Xylem-feeding Insects Research Articles

Management of Almond Leaf Scorch Disease: Long-Term Data on Yield, Tree Vitality, and Disease Progress.

Almond leaf scorch disease (ALSD) has been a chronic problem for California almond growers. This disease is caused by the bacterial pathogen Xylella fastidiosa and is transmitted by xylem-feeding insects. Previous research suggested that retaining, rather than roguing, ALSD-affected trees may be more economically beneficial because ALSD-affected trees produced a reasonable yield and did not die over a 3-year period. Because almond orchards are kept in production for approximately 25 years, longer-term data are needed to fully evaluate the merits of retaining ALSD-affected trees. Extension of yield evaluations from 3 to 5 years demonstrated that yield loss due to ALSD was consistent over 5 years, with yields of ALSD-affected trees reduced by 20 and 40% compared with unaffected trees for 'Nonpareil' and 'Sonora', respectively. To assess risk of ALSD-affected trees serving as a source of inocula for secondary (tree-to-tree) spread and to evaluate vitality of ALSD-affected trees, previous surveys of two orchards were extended from 3 to 6 or 7 years. The relationship between disease incidence (percentage of trees infected) and survey year was linear for all cultivars examined at both orchards. Furthermore, at each orchard, the spatial location of infections detected after the first survey was random with respect to the spatial location of infections identified during the first survey, suggesting that ALSD-affected trees retained in orchards did not serve as a source for secondary spread. Over the 6- to 7-year study period, death of ALSD-affected trees was rare, with only 9% of ALSD-affected trees dying. Because orchards used in this study had relatively high disease incidence, 61 orchards containing Sonora were surveyed to determine typical levels of ALSD incidence. ALSD was widespread, with at least one infected tree in 56% of orchards surveyed, but incidence was typically low (mean incidence = 0.47%). Collectively, the results suggest that retaining ALSD-affected trees may be economically beneficial in older orchards.

XatA, an AT-1 autotransporter important for the virulence of Xylella fastidiosa Temecula1.

Xylella fastidiosa Temecula1 is the causative agent of Pierce's disease of grapevine, which is spread by xylem-feeding insects. An important feature of the infection cycle is the ability of X. fastidiosa to colonize and interact with two distinct environments, the xylem of susceptible plants and the insect foregut. Here, we describe our characterization of XatA, the X. fastidiosa autotransporter protein encoded by PD0528. XatA, which is classified as an AT-1 (classical) autotransporter, has a C-terminal β-barrel domain and a passenger domain composed of six tandem repeats of approximately 50 amino acids. Localization studies indicate that XatA is present in both the outer membrane and membrane vesicles and its passenger domain can be found in the supernatant. Moreover, XatA is important for X. fastidiosa autoaggregation and biofilm formation based on mutational analysis and the discovery that Escherichia coli expressing XatA acquire these traits. The xatA mutant also shows a significant decrease in Pierce's disease symptoms when inoculated into grapevines. Finally, X. fastidiosa homologs to XatA, which can be divided into three distinct groups based on synteny, form a single, well-supported clade, suggesting that they arose from a common ancestor.

Seasonal Abundance of Draeculacephala minerva and Other Xylella fastidiosa Vectors in California Almond Orchards and Vineyards

