicated that for most pesticides, the phloem flux route did not contribute a significant portion of the pesticide uptake to potato tubers compared with the soil diffusion route. This was further characterized, using the differential factor (DF), to evaluate the difference in the simulated results between the proposed model and classic models. The largest DF (~0.11) was obtained for pesticides with moderate lipophilicity (i.e., log KOW of 3.0), indicating that only a difference of 10% was generated between the two models. The 10% increase in pesticide concentration (or BCFs) in potatoes, simulated by the phloem-adjusted model, was within the acceptable uncertainty interval of the classic model, thus confirming the validity of using the classic model to predict the pesticide uptake process in potato tubers. However, we found that the negligibility of the phloem flux route was not merely due to hydrophobicity (i.e., hypothesis of the classic model), but was related to the i) plant physiology of potatoes, ii) lipophilicity of a pesticide, and iii) the diffusivity of a pesticide in water. Although future studies on pesticide concentrations in phloem sap and the dynamic growth of potatoes need to be undertaken, the model developed in this study reveals a more comprehensive pesticide uptake process in potatoes, which can promote the understanding of the pesticide uptake mechanism in potatoes.

Localization of (+)-Catechin in Picea abies Phloem: Responses to Wounding and Fungal Inoculation.

To understand the positional and temporal defense mechanisms of coniferous tree bark at the tissue and cellular levels, the phloem topochemistry and structural properties were examined after artificially induced bark defense reactions. Wounding and fungal inoculation with Endoconidiophora polonica of spruce bark were carried out, and phloem tissues were frequently collected to follow the temporal and spatial progress of chemical and structural responses. The changes in (+)-catechin, (-)-epicatechin, stilbene glucoside, and resin acid distribution, and accumulation patterns within the phloem, were mapped using time-of-flight secondary ion mass spectrometry (cryo-ToF-SIMS), alongside detailed structural (LM, TEM, SEM) and quantitative chemical microanalyses of the tissues. Our results show that axial phloem parenchyma cells of Norway spruce contain (+)-catechins, the amount of which locally increases in response to fungal inoculation. The preformed, constitutive distribution and accumulation patterns of (+)-catechins closely follow those of stilbene glucosides. Phloem phenolics are not translocated but form a layered defense barrier with oleoresin compounds in response to pathogen attack. Our results suggest that axial phloem parenchyma cells are the primary location for (+)-catechin storage and synthesis in Norway spruce phloem. Chemical mapping of bark defensive metabolites by cryo-ToF-SIMS, in addition to structural and chemical microanalyses of the defense reactions, can provide novel information on the local amplitudes and localizations of chemical and structural defense mechanisms and pathogen-host interactions of trees.

Positron-emitting tracer imaging of fluoride transport and distribution in tea plant.

BACKGROUND: Tea (Camellia sinensis (L.) O. Kuntze) is a hyper-accumulator of fluoride (F). To understand F uptake and distribution in living plants, we visually evaluated the real-time transport of F absorbed by roots and leaves using a positron-emitting (18 F) fluoride tracer and a positron-emitting tracer imaging system. RESULTS: F arrived at an aerial plant part about 1.5 h after absorption by roots, suggesting that tea roots had a retention effect on F, and then was transported upward mainly via the xylem and little via the phloem along the tea stem, but no F was observed in the leaves within the initial 8 h. F absorbed via a cut petiole (leaf 4) was mainly transported downward along the stem within the initial 2 h. Although F was first detected in the top and ipsilateral leaves, it was not detected in tea roots by the end of the monitoring. During the monitoring time, F principally accumulated in the node. CONCLUSION: F uptake by the petiole of excised leaf and root system was realized in different ways. The nodes indicated that they may play pivotal roles in the transport of F in tea plants. © 2020 Society of Chemical Industry.

