Scielo RSS <![CDATA[Chilean journal of agricultural research]]> vol. 76 num. 1 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<b>Soybean morphophysiology and yield response to seeding systems and plant populations</b>]]> Soybean (Glicine max [L.] Merr.) is recognized worldwide for its economic importance; it has the ability to adapt to environmental and management changes, particularly when using different spacing and plant populations. This study aimed to investigate the influence of morphological changes of the crisscross seeding system on grain growth and yield. Work was conducted at the Experimental Station of Anapolis, Goiás, Brazil, of the Technical Assistance Agency, Rural Extension and Agricultural Research of Goiás (EMATER) for the 2013-2014 harvest. The experimental design was a randomized block and 2 x 3 x 3 factorial, with four replicates. Treatments consisted of two seeding systems (conventional-in line and crossed-crisscross), three soybean cultivars with different growth habits (&rsquo;BRS Valiosa RR&rsquo; determined, &rsquo;NA 7337 RR&rsquo; semi-determined, and &rsquo;BMX Potencia RR&rsquo; indeterminate) and three sowing densities (245 000, 350 000, and 455 000 plants ha-1). Results showed that at 50 d after emergence the cross-seeding system showed higher closing among lines promoted by the increase in population. Leaf area and the leaf area index were not affected by the seeding system. Leaf area was lower with increasing plant density with no significant difference in relation to the leaf area index. The cross-system enabled a potential yield of 4504 kg ha-1 corresponding to an approximate 8% increase compared with conventional sowing using equidistant lines with 0.5 m spacing. <![CDATA[<b>Germplasm evaluation of heat tolerance in bread wheat in Tel Hadya, Syria</b>]]> Breeding for heat tolerance in bread wheat (Triticum aestivum L.) is a serious global concern due to the increasing threats of high temperature. Thus, 189 wheat genotypes coded from 1 to 189 were evaluated for heat tolerance in normal and late seasons in the International Centre for Agricultural Research in Dry Areas (ICARDA), Tel Hadya, Syria, from 2010 to 2012. The experiments were laid out in alpha lattice designs with two replicates. Data collected on the grain yield, days to heading and maturity, grain filling duration and plant height were subjected to restricted maximum likelihood (REML) analysis for generation of the best linear unbiased estimates (BLUEs). Very highly significant effects (p < 0.001) of genotype, season, and genotype by season interaction on grain yield and other traits were obtained. The grain yield and other traits performance of the wheat genotypes were significantly (p < 0.05) higher in the normal season than in the late season. Genotype 148 was among the 30 top grain yielding genotypes in all the environments, while genotypes 172 and 124 were among the top yielding genotypes in all the environments except in late season 2. The relative heat tolerance of the genotypes ranged from -33.69% to -77.95% in late season 1 vs. normal season 1 and -65.28% to -95.83% in late season 2 vs. normal season 2. The high variability obtained in the germplasm underlies sufficient genetic variability for improving heat tolerance in bread wheat. <![CDATA[<b>Characterization of genetic diversity of native ’Ancho’ chili populations of Mexico using microsatellite markers</b>]]> &rsquo;Ancho&rsquo; type chilis (Capsicum annuum L. var. annuum) are an important ingredient in the traditional cuisine of Mexico and so are in high demand. It includes six native sub-types with morphological and fruit color differences. However, the genetic diversity of the set of these sub­types has not been determined. The objective of this study was to characterize the genetic diversity of native Mexican ancho chili populations using microsatellites and to determine the relationship among these populations. Twenty-four microsatellite loci were used to analyze 38 native populations of &rsquo;Ancho&rsquo; chilis collected in seven states of Mexico; three populations different from the ancho type (&rsquo;Piquin&rsquo;, &rsquo;Guajillo&rsquo;, and &rsquo;Chilaca&rsquo;) and three hybrids (Capulin, Abedul, and green pepper) were included as controls. The number of alleles per locus, number and percentage of polymorphic loci, polymorphic information content (PIC), expected heterozygosity, and Wright F statistics were obtained. Moreover, an analysis of principal components and a cluster analysis were carried out. We detected 220 alleles, with an average of 9.2 alleles per locus; PIC varied between 0.07 and 1, and expected heterozygosity was between 0.36 and 0.59. Also we identified 59 unique alleles and eight alleles common to all of the populations. The F statistics revealed broad genetic differentiation among populations. Both the analysis of principal components and the cluster analysis were able to