bluuebunny/crossref_metadata_2025 huggingface dataset:
Altered T Wave Dynamics in a Contracting Cardiac Model
Authors: SMITH NICOLAS P. , BUIST MARTIN L. , PULLAN ANDREW J.
Published: October 2003

Introduction: The implications of mechanical deformation on calculated body surface potentials are investigated using a coupled biophysically based model.

Methods and Results: A cellular model of cardiac excitation‐contraction is embedded in an anatomically accurate two‐dimensional transverse cross‐section of the cardiac ventricles and human torso. Waves of activation and contraction are induced by the application of physiologically realistic boundary conditions and solving the bidomain and finite deformation equations. Body surface potentials are calculated from these activation profiles by solving Laplace's equation in the passive surrounding tissues. The effect of cardiac deformation on electrical activity, induced by contraction, is demonstrated in both single‐cell and tissue models. Action potential duration is reduced by 7 msec when the single cell model is subjected to a 10% contraction ramp applied over 400 msec. In the coupled electromechanical tissue model, the T wave of the ECG is shown to occur 18 msec earlier compared to an uncoupled excitation model. To assess the relative effects of myocardial deformation on the ECG, the activation sequence and tissue deformation are separated. The coupled and uncoupled activation sequences are mapped onto the undeforming and deforming meshes, respectively. ECGs are calculated for both mappings.

Conclusion: Adding mechanical contraction to a mathematical model of the heart has been shown to shift the T wave on the ECG to the left. Although deformation of the myocardium resulting from contraction reduces the T wave amplitude, cell stretch producing altered cell membrane kinetics is the major component of this temporal shift. (J Cardiovasc Electrophysiol, Vol. 14, pp. S203‐S209, October 2003, Suppl.)
Quantitative Reconstruction of Cardiac Electromechanics in Human Myocardium:
Authors: SACHSE FRANK B. , SEEMANN GUNNAR , CHAISAOWONG KRAISORN , WEIß DANIEL
Published: October 2003

Introduction:Myocytes from normal and failing myocardium show significant differences in electromechanical behavior. Mathematical modeling of the behavior provides insights into the underlying physiologic and pathophysiologic mechanisms. Electromechanical models of cardiomyocytes exist for various species, but models of human myocytes are lacking.

Methods and Results:A mathematical model of electromechanics in normal and failing cardiac myocytes in humans was created by assembly and adaptation of parameters of an electrophysiologic model at the level of single cells and a force development model at the level of the sarcomere. The adaptation was performed using data from recent studies of ventricular myocytes and myocardium. The model was applied to quantitatively reconstruct measurement data from different experimental studies of normal and failing myocardium. Several simulations were performed to quantify the transmembrane voltageVm, intracellular concentration of calcium[Ca2+]i, the [Ca2+]i–force relationship, and force transients. Furthermore, frequency dependencies and restitution of action voltage duration to 90% recovery APD90, peak [Ca2+]i, duration to 50% force recovery FD50, and peak force were determined.

Conclusion:The presented mathematical model was capable of quantitatively reconstructing data obtained from different studies of electrophysiology and force development in normal and failing myocardium of humans. In future work, the model can serve as a component for studying macroscopic mechanisms of excitation propagation, metabolism, and electromechanics in human myocardium.(J Cardiovasc Electrophysiol, Vol. 14, pp. S210‐S218, October 2003, Suppl.)
Quantitative Reconstruction of Cardiac Electromechanics in Human Myocardium:
Authors: SEEMANN GUNNAR , SACHSE FRANK B. , WEIß DANIEL L. , DÖSSEL OLAF
Published: October 2003

Introduction: Regional heterogeneity of electrophysiologic properties within the human ventricles is based on changes in ion channel kinetics and density inside the wall. The heterogeneity not only influences the electrophysiologic properties but also cellular force development. In this study, the influence of heterogeneity was investigated using mathematical models.

Methods and Results: An overview of measurements of the heterogeneity of electrophysiology and force development is presented. This knowledge is transferred to an electromechanical heart model composed of a human ionic cell model describing electrophysiologic properties and a model for the development of forces. Heterogeneity is included in the ionic model by changing ion channel kinetics and density. The characteristics and dependencies of the electromechanical model are demonstrated in a single‐cell environment and a multicell environment. In the single‐cell environment, the effects of heterogeneity on electrical activity are demonstrated. The notch in the action potential decreases from epicardium to endocardium, and action potential duration is longest in the mid‐myocardium. The developed forces are largest in the subendocardial cells and decrease continuously toward the epicardium. The multicell environment describes a transmural line of cells in the left ventricular free wall using a bidomain approach. The transmural ECG shows typical characteristics with a positive monophasic T wave.

Conclusions: This work demonstrates the need to incorporate regional heterogeneity in order to model human cardiac electromechanics. The results of electrophysiologic simulations correspond to measured data. The dependencies of regional heterogeneity on force development need to be validated in experiments, because little is known about the influence of heterogeneity on electromechanical coupling. (J Cardiovasc Electrophysiol, Vol. 14, pp. S219‐S228, October 2003, Suppl.)
Spontaneous Initiation and Termination of Complex Rhythms in Cardiac Cell Culture
Authors: BUB GIL , TATENO KATSUMI , SHRIER ALVIN , GLASS LEON
Published: October 2003

Introduction: Complex cardiac arrhythmias often start and stop spontaneously. These poorly understood behaviors frequently are associated with pathologic modification of the structural heterogeneity and functional connectivity of the myocardium. To evaluate underlying mechanisms, we modify heterogeneity by varying the confluence of embryonic chick monolayer cultures that display complex bursting behaviors. A simple mathematical model was developed that reproduces the experimental behaviors and reveals possible generic mechanisms for bursting dynamics in heterogeneous excitable systems.