Active phloem sap collection by Trigona spinipes (Fabricius) (Hymenoptera, Apidae)in Artemisia annuaLinn (Asteraceae)

Trigona spinipes Fabricius (Apidae: Meliponini), is a common stingless bee widely seen in urban and rural areas in Brazil, popularly known as irapuá, arapuá or bee-dog. Although these bees are considered pollinators of some cultivated plants, they are better known for the damage they cause in different crops. During experimental agroecological cultivation of Artemisia (Artemisia annuaLinn, Asteraceae), in Jaguariúna (SP, Brazil), stingless bees Trigona spinipes (Fabricius) were observed sucking phloem sap directly from the plant, a phenomenon not yet described in scientific literature. This study aimed to register and describe the phloem sap-sucking behavior performed by T. spinipesfor the first time, as well as to assess the potential impact of this behavior on A. annuacultivation. The behavior and the material collected by bees and the severity of attack were also analyzed. The aging and premature death of observed A. annuaspecimens occurred because of extensive lesions caused by T. spinipes, confirming the negative consequence of sap-sucking attacks of T. spinipesbees on the plants. Factors that could induce this unusual behavior were presented, pointing out the need for future studies on the development of strategies to protect plants, without causing damage to the T. spinipesbee populations, which are elements of Brazilian bee fauna and, therefore, protected by law.

A Method to Study the Distribution Patterns for Metabolites in Xylem and Phloem of Spatholobi Caulis.

Spatholobi Caulis (SC), the vine stem of Spatholobus suberectus Dunn, is a widely used traditional Chinese medicine (TCM) for the treatment of blood stasis syndrome and related diseases. Xylem and phloem are the main structures of SC and the color of xylem in SC is red brown or brown while the phloem with resin secretions is reddish brown to dark brown. They are alternately arranged in a plurality of concentric or eccentric rings. In order to investigate the distribution patterns of metabolites in xylem and phloem of SC, an analytical method based on UFLC-QTRAP-MS/MS was established for simultaneous determination of 22 constituents including four flavanols, nine isoflavones, two flavonols, two dihydroflavones, one flavanonol, one chalcone, one pterocarpan, one anthocyanidin and one phenolic acid in the samples (xylem and phloem) from Laos. Furthermore, according to the contents of 22 constituents, heat map, principal components analysis (PCA), orthogonal partial least squares discriminant analysis (OPLS-DA) and t-test were used to evaluate the samples and discover the differences between xylem and phloem of SC. The results indicated that the measured ingredients in xylem and phloem were significantly different. To be specific, the contents of flavonoids in xylem were higher than that in phloem, while the content of protocatechuic acid showed a contrary tendency. This study will not only reveal the distribution patterns of metabolites in xylem and phloem of SC but also facilitate further study on their quality formation.

Illumination on "Reserving Phloem and Discarding Xylem" and Quality Evaluation of Radix polygalae by Determining Oligosaccharide Esters, Saponins, and Xanthones.

The root of Polygala tenuifolia Willd. or Polygala sibirica L. exhibits protective effects on the central nervous system and is frequently used to treat insomnia, amnesia, and other cognitive dysfunction. In our study, we studied nine bioactive compounds spanning oligosaccharide esters, saponins, and xanthones by using a sensitive, efficient, and validated method established on ultra-performance liquid chromatography coupled with triple quadrupole mass spectrometry. The quantified result of interesting compounds proved that accumulation of those compounds were found in phloem rather than in xylem. By taking the standardized result of nine compound contents into account, the "Spider-web" analytical result of xylem and phloem from Radix polygalae (RP) unveiled the rationality of RP's classical use in clinic including discarding the xylem and reserving the phloem. Moreover, the remarkable variation was also revealed from the quantitative result of 45 samples with different diameters from the different origins, which did not significantly correlate with the variation of RP's diameter. Our study could shed the light on the quality assessment of RP for further research and illustrate the scientific connotation of the processing method of "discarding the xylem and reserving the phloem".

Nutrition versus defense: Why Myzus persicae (green peach aphid) prefers and performs better on young leaves of cabbage.

Plant leaves of different ages differ in nutrients and toxic metabolites and thus exhibit various resistance levels against insect herbivores. However, little is known about the influence of leaf ontogeny on plant resistance to phloem-feeding insects. In this study, we found that the green peach aphid, Myzus persicae, preferred to settle on young cabbage leaves compared with mature or old leaves, although young leaves contained the highest concentration of glucosinolates. Furthermore, aphids feeding on young leaves had higher levels of glucosinolates in their body, but aphids performed better on young leaves in terms of body weight and population growth. Phloem sap of young leaves had higher amino acid:sugar molar ratio than mature leaves, and aphids feeding on young leaves showed two times longer phloem feeding time and five times more honeydew excretion than on other leaves. These results indicate that aphids acquired the highest amount of nutrients and defensive metabolites when feeding on young cabbage leaves that are strong natural plant sinks. Accordingly, we propose that aphids generally prefer to obtain more nutrition rather than avoiding host plant defense, and total amount of nutrition that aphids could obtain is significantly influenced by leaf ontogeny or source-sink status of feeding sites.