Almond leaf scorch (ALS) disease is caused by the bacterium Xylella fastidiosa and transmitted by xylem-feeding insects. Reports of increased incidence of ALS-diseased trees in California prompted surveys in three almond [Prunus dulcis (Mill.) D. A. Webb]-growing regions, from June 2003 to September 2005, to determine insect vector species composition and abundance. For comparison, sampling in and near vineyards in the San Joaquin Valley, California, also was completed. Sampling in or near almond orchards collected >42,000 Cicadomorpha of which 4.8% were xylem feeders, including 1912 grass sharpshooter, Draeculacephala minerva Ball; five Xyphon fulgida Nottingham; and a single spittlebug, Philaenus spumarius L. The most abundant vector was D. minerva. Season-long sampling indicated that D. minerva was a year-round resident in and/or near almonds in the Sacramento Valley, but not in the San Joaquin Valley. Similarly, D. minerca was rare in vineyards in the San Joaquin Valley, but was abundant in irrigated pastures near vineyards. D. minerva was most frequently collected along orchard margins, and peak densities were observed in summer, the period of time when bacterial titers are reported to increase in infected trees. Screening of D. minerva for presence of X.fastidiosa found that 1.1% of insects collected near almond orchards and 4.5% of insects collected from pastures tested positive. The X. fastidiosa subspecies and genotype detected in insects collected from orchards matched those collected from ALS-diseased almond trees in the same orchard. Of the few X. fulgida and P. spumarius collected, none tested positive for X. fastidiosa. Results are discussed with respect to X. fastidiosa vector control and detection methods.

Evaluation of Xylem-Feeding Insects (Hemiptera: Auchenorrhyncha) in Texas Vineyards: Distribution along State-Wide Environmental Gradients

The goal of this project was to analyze a large collection of insect trap data accumulated by the Texas Pierce's Disease Research and Education Program. The traps were set in grape, Vitis, vineyards across Texas to monitor the abundance and distribution of xylem fluid-feeding insects that may vector Pierce's disease. This study evaluated the three most abundant xylem fluid-feeding insects in Texas vineyards: the glassy-winged sharpshooter, Homalodisca vitripennis (Germar); a smaller green sharpshooter, Graphocephala versuta (Say); and the sunflower spittlebug, Clastoptera xanthocephala Germar. Canonical Correspondence Analysis was used to analyze insect abundance against environmental gradients of ecoregion, elevation, annual precipitation, and cold hardiness from 2003–2007 in each of 40 vineyards. Canonical Correspondence Analysis showed that distribution of species along environmental gradients differed significantly (p = 0.001) and the environmental gradients explained almost 67% of the variability in insect distribution across the state. The Canonical Correspondence Analysis plot also suggested niche differences among these insect species.

Epidemiology of Diseases Caused by Xylella fastidiosa in California: Evaluation of Alfalfa as a Source of Vectors and Inocula.

Pierce's disease and almond leaf scorch disease have been chronic problems for California grape and almond growers, respectively. Both diseases are caused by the xylem-limited, bacterial pathogen Xylella fastidiosa, which is transmitted by xylem-feeding insects. We evaluated the potential for alfalfa to serve as a source of vectors and inocula in California. Analysis of Geographic Information Systems maps on the distribution and abundance of grape, almond, and alfalfa plantings determined that 94,521 ha of almond and grape were planted within 1.6 km of an alfalfa field. Seasonal trends of X. fastidiosa detection were monitored outdoors and in the greenhouse in five needle-inoculated alfalfa cultivars (CUF101, Moapa69, WL342, WL530HQ, and WL625HQ) over 2 years. Results suggest that cool winter temperatures reduced X. fastidiosa populations to undetectable levels but did not eliminate infections. Sampling of alfalfa fields to assess incidence of X. fastidiosa corroborated this result, with positive samples detected in summer only. Incidence of X. fastidiosa in alfalfa during summer was low, with only 6 positive samples out of 1,156 samples collected over 3 years. Insect trapping in alfalfa fields over 3 years found that the green sharpshooter (Draeculacephala minerva) was the most abundant vector. Within alfalfa fields, green sharpshooter abundance was highest in weedy areas, suggesting a preference for weeds over alfalfa. These results confirm that weedy alfalfa fields can serve as an important source of vectors. Incidence of X. fastidiosa in alfalfa was low, possibly due to preference of vectors for weeds over alfalfa.