Methods and Results: Wave propagation was mapped in embryonic chick myocytes monolayers using calcium‐sensitive dyes. Monolayer confluence was varied by plating cultures with different cell densities and by varying times in culture. At high plating densities, waves propagate without breaks, whereas monolayers plated at low densities display spirals with frequent breaks and irregular activation fronts. Monolayers at intermediate densities display bursting rhythms in which there is paroxysmal starting and stopping of spiral waves of activity. Similar spatiotemporal patterns of activity were also observed as a function of the time in culture; irregular activity dominates the first 30 hours, followed by repetitive bursting dynamics until 54 hours, after which periodic target patterns or stable spirals prevail. In some quiescent cultures derived from older embryos, it was possible to trigger pacemaker activity following a single activation. We are able to reproduce all of these behaviors by introducing spatial heterogeneity and varying neighborhood size, equivalent to cell connectivity, in a spontaneous cellular automaton model containing a rate‐dependent fatigue term.

Conclusion: We observe transitions from irregular propagating waves, to spiral waves that spontaneously start and stop, to target waves originating from localized pacemakers in cell culture and a simple theoretical model of heterogeneous excitable media. The results show how physiologic properties of spontaneous activity, heterogeneity, and fatigue can give rise to a wide range of different complex dynamic behaviors similar to clinically observed cardiac arrhythmias. (J Cardiovasc Electrophysiol, Vol. 14, pp. S229‐S236, October 2003, Suppl.)
Effects of Lidocaine on Shock‐Induced Vulnerability
Authors: LI LI , NIKOLSKI VLADIMIR , EFIMOV IGOR R.
Published: October 2003

Introduction: Lidocaine is known to increase the defibrillation threshold (DFT) of monophasic shocks (MS) and have no effect on DFT of biphasic shocks (BS). The aim of this study was to enhance our understanding of the mechanisms of vulnerability and defibrillation through the investigation of this difference.

Methods and Results: We studied the effect of 15 μM lidocaine on shock‐induced vulnerability using fluorescent imaging of Langendorff‐perfused rabbit hearts. Vulnerability was assessed as vulnerable window with shock strengths of 15 to 150 V and vulnerable period (VP) with shock delivery phase of 0% to 100% of action potential duration (% APD). With MS, lidocaine caused a significant increase in both the upper limit of vulnerability (ULV, 71 ± 17 V vs 120 ± 1.5 V, P < 0.01) and upper limit of VP (91 ± 8.0% APD vs 110 ± 4.2% APD, P < 0.01). With BS, lidocaine had no effect on ULV (40 ± 3.4 V vs 45 ± 4.5 V) and did not increase the upper limit of VP (78 ± 8.9% APD vs 96 ± 12% APD, P < 0.01). Lidocaine caused reduction of the conduction velocity during pacing (0.58 ± 0.08 m/s vs 0.44 ± 0.05 m/s, P < 0.01), shock‐induced break excitation (0.82 ± 0.17 m/s vs 0.30 ± 0.07 m/s, P < 0.01), and postshock reentry (0.34 ± 0.07 m/s vs 0.19 ± 0.08 m/s, P < 0.01). Lidocaine had no effect on shock‐induced virtual electrode polarization.

Conclusion: Lidocaine increased MS ULV due to slowing of shock‐induced break‐excitation wavefronts, which resulted in enhanced probability of survival of virtual electrode induced phase singularity. Lidocaine had no effect on BS ULV because no break excitation was induced by BS. Reduction of conduction velocity by lidocaine resulted in increased dispersion of repolarization and led to upper limit of VP increase for both MS and BS. (J Cardiovasc Electrophysiol, Vol. 14, pp. S237‐S248, October 2003, Suppl.)
Postshock Arrhythmogenesis in a Slice of the Canine Heart
Authors: HILLEBRENNER MATTHEW G. , EASON JAMES C. , CAMPBELL CRAIG A. , TRAYANOVA NATALIA A.
Published: October 2003

Introduction: Recent evidence has demonstrated that defibrillation shocks terminate or reset reentrant activity in the myocardium through the generation of virtual electrode polarization (VEP). Previous research has revealed that the shock establishes phase singularities (PSs) in the tissue via the VEP mechanism. The aim of this study was to examine, as a function of shock strength and electrode configuration, the relationship between end‐shock PSs and the reentrant circuits established after failed defibrillation attempts.

Methods and Results: The study uses a complex three‐dimensional finite‐element bidomain model of a slice of the canine heart characterized by realistic geometry and fiber architecture and undergoing a single scroll wave. Defibrillation shocks of increasing strength are delivered through three different electrode configurations. The results demonstrated that >98% of all PSs have a lifetime of half a reentrant cycle or less. Stronger shocks result in a faster rate of annihilation of postshock PSs. For failed shocks, the surviving PSs underlie the activity of one or more scroll waves, which remain stationary in the slice. For all electrode configurations tested, the increase in shock strength leads to a rapid initial increase in the number of postshock reentries followed by a slower decrease; similar behavior is observed with regard to end‐shock PSs.