Stereochemical identification of glucans by oligothiophenes enables cellulose anatomical mapping in plant tissues.

Efficient use of plant-derived materials requires enabling technologies for non-disruptive composition analysis. The ability to identify and spatially locate polysaccharides in native plant tissues is difficult but essential. Here, we develop an optical method for cellulose identification using the structure-responsive, heptameric oligothiophene h-FTAA as molecular fluorophore. Spectrophotometric analysis of h-FTAA interacting with closely related glucans revealed an exceptional specificity for ß-linked glucans. This optical, non-disruptive method for stereochemical differentiation of glycosidic linkages was next used for in situ composition analysis in plants. Multi-laser/multi-detector analysis developed herein revealed spatial localization of cellulose and structural cell wall features such as plasmodesmata and perforated sieve plates of the phloem. Simultaneous imaging of intrinsically fluorescent components revealed the spatial relationship between cell walls and other organelles, such as chloroplasts and lignified annular thickenings of the trachea, with precision at the sub-cellular scale. Our non-destructive method for cellulose identification lays the foundation for the emergence of anatomical maps of the chemical constituents in plant tissues. This rapid and versatile method will likely benefit the plant science research fields and may serve the biorefinery industry as reporter for feedstock optimization as well as in-line monitoring of cellulose reactions during standard operations.

Uptake, Translocation, Metabolism, and Distribution of Glyphosate in Nontarget Tea Plant (Camellia sinensis L.).

The uptake, translocation, metabolism, and distribution behavior of glyphosate in nontarget tea plant were investigated. The negative effects appeared to grown tea saplings when the nutrient solution contained glyphosate above 200 mg L-1. Glyphosate was highest in the roots of the tea plant, where it was also metabolized to aminomethyl phosphonic acid (AMPA). The glyphosate and AMPA in the roots were transported through the xylem or phloem to the stems and leaves. The amount of AMPA in the entire tea plant was less than 6.0% of the amount of glyphosate. The glyphosate level in fresh tea shoots was less than that in mature leaves at each day. These results indicated that free glyphosate in the soil can be continuously absorbed by, metabolized in, and transported from the roots of the tea tree into edible leaves, and therefore, free glyphosate residues in the soil should be controlled to produce teas free of glyphosate.

Oil Secretory System in Vegetative Organs of Three Arnica Taxa: Essential Oil Synthesis, Distribution and Accumulation.

Arnica, a genus including the medicinal species A. montana, in its Arbo variety, and A. chamissonis, is among the plants richest in essential oils used as pharmaceutical materials. Despite its extensive use, the role of anatomy and histochemistry in the internal secretory system producing the essential oil is poorly understood. Anatomical sections allowed differentiation between two forms of secretory structures which differ according to their distribution in plants. The first axial type is connected to the vascular system of all vegetative organs and forms canals lined with epithelial cells. The second cortical type is represented by elongated intercellular spaces filled with oil formed only between the cortex cells of roots and rhizomes at maturity, with canals lacking an epithelial layer.Only in A. montana rhizomes do secretory structures form huge characteristic reservoirs. Computed tomography illustrates their spatial distribution and fusiform shape. The axial type of root secretory canals is formed at the interface between the endodermis and cortex parenchyma, while, in the stem, they are located in direct contact with veinal parenchyma. The peripheral phloem parenchyma cells are arranged in strands around sieve tube elements which possess a unique ability to accumulate large amounts of oil bodies. The cells of phloem parenchyma give rise to the aforementioned secretory structures while the lipid components (triacylglycerols) stored there support the biosynthesis of essential oils by later becoming a medium in which these oils are dissolved. The results indicate the integrity of axial secretory structures forming a continuous system in vegetative plant organs.

The CYP51F1 Gene of Leptographium qinlingensis: Sequence Characteristic, Phylogeny and Transcript Levels.

