Cristina Alfaro

University of Valencia, Valenza, Valencia, Spain

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Publications (16)35.44 Total impact

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    ABSTRACT: Volatile compounds are together with sugars and organic acids the main determinants of tomato fruit flavour and are therefore important for consumer acceptance. Consequently, in the last years many studies have been performed using different volatile analytical techniques on a large diversity of tomato fruits, aimed mainly at detecting the compounds affecting flavour or at the identification of QTLs and key genes involved in fruit volatile contents. The comparison of three of the analytical methods most commonly applied (headspace, solid phase microextraction, adsorption on Tenax followed by thermal desorption) revealed not only differences in sensitivity, but also dramatic variations in the volatile profile obtained by each of these techniques. The volatile profile was also largely influenced by the way samples were processed before analysis. Four widely used sample processing methods were compared (whole tomato, sliced fruit and two different types of fruit paste), each one producing a characteristic volatile pattern. Therefore, great care should be taken when comparing results available from the literature obtained by means of different methods, or when using the volatile levels obtained in an experiment to predict their influence on tomato flavor or consumer preference, or to assess the success of breeding programs.
    No preview · Article · Jul 2015 · Metabolomics
  • S. Vacas · C. Alfaro · J. Primo · V. Navarro-Llopis
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    ABSTRACT: The rejection of citrus fruit caused by infestations of the California red scale (CRS), Aonidiella aurantii (Maskell) (Hemiptera: Diaspididae), raises concerns about its management. This fact has led to the introduction of new integrated control methods in citrus orchards, including the implementation of techniques based on pheromones. Previous works described efficient mating disruption pheromone dispensers to control A. aurantii in the Mediterranean region. The main aims of the present study were to adjust the timing of dispenser applications and study the importance of controlling the early first generation of A. aurantii by testing two different application dates: before and after the first CRS male flight. The efficacy of the different mating disruption strategies was tested during 2010 in an experimental orchard and these results were confirmed during 2011 in a commercial citrus farm. Results showed that every mating disruption strategy achieved significantly lower male captures in monitoring pheromone traps compared with untreated plots, as well as mean fruit infestation reductions of about 80 %. The control of the first CRS generation is not essential for achieving a good efficacy as demonstrated in two locations with different pest pressure. The late application of MD dispensers before the second CRS male flight has proven to be effective, suggesting a new advantageous way to apply mating disruption.
    No preview · Article · Jun 2014 · Journal of Pest Science
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    ABSTRACT: In recent years, environmentally safe measures to control the California red scale (CRS), Aonidiella aurantii (Maskell), have been successfully implemented. These measures include mating disruption (MD) and biological control. The goal of this study was to examine the effect of high concentrations of the CRS sex pheromone on its life history parameters and scale-cover surface area under controlled laboratory conditions. The developmental time of both males and females of CRS increased with exposure to airborne pheromone. MD had an effect on both the total number of progeny and on the crawler production period for females. Accordingly, demographic parameters such as net fecundity (R(0) ) and intrinsic rate of increase (r(m) ) were significantly lower in the pheromone-treated populations. The largest scale-cover surface areas were observed in the CRS reared in the pheromone environment. A clear influence of airborne pheromone on the biology of CRS has been demonstrated. In addition to the classical mating disruption benefits of this technique, additional benefits, such as increase in the duration of exposure to natural enemies and increase in size, which benefits some species of parasitoids, have been confirmed.
