Stored-grain Insects Research Articles

Contact toxicity and repellency of the essential oil from Mentha haplocalyx Briq. against Lasioderma serricorne.

The chemical composition of the essential oil obtained by hydrodistillation from the aerial parts of Mentha haplocalyx was investigated by GC-FID and GC/MS analyses. In sum, 23 components, representing 92.88% of the total oil composition, were identified, and the main compounds were found to be menthol (59.71%), menthyl acetate (7.83%), limonene (6.98%), and menthone (4.44%). By bioassay-guided fractionation (contact toxicity), three compounds were obtained from the essential oil and identified as menthol, menthyl acetate, and limonene. The essential oil and the three isolated compounds exhibited potent contact toxicity against Lasioderma serricorne adults, with LD50 values of 16.5, 7.91, 5.96, and 13.7 μg/adult, respectively. Moreover, the oil and its isolated compounds also exhibited strong repellency against L. serricorne adults. At the lower concentrations tested and at 2 h after exposure, menthol showed even significantly stronger repellency than the positive control DEET. The study revealed that the bioactivity properties of the essential oil can be attributed to the synergistic effects of its diverse major and minor components, which indicates that the M. haplocalyx oil and its isolated compounds have potential for the development as natural insecticides and/or repellents to control insects in stored grains and traditional Chinese medicinal materials.

Essential oil of Cinnamodendron dinisii Schwanke for the control of Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae)

ABSTRACT The use of natural compounds is a less aggressive alternative for the control of insects in stored grains, in relation to synthetic chemical agents. Plants with insecticidal properties can be used as a source of these compounds to the direct application in pest control. In this work, the essential oil of Cinnamodendron dinisii was chemically characterized and tested regarding its insecticidal and repellent effect on the control of Sitophilus zeamais in stored grains. The essential oil was obtained by hydrodistillation and analyzed by gas chromatography–mass spectrometry (GC-MS). The insecticidal potential was evaluated through the maintenance of the insects during 24 hours in contact with several doses of the oil, in the absence of feed substrate. The Bioassays of repellency were conducted with lethal doses (LD5, LD25, LD50 and LD95) obtained from insecticidal bioassay. In order to compare the treatments, the preference index (PI) was used. The essential oil of C. dinisii had insecticidal activity against S. zeamais, causing a linear and crescent mortality with LD of 0.04, 0.17, 0.34 and 0.63 µL/cm2, respectively. The repellency ranged from 55.4% to 85.2%, using the LD values previously mentioned. The DL5 was neutral regarding repellence (PI index -0,09), but from DL25 on, the PI index was between -0.1 and -1.0, indicating repellence activity.

Bioactivity and chemical constituents of the essential oil from Dendranthema indicum (L.) Des Moul. against two stored insects.

Dendranthema indicum (L.) Des Moul. is a perennial herb commonly used as a traditional Chinese medicine for a long time. In this work, we took Dendranthema indicum as a target plant and two stored insects which include Tribolium castaneum and Stegobium paniceum adults as target insects. Essential oil obtained from Dendranthema indicum was analyzed by gas chromatography-mass spectrometry (GC-MS). A total of 31 components representing 92.44% of the oil were identified and the main compounds were found to be chamazulene (15.93%), β-caryophyllene (13.78%), germacrene D (9.11%), and b-cis-farnesene (6.59%). With a further isolation, three constituents were obtained from the essential oil and identified as chamazulene, β-caryophyllene and eucalyptol. Significantly, in the progress of assay, it showed that the essential oil and chamazulene exhibited stronger insecticidal and repellent activities against Stegobium paniceum than Tribolium castaneum. The results indicate that additional to its traditional use as Chinese medicinal herb, the essential oil of Dendranthema indicum aerial parts and isolated compounds have potential to be developed into natural insecticides or repellents for control of insects in stored grains.