Leptographium qinlingensis is a fungal associate of the Chinese white pine beetle (Dendroctonus armandi) and a pathogen of the Chinese white pine (Pinus armandi) that must overcome the terpenoid oleoresin defenses of host trees. L. qinlingensis responds to monoterpene flow with abundant mechanisms that include export and the use of these compounds as a carbon source. As one of the fungal cytochrome P450 proteins (CYPs), which play important roles in general metabolism, CYP51 (lanosterol 14-α demethylase) can catalyze the biosynthesis of ergosterol and is a target for antifungal drug. We have identified an L. qinlingensis CYP51F1 gene, and the phylogenetic analysis shows the highest homology with the 14-α-demethylase sequence from Grosmannia clavigera (a fungal associate of Dendroctonus ponderosae). The transcription level of CYP51F1 following treatment with terpenes and pine phloem extracts was upregulated, while using monoterpenes as the only carbon source led to the downregulation of CYP5F1 expression. The homology modeling structure of CYP51F1 is similar to the structure of the lanosterol 14-α demethylase protein of Saccharomyces cerevisiae YJM789, which has an N-terminal membrane helix 1 (MH1) and transmembrane helix 1 (TMH1). The minimal inhibitory concentrations (MIC) of terpenoid and azole fungicides (itraconazole (ITC)) and the docking of terpenoid molecules, lanosterol and ITC in the protein structure suggested that CYP51F1 may be inhibited by terpenoid molecules by competitive binding with azole fungicides.

[The development, differentiation and composition of flax fiber cells]. / Rozwój, róznicowanie sie i sklad komórek wlókna lnianego.

Having vascular origin, flax fiber belongs to the sclerenchyma (steroids) and its structure is limited to the cell wall. What determines fiber properties is its composition, which in practice means the composition of the secondary cell wall. It consists of four main polymers which constitute approximately 90% of the fiber: cellulose, hemicellulose, pectin, lignin, and a variety of secondary metabolites, proteins, waxes and inorganic compounds. The cell wall is a structure with a high complexity of both the composition and interactions of the particular elements between themselves. It is determined by differentiation and cell growth as well as environmental factors, biotic and abiotic stresses. The molecular background of these processes and mechanisms regulating the synthesis and rearrangement of secondary cell walls components are being intensively studied. In this work we described the latest news about the development, composition and metabolism of flax fiber cell wall components together with the molecular explanation of these processes.

Novel diagnosis for citrus stubborn disease by detection of a spiroplasma citri-secreted protein.

Citrus stubborn disease (CSD), first identified in California, is a widespread bacterial disease found in most arid citrus-producing regions in the United States and the Mediterranean Region. The disease is caused by Spiroplasma citri, an insect-transmitted and phloem-colonizing bacterium. CSD causes significant tree damage resulting in loss of fruit production and quality. Detection of CSD is challenging due to low and fluctuating titer and sporadic distribution of the pathogen in infected trees. In this study, we report the development of a novel diagnostic method for CSD using an S. citri-secreted protein as the detection marker. Microbial pathogens secrete a variety of proteins during infection that can potentially disperse systemically in infected plants with the vascular flow. Therefore, their distribution may not be restricted to the pathogen infection sites and could be used as a biological marker for infection. Using mass spectrometry analysis, we identified a unique secreted protein from S. citri that is highly expressed in the presence of citrus phloem extract. ScCCPP1, an antibody generated against this protein, was able to distinguish S. citri-infected citrus and periwinkle from healthy plants. In addition, the antiserum could be used to detect CSD using a simple direct tissue print assay without the need for sample processing or specialized lab equipment and may be suitable for field surveys. This study provides proof of a novel concept of using pathogen-secreted protein as a marker for diagnosis of a citrus bacterial disease and can probably be applied to other plant diseases.

[Accumulation law of epigoitrin in roots of Isatis indigotica of different breed types].