    Full-text · Article · Jul 2012 · Pest Management Science
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    ABSTRACT: New directives on sustainable use of pesticides have encouraged research on efficient alternative pest control methods. In the case of the California red scale (CRS), Aonidiella aurantii (Maskell), this imperative, along with the many difficulties in controlling this pest, have led to the investigation of new approaches. Previously developed mating disruption (MD) dispensers, together with the augmentative releases of the parasitoid Aphytis melinus DeBach, are here considered as a combined strategy for use against A. aurantii. Efficacy of MD was demonstrated by a mean reduction of 80% in CRS male catches and a mean fruit damage reduction of 83% compared with the control. A delay in the development of A. aurantii instars was observed in the MD plot. This delay increased the period of exposure of the susceptible instars to natural enemies, which resulted in higher predation and parasitism levels in the MD plot. Under laboratory conditions, A. melinus mating behaviour and effects on A. aurantii were not significantly altered in a CRS-pheromone-saturated environment. Mating disruption pheromone did not affect the behaviour or level of parasitism by A. melinus or the incidence of other generalist predators. Therefore, A. aurantii pheromone appears to be compatible with augmentative releases and biological control, making its use a good strategy for CRS management.
    Full-text · Article · Jan 2012 · Pest Management Science
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    ABSTRACT: The tomato leafminer (Tuta absoluta Povolny) has rapidly colonised the whole Mediterranean and South-Atlantic coasts of Spain, and it has become a key problem in both outdoor and greenhouse crops. New control methods compatible with biological control are required, and mating disruption appears to be a perfect method in current agriculture, as it is an environmentally friendly and residue-free technique. IPM packages tested have included the use of pheromones to detect populations, but there has not been much previous research on mating disruption of T. absoluta. In this work, pheromone doses varying from 10 to 40 g ha(-1), emitted at a constant rate over 4 months, were tested in greenhouses with different levels of containment in order to evaluate the efficacy of mating disruption on T. absoluta. Trials on containment level revealed that the flight of T. absoluta was satisfactorily disrupted with an initial pheromone dose of 30 g ha(-1), and levels of damage did not significantly differ from those in reference plots with insecticide treatments. Later efficacy trials confirmed previous experiences, and release studies showed that control of damage and flight disruption were taking place when releasing at least 85 mg pheromone per ha per day. Effective control using pheromone application against T. absoluta can be achieved, in greenhouses with high containment levels, for 4 months, with initial doses of 30 g ha(-1). Further research must be conducted in order to evaluate the prospect of outdoor application of mating disruption systems.
    No preview · Article · Nov 2011 · Pest Management Science
  • V Navarro-Llopis · S Vacas · J Sanchis · J Primo · C Alfaro
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    ABSTRACT: During 2008 and 2009, the efficacy of the combination of two Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), control techniques, sterile insect technique (SIT) and a chemosterilant bait station system (Adress), was tested in three crops: citrus (Citrus spp.), stone fruit (Prunus spp.), and persimmon (Diospyros spp.). Two thousand sterile males were released per ha each week in the whole trial area (50,000 ha, SIT area). For 3,600 ha, within the whole trial area, 24 Adress traps per ha were hung (SIT + Adress area). Ten SIT + Adress plots and 10 SIT plots in each of three different fruit crops were arranged to assess Mediterranean fruit fly population densities and fruit damage throughout the trial period. To evaluate the efficacy of each treatment, the male and female populations were each monitored from August 2008 to November 2009, and injured fruit was assessed before harvest. Results showed a significant reduction in the C. capitata population in plots treated with both techniques versus plots treated only with the SIT. Likewise, a corresponding reduction in the percentage of injured fruit was observed. These data indicate the compatibility of these techniques and suggest the possibility of using Adress coupled with SIT to reduce C. capitata populations in locations with high population densities, where SIT alone is not sufficiently effective to suppress fruit fly populations to below damaging levels.