separate the populations by origin (southern, central, and northern Mexico). The broad genetic diversity detected in the native ancho chili populations of Mexico was found in greater proportion within the populations than between populations. <![CDATA[<b>Exogenous application of brassinolide can alter morphological and physiological traits of <i>Leymus chinensis</i> (Trin.) Tzvelev under room and high temperatures</b>]]> Plant growth regulating substances are involved in the physiological and metabolic processes of plants and enable them to cope with numerous environmental stresses. The effect of exogenously applied brassinolide (BR) with various concentrations (0.01, 0.1, and 1.0 mg L-1) was studied on morphological and physiological traits of Leymus chinensis (Trin.) Tzvelev under room and high temperatures in pots. The experimental results revealed that high temperature stress substantially perturbed growth, photosynthetic pigments, and root activity of L. chinensis; however, the deleterious effects of high temperature were partially ameliorated by the foliar application of BR. Compared to room temperature, high temperature stress decreased the plant height, leaf area, plant fresh and dry weight, chlorophyll a and b content, chlorophyll a/b ratio as well as root activity, while exacerbated the membrane damage as indicated by enhanced production of malondialdehyde (MDA). Accumulation of proline content, soluble protein and sugar content in L. chinensis improved by heat stress, compared with normal temperature; application of BR further improved their production thus aiding in the attainment of tolerance against heat stress. Elevated levels of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) were observed under heat stress compared to room temperature, however, application of BR further proved beneficial in this regard. Our results indicated that BR could improve the growth and development of L. chinensis by enhancing the biosynthesis of photosynthetic pigments, osmolytes and antioxidant enzymes system in plants under both room and high temperature. <![CDATA[<b>Milk production, grazing behavior and nutritional status of dairy cows grazing two herbage allowances during winter</b>]]> Winter grazing provides a useful means for increasing the proportion of grazed herbage in the annual diet of dairy cows. This season is characterized by low herbage growth rate, low herbage allowance, and low herbage intake and hence greater needs for supplements to supply the requirements of lactating dairy cows. The aim of this study was to determine the influence of herbage allowance (HA) offered to autumn calving dairy cows grazing winter herbage on milk production, nutritional status, and grazing behavior. The study took 63 d using 32 multiparous Holstein-Friesian dairy cows. Prior to experimental treatment, milk production averaged 20.2 ± 1.7 kg d-1, body weight was 503 ± 19 kg, and days in milking were 103 ± 6. Experimental animals were randomly assigned to two treatments according to HA offered above ground level: low (17 kg DM cow-1 d-1) vs. high HA (25 kg DM cow¹ d¹). All cows were supplemented with grass silage supplying daily 6.25 and 4.6 kg DM of concentrate (concentrate commercial plus high corn moisture). Decreasing HA influenced positively milk production (+25%), milk protein (+20 kg), and milk fat (+17 kg) per hectare; however no effects on milk production per cow or energy metabolic status were observed in the cows. In conclusion, a low HA showed to be the most significant influencing factor on milk and milk solids production per hectare in dairy cows grazing restricted winter and supplemented with grass silage and concentrate; but no effect on the milk production per cow was found. <![CDATA[<b>Genetic diversity of Colombian sheep by microsatellite markers</b>]]> In Colombia the sheep production systems are managed under extensive conditions and mainly correspond to peasant production systems so their genetic management has led to increased homozygosity and hence productivity loss. The aim of this study was to determine the genetic diversity in 549 individuals corresponding to 13 sheep breeds in Colombia, using a panel of 11 microsatellite molecular markers. One hundred and fifty seven alleles were found (average of 14.27 alleles/locus), with a range of observed and expected heterozygosity from 0.44 to 0.84 and 0.67 to 0.86, respectively. Thirty-three of 143 Hardy Weinberg tests performed showed significant deviations (p < 0.05) due to a general lack of heterozygous individuals. The Fis ranged from 0.01 in Corriedale to 0.15 for the Persian Black Head breed, suggesting that there are presenting low to moderate levels of inbreeding. Overall, Colombian sheep showed high levels of genetic diversity which is very important for future selection and animal breeding programs. <![CDATA[<b>Insecticidal activity of powder and essential oil of <i>Cryptocarya alba</i> (Molina) Looser