OBJECTIVE: To study the distribution law of epigoitrin in roots of Isatis indigotica of different breed types and provide a scientific basis for screening of high-quality Isatis indigotica breed. METHODS: Determined the contents of epigoitrin in tap root and lateral root of Chinese-cabbage-leaf Isatis, cabbage-leaf Isatis, mustard-leaf Isatis and tetraploid Isatis by HPLC. Also, compared the contents of epigoitin in xylem and phloem of Isatis indigotica. RESULTS: Contents of epigoitrin in the tap root and lateral root of Isatis indigotica of the different breed types were significant different. In four breed types of Isatis indigotica, contents of epigoitrin in the tap root and phloem were higher than those in the lateral root and xylem, respectively. CONCLUSION: Contents of epigoitrin in the lateral root of Isatis indigotica are higher than those of tap root and epigoitrin distributes mainly in phloem.

[Pharmacognostical study on Berchemia floribunda].

OBJECTIVE: To study the pharmacognostical characteristics of stem and root of Berchemia floribunda for its further research and usage. METHODS: The plant was researched by macroscopic identification, microscopic identification and thin layer chromatography. RESULTS: The transverse section of B. floribunda root was eccentric. There were many fiber bundles in the secondary phloem and two different stone cells distributed in stem and root respectively. The results of TLC could identify the stem and root of B. floribunda. CONCLUSION: The microscopic characteristics of B. floribunda stem and root can be used as reference for its identification. Quercetin can be used as the characteristic component to identify the stem and root.

Practical considerations for the use of pollen δ13C value as a paleoclimate indicator.

RATIONALE: Workers have shown a correlation between temperature and the pollen δ(13)C value, and therefore suggested using pollen δ(13)C values to reconstruct paleotemperature. To evaluate the potential for pollen δ(13)C values to be used as a paleotemperature proxy, it is essential to quantify the variability in pollen δ(13)C values and to evaluate the effect of temperature on pollen δ(13)C values, in isolation, under controlled environmental conditions. METHODS: Pollen was isolated from 146 Hibiscus flowers from 26 plants within a single climate environment to evaluate isotopic variability in pollen δ(13)C values. The nearest leaf (n = 82) and flower phloem (n = 30) were also sampled to measure the δ(13)C variability in carbon providing the raw material for new growth. To evaluate the correlation between temperature and pollen δ(13)C values, we isolated pollen from 89 Brassica rapa plants grown in controlled growth chambers with temperatures ranging from 17 to 32°C. RESULTS: The range in pollen δ(13)C values collected from different flowers on the same Hibiscus plant was large (average = 1.6‰), and could be as much as 3.2‰. This amount of variability was similar to that seen between flower-adjacent leaves, and phloem extracted from styles of individual flowers. In controlled growth chamber experiments, we saw no correlation between temperature and the pollen (R(2) = 0.005) or leaf (R(2) = 0.10) δ(13)C values. CONCLUSIONS: We measured large variability in pollen δ(13)C values. When temperature was isolated from other environmental parameters, temperature did not correlate with the pollen δ(13)C value. These results complicate the supposed relationship between temperature and pollen δ(13)C values and caution against using nanogram isotope analytical techniques for characterizing whole-plant individuals.

Herbivory by a Phloem-feeding insect inhibits floral volatile production.

There is extensive knowledge on the effects of insect herbivory on volatile emission from vegetative tissue, but little is known about its impact on floral volatiles. We show that herbivory by phloem-feeding aphids inhibits floral volatile emission in white mustard Sinapis alba measured by gas chromatographic analysis of headspace volatiles. The effect of the Brassica specialist aphid Lipaphis erysimi was stronger than the generalist aphid Myzus persicae and feeding by chewing larvae of the moth Plutella xylostella caused no reduction in floral volatile emission. Field observations showed no effect of L. erysimi-mediated floral volatile emission on the total number of flower visits by pollinators. Olfactory bioassays suggested that although two aphid natural enemies could detect aphid inhibition of floral volatiles, their olfactory orientation to infested plants was not disrupted. This is the first demonstration that phloem-feeding herbivory can affect floral volatile emission, and that the outcome of interaction between herbivory and floral chemistry may differ depending on the herbivore's feeding mode and degree of specialisation. The findings provide new insights into interactions between insect herbivores and plant chemistry.

[Investigation on correlation between ratio of xylem to phloem of Radix Isatidis and efficacy, chemical composition].