Susceptibility to sulfuryl fluoride and lack of cross-resistance to phosphine in developmental stages of the red flour beetle,Tribolium castaneum(Coleoptera: Tenebrionidae)

Our aim was to ascertain the potential of sulfuryl fluoride (SF) as an alternative fumigant to manage phosphine-resistant pests. We tested the susceptibility of all life stages of red flour beetle, Tribolium castaneum (Herbst), to SF and assessed the presence of cross-resistance to this fumigant in phosphine-resistant strains of this species. Analysis of dose-response data indicated that the egg was the stage most tolerant to SF under a 48 h exposure period. At LC50 , eggs were 29 times more tolerant than other immature stages and adults, and required a relatively high concentration of 48.2 mg L(-1) for complete mortality. No significant differences in tolerance to SF were observed among the three larval instars, pupae and adults, and all of these stages were controlled at a low concentration of 1.32 mg L(-1) . Phosphine-resistant strains did not show cross-resistance to SF. Our research concluded that the current maximum registered rate of SF, 1500 gh m(-3) , is adequate to control all the post-embryonic life stages of T. castaneum over a 48 h fumigation period, but it will fail to achieve complete mortality of eggs, indicating the risk of some survival of eggs under this short exposure period. As there is no cross-resistance to SF in phosphine-resistant insects, it will play a key role in managing phosphine resistance in stored-grain insect pests.

Sub-lethal Activity of Plant Volatile Essential Oils in Management of Red Flour Beetle Tribolium castaneum (Coleoptera: Tenebrionidae)

:Stored food faces severe damage due to infestation by insects. The essential oils extracted from leaves of Mentha arvensis and peels of Citrus reticulata by hydrodistillation method were screened as fumigant for chronic activity against red flour beetle Tribolium castaneum (Coleoptera: Tenebrionidae) in laboratory assay. Both essential oils showed chronic activity in a dose dependent manner. Fumigation with sub-lethal concentration of essential oils significantly (p < 0.01) reduced hatchability of adults, inhibited pupation and adult emergence in larvae and also reduced percent grain infestation against T. castaneum in comparison to control groups. Fumigation of insect with sub-lethal concentration of both essential oils inhibited Acetylcholinesterase activity. Reduction in AChE activity was 67.50 and 61.25 % of the control, after 24 h of fumigation with sub-lethal concentration of both essential oils. From this study, it is concluded that these essential oils have potential for application in Insect Pest Management programs for stored-grain insect pests by chronic exposure because of their fumigant action.

Evaluation of insecticidal activity of the essential oil of Allium chinense G. Don and its major constituents against Liposcelis bostrychophila Badonnel

Water-distilled essential oil from the dried bulbs of Allium chinense (Liliaceae) was analyzed by gas chromatography–mass spectrometry (GC–MS). Eighteen compounds, accounting for 98.4% of the total oil, were identified and the main components of the essential oil of A. chinense were methyl allyl trisulfide (30.7%), dimethyl trisulfide (24.1%), methyl propyl disulfide (12.8%) and dimethyl disulfide (9.6%) followed by methyl allyl disulfide (3.4%) and methyl propyl trisulfide (3.6%). The essential oil exhibited contact toxicity against the booklice (Liposcelis bostrychophila) with an LC50 value of 441.8μg/cm2 while the two major constituents, dimethyl trisulfide and methyl propyl disulfide had LC50 values of 153.0μg/cm2 and 738.0μg/cm2 against the booklice, respectively. The essential oil of A. chinense possessed strong fumigant toxicity against the booklice with an LC50 value of 186.5μg/l while methyl allyl trisulfide (LC50=90.4μg/l) and dimethyl trisulfide (LC50=114.2μg/l) exhibited stronger fumigant toxicity than methyl propyl disulfide (LC50=243.4μg/l) and dimethyl disulfide (LC50=340.8μg/l) against the booklice. The results indicated that the essential oil and its major constituents have potential for development into natural insecticides or fumigants for control of insects in stored grains.

Repellent and insecticidal effects of the essential oil of Kaempferia galanga rhizomes to Liposcelis bostrychophila (Psocoptera: Liposcelidae).