against <i>Sitophilus zeamais</i> Motschulsky</b>]]> Cereals constitute a relevant part of human and domestic animal diet. Under storage conditions, one of the most significant problems of these crops is insect pests as the maize weevil (Sitophilus zeamais Motschulsky). This insect species is usually controlled by means of synthetic insecticides but problems as toxic residues and resistance has led to the search for more friendly control alternatives such as botanical insecticides. The aim of this research was to evaluate, under laboratory conditions, the insecticidal properties of the powder and the essential oil of peumo (Cryptocarya alba [Molina] Looser; Lauraceae) leaves against S. zeamais. The variables assessed were toxicity by contact and fumigant activity, adult emergence (F1), repellent effect, and impact on wheat (Triticum aestivum L.) seed germination. A completely randomized design was used with five treatments and 10 replicates. The higher mortality levels were obtained at 80 g powder kg-1 grain and 40 mL essential oil kg-1 grain of C. alba; in both cases, the mortality of adult S. zeamais surpassed 80%. The emergence of adults S. zeamais (F1) was reduced by 100% at 80 g powder kg-1 grain and 40 mL essential oil kg-1 grain. Germination of wheat seeds treated with C. alba powder and essential oil was not affected. Both, the powder and the oil treatments showed repellent effect, but not fumigant activity. <![CDATA[<b><i>Malpighia emarginata</i></b><b> DC. bagasse acetone extract</b>: <b>Phenolic compounds and their effect on <i>Spodoptera frugiperda</i> (J.E. Smith) (Lepidoptera: Noctuidae)</b>]]> Annually, several tons of residues that are rich in phenolic compounds are produced during the processing of acerola (Malpighia emarginata DC.) juice. Adding value to these residues is of great interest, since they can be a viable solution in the search for natural substances with insecticidal action and low impact on the environment and humans. Taking into account the economic losses from the attacks by the fall armyworm Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) in different crops, the objective of this study was to evaluate the effect of the extract of acerola bagasse flour (ABF) against this insect and determine the phenolic compounds in this extract. Bagasse of acerola (BRS238 or Frutacor clon) generated after juice production, was frozen and lyophilized. To obtain the extract, 6 g ABF was mixed with 60 mL acetone:water solution (7:3 v/v), and the extract was lyophilized. Spodoptera frugiperda caterpillars, 48 h-old, obtained by the maintenance breeding, were transferred to glass tubes supplied with an artificial diet containing the ABF extract at 0, 250, 500, 1000, and 2000 mg L-1 diet. The following variables were evaluated: duration and survival of larval and pupal stages, pupal weight, sex ratio, adult longevity, oviposition period, number of egg masses, and total number of eggs. The ABF extract contained several phenolic compounds including gallic acid, epigallocatechin gallate, catechin, p-coumaric acid, salicylic acid, and quercetin. The extract was toxic to S. frugiperda, prolonging the pre-pupal stage and increasing the mortality of caterpillars. <![CDATA[<b>Feeding and oviposition deterrent activities of microencapsulated cardamom oleoresin and eucalyptol against <i>Cydia pomonella</i></b>]]> Behavioral manipulation of codling moth with spice-based deterrents may provide an alternative control strategy. Microencapsulation technology could lead to more effective use of spice essential oils and oleoresins in the field by extending their residual activity. The feeding and oviposition deterrent potential of the microencapsulated cardamom (Elettaria cardamomum [L.] Maton) oleoresin (MEC-C) and eucalyptol (MEC-E) were evaluated against codling moth, Cydia pomonella Linnaeus, 1758. MEC-C capsules contained both 1,8-cineole and a-terpinyl acetate, whereas MEC-E capsules contained only 1,8-cineole. In larval feeding bioassays, MEC-E exhibited the lowest feeding deterrent activity (33%) while MEC-C at 100 mg mL-1 had the highest (91%). The highest oviposition deterrence activity against gravid females was also shown by MEC-C at 100 mg mL-1 with 84% effective repellency. In 2010 and 2011, two apple orchards were divided into four 1 ha blocks and sprayed with the following treatments in ultra-low volume sprays: (a) MEC-E at 100 g L-1, (b) MEC-C at 50 g L-1, (c) MEC-C at 100 g L-1, and (d) MEC-pyrethrin at 15 mL L-1. Water-treated abandoned orchards were used as negative controls. Moth catches were monitored weekly using Ajar traps baited with the combination of codlemone, pear ester, and terpinyl acetate. Based on pooled data, mean cumulative moth catch per trap per week was significantly higher in the MEC-E blocks (26.3 male and 13.5 female moths) than those in other treatments except the abandoned blocks. At mid-season and pre-harvest damage assessment, the