OBJECTIVE: Explore contribution of ratio of xylem to phloem(RXP) to evaluate the quality of Radix Isatidis. METHODS: Antivirus activity and chemical compositions of xylem, phloem and Radix Isatidis of different RXP were determined by RBC agglutination test and unique chromatogram. Meanwhile, correlation between RXP and bioactivity,components was investigated. RESULTS: the activity of medical material of Radix Isatidis whose RXP was 1:2 or 1:1 is equal to that of phloem sample, while is stronger than that of cylem sample. There was a good consistency among the chemical figureprints of three samples (Radix Isatidis, xylem and phloem). When the RXP was 2:1, the medical material of Radix Isatidi and its xylem had the same activity. But the activity of phloem was not obvious. Their consistency of chemical fingerprint was bad, and the activity of Radix Isatidis which had RXP of 1:2 or 1:1 was better than that formed by xylem and phloem of 2:1. The Radix Isatidis of RXP of 1:2 or 1:1 had less similarity of chemical figureprint with that having RXP of 2:1. CONCLUSION: The quality of Radix Isatidis made up by the various RXP had significant difference. Radix Isatidis whose RXP is less than 1:1 had good quality and better activity. As a characteristic parameter of biologic morpha, the RXP can be applied to identifying the quality of Radix Isatidis, and also provided a reference to evaluation of other medical material of roots.

Gene discovery for the bark beetle-vectored fungal tree pathogen Grosmannia clavigera.

BACKGROUND: Grosmannia clavigera is a bark beetle-vectored fungal pathogen of pines that causes wood discoloration and may kill trees by disrupting nutrient and water transport. Trees respond to attacks from beetles and associated fungi by releasing terpenoid and phenolic defense compounds. It is unclear which genes are important for G. clavigera's ability to overcome antifungal pine terpenoids and phenolics. RESULTS: We constructed seven cDNA libraries from eight G. clavigera isolates grown under various culture conditions, and Sanger sequenced the 5' and 3' ends of 25,000 cDNA clones, resulting in 44,288 high quality ESTs. The assembled dataset of unique transcripts (unigenes) consists of 6,265 contigs and 2,459 singletons that mapped to 6,467 locations on the G. clavigera reference genome, representing ~70% of the predicted G. clavigera genes. Although only 54% of the unigenes matched characterized proteins at the NCBI database, this dataset extensively covers major metabolic pathways, cellular processes, and genes necessary for response to environmental stimuli and genetic information processing. Furthermore, we identified genes expressed in spores prior to germination, and genes involved in response to treatment with lodgepole pine phloem extract (LPPE). CONCLUSIONS: We provide a comprehensively annotated EST dataset for G. clavigera that represents a rich resource for gene characterization in this and other ophiostomatoid fungi. Genes expressed in response to LPPE treatment are indicative of fungal oxidative stress response. We identified two clusters of potentially functionally related genes responsive to LPPE treatment. Furthermore, we report a simple method for identifying contig misassemblies in de novo assembled EST collections caused by gene overlap on the genome.

Boring in response to bark and phloem extracts from North American trees does not explain host acceptance behavior of Orthotomicus erosus (Coleoptera: Scolytidae).

When invasive herbivorous insects encounter novel plant species, they must determine whether the novel plants are hosts. The Mediterranean pine engraver, Orthotomicus erosus (Wollaston), an exotic bark beetle poised to expand its range in North America, accepts hosts after contacting the bark. To test the hypothesis that O. erosus accepts hosts on the basis of gustatory cues, we prepared bark and phloem extracts from logs of four North American tree species that we had used in previous host acceptance experiments. Water, methanol, and hexane extracts of red pine, tamarack, balsam fir, and paper birch were presented alone and in combination on a neutral filter paper substrate in a section of a plastic drinking straw. Boring behavior in response to the three-extract combinations differed from the pattern of acceptance previously observed among species when the beetles were in contact with the bark surface. Only the aqueous extracts of tamarack, Larix laricina, increased the initiation and the extent of boring by O. erosus on the filter paper substrate. We conclude that the effects of extracted chemicals do not match the behavior of the beetles observed when penetrating excised bark and phloem discs, indicating that host selection by O. erosus may not be predictable from bark and phloem chemistry alone. Instead, host acceptance may be determined by nongustatory stimuli or by a combination of stimuli including gustatory and nongustatory cues.