Karyotype and male pre-reductional meiosis of the sharpshooter Tapajosa rubromarginata (Hemiptera: Cicadellidae)

Cicadellidae in one of the best represented families in the Neotropical Region, and the tribe Proconiini comprises most of the xylem-feeding insects, including the majority of the known vectors of xylem-born phytopathogenic organisms. The cytogenetics of the Proconiini remains largely unexplored. We studied males of Tapajosa rubromarginata (Signoret) collected at El Manantial (Tucumán, Argentina) on native spontaneous vegetation where Sorghum halepense predominates. Conventional cytogenetic techniques were used in order to describe the karyotype and male meiosis of this sharpshooter. T. rubromarginata has a male karyological formula of 2n = 21 and a sex chromosome system XO:XX (male:female). The chromosomes do not have a primary constriction, being holokinetic and the meiosis is pre-reductional, showing similar behavior both for autosomes and sex chromosomes during anaphase I. For this stage, chromosomes are parallel to the acromatic spindle with kinetic activities in the telomeres. They segregate reductionally in the anaphase I, and towards the equator during the second division of the meiosis. This is the first contribution to cytogenetic aspects on proconines sharpshooters, particularly on this economic relevant Auchenorrhyncha species.

Organic Farm Soil Improves Strawberry Growth But Does Not Diminish Spittlebug Damage

Soil microorganisms are central to the success of low-input agriculture. Among these microbes, arbuscular mycorrhizal fungi (AMF) are integral components of soil communities and are well known for facilitating nutrient uptake by plants. These root symbionts can alter tolerance and resistance of plants to pathogens, and there is mounting evidence that AMF can similarly affect plant-herbivore relations. A greenhouse experiment tested whether inoculation with soil containing AMF alters tolerance of strawberry plants to herbivory by a xylem-feeding insect, the meadow spittlebug Philaenus spumarius. Commercially produced, bare-root ‘Ozark Beauty’ strawberry plants (a day-neutral cultivar) were inoculated with organic farm soil containing AMF spores or with AMF-free soil filtrate and subsequently challenged with one of five herbivore loads. Inoculation with soil increased survival, flowering, runner production, and root and shoot mass. Twenty-four days of spittlebug feeding reduced leaf mass but the negative impact was small compared with positive effects of inoculation with soil containing AMF. Effects of both treatments were additive: compared with AMF-free filtrate, soil inoculum did not alter tolerance of the plant to this xylem-feeding herbivore but did increase plant productivity.

Silicon as a plant defence against insect herbivory: response to Massey, Ennos and Hartley

1. Silicon (Si) has received increased attention as a nutrient capable of providing some measure of defence for plants against fungal pathogens, and insect and mammalian herbivores. 2. On the basis of a study including two generalist insect folivores and a phloem feeder, Massey, Ennos & Hartley (2006; Journal of Animal Ecology, 75, 595-603) have drawn attention to a putative distinction between the effects of plant Si in defending against folivorous and phloem-feeding insects. On the basis of their results they imply that phloem feeders are less likely to be adversely affected by increased plant Si than folivores. 3. However, in making this suggestion, Massey et al. have ignored many previous studies demonstrating a clear effect of plant Si on a range of phloem-feeding and some xylem-feeding insects, and that this effect stems not only from leaf mechanical properties based on opaline silica, but also from induced chemical defences seemingly mediated by soluble Si. 4. Furthermore, Massey et al. cannot claim that their study was the first demonstration of a direct effect of Si on insect herbivore preference and performance; there have been numerous earlier studies demonstrating this from folivores, stem borers, and phloem and xylem feeders. 5. We contend that current evidence indicates that Si is likely to be involved to a similar extent in enhancing resistance to all four insect feeding guilds and that any conclusion to the contrary is, at this stage, premature.