Conclusion: These results present new evidence regarding the mechanisms underlying failure of defibrillation shocks. (J Cardiovasc Electrophysiol, Vol. 14, pp. S249‐S256, October 2003, Suppl.)
Delayed Success in Termination of Three‐Dimensional Reentry:
Authors: ZEMLIN CHRISTIAN , MIRONOV SERGEY , PERTSOV ARKADY
Published: October 2003

Introduction: Defibrillation shocks slightly stronger than cardioversion threshold may defibrillate not immediately but after a transient period of postshock activity (delayed success). The effect of a defibrillation shock is that it polarizes the tissue, primarily at the surfaces; therefore, surface polarization may play an important role at near‐threshold shock intensities.

Methods and Results: We numerically investigate the effect of a monophasic transmural electrical shock on a three‐dimensional (3D) reentrant wave (scroll wave). For simplicity, we assume uniform polarization of the epicardial and endocardial surfaces. We demonstrate that the effect of surface polarization alone is sufficient to induce delayed termination of self‐sustained activity (3–4 beats after the shock). In agreement with experimental observations, both successful and failed shocks cause prolongation of the action potentials on the depolarized side and shortening on the hyperpolarized side, while at the same time inducing a shift from a reentrant to a focal activation pattern. Our simulations suggest that the outcome of the shock is determined by its effect on the shape of the scroll wave's center of rotation (filament). We propose a simple rule to predict the postshock filament shape that allows us to make accurate predictions of success and failure of a termination attempt.

Conclusion: Surface polarization due to an electrical shock can terminate a reentrant scroll wave. This mechanism may explain the phenomenon of delayed success in defibrillation. (J Cardiovasc Electrophysiol, Vol. 14, pp. S257‐S263, October 2003, Suppl.)
Propagation of tomato spotted wilt virus in Frankliniella occidentalis does neither result in pathological effects nor in transovarial passage of the virus
Authors: Wijkamp Ineke , Goldbach Rob , Peters Dick
Published: October 2003

The effect of tomato spotted wilt virus (TSWV) on Frankliniella occidentalis Pergande (Thysanoptera; Thripidae) following a 6‐hour acquisition access period on infected plants was investigated. No statistically significant differences were observed among viruliferous, non‐viruliferous and control thrips with respect to developmental time, reproduction rate and survival. Thrips larvae, exposed or non‐exposed to TSWV, developed from egg to adult in 13.1 and 13.2 days, respectively. Exposed females produced an average of 28.3 larvae whereas control thrips produced 22.3 larvae and longevity was 13.4 and 12.5 days, respectively. None of these values were significantly different. Population reproductive statistics, net reproductive rate (R0), mean generation time (T) and intrinsic rate of increase (rm) were calculated from the life fertility tables. R0 and rm were higher for viruliferous thrips as compared to non‐viruliferous and non‐exposed thrips. Virus transmission studies revealed that viruliferous thrips were able to transmit virus until death and that TSWV was not transovarially transmitted.
Evidence that mass trapping suppresses pink bollworm populations in cotton fields
Authors: Mafra‐Neto Agenor , Habib Mohamed
Published: October 2003

Mass trapping was used to control pink bollworm (PBW), Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae), populations in cotton fields in Brazil. Oil traps containing lures with a high dose of pheromone, installed at a density of 20 traps per ha soon after the occurrence of the first cotton fruits (or bolls), suppressed PBW populations below detection levels using Delta traps and manual examination of 100 green cotton bolls per ha. Pheromone sources of 0.2 g (approximately 150 NoMate® fibers) were effective in attracting PBW male moths to oil traps for at least three weeks. Trap captures showed that PBW males located the high concentration pheromone plumes, oriented upwind, and landed on or inside the traps. The long life of the pheromone sources and the long lasting viscosity of the oil surface ensured low trap maintenance, thus rendering mass trapping viable as an alternative technique for the control of P. gossypiella populations in commercial cotton fields. We discuss probable mechanisms promoting suppression of PBW populations in fields with mass trapping control.
The predatory mite Hypoaspis miles: biological and demographic characteristics on two prey species, the mushroom sciarid fly, Lycoriella solani, and the mould mite, Tyrophagus putrescentiae
Authors: Enkegaard A. , Sardar M. A. , Brødsgaard H. F.
Published: October 2003