The aim of this research was to determine chemical composition and repellent and insecticidal activities of the essential oil of Kaempferia galanga L. rhizomes against the booklouse, Liposcelis bostrychophila Badonnel, and to isolate insecticidal or repellent constituents from the oil. The essential oil was obtained by hydrodistillation and analyzed by gas chromatography-mass spectrometry. Twenty-eight components of the oil were identified. The major compounds in the oil were ethyl-rho-methoxycinnamate (38.6%), ethyl cinnamate (23.2%), 1,8-cineole (11.5%), trans-cinnamaldehyde (5.3%), and borneol (5.2%). Based on bioactivity-guided fractionation, four active constituents were isolated from the oil and identified as 1,8-cineole, ethyl cinnamate, ethyl rho-methoxycinnamate, and trans-cinnamaldehyde. The essential oil exhibited contact toxicity against the booklouse with an LC50 value of 68.6 microg/cm2. Ethyl cinnamate (LC50 = 21.4 microg/cm2) exhibited stronger contact toxicity than ethyl rho-methoxycinnamate and trans-cinnamaldehyde (LC50 = 44.6 and 43.4 microg/cm2, respectively) while 1,8-cineole showed weak acute toxicity. The essential oil also possessed fumigant toxicity against the booklouse with a LC50 value of 1.5 mg/liter air. 1,8-Cineole and trans-cinnamaldehyde (LC50 = 1.1 and 1.3 mg/liter, respectively) possessed stronger fumigant toxicity against the booklouse than ethyl cinnamate and ethyl rho-methoxycinnamate (LC50 = 10.2 and 10.2 mg/liter air, respectively). trans-Cinnamaldehyde was strongly repellent to booklice, whereas ethyl cinnamate and ethyl rho-methoxycinnamate were weakly repellent and 1,8-cineole did not repel booklice. The results indicate that the essential oil and its constituent compounds have potential for development into natural insecticides or fumigants and repellents for control of insects in stored grains.

Chemical composition and insecticidal activities of the essential oil of Perilla frutescens (L.) Britt. aerial parts against two stored product insects

The chemical composition of the essential oil of Perilla frutescens (L.) Britt. aerial parts and its insecticidal activity against Tribolium castaneum and Lasioderma serricorne were investigated. The essential oil of P. frutescens was obtained by hydrodistillation and a total of 34 components in the essential oil were identified with GC–MS. It was found that the main compounds included 2-furyl methyl ketone (71.83 %), decahydro-1-methyl-2-methylene-naphthalene (10.47 %), limonene (5.16 %) and caryophyllene (1.66 %). With a further isolation, the two active constituents were obtained from the essential oil and identified as 2-furyl methyl ketone, limonene. In the progress of assay, it showed that the essential oil and 2-furyl methyl ketone exhibited stronger contact and fumigant activities against the two stored product insects than limonene. Moreover, the essential oil and its constituents exhibited the comparable repellency against the two stored product insects, relative to the positive control, DEET. The results indicate that the essential oil of P. frutescens aerial parts and its isolated compounds have potential for development into natural insecticides or fumigants as well as repellents for control of insects in stored grains.

Stored-grain insect population commingling densities in wheat and corn from pilot-scale bucket elevator boots

Grain elevator boot and pit areas facilitate the commingling of insects with the grain moving through the elevator leg. A removable boot was developed to facilitate residual grain removal and preservation in the boot and to quantify the commingling magnitude as a function of stored-product insect density. This study included two species that develop inside kernels, Rhyzopertha dominica and Sitophilus oryzae, and three species that develop outside kernels, Tribolium castaneum, Oryzaephilus surinamensis and Cryptolestes ferrugineus. The removable boots were loaded with infested residual grain and remained undisturbed for 0, 8, 16, or 24 weeks (wk). After each time point, uninfested grain was transferred through the infested boot. The adult beetles that commingled with the clean grain were sifted and counted. Further, the commingled lots were examined after 8 wk for adult progeny. The insect densities in the infested bucket elevator leg boots affected the insect densities transferred through the elevator leg to other locations. The insect density in clean wheat or corn transferred over infested boots was 1 insect/kg immediately after transfer, but this density doubled in 8 wk. More internally developing insects were collected by the elevator buckets when the clean grain flowed over the infested grain compared with the externally developing insects. β-Cyfluthrin application as a residual insecticide reduced the insect densities in the elevator boot, which consequently reduced the insect transfer to clean grain. Cleaning the bucket elevator boot area and applying residual insecticide monthly should minimize clean grain contamination.

Isolation of Insecticidal Constituents from the Essential Oil ofAgeratum houstonianumMill. againstLiposcelis bostrychophilaBadonnel

The aim of this research was to determine chemical composition and insecticidal activities of the essential oil ofAgeratum houstonianumMill. aerial parts against booklice,Liposcelis bostrychophilaBadonnel, and to isolate any insecticidal constituents from the oil. Essential oil ofA. houstonianumwas obtained by hydrodistillation and analyzed by GC-MS. A total of 35 components in the essential oil were identified. The major compounds were precocene II (62.68%), precocene I (13.21%), andβ-caryophyllene (7.92%). Based on bioactivity-guided fractionation, precocene II and precocene I were isolated and identified as the active constituents. The essential oil exhibited contact toxicity againstL. bostrychophilawith an LC50value of 50.8 μg/cm2. Precocene II (LC50= 30.4 μg/cm2) exhibited stronger acute toxicity than precocene I (LC50= 64.0 μg/cm2) against the booklice. The essential oil and the two isolated constituents also possessed strong repellent activity againstL. bostrychophila. The results indicated that the essential oil and its constituent compounds have potential for development into natural insecticides or repellents for control of insects in stored grains.