Xylem sap analysis reveals new facts of salt tolerance in rice genotypes

Salinity damage in rice and other salt-sensitive species is due to excessive transport of NaCl through the root system to the leaves and consequently low salt transport to the shoot can be a major trait determining salt resistance. Since the rapid uptake of sodium ions is such a crucial part of the response of rice to salinity, physiological experiments were carried out to compare bypass flow in two genotypes of rice (IR4630 and IR15324) differing in salt tolerance, because it has been suggested that an apoplastic pathway, bypass flow, is a major contributory pathway for Na+ entrance into rice plants. Experiments on the youngest fully expanded photosynthetic leaf (the third from the base), using PTS as a tracer for apoplastic movement and Philaenus spumarius (a xylem-feeding insect) as a means to sample the xylem sap, did not demonstrate any apparent difference in bypass flow between the two lines. The similarity of Na+ concentration in the xylem sap of both genotypes paralleled the results of PTS (a fluorescent dye used as an apoplastic tracer for the transpiration stream) measurements. Despite the similarity of Na+ concentration in the xylem sap of the third leaves, the Na+ concentration in the bulk of these leaves of IR15324 plants (the sensitive line) was about twice that of IR4630 (the tolerant line). Measurements of transpiration over 8 d of salinisation showed the similarity of rates in both lines providing evidence that the greater accumulation of NaCl in IR15324 than in IR4630 plants was unlikely to be due to a difference in the delivery of salt to the leaves by an apoplastic route. Results of the current work suggest that the difference in salt tolerance might be a consequence of damage to leaves 1 and 2 of IR15324 that allowed Na+ to leak into the phloem - and consequently move to leaf 3.

Infectividade natural por Xylella fastidiosa Wells et al. de cicadelíneos (Hemiptera: Cicadellidae) de lavouras cafeeiras do Paraná

Xylella fastidiosa Wells et al., a gram-negative and xylem limited bacterium, causes significative economic on several crops, such as the leaf scorch in coffee. It is transmitted by xylem feeding insects and four sharpshooters species have been reported as vectors of X. fastidiosa in coffee. The objective of this study was to determine the natural infectivity of X. fastidiosa in five species of sharpshooters from coffee trees: Acrogonia citrina Marucci & Cavichioli, Bucephalogonia xanthophis (Berg), Dilobopterus costalimai Young, Oncometopia facialis (Signoret) and Sonesimia grossa (Signoret). Samples were collected from coffee plantations in five counties of the North and Northwest regions of the State of Parana, Brazil, from October 1998 through November 2001. A total of 806 samples containing three to five insects were examined for the presence of X. fastidiosa by using PCR and nested PCR tests. X. fastidiosa was present in samples of all five species of sharpshooters collected in the two coffee regions. The average level of natural infectivity potential was 30.4%. However, this natural infectivity ranged from 2.2% for O. facialis to 68.8% for A. citrina. Sharpshooters collected in the spring tended to have lower natural infectivity of X. fastidiosa as compared to those collected in other seasons. The results obtained showed the high potential of dissemination of X. fastidiosa by different insect vectors in coffee trees in Parana.

GENOMIC HARDWIRING AND PHENOTYPIC PLASTICITY OF TERPENOID-BASED DEFENSES IN CONIFERS

Over evolutionary history, conifers have faced a myriad of threats from phloem- and xylem-feeding insects, defoliating insects, and fungal pathogens. Among the trees' defenses, terpenoids appear to play a major role by harming, disabling, deterring, repelling, or otherwise reducing the fitness of potential invaders. Each of the three classes of terpenoids in conifers, monoterpenes, sesquiterpenes, and diterpenes, are composed of a large number of representative compounds. In most cases, the presence of a particular terpenoid compound in the oleoresin or volatile emissions from a specific conifer can be accounted for by the expression of one of many committed terpene synthase (TPS) genes. However, while each TPS may produce one or a few major products, many produce a variety of minor products with relatively constant component ratios in the product blends. TPS genes exist in conifers in large and functionally diverse, yet monophyletic, gene families. Within these gene families, new biochemical functions of TPS appear to have evolved by gene duplication and changes in the amino acid sequence of the enzyme's active site. In addition, TPS genes may be differentially expressed prior to, during, and following attack by insects or pathogens. Thus, while the production of any particular terpenoid is hardwired into a conifer's genome, these trees have the capacity to change the mixture of terpenoids in oleoresin secretions and volatile emissions. Anatomical changes may also accompany induced terpenoid production, supplementing the plasticity of the molecular and biochemical events.