The biology of Hypoaspis miles Berlese (Acarina: Hypoaspidae) fed on mushroom sciarid larvae (Lycoriella solani Winnertz) (Diptera: Lycoriidae) and mould mites (Tyrophagus putrescentiae Schrank) (Acari: Acaridae), was investigated by laboratory experiments at 20 °C, 75% r.h. and LD16:D8 hours. H. miles had a significantly shorter development time and a significantly lower juvenile mortality when fed on sciarid larvae than on mould mites, the development time being 14.5 days and the mortality 3.5% on the former prey. The preoviposition and postoviposition periods of H. miles were not uninfluenced by the prey species and were 5–9 and 32–37 days, respectively. Oviposition periods of 53.2 and 68.5 days and female longevities of 82 and 109.6 days were observed on diets of sciarid larvae and mould mites, respectively. Male longevity (168–219 days) was uninfluenced by the prey species. The egg production of H. miles on sciarid larvae was estimated to be 44.4 ± 4.33 eggs per female, as compared to 22.43 ± 1.79 eggs per female on mould mites. The sex‐ratio of the offspring was significantly influenced by the prey species, the ratios (♀/(♀+♂)) being 0.66 on sciarid larvae and 0.54 on mould mites. The net reproductive rate (R0) for H. miles fed on sciarid larvae was approximately 27 which was three times higher than for mites feeding on mould mites. The innate capacity of increase (rm) was highest (0.0747 day−1) when sciarid larvae served as food, giving a doubling time of 9.3 days as compared to 12.8 days on mould mites. The generation times were 44.28 on sciarid larvae and 40.67 days on mould mites. The daily food consumption rate of juvenile and adult H. miles was 0.24 and 0.86 sciarid larvae and 10.8 and 21.7 mould mites, respectively. In terms of weight consumed, however, the consumption of sciarid larvae was 2–3.5 times the weight of mould mites. The ratio of females to males influenced the oviposition period and egg production of H. miles, with virgin females laying fewer eggs over a longer period of time as compared with females with access to males. The egg production in relation to the sex‐ratio was described by models predicting a maximum number of eggs per female of 22.3 to be attained at a sex ratio of 0.69 (♀/(♀+♂)) and a maximum daily number of eggs per female of 0.33 to be attained at a sex ratio of 0.37 (♀/(♀+♂)).
Reproduction of Diaeretiella rapae on Russian wheat aphid hosts at different temperatures
Authors: Bernal Julio , González D.
Published: October 2003

Diaeretiella rapae (M'Intosh), a polyphagous and cosmopolitan parasite of aphids, was imported from China to the USA for biological control of Diuraphis noxia (Mordwilko), a pest of small grains. We studied several aspects of its biology on D. noxia hosts in the laboratory at 3 constant temperatures, 10.0, 21.1, and 26.7 °C. Females lived significantly longer than males at all 3 temperatures, and longevity was greatest at 10 °C, followed by 21.1 and 26.7 °C. Fecundity (= number of mummies) did not differ significantly among the 3 temperatures studied. The ovarian egg‐load was 129.1 ± 9.3, and was significantly affected by the size of adult females. A pre‐oviposition period (0.95 ± 0.26 days) was detected at 10 °C, but not at the other temperatures. Pre‐imaginal survivorship was similar among temperatures, while Ro and Tc decreased with temperature, and rm increased with temperature. The offspring sex ratio (proportion females) was lowest at 26.7 °C, and similar between 10.0 and 21.1 °C. In addition, the offspring sex ratio significantly declined with the age of the female parent. The suitability of D. rapae for colonization against D. noxia in North America is discussed in relation to its responses to temperature and the climate of its home range.
Comparison of damage to Eucalyptus caused by Amorbus obscuricornis and Gelonus tasmanicus
Authors: Steinbauer M. J. , Taylor G. S. , Madden J. L.
Published: October 2003

Amorbus obscuricornis (Westwood) and Gelonus tasmanicus (Le Guillou) (Heteroptera: Coreidae) are specific to Eucalyptus (Myrtaceae). A. obscuricornis feeds almost exclusively upon apical shoots and causes a characteristic wilting and necrosis. By comparison, the feeding activities of G. tasmanicus result in no obvious phytotoxicosis. Salivary gland extracts from both species exhibited sucrase activity but no pectinmethylesterase (PME) activity. Saliva from A. obscuricornis also exhibited considerable oxidase activity. Sucrase activity was significantly higher in extracts derived from G. tasmanicus than from A. obscuricornis, but this could not explain the observed differences in phytotoxic symptoms. It is suggested that differences in plant damage are attributable to the site of feeding activity (i.e. young versus mature tissue), which predetermines the reactivity of host tissues, and/or the quantity of salivary enzymes injected.
Response of Ceratitis capitata to citrus chemicals under semi‐natural conditions
Authors: Katsoyannos B. I. , Kouloussis N. A. , Papadopoulos N. T.
Published: October 2003

Responses of Mediterranean fruit fly Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) adults to chemicals from citrus fruits were quantified in choice tests conducted in large field cages housing naturally planted orange trees, on the Greek island of Chios. Both sexes responded strongly to chemicals released from artificial cuts made in the pulp of peeled oranges and also to natural or commercial orange juice applied to the surface of yellow 7.0 cm diameter spheres. Males also responded strongly to chemicals released from cuts made in the oily region of the orange peel, or flavedo and less to sour orange and lemon. In contrast, females did not respond to flavedo chemicals. Male response to peel chemicals occurred throughout the day and increased as the number of cuts per fruit increased from 2 to 8. Contact of male mouthparts with sap from cuts, and mating attempts between males on or near the cuts were frequently observed. The males also responded to commercial essential orange oils applied to yellow spheres, but less to essential mandarin oils. The role of citrus chemicals in host finding behaviour of C. capitata and their potential use for the development of effective traps for monitoring and controlling the fly are discussed. The experimental method followed in this study can be used as a standard technique for evaluation of the quality of flies to be used in sterile insect technique programmes.
The response of German cockroaches to toxic baits:strain differences and the effects of selection pressure
Authors: Negus Tracy F. , Ross Mary H.
Published: October 2003