    No preview · Article · Oct 2011 · Journal of Economic Entomology
  • V. Navarro-Llopis · C. Alfaro · J. Primo · S. Vacas
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    ABSTRACT: Attractants and pheromones are commonly used in integrated pest management programs in crop systems. However, pheromone dispensers employed in monitoring traps and lure and kill devices are not usually well studied and attractants are released at uncontrolled rates leading to low treatment efficacies and misleading monitoring estimations. Fruit flies are pests of economic importance and monitoring is essential in order to program insecticidal treatments. Moreover, lure and kill techniques are being increasingly used, but the cost of these techniques depends on the number of required traps and, therefore, on the efficacy of the attractants. Ceratitis capitata and Bactrocera oleae are the two main fruit flies in Mediterranean countries, and the effect of different doses of trimedlure and spiroacetal on fly attraction has been studied. Results showed that a release rate over 1.28 mg/day of spiroacetal reduces B. oleae attraction and emission values over 2.4 mg of trimedlure per day did not increase C. capitata catches. Under the environmental conditions of our study, an optimum release rate for pheromone attraction in B. oleae was determined. Emission values over this optimum level reduced B. oleae attraction. However, when a parapheromone was used with C. capitata, a fruit fly of the same family, the optimum emission value was not found and higher quantities of parapheromone attracted the same number of flies. The saturation effect of high concentrations of pheromone and parapheromone is discussed.Highlights► An optimum pheromone release rate has been found in Bactrocer oleae ► This optimum does not exist in Ceratitis capitata parapheromone trimedlure. ► Optimum release rate of 1.28 mg/day of spiroacetal has been found for B. oleae. ► Release rate of trimedlure over 2.4 mg/day does not increase C. capitata catches. ► These findings are essential for monitoring and attract and kill techniques.
    No preview · Article · Jul 2011 · Crop Protection
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    ABSTRACT: Since the discovery of Lobesia botrana Denis & Schiffermüller (Lepidoptera: Tortricidae) sex pheromone, it has played an important role in the control and detection of this pest, for example, through the use of pheromone-baited traps and mating disruption techniques. Rubber septa are the most common pheromone dispensers used in monitoring traps, but often dispenser performance is not optimized. The key to improve methods based on pheromones as attractants (monitoring, mass trapping, or ‘attract and kill’) is to know the optimum emission interval, because release rates can strongly affect the attraction. In this work, five levels of pheromone load with different release rates were compared in traps using mesoporous pheromone dispensers to investigate the optimum release rate maximizing L. botrana catches. Residual pheromone loads of the dispensers were extracted and quantified by gas chromatography, to study release profiles and to estimate the various emission levels. The efficacy of pheromone emission was measured in field trials as number of moths caught. A quadratic model was fitted to relate the numbers caught vs. the daily emission rates. The resulting quadratic term was statistically significant, confirming the existence of a relative maximum for L. botrana catches. Taking into account that the trial was carried out only in one location, an optimum emission value of ca. 400 μg per day could be considered to enhance the attraction of L. botrana under West-Mediterranean weather conditions.
    No preview · Article · May 2011 · Entomologia Experimentalis et Applicata
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    ABSTRACT: Considerable efforts have been devoted to understanding the courtship behavior and pheromone communication of medflies; however, the sex pheromone composition is still a controversial subject. The discovery of new components affecting medfly behavior would be of interest for medfly control methods based on semiochemicals. This work describes volatile compounds emitted by Ceratitis capitata collected using solid phase microextraction. The volatile study was conducted according to an experimental design with three factors (sex, age, and mating status) assumed to be relevant for better understanding the chemical communication. Emission data were treated by means of principal component analysis, a statistical methodology not previously applied to the study of volatiles emitted by fruit flies. The characterization of emission patterns could be useful for the selection of compounds to be further investigated in biological assays to improve knowledge of the key semiochemicals involved in medfly behavior.
    No preview · Article · Jan 2011 · Journal of Agricultural and Food Chemistry
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    ABSTRACT: The control of California red scale, Aonidiella aurantii (Maskell), has encountered many difficulties, which has raised interest in alternative control methods. Up to now, the A. aurantii sex pheromone has been used only for monitoring. In a previous work the authors described a biodegradable mesoporous pheromone dispenser for mating disruption. To verify the efficacy of these dispensers, three field trials were conducted, and the results are shown in this paper. The study of the release profile of these dispensers revealed a mean pheromone emission value of 269 microg day(-1) and levels of residual pheromone of 10% at the end of 250 days. During the second flight, an A. aurantii male catch reduction of 98% was achieved in the mating disruption plot of trial 1, 93.5% in trial 2 and 76.7% in trial 3. During the third flight, reductions were 94.1, 82.9 and 68.1% in trials 1, 2 and 3 respectively. Considering damaged fruit with more than five scales, reductions of about 80 and 60% were obtained in the mating disruption plots of trials 2 and 3, respectively, compared with an untreated plot, and a reduction of about 70% in trial 1 compared with an oil-treated plot. Mating disruption has been found to be an efficient technique to control this pest, working equally well to a correctly sprayed oil treatment. Further studies are needed to improve the determination of the time of dispenser application and evaluate the effects of the pheromone on natural enemies.