Continuous measurement of macronutrient ions in the transpiration stream of intact plants using the meadow spittlebug coupled with ion chromatography.

A method is described for continuous, nondestructive analysis of xylem-borne mineral nutrients in intact transpiring plants. The method uses the xylem-feeding insect the meadow spittlebug (Philaenus spumarius L. [Homoptera: Cercopidae]). This insect will feed from a wide range of plant species and organs. Insect excreta can be collected at all times of the day and night, and its mineral ion content can be analyzed rapidly, and without purification, by ion chromatography. The excreta will have a mineral content virtually identical to that of xylem sap. Cages suitable for containing the insects and collecting excreta from any desired location on plants in both laboratory and greenhouse are described. Even in the greenhouse, evaporation had only a minor effect on the sample ion content. Example results are presented which illustrate dynamics, over several days, in the xylem concentrations of sodium (Na(+)), potassium (K(+)), NH(4)(+), magnesium (Mg(2+)), calcium (Ca(2+)), chloride (Cl(-)), NO(3)(-), PO(4)(3-), and SO(4)(2-). These data were collected from young plants growing in pots of compost in the laboratory and from fully mature pepper (Capsicum annuum L. cv Bellboy) plants growing in hydroponics (rockwool) in the greenhouse. This method should facilitate studies of macronutrient uptake and transport in a range of plants and environments.

Mineral content of excreta from the spittlebug Philaenus spumarius closely matches that of xylem sap

Summary Analysis of xylem sap from intact transpiring plants is possible using excreta of xylem feeding insects. However, the extent to which the inorganic composition of ingested sap is altered by its passage through the insect has not been fully evaluated. The impact of the xylem feeding insect Philaenus spumarius (meadow spittlebug) on the inorganic composition of ingested sap from tomato (Lycopersicon esculentum) is reported here. Two nondestructive experimental approaches were used. Sap exuding due to root pressure from a cut tomato stem was compared with excreta from a caged insect feeding just below the cut surface. A second method involved pumping a solution of inorganic ions through a section of tomato stem upon which an adult insect was caged. The composition of insect excreta was compared with that of the input and output solutions. Overall, the concentrations of inorganic ions were similar in ingested fluid and excreta except for ammonium, which was generally elevated in excreta samples. It is demonstrated that excreta of P. spumarius can be used for continual monitoring of most inorganic ions in xylem sap of intact transpiring plants, and that stem perfusion is a useful tool for quantifying the effect of the insect on solutions of known composition.

Differences in tolerance to infertile acid soil stress among germplasm accessions and genetic recombinants of the tropical forage grass genus, Brachiaria

Several Brachiaria species are the most widely grown forages in tropical America. A field study was conducted during two seasons (1994, wet and 1995, dry) in a medium-textured Oxisol at Carimagua, Colombia. The main objective of the study was to evaluate genotypic variation in plant attributes for tolerance to low fertility, acid soil stress conditions (pH 4.9) among germplasm accessions and genetic recombinants of Brachiaria. The entries included 43 genetic recombinants selected from a breeding population, four parental accessions and an additional eight germplasm accessions. Small amounts of fertilizer were applied at establishment (kg ha −1: 40 N, 20 P, 20 K, 14 Ca, 12 Mg and 12 S). A number of plant attributes including forage yield, leaf area, shoot nutrient composition and shoot nutrient uptake were measured during both seasons. Significant genetic variation was observed in several plant attributes such as leaf area, shoot nutrient content, nutrient partitioning to leaves, shoot nutrient uptake, and forage yield in both seasons. Forage yield ranged from 59 to 343 g plant −1 in the wet season and 5 to 174 g plant −1 in the dry season. Correlation between forage yield and shoot nutrient uptake indicated the importance of nutrient acquisition, particularly of phosphorus ( r=0.90; P<0.0001), for adaptation to infertile acid soil stress. Two genetic recombinants (BRN093/3009, FM9201/1873) were productive when grown under infertile acid soil stress in both wet and dry seasons. But, neither of these two recombinants is highly resistant to xylem-feeding insects known as spittlebugs (Homoptera: Cercopidae). One spittlebug-resistant genetic recombinant (BRN093/1371) exhibited several desirable attributes such as superior leaf area and leaf biomass, greater N content in leaves, and greater partitioning of N and P to leaves that could contribute to adaptation and persistence in these soils. This recombinant is being utilized in a breeding program to develop superior Brachiaria lines.