Strain differences in the response of German cockroaches to toxic baits and their potential to evolve resistance to them was evaluated in choice tests. Percentage bait consumption (amount of bait consumed divided by total food consumed) was used to estimate relative attractancy/repellency of the baits. One strain apparently had low level resistance to abamectin, but no evidence of resistance was found in other strains tested with either Roach Ender or a gel bait (abamectin‐based baits). Incipient behavioral resistance occurred in two strains selected for three generations with Roach Ender; a stronger response in a strain selected with the gel bait is attributed to the development of behavioral resistance. Baygon bait was highly repellent. Low level resistance to propoxur caused a large decrease in mortality compared with susceptible strains. Strong behavioral resistance developed in strains selected with Stapleton's Magnetic Roach Food.
EAG measurement of pheromone distribution in apple orchards treated for mating disruption of Cydia pomonella
Authors: Milli Roland , Koch Uwe T. , de Kramer Jacobus J.
Published: October 2003

Pheromone concentrations were measured in an apple orchard using an advanced EAG device featuring short‐term recalibration of the antenna with two calibration standards, a lightweight remotely operated probe and automated measurement cycles. The effects of wind direction on pheromone density and distribution at the edge of the orchard were studied as well as the change of pheromone density with height from 1 to 6.5 m. Results show that pheromone can be found at heights of up to 6 m when moderate winds are present. Very low wind speeds tend to reduce the height of the pheromone cloud. Clean wind entering the orchard creates a transition zone up to 15 m wide where the pheromone is depleted. At the down‐wind edge of the orchard, pheromone signals were recorded at distances of up to 60 m downwind from the treated zone at concentrations in the same order of magnitude as within the treated orchards. The consequences of these results concerning the design and interpretation of mating disruption field tests are discussed.
Different sensitivities of the sugar receptor of the lateral styloconic sensillum in fourth‐ and sixth‐instar larvae of the spruce budworm Choristoneura fumiferana
Authors: Panzuto M. , Albert P. J.
Published: October 2003

Female fourth‐ and sixth‐instar larvae, Choristoneura fumiferana, were tested individually for the response of the sugar cell on the lateral styloconic sensillum to 25 mM/l concentrations of 12 carbohydrates. The spruce budworm showed an age‐related change in responsiveness of the sugar cell. The order of stimulating effectiveness for fourth‐instars was melibiose > sucrose > raffinose.These storage di‐ and trisaccharides are present in the host plant at the beginning of budbreak. Sixth‐instars responded to sucrose > fructose > m‐inositol. These findings are in accordance with those of a previous behavioural study on feeding preferences of sixth‐instars. The response for both melibiose and raffinose does not change from fourth‐ to sixth‐instars; however, it does for sucrose, fructose and m‐ inositol.
Effect of an entomopathogen on adaptation of Heliothis virescens populations to transgenic host plants
Authors: Johnson M. Tracy , Gould Fred , Kennedy George G.
Published: October 2003

The role of an entomopathogen in evolution of herbivore adaptation to partially resistant host plants was examined using a tritrophic system in the laboratory. We hypothesized that a pathogen should interact with herbivore behavior to accelerate herbivore adaptation to toxic plants: individuals not adapted to toxin tend to move more on toxic plants, and therefore are more likely to encounter a lethal dose of pathogen, further increasing the probability that they will be eliminated by selection. Heliothis virescens (F.) (Noctuidae) was selected for adaptation to transgenic tobacco containing a sublethal concentration of Bacillus thuringiensis Berliner toxin under two treatment regimes: larvae placed on plants treated with infective conidia of the entomopathogenic fungus, Nomuraea rileyi (Farlow) Samson, and larvae placed on plants without fungus.

Selection was initiated with a genetically heterogeneous strain created by crossing two laboratory strains of H. virescens, one not adapted to B. thuringiensis toxin, and one highly adapted (>1000‐fold) to toxin. This cross was performed four times to create four independent populations. Selection was initiated with F2 offspring from each cross and continued for 8–10 consecutive generations. Adaptation to toxin within each treatment population was quantified every generation by measuring survival and growth of larvae on artificial diet containing a low concentration of B. thuringiensis toxin.

In three of four replicates, H. virescens populations exposed to N. rileyi adapted to B. thuringiensis toxin more quickly than populations not exposed. These results supported our hypothesis that the pathogen should accelerate adaptation to toxic plants. However, this hypothesis was contradicted by the result in one replicate, in which the population not exposed to fungus adapted to toxic plants faster. This opposite result could not be explained, but it suggests that there may be substantial variation in herbivore evolution in tritrophic systems.

H. virescens populations selected in the presence of fungus and in the absence of fungus did not differ in feeding or in mortality when placed on leaf disks treated with conidia. Thus, populations exposed to N. rileyi on plants for 7–8 generations displayed neither physiological nor behavioral adaptation to N. rileyi.
Control of codling moth in organically‐managed apple orchards by combining pheromone‐mediated mating disruption, post‐harvest fruit removal and tree banding
Authors: Judd G. J. R. , Gardiner M. G. T. , Thomson D. R.
Published: October 2003