percentage of infested fruits with live larvae in the high dose MEC-C-treated blocks was reduced to 1.9% and 2.3% in 2010 and to 1.1% and 1.8% in 2011, respectively. Since fruit damage exceeded the economic damage threshold of 1%, high-dose MEC-C treatment may only offer supplementary protection against codling moth in integrated pest management programs. <![CDATA[<b>Toxicity of essential oils of <i>Piper marginatum</i> Jacq. against <i>Tetranychus urticae</i> Koch and <i>Neoseiulus californicus</i> (McGregor)</b>]]> Tetranychus urticae Koch (Acari: Tetranychidae) is an economically important pest of agricultural and ornamental crops worldwide. It has been shown that many of natural plant-based pesticides have fewer side effects compared with synthetic chemicals. The essential oils of plants have been broadly studied for pest-control, including toxic and repellent effects, antifeedant, ovicidal, and other properties. Essential oils from stems, flowers, and leaves of Piper marginatum Jacq. were evaluated in the laboratory regarding their acaricidal potential against the two-spotted spider mite (T. urticae) and the results were compared with eugenol as a positive control. The oils were also evaluated with regard to the susceptibility of the natural enemy of T. urticae (Neoseiulus californicus McGregor). Based on LC50 estimates, oils from stems and flowers exhibited the same toxicity and differed significantly from the leaf oil with LC50 0.37, 0.56, and 3.77 μL L-1, respectively. None of the oils tested exhibited toxicity greater than or equal to that of the positive control. The oil mortality rate was significantly lower for N. californicus (50% to 70%) than for T. urticae (> 95%). The P. marginatum oils also deterred oviposition. Among the chemical constituents tested, sesquiterpenes were more toxic with an LC50 of 2.89 μL L-1 than phenylpropanoids Z-asarone and E-asarone with LC50 6.64 and 8.51 μL L-1, respectively. The acaricidal properties, oviposition deterrence and selectivity make these oils strong candidates for use as the active ingredient in a plant-based acaricidal agent. <![CDATA[<b>Molecular, morphological and pathogenic characterization of six strains of <i>Metarhizium</i> spp. (Deuteromycotina: Hyphomycetes) for the control of <i>Aegorhinus superciliosus</i> (Coleoptera: Curculionidae)</b>]]> Aegorhinus superciliosus is an important pest on blueberry (Vaccinium corymbosum L.) and other fruit trees. The use of entomopathogenic fungi as Metarhizium spp. has been evaluated for the control of this insect, but variability has been observed among different strains. The aim of this study was to characterize six promising strains of Metarhizium spp. for the control of A. superciliosus. The studied strains were QuM173c, Qu-M363, Qu-M171a, Qu-M156a, Qu-M421, and Qu-M430, all of which belonged to the Chilean Collection of Microbial Genetic Resources (ChCMGR) of the Institute) de Investigaciones Agropecuarias (INIA), Chile. Molecular characterization was made by sequencing the ITS region (Internal Transcribed Spacers, ITS-5.8S rDNA). The morphology of conidia was evaluated through scanning electron microscopy and radial colony growth was evaluated in potato dextrose agar (PDA), Sabouraud dextrose agar (SDA), agar enriched with larvae of Galleria mellonella (Lepidoptera: Pyralidae) (GA), and agar enriched with adults of A. superciliosus (AA). Pathogenicity was studied based on mortality of adults of A. superciliosus inoculated with conidia. Sequencing of the ITS-5.8S rDNA region indicates that the strains belong to the clade of M. anisopliae var. anisopliae, except for Qu-M171a, which was identified as M. anisopliae var. lepidiotum. Conidia average length for the six strains was 5.09 pm and average conidia width was 1.92 pm. Radial colony growth differences were observed between strains (p < 0.01) and between different growth media (p < 0.01). The strains exhibited the highest colony growth in the GA medium, while in the AA medium they showed the lowest (p < 0.01). Pathogenicity tests show that Qu-M430 reached a 90% mortality rate (p < 0.01). Results show that there is variability between the studied strains, which is expressed in their morphology, molecular characteristics and pathogenicity towards A. superciliosus. <![CDATA[<b>Diurnal pattern of nitrous oxide emissions from soils under different vertical moisture distribution conditions</b>]]> The diurnal pattern of nitrous oxide (N2O) emissions is essential in understanding how weather and soil conditions influence the daily mean estimate of N2O fluxes. Incubation experiments were conducted to investigate the effects of vertical soil moisture distribution patterns on diurnal variation of N2O emissions. Clear diurnal patterns of N2O emissions on both surface watering (SW) and subsurface watering (SUW) treatments (SUW12, SUW15, and SUW18) were detected from soil sample (I), silty clay, and soil sample (II), sandy