Applications of the compensating pressure theory of water transport

Some predictions of the recently proposed theory of long-distance water transport in plants (the Compensating Pressure Theory) have been verified experimentally in sunflower leaves. The xylem sap cavitates early in the day under quite small water stress, and the compensating pressure P (applied as the tissue pressure of turgid cells) pushes water into embolized vessels, refilling them during active transpiration. The water potential, as measured by the pressure chamber or psychrometer, is not a measure of the pressure in the xylem, but (as predicted by the theory) a measure of the compensating pressure P. As transpiration increases, P is increased to provide more rapid embolism repair. In many leaf petioles this increase in P is achieved by the hydrolysis of starch in the starch sheath to soluble sugars. At night P falls as starch is reformed. A hypothesis is proposed to explain these observations by pressure-driven reverse osmosis of water from the ground parenchyma of the petiole. Similar processes occur in roots and are manifested as root pressure. The theory requires a pump to transfer water from the soil into the root xylem. A mechanism is proposed by which this pump may function, in which the endodermis acts as a one-way valve and a pressure-confining barrier. Rays and xylem parenchyma of wood act like the xylem parenchyma of petioles and roots to repair embolisms in trees. The postulated root pump permits a re-appraisal of the work done by evaporation during transpiration, leading to the proposal that in tall trees there is no hydrostatic gradient to be overcome in lifting water. Some published observations are re-interpreted in terms of the theory: doubt is cast on the validity of measurements of hydraulic conductance of wood; vulnerability curves are found not to measure the cavitation threshold of water in the xylem, but the osmotic pressure of the xylem parenchyma; if measures of xylem pressure and of hydraulic conductance are both suspect, the accepted view of the hydraulic architecture of trees needs drastic revision; observations that xylem feeding insects feed faster as the water potential becomes more negative are in accord with the theory; tyloses, which have been shown to form in vessels especially vulnerable to cavitation, are seen as necessary for the maintenance of P, and to conserve the supplementary refilling water. Far from being a metastable system on the edge of disaster, the water transport system of the xylem is ultrastable: robust and self-sustaining in response to many kinds of stress.

Why are there no small species among xylem-sucking insects?

Xylem-sucking herbivores must cope with negative tension and extremely low nutrient concentration of xylem fluid. We test the hypothesis that the energetic cost of xylem fluid extraction grows with decreasing body size, as small species have relatively high metabolic rates and small feeding apparatus. The suction pressure gradient needed for feeding (P), calculated using Poiseuille's Law, and the cibarial pump load (L), estimated as xylem fluid volume per unit volume of cibarial muscles, were used to quantify energetic costs associated with feeding. Interspecific relationships between body size and frontoclypeus (cibarial pump) volume, proboscis length and food canal diameter were quantified using the structural relations model and model I (‘ordinary’) regressions applied on species as data points (phylogeny ignored), and on independent (intrageneric) contrasts (taxonomy used as a surrogate of phylogeny). All the dimensions of feeding apparatus changed approximately isometrically with body volume. In consequence, the suction pressure gradient P∼ (body volume)−0.21, and the cibarial pump load L∼ (body volume)−0.17. These relationships result in an allometric change in energetic costs associated with xylem feeding. Energy needed to overcome the resistance of feeding apparatus (P) becomes negligible for any species longer than about 8mm, and there is an important decrease in the L values in species over about 17mm in body length. These allometric trends can result in large species having a wider range of potential (energetically profitable) host plants than small species. Analysis of body size distributions in xylem-feeding insects, which all belong to the Auchenorrhyncha (Hemiptera), showed that xylem feeders tend to be larger than phloem feeders, especially in terms of the minimum body size. Two evolutionary transitions from phloem to xylem feeding in Hemiptera were associated with an increase in the minimum body size. A possibility that the evolution of minimum body size in xylem feeders is energetically constrained is discussed.