An integrated programme of pheromone‐mediated mating disruption using Isomate‐C®, post‐harvest removal of fruit, and trapping overwintering larvae with cardboard tree bands, was used to control codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), in four commercial ‘organic’ apple orchards in Cawston, British Columbia during 1989–1992. One application of 1000 dispensers ha−1 on May 1 delivered estimated seasonal totals of 16.6, 16.5 and 19.9 g of E,E‐8,10‐dodecadien‐1‐ol [=codlemone] ha−1 in 1990, 1991 and 1992, respectively, at median rates of 8.4, 8.3, and 13.3 mg · ha−1· h−1 during dusk flight periods of first brood and 5.3, 4.7 and 4.6 mg · ha−1· h−1 in second brood, respectively. Over this 3‐year period damage from codling moth at harvest ranged from 0.08 to 2.4%, and averaged <0.7% in these four organic orchards, while damage in five conventional orchards receiving sprays of azinphosmethyl ranged from 0.02 to 1.85%, and averaged 0.5%. Damage in an experimental orchard that was banded only, ranged from 43.5 to 56.7%, and averaged 48.9%. Between 1990 and 1992 cumulative male catches in Pherocon 1‐CP wing traps baited with 10 mg of codlemone declined by 52% and densities of overwintering codling moth larvae declined an average of 49.5% in all organic orchards. Overwintering populations in the banded experimental orchard showed an increase of 57.7% during this study period. We conclude that an integrated programme of pheromone‐mediated mating disruption, post‐harvest fruit removal and tree banding, controls codling moth effectively enough to make organic apple production viable in British Columbia.
The influence of tactile and other non‐chemical factors on the ovipositional responses of the generalist herbivore Epiphyas postvittana
Authors: Foster S. P. , Howard A. J. , Harris M. O.
Published: October 2003

A bioassay to test the ovipositional responses of the generalist herbivore, Epiphyas postvittana, was developed, and various non‐chemical factors that influenced the laying, and number of eggs laid, by females were tested. In choice experiments using various models, surface texture was found to be an important factor influencing ovipositional behaviour, with females preferring to lay on smoother rather than rougher surfaces. Another surface texture feature that influenced oviposition was a raised wax ridge on a smooth surface. The wax ridge stimulated more eggs to be laid within close proximity to the ridge. Observations of females showed that the increased numbers of eggs laid on models with a wax ridge resulted not from increased landing, time spent, or numbers of eggs laid per ovipositional bout, but rather through an increased probability of ovipositing after landing on models with a wax ridge compared to models without the ridge. Spatial features of the models were also found to influence egglaying by females. Females showed a tendency to lay on the upper rather than the lower surface of models, although this appeared to depend upon how stimulatory the upper surface of the model was. Females also laid more eggs on models with a dense array of leaves than on models with a more spread‐out array.
Provenance, experience and plant utilisation by the polyphagous aphid, Aphis fabae
Authors: Douglas A. E.
Published: October 2003

Twenty‐nine clones of Aphis fabae Scopoli (Aphididae: Homoptera) were isolated into laboratory culture from the primary host plants Euonymus europaeus and Viburnum opulus and the secondary host plants Arctium lappus, Impatiens glandulifera, Tropaeolum majus and Vicia faba. All clones performed well on either T. majus or V. faba, with mean intrinsic rates of increase (rm) in the range 0.35–0.41 aphids aphid−1 day−1, but none performed well on both plant species. Each clone could, therefore, be described as affiliated to either V. faba or T. majus. All of the 13 T. majus‐affiliated clones and 15 of the 16 V. faba‐affiliated clones could not be maintained beyond two parthenogenetic generations on the contrary plant. These results confirm that the performance of A. fabae on T. majus and V. faba is negatively correlated. Exceptionally, one V. faba‐affiliated clone (clone AED95/119) persisted indefinitely on T. majus, exhibiting a progressive improvement in performance across four parthenogenetic generations: larval mortality dropped from 80% to <20%, mean adult weight almost doubled from 0.28 to 0.53 mg, and mean number of embryos per adult aphid increased threefold from 8.6 to 24.4 embryos. The mean rm of clone AED95/119 that had been reared on T. majus for more than 4 generations was 0.17 aphids aphid−1 day−1, significantly lower than the value of 0.34 aphids aphid−1 day−1 on V. faba. It was also shown that the rm on V. faba did not differ significantly between aphids of clone AED95/119 that had been derived from long‐term cultures on V. faba and T. majus. It is concluded that the negative correlation between performance on V. faba and T. majus is not genetically fixed, but may diminish with exposure to T. majus. The implication is that this clone may have a capacity to utilise T. majus that is independent of its capacity to utilise V. faba, and is expressed only on sustained exposure to T. majus. It is suggested that, although the ‘latent’ capacity to utilise T. majus is probably not exhibited widely under natural conditions, aphids possessing it may be at a selective advantage when more suitable host plants are temporarily unavailable.
Choosing a place to grow. Importance of within‐plant abiotic microenvironment for Yponomeuta mahalebella
Authors: Alonso Conchita
Published: October 2003

The caterpillars of Yponomeuta mahalebella Latr. (Lepidoptera: Yponomeutidae) are monophagous on Prunus mahaleb (Rosaceae) leaves. Adult females deposit eggs in batches, which determines larval gregarious behaviour. Coupled with gregarious behaviour, caterpillars spin silk tents within they will feed until pupation. Distribution of tents in the field, their effect in microenvironmental larval growth conditions and the consequences for adult body mass and survival of larvae were studied.