Bioactivity of essential oil of Artemisia argyi Lévl. et Van. and its main compounds against Lasioderma serricorne.

Artemisia argyi Lévl. et Van., a perennial herb with a strong volatile odor, is widely distrbuted in the world. Essential oil obtained from Artemisia argyi was analyzed by gas chromatography-mass spectrometry (GC-MS). A total of 32 components representing 91.74% of the total oil were identified and the main compounds in the oil were found to be eucalyptol (22.03%), β-pinene (14.53%), β-caryophyllene (9.24%) and (-)-camphor (5.45%). With a further isolation, four active constituents were obtained from the essential oil and identified as eucalyptol, β-pinene, β-caryophyllene and camphor. The essential oil and the four isolated compounds exhibited potential bioactivity against Lasioderma serricorne adults. In the progress of assay, it showed that the essential oil, camphor, eucalyptol, β-caryophyllene and β-pinene exhibited strong contact toxicity against L. serricorne adults with LD50 values of 6.42, 11.30, 15.58, 35.52, and 65.55 μg/adult, respectively. During the fumigant toxicity test, the essential oil, eucalyptol and camphor showed stronger fumigant toxicity against L. serricorne adults than β-pinene (LC50 = 29.03 mg/L air) with LC50 values of 8.04, 5.18 and 2.91 mg/L air. Moreover, the essential oil, eucalyptol, β-pinene and camphor also exhibited the strong repellency against L. serricorne adults, while, β-caryophyllene exhibited attracting activity relative to the positive control, DEET. The study revealed that the bioactivity properties of the essential oil can be attributed to the synergistic effects of its diverse major and minor components. The results indicate that the essential oil of A. argyi and the isolated compounds have potential to be developed into natural insecticides, fumigants or repellents in controlling insects in stored grains and traditional Chinese medicinal materials.

Functional Morphology of the Crop and Proventriculus of Sitophilus zeamais (Coleoptera: Curculionidae)

Abstract Sitophilus zeamais Motschulsky, 1855 (Coleoptera: Curculionidae) is one of the most aggressive pests of stored grains, causing significant decrease in the nutritional quality of the grains and major losses in economic trade. The ability of this pest to damage grains and other products is directly related to the morphology of the alimentary canal. Considering the importance of the foregut in the digestion, this study aimed to describe the morphology of the crop and proventriculus in S. zeamais adults. The tissues were isolated, processed, and analyzed by using light microscopy, scanning electron microscopy, and transmission electron microscopy. The crop functioned as a storage organ, and its cells showed functional characteristics related to protein synthesis. High densities of prokaryotic microorganisms and spicules were found in the lumen. The proventriculus exhibited eight chitinous teeth, which were responsible for grinding and filtering food particles. This organ formed the stomodeal valve, which controlled the unidirectional flow of food through the alimentary canal. The alimentary canal is the primary surface of contact between the external environment and an insect's internal environment, and knowledge of its morphology is required to better understand the physiology of stored-grain insect pests.

Impact of temperature and relative humidity on life history parameters of adult Sitotroga cerealella (Lepidoptera: Gelechiidae)

The Angoumois grain moth, Sitotroga cerealella (Olivier) (Lepidoptera: Gelechiidae), is a pest of stored corn, Zea mays L., and other grains throughout the world. Sitotroga cerealella are routinely exposed to temperatures below 20 °C in regions of the U.S. where corn is grown, yet there are no data describing adult life history parameters below 20 °C. We determined longevity, fecundity, and survivorship of eggs at a range of temperatures that represent environmental conditions to which S. cerealella are exposed in corn stored in the U.S. Longest male longevity was 31 d at 10 °C, and shortest male longevity was 4 d at 35 and 40 °C. Longest female longevity was 29 d at 15 °C, and shortest female longevity was 5 days at 35 and 40 °C. Duration of the preoviposition period was as long as 16 d at 10 °C and as short as 1 d at 30–40 °C. All females laid eggs at 20–30 °C, 50–94% of females laid eggs at 15 °C, and 17–61% of females laid eggs at 10, 35, or 40 °C. Females laid the most eggs, nearly 100, at 20 and 25 °C and 75% r.h., while 6 or fewer eggs were laid at 10, 35, or 40 °C. Between 68 and 98% of eggs hatched at 20–30 °C, while 20% or fewer eggs hatched at 35 °C and no eggs hatched at 40 °C. An average of less than one egg was laid at 10 °C, but 58–100% of eggs hatched at 10 °C. Our results emphasize the importance of including data on population growth of stored-grain insect pests at low temperatures in computer models for simulating insect population growth in grain.