A new technique to immobilize an aphid or a mealybug on plants using a high‐frequency microcautery unit

Entomologia Experimentalis et ApplicataVolume 80, Issue 1 p. 239-241 A new technique to immobilize an aphid or a mealybug on plants using a high-frequency microcautery unit P. A. Calatayud, P. A. Calatayud ORSTOM, Laboratoire d'Entomologie, Parc Scientifique Agropolis II, 34397 Montpellier Cedex 5, FranceSearch for more papers by this authorC. Nardon, C. Nardon INRA-INSA, Laboratoire de Biologie Appliquée 406, 20 Avenue Albert Einstein, 69621 Villeurbanne Cedex, FranceSearch for more papers by this authorY. Rahbé, Y. Rahbé INRA-INSA, Laboratoire de Biologie Appliquée 406, 20 Avenue Albert Einstein, 69621 Villeurbanne Cedex, FranceSearch for more papers by this author P. A. Calatayud, P. A. Calatayud ORSTOM, Laboratoire d'Entomologie, Parc Scientifique Agropolis II, 34397 Montpellier Cedex 5, FranceSearch for more papers by this authorC. Nardon, C. Nardon INRA-INSA, Laboratoire de Biologie Appliquée 406, 20 Avenue Albert Einstein, 69621 Villeurbanne Cedex, FranceSearch for more papers by this authorY. Rahbé, Y. Rahbé INRA-INSA, Laboratoire de Biologie Appliquée 406, 20 Avenue Albert Einstein, 69621 Villeurbanne Cedex, FranceSearch for more papers by this author First published: July 1996 https://doi.org/10.1111/j.1570-7458.1996.tb00926.xCitations: 2AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume80, Issue1Special Issue: 9th International Symposium on Insect‐Plant RelationshipsJuly 1996Pages 239-241 RelatedInformation

Physiological and behavioral adaptations of three species of leafhoppers in response to the dilute nutrient content of xylem fluid

Physiological and behavioral processes of three species of leafhoppers were examined in relation to the extremely dilute content of their food source (xylem fluid). Segregated sexes of Homalodisca coagulata (Say), Homalodisca insolita (Wlk.) and Cuerna costalis (F.) were caged on two hosts, Lagerstroemia indica L. and Catharanthus roseus (L.). Excreta was analyzed and compared to the composition of xylem fluid of the hosts during day and night feeding. Both xylem fluid and insect excreta were analyzed for amino acids, organic acids and sugars and excreta was also analyzed for common excretory products. Efficiencies of metabolic conversion of organic compounds (defined by quantity ingested versus quantity excreted), and total nitrogen and carbon retention were calculated. Diurnal feeding patterns as well as total daily ingestion rates were recorded. Four primary similarities were noted in diet utilization regardless of leafhopper species, host species or sex: (1) excretion of ammonia as the primary waste product; (2) high efficiency of conversion for all organic compounds ingested from xylem fluid; (3) high daily feeding rates (100–300 times dry body weight per day and (4) adjustment of feeding rates to diurnal fluctuations in xylem fluid chemistry. Although these processes were operative for all leafhoppers examined, the extent of their usage and subsequent energy gain and nitrogen accumulation varied greatly with host species and insect sex. These processes maximize efficiency of diet utilization and are discussed in relation to nutritional and caloric requirements of xylem feeding insects.