There was a significant trend for tents to be placed with a southward orientation. Within‐plant tent orientation was related to the sun‐shade pattern experienced, which was the main effect determining thermal differences between the inside and the outside of the tent. These differences appeared to affect larval growth and survival, with higher survival of larvae and heavier adults emerging from tents oriented to the south‐east and east, respectively.
The impact of Meu1‐mediated resistance in tomato on longevity, fecundity and behavior of the potato aphid, Macrosiphum euphorbiae
Authors: Kaloshian I. , Kinsey M. G. , Ullman D. E. , Williamson V. M.
Published: October 2003

The effect of the tomato resistance gene, Meu1, on feeding, longevity, fecundity and developmental rate of the pink biotype of the potato aphid, Macrosiphum euphorbiae (Thomas) (Hemiptera, Aphididae), was determined using nearly isogenic tomato (Lycopersicon esculentum Mill, Solanaceae) lines. Aphid mortality was significantly higher on resistant plants, with 60% of the aphids dying by the 4th day of exposure. By the 10th day, all the aphids on the resistant plants were dead whereas 100% of the aphids on susceptible plants were alive. Meu1‐mediated resistance resulted in significantly decreased fecundity with a ten‐fold decrease in the net fertility rate (4.5 and 45.7 progeny per aphid on resistant and susceptible tomato, respectively). A qualitative analysis showed that honeydew was produced by aphids on resistant and susceptible plants, suggesting that aphids initiate feeding on both plant types. However, significantly lower quantities of honeydew were present when aphids were caged on resistant plants. There were also significant differences in aphid location on resistant and susceptible leaves. Experiments evaluating behavior in less than 24 h showed that aphids left resistant leaves after relatively short exposure (3–6 h). Aphids transferred from resistant to susceptible tomato at intervals between 3 h and 24 h resumed feeding as evidenced by presence of honeydew. Although the mechanism by which Meu1‐mediated resistance operates is not yet known, our data suggest that resistance factors act rapidly after initiation of feeding and that lower fecundity and longevity are related to reduction in aphid feeding.
Postharvest disinfestation of diapausing and non‐diapausing twospotted spider mite (Tetranychus urticae) on persimmons: hot water immersion and coolstorage
Authors: Lester Philip J. , Dentener Peter R. , Bennett Keren V. , Connolly Patrick G.
Published: October 2003

The mortality response of diapausing and non‐diapausing twospotted spider mite (Tetranychus urticae Koch) on persimmons to hot water immersion treatments between 44 and 54 °C was examined, for potential as a quarantine treatment. The mean immersion time for mean 99% mortality (LT99) of diapausing mites at 44 °C was 211 min, and this time decreased with increasing temperature to 3.6 min at 54 °C. Non‐diapausing mites were found to be less tolerant to temperatures below 48 °C, with an estimated LT99 of 102 min at 44 °C, but had similar thermotolerance above 48 °C. In 47 °C water the immersion time required to kill 99% of diapausing mites was estimated at 67 min. This time was not reduced by subsequent coolstorage at 0 °C for up to eight weeks. Rather, coolstorage had the effect of keeping mites alive, relative to LT99 estimates calculated for mites stored at 20 °C. Similarly the thermotolerance of mites did not change with increased time in diapause, even though mites in diapause for 12 weeks had high control mortality. Hot water immersion appears to be a potentially useful disinfestation method for persimmons.
The influence of hosts, temperature and food sources on the longevity of Trichogramma platneri
Authors: McDougall S. J. , Mills N. J.
Published: October 2003

Feeding experiments were conducted with Trichogramma platneri Nagarkatti (Hymenoptera: Trichogrammatidae) reared from the Angoumois grain moth, Sitotroga cerealella (Oliver) (Lepidoptera: Gelechiidae). T. platneri provisioned with host eggs do not live any longer than T. platneri without host eggs. Longevity of T. platneri is inversely related to temperature declining from 53 days at 10 °C to 3 days at 35 °C for honey‐fed parasitoids and from 9 days at 10 °C to 1 day at 35 °C for unfed parasitoids. Sugar sources are necessary to prolong longevity of T. platneri, but a source of amino acid did not promote longevity. Honey solutions greater than 10%, and 43% fructose and sucrose solutions increased longevity 10–13 fold to 15–20 days in comparison to water when fed daily to T. platneri. Parasitoids fed only at the onset of the trial had greater longevity than unfed parasitoids but had a shorter longevity than parasitoids fed daily, due to the evaporation of the sugar solutions and consumption of the honey. Aphid honeydew is a suitable field‐available sugar source supporting longevity up to 10 days, but is not as good as other sugar sources. Stabilizing additives did not reduce evaporation of a dilute sugar solution nor prolong longevity of T. platneri. Simulating a daily dew fall by misting vials, to redissolve the crystallized food residues left after providing food at the onset of the trial, failed to increase parasitoid longevity.
The influence of clutch size on survival and reproductive potential of Hessian fly
Authors: Withers T. M. , Madie C. , Harris M. O.
Published: October 2003

The clutch size laid by Hessian flies (Mayetiola destructor Say) (Diptera: Cecidomyiidae) was manipulated over a range of 1 to 30 eggs on single wheat plants (Triticum aestivum, L.). Pupae developing from egg clutches were removed from plants, counted and reared through to adult eclosion. Wing lengths of adult males and females were recorded and used as an indicator of body size. Survival to pupal and adult stages, as well as mean wing length of resulting males and females, decreased as clutch size increased. Wing length of females from clutches showed a positive linear relationship with potential fecundity. The benefits of small clutches for a female Hessian fly's offspring are discussed in the context of the foraging behaviour of the ovipositing female. We predict that under high probabilities of survival and availability of host plants, females will lay smaller‐sized clutches per plant. However when the probability of survival is low and host plants scare, the female will respond by laying larger‐sized clutches.
Effect of insectary rearing on host preference and oviposition behavior of the fruit fly parasitoid Diachasmimorpha longicaudata
Authors: Bautista Renato C. , Harris Ernest J.
Published: October 2003