    No preview · Article · Jul 2010 · Pest Management Science
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    ABSTRACT: The chemosterilisation technique has been demonstrated to reduce the population and fruit damage of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), in citrus orchards. Field trials showed efficacy by reducing the fruit fly population, which was progressively achieved by continuous application of lufenuron to several generations. Different authors have suggested that field trials should be carried out in isolated or wide areas in order to reduce fruit fly intrusion and obtain best results. To this end, a wide-area trial over 3600 hectares has been under investigation in Valencia (Spain) since 2002 to validate the chemosterilisation technique against the fruit fly. The whole area was treated with 24 traps ha(-1), using more than 86,000 traps in the field trial. A continuous decrease in fruit fly population was observed over the 4 years under trial. Moreover, results showed a significant reduction in persimmon damage in the chemosterilant treatment area compared with a malathion aerial treatment area. In the case of citrus damage, no significant differences were obtained between malathion and chemosterilant treatments. The chemosterilant method reduces Mediterranean fruit fly populations, and therefore it is a candidate treatment to replace aerial treatments with insecticides in order to suppress this pest. In addition, the efficacy of chemosterilant treatment is increasing year after year. The possibility of using this technique combined with other control methods is discussed.
    No preview · Article · May 2010 · Pest Management Science
  • S Vacas · C Alfaro · V Navarro-Llopis · J Primo
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    ABSTRACT: Semiochemical-based pest management programs have been increasingly used to provide environmentally friendly methods for the control of major insect pests. The efficacy of the mating disruption technique has been demonstrated for several moth pests. Unfortunately, not many experiments on mating disruption to control diaspididae species have been documented. In this work, biodegradable dispensers for mating disruption with increasing pheromone loads were used in order to study the potential of this technique for the control of Aonidiella aurantii Maskell. Field trial results demonstrated that dispensers loaded with 50 mg (a.i.) (20 g ha-1) and 100 mg (a.i.) (40 g ha-1) of sex pheromone were the most suitable, achieving significant reductions in male catches, compared to an untreated plot. In treated plots, virtually a 70% reduction in damage to fruit was recorded. Pheromone release profiles of all the dispensers were also studied under field conditions. We found that emission values >250 microg day-1 were the most suitable. This study suggests a new biodegradable dispenser capable of interfering with normal A. aurantii chemical communication. The use of mating disruption as a control method against A. aurantii is discussed.
    No preview · Article · Aug 2009 · Bulletin of entomological research
  • C. Alfaro · V. Navarro-Llopis · J. Primo
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    ABSTRACT: The rice striped stem borer, Chilo suppressalis (Walker) (Lepidoptera: Pyralidae) is one of the most important rice pests worldwide. Rice is frequently grown in an intensive production system in areas adjacent to environmentally sensitive areas. Therefore, the use of insecticides is problematic and new techniques, including mating disruption, are being introduced. Due to the high cost of pheromones, it is essential to optimize the density of the pheromone dispensers. The main purpose of this research was to determine the minimal dosage and optimal dispenser distribution for effective mating disruption of C. suppressalis. To this end, we conducted a wide-area trial to test several dispenser densities, 31, 25 and 16 dispensers/ha during 3 years. Results were compared with a standard mating disruption treatment (51 dispensers/ha) and a standard aerial chemical treatment with tebufenozide. Treatment efficacy was determined by pheromone trap catches and crop damage assessment. The release rate of the pheromone dispensers was also quantified. The results of these trials suggest that such treatments provide effective pest control even with reduced pheromone dispenser densities. Longer-lasting dispensers with lower residual load at the end of trials will greatly improve the efficacy of mating disruption for C. suppressalis. Moreover, an important consideration is that these newly tested dispenser densities imply a significant reduction in the cost of the treatment. These results are essential in order to expand the use of mating disruption in rice crop protection.