loam, where peak N2O fluxes usually occurred between 12:00 and 18:00 h. Different vertical watering patterns resulted in changes in the daily range of N2O fluxes and peak time. Mean fluxes from the SUW12, SUW15, and SUW18 treatments were 37.4%, 32.7%, and 43.3% lower than those from SW treatments from soil sample I, and 32.0%, 40.3%, and 41.1% from soil sample II. Moisture distribution patterns under SUW soils could be effective to mitigate N2O emissions. The N2O emissions from soil sample I ranged from178.3 to 2741.0 μg N2O m-2 h-1, which was more than in soil sample II with 7.0 to 83.7 μg N2O m-2 h-1. The different soil texture and N content level might account for the differences in magnitude of N2O fluxes from soils. The optimal soil moisture condition for peak N2O fluxes in the SW treatment had relatively narrower ranges than the SUW treatments with 46% to 60% water-filled pore space (WFPS) for soil sample I and 26% to 34% WFPS for soil sample II even though surface soil moisture for peak N2O fluxes were somewhat different from the previously reported optimal soil moisture range of 45% to 75% WFPS. <![CDATA[<b>Whole plant open chamber to measure gas exchange on herbaceous plants</b>]]> Much of our understanding about CO2 and H2O gas exchange in plants has been gained from studies at leaf level. Extrapolation of results to whole plant is difficult and not always accurate. In order to overcome this limitation, a chamber was designed to measure gas exchange at the whole plant level. The chamber developed in this work consisted on an acrylic cylinder 0.70 m high and 0.60 m wide. An incorporated blower was used to circulate air through the chamber and plant canopy from the bottom inlet upwards to the outlet tube providing a maximum flow of 0.072 m³ s-1. Air CO2 and water concentration were monitored with an infrared gas analyzer and temperature gradients were measured periodically with sensors. Air flow rates inside the chamber were 0.007, 0.012, 0.022, 0.047, and 0.072 m³ s-1. A comparative study showed that 0.022 or 0.047 m³ s-1 air flow rates did not modify substantially the natural environment within the chamber; measurements are close to real and exterior ones; temperature increased below 4 °C; photosynthetically active radiation (PAR) was reduced by 5%; and photosynthesis and evapotranspiration showed mean values with nonsignificant variations (22 ± 3.8 μmol CO2 m-2 s-1, and 15 ± 4.0 mmol H2O m-2 s-1, respectively). This chamber could be a useful tool to measure gas exchange of whole plants in herbaceous species under conditions of high evapotranspiration and for extended periods of time. <![CDATA[<b>Priming effects of leaves of <i>Laurus nobilis</i> L. and 1,8-cineole on carbon mineralization</b>]]> Plant secondary compounds can have stimulating effect on C cycling and change its rate in soils. We examined how leaves of bay laurel (Laurus nobilis L.; Lauraceae) and 1,8-cineole (CIN), one of its constituents, affect soil C mineralization and its rate. Leaves and soil samples of bay laurel were taken from Cukurova University Campus (Adana, Turkey) growing naturally under Mediterranean climate conditions. Leaves and CIN were considered as the two forms of organic C sources. After determining the level of 1,8-cineole in leaves by gas chromatography-mass spectrometry, soils were mixed with powdered leaves and 1,8-cineole based on their C contents at same and half doses of soil organic C level. Carbon mineralization of all soils was determined over 54 d (28 °C, 80% field capacity). While 1,8-cineole was found as a major constituent of leaves (65% of essential oil), all doses of leaves and CIN increased soil microbial activity. There were significant differences for C mineralization rate between control and all applications (P < 0.05). High C levels of all treatments decreased C mineralization rate compared to control soils. In summary, all treatments stimulated C mineralization and it is possible to conclude that soil microorganisms adapted to use CIN as an energy source. <![CDATA[<b>Direct measurement and prediction of bulk density on alluvial soils of central Chile</b>]]> The significance of soil bulk density (ρ) as a key indicator of soil quality was examined in this study. Bulk density values obtained by direct methods (clod, cylinder, and excavation) with three sample sizes (small, medium, and large) were compared with those obtained by 10 published pedotransfer functions (PTFs) for two alluvial soils (a massive fine-textured Fluventic Haploxeroll and an aggregated, coarse-textured Fluventic Haploxerept) of central Chile. With the exception of small cylinders in fine-textured soil, there were nonsignificant differences between the methods and sample sizes assessed. On the coarse-textured soil, there were nonsignificant differences between the excavation and clod methods, but medium-sized cylinders differed from other cylinder sizes. In general, the clod technique tended