Diachasmimorpha longicaudata (Ashmead) has been produced in the laboratory for >160 generations on the larvae of oriental fruit fly, Bactrocera dorsalis (Hendel), the propagation hosts raised routinely on a semi‐synthetic wheat diet formulation. Choice tests using modified stinging units were conducted in the laboratory to investigate whether insectary rearing had altered the host seeking and oviposition behavior of female parasitoids. Results showed that fruit fly larvae that developed in papaya, Carica papaya L. var. ‘solo’, were less preferred for oviposition than fruit fly larvae that developed on wheat diet when both were exposed concurrently to naive D. longicaudata females (= females without prior oviposition experience). The substrates (pureed papaya or wheat diet) in which treatment larvae were exposed to parasitoids did not affect oviposition preference of gravid D. longicaudata for wheat diet‐reared fruit fly larvae. Our study demonstrated the possibility that rearing in an insectary system may have modified the parasitization behavior of female D. longicaudata.
Differential acquisition of chrysanthemum yellows phytoplasma by three leafhopper species
Authors: Bosco Domenico , Minucci Claudia , Boccardo Guido , Conti Maurizio
Published: October 2003

Chrysanthemum yellows (CY) phytoplasma has been transmitted with three leafhopper species: Euscelidius variegatus (Kirschbaum), Macrosteles quadripunctulatus (Kirschbaum) and Euscelis incisus (Kirschbaum): the first two species are reported as CY phytoplasma vectors for the first time. Leafhoppers were allowed to acquire the pathogen from the following source plants: Apium graveolens L., Catharanthus roseus L., Chrysanthemum carinatum Schousboe L. and C. frutescens L. DNA extracted from healthy or inoculative leafhoppers‐exposed plants were analyzed by dot‐blot and Southern hybridizations with a molecular probe constructed onto a fragment of European aster yellows phytoplasma DNA. The three leafhopper species were able to transmit CY phytoplasma after acquisition on chrysanthemum, but only M. quadripunctulatus and E. variegatus transmitted after feeding on periwinkle, and none acquired it from celery. All plant species tested were susceptible to CY, but while chrysanthemum and periwinkle were suitable for both inoculation and acquisition, celery did not seem to be a good source of phytoplasma for further inoculations. It is concluded that host plants influence leafhoppers' vectoring ability, possibly due to the different feeding behaviour of the insects on diverse plant species. Since CY, like several other phytoplasmas, can be transmitted by different insect species, it is likely that a close transmission specificity probably does not exist between phytoplasmas and their leafhopper vectors.
Monitoring of rice weevil, Sitophilus oryzae, feeding behavior in maize seeds and the occurence of supernumerary molts in low humidity conditions
Authors: Pittendrigh B. R. , Huesing J. E. , Shade R. E. , Murdock L. L.
Published: October 2003

Rice weevils, Sitophilus oryzae (L.), complete their development from egg to early adulthood inside grains of wheat, rice or maize, but little is known about their feeding behavior within the seeds. An ultrasonic insect feeding monitor was used to characterize the feeding patterns of individual rice weevils as they developed in maize grains. Weevils reared in grains held at ca. 40% r.h. took longer to develop from egg to pupation than those reared in grains kept at ca. 70% r.h. Feeding patterns revealed that larvae developing in grains held at ca. 70% r.h. had only four instars, whereas supernumerary molts (five instars) occurred in certain individuals reared in grain held at ca. 40% r.h. The supernumerary molts may represent a response of the insect to stresses associated with low moisture levels in the seeds.
Comparative susceptibility of two different hosts to genotypic variants of the Anticarsia gemmatalis nuclear polyhedrosis virus
Authors: Ribeiro H. C. T. , Pavan O. H. O. , Muotri A. R.
Published: October 2003

The susceptibility of third instar larvae of Anticarsia gemmatalis (Lepidoptera: Noctuidae) and Diatraea saccharalis (Lepidoptera: Pyralidae) to ten distinct plaque purified genotypic variants of a selected isolate of the Anticarsia gemmatalis multiple‐embedded nuclear polyhedrosis virus (AgMNPV), was compared. Despite the fact that this isolate, AgMNPV‐Ds20, represents a wild strain of the AgMNPV selected for higher virulence to D. saccharalis, an alternate host, most of the variants are much more virulent to the original host Anticarsia than to Diatraea. Bioassays have shown an over one hundred‐fold variation in LD50 values ranging from 1700 polyhedron inclusion bodies (PIBs) to more than 200 000 PIBs/larva. The PIB production in infected larvae increased with the pathogenicity of the variant to the host, showing an average ten‐fold reduction in Diatraea when compared to Anticarsia for the same variant. The virus particle yield ranged from 6×107 to more than 109 PIBs/g of infected larvae in Diatraea and from 8×108 to more than 1010 PIBs/g of infected Anticarsia larvae. The data show a clear difference of the pathogenicity of the genotypic variants of AgMNPV in vivo both between the original and alternate host and between the individual variants for the same host. These differences found in vivo indicate that monitoring of shifts in variant frequency of wild and laboratory‐propagated viral isolates in these highly heterogeneous populations would help ensure the efficacy of biological control programs.