    No preview · Article · Jul 2009 · Crop Protection
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    ABSTRACT: Traditional chemical control against Chilo suppressalis Walker is currently being replaced in Spain by new methods based on pheromones. A key step to improve the efficacy of these methods is the determination of the optimum pheromone release rate, which is still uncertain for this pest. In this work, the pheromone release profile and the field performance of a new mesoporous dispenser was compared with a standard commercial dispenser. For this purpose, pheromone loads were extracted from field-aged dispensers and quantified by gas chromatography with flame ionization detector. In addition, a field trial was carried out with traps baited with one, two, or three mesoporous dispensers per trap, as well as with traps containing one standard dispenser. We found that the highest number of field catches did not correspond to the highest pheromone emission rate, which suggests a repellent effect of the insect if the emission is excessive. The results suggest that the attractant activity was maximized by emitting approximately 34 microg/d. The efficacy of the mesoporous dispenser and its possible improvements are discussed.
    No preview · Article · Jul 2009 · Journal of Economic Entomology
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    ABSTRACT: The control of the raw material has a great influence on the final quality of wine. Nowadays, wineries have practically not incorporated an effective quality control of grape juice on their production process. Although wine aroma has been widely analysed, grape juice aroma for wine-making has been poorly studied. In this study, two headspace-based technique methodologies have been proposed to characterise the aroma of grape juice: static headspace (SHS) and headspace solid phase microextraction (HS-SPME). Both techniques were applied on the samples from three maturation stages of two red grape cultivars: Tempranillo and Bobal, ranked first in Spanish and in Valencian Community cultivars, respectively. This study identifies the principal volatile compounds of grape juice: C6 compounds, especially alcohols and aldehydes, using both techniques. It was confirmed that SHS and HS-SPME techniques could be incorporated into the process of the grape quality control in wineries as a result of its operational simplicity, low cost and reduced ecological impact compared with other conventional organic solvent-based techniques.
    No preview · Article · Feb 2009 · International Journal of Food Science & Technology
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    ABSTRACT: Knowledge about the behaviour of trimedlure (TML) dispensers is essential to ensure the efficacy of monitoring and control methods based on TML as attractant. There are several commercially available TML dispensers, and each of them has a different useful life and TML release profile. Their emission is also affected differently by environmental factors. Even the same type of dispenser sometimes shows an important variability in the TML release rate. Because of the importance of methods based on TML lures in the control of the Mediterranean fruit fly and the influence of the TML dispenser on the efficacy of these control methods, we developed a non-destructive flow-through system to measure the TML release rate. This volatile collection method (VCM) adsorbs TML vapour on a Tenax TA desorption tube, and TML is quantified by Thermal desorption coupled with gas chromatography/mass spectrometry. Two types of TML dispensers, a polymeric (Aralure) and a mesoporous (Epalure), were field aged during 3 months. The TML release rates of these dispensers were determined by both, VCM and solvent extraction method. In this study, the correlation between both measurement methods is shown. A field trial has also been carried out to correlate trap catches and TML emission of each type of tested dispenser. The VCM allows a quick and accurate evaluation of the current behaviour of commercial dispensers along their useful life. It also allows comparing the TML release rate between different dispensers. We believe that the VCM can be useful for dispenser manufacturers to determine seasonal dispenser performance before a new product is introduced in the market, and to rapidly verify TML dispenser release when field-aged dispenser efficacy is in question. Thus, it can be employed as a quality control of commercial dispensers.
    No preview · Article · Nov 2008 · Journal of Applied Entomology