to give higher values than the other methods. Using basic information (texture and organic matter/C content) from the existing PTFs for both sites, a better fit for coarse-textured than fine-textured soils was obtained. This indicates that it is necessary to define a set of locally calibrated PTFs that address the complexity of the soil resource throughout Chile. <![CDATA[<b>Arsenic translocation in rice cultivation and its implication for human health</b>]]> Arsenic (As) is a toxic metalloid for plants and animals. Large amounts of As have been released in arable soils through anthropogenic activities, use of contaminated irrigation water, and mining among others. Rice (Oryza sativa L.) is one of the most consumed cereals worldwide; it is an important route of exposure for As. The objective of this review was to explain possible mechanisms involved in As absorption that contaminate rice plant through the soil and water, and to mention studies that have been conducted to minimize the risk of human exposure. The root is able to absorb and accumulate large amounts of As, but only small amounts are translocated to the grain and tillers. Arsenic concentrations in rice tissues decrease from the root to the grain. Information about As translocation in rice is sparse and research is directed toward studying the molecular mechanism of absorption and accumulation in the grain because it has not yet been explained. Some rice varieties have been developed that are resistant to high soil As concentrations and are not able to translocate the metalloid toward the root. Many studies suggest that not all ingested inorganic As accumulated in the gastrointestinal tract is absorbed into the bloodstream and produces toxicity. It is therefore recommended that As bioavailability be evaluated in imported or domestic Chilean rice to more precisely estimate human health risk <![CDATA[<b>Photosynthetic behavior, growth and essential oil production of <i>Melissa officinalis</i> L. cultivated under colored shade nets</b>]]> The modulation of light is of importance during cultivation of medicinal plants to obtain desirable morphological and physiological changes associated with the maximum production of active principles. This study aimed to evaluate the effect of the light spectrum transmitted by colored shade nets on growth, essential oil production and photosynthetic behavior in plants of lemon balm (Melissa officinalis L.) Plants were cultivated in pots for 4-mo under black, red, and blue nets with 50% shading, and full sunlight exposure. Biometric and anatomical variables, essential oil yield, global solar radiation, photon flux density, chlorophyll content, and gas exchange parameters were measured in M. officinalis leaves. The results showed that despite being considered a partial shade plant, this species is able to adapt to full sunlight conditions without increasing biomass production. The spectral changes provided by colored shade nets did not caused any noticeable change in leaf anatomy of M. officinalis. However, the use of blue net resulted in increments of 116% in plant height, 168% in leaf area, 42% in chlorophyll content and 30% in yield of essential oil in lemon balm plants. These plant&rsquo;s qualities make the use of blue net a cultivation practice suitable for commercial use. <![CDATA[<b>Dissipation of four insecticides in tomato fruit using high performance liquid chromatography and QuEChERS methodology</b>]]> Insecticides play an important role in increasing agricultural production, but their extensive use has led to environmental problems including health hazards to humans. The present study was carried out to investigate the residual levels and dissipation behavior of four insecticides, namely abamectin, thiamethoxam, spinosad, and chlorpyrifos, in tomato (Solanum lycopersicum L.) fruits under Egyptian field condition. The insecticide residues were determined after application of insecticides for three times at recommended rates. The extraction of insecticide residues was carried out by using QuEChERS method. The determination of residual levels was performed by high performance liquid chromatography coupled with diode array detector (HPLC-DAD). Recoveries were between 85% and 130%, with relative standard deviations from 1.8% to 17.0% at two fortified levels. The dissipation rates of insecticides followed first-order kinetics (Ct = 0.2627 e-0.17t, Ct = 3.7183 e-0.275t, Ct = 0.1778 e-0.407t, Ct = 0.6074 e-0.11t for abamectin, chlorpyrifos, spinosad and thiamethoxam, respectively). The values of half-life of insecticides were 4.1, 2.5, 1.7, and 6.3 d for abamectin, chlorpyrifos, spinosad and thiamethoxam, respectively. The results indicated that tomato fruits could be safely consumed after 7, 15, < 1 and 10 d of application at recommended rates for abamectin, chlorpyrifos, spinosad and thiamethoxam, respectively, according to the recommended EU maximum residue limits (MRLs).