Identification of Repellent and Insecticidal Constituents of the Essential Oil of Artemisia rupestris L. Aerial Parts against Liposcelis bostrychophila Badonnel

The aim of this research was to determine the chemical composition and insecticidal and repellent activity of the essential oil of Artemisia rupestris L. aerial parts against the booklice Liposcelis bostrychophila Badonnel and isolation of insecticidal and repellent constituents from the essential oil. The essential oil of A. rupestris was obtained by hydrodistillation and analyzed by GC-MS. A total of 30 components of the essential oil of A. rupestris was identified and the principal compounds in the essential oil were α-terpinyl acetate (37.18%), spathulenol (10.65%), α-terpineol (10.09%), and linalool (7.56%), followed by 4-terpineol (3.92%) and patchoulol (3.05%). Based on bioactivity-guided fractionation, the four active constituents were isolated from the essential oil and identified as α-terpineol, α-terpinyl acetate, 4-terpineol and linalool. The essential oil of A. rupestris exhibited contact toxicity against L. bostrychophila with LD50 value of 414.48 µg/cm2. α-Terpinyl acetate (LD50 = 92.59 µg/cm2) exhibited stronger contact toxicity against booklice than α-terpineol (LD50 = 140.30 µg/cm2), 4-terpineol (LD50 = 211.35 µg/cm2), and linalool (LD50 = 393.16 µg/cm2). The essential oil of A. rupestris (LC50 = 6.67 mg/L air) also possessed fumigant toxicity against L. bostrychophila while the four constituents, 4-terpineol, α-terpineol, α-terpinyl acetate and linalool had LC50 values of 0.34, 1.12, 1.26 and 1.96 mg/L air, respectively. α-Terpinol and α-terpinyl acetate showed strong repellency against L. bostrychophila, while linalool and 4-terpinol exhibited weak repellency. The results indicate that the essential oil of A. rupestris aerial parts and its constituent compounds have potential for development into natural insecticides or fumigants as well as repellents for control of insects in stored grains.

Study of the Vibration Screening for Image Recognition of the Stored-Grain Insects

The automatic vibration screening of the insects is the important part in the image recognition of the stored-grain insects. A screening detection device of the stored-grain insects was developed to analyze the vibration screening properties of Coleopteran insects. The main structure of the device included a vibration screening unit, a dust removal unit of the grain insects, a binocular machine vision unit and an automatic transporting unit. The adults of Sitophilus Oryzae were taken as the screening objects. Full factorial design was used in order to find out the better vibration screening parameters. Then orthogonal experiment was designed to optimize the screening parameters further, and distinguish between the primary factors and the secondary factors. The optimal vibration screening parameters of the detection device for the stored-grain insects were determined by a series of experiments. The best parameters were that the amplitude of the vibration sieve was 3.5 mm, the vibrating direction angle was 30oand the crank plate speed was 600r/min.

Variation in susceptibility of laboratory and field strains of three stored‐grain insect species to β‐cyfluthrin and chlorpyrifos‐methyl plus deltamethrin applied to concrete surfaces

The efficacy of commercial formulations of β-cyfluthrin and chlorpyrifos-methyl plus deltamethrin applied to clean, concrete surfaces similar to that of empty bins against field strains of stored-grain insects is unknown. We exposed adults of 16 strains of the red flour beetle, Tribolium castaneum (Herbst); eight strains of the sawtoothed grain beetle, Oryzaephilus surinamensis (L.); and two strains of the lesser grain borer, Rhyzopertha dominica (F.), collected mainly from farm-stored grain in Kansas, USA, to β-cyfluthrin and chlorpyrifos-methyl plus deltamethrin applied to concrete surfaces and determined knockdown and mortality. Knockdown and mortality differences among species and strains to the insecticides tested were significant. Mortality of all species was less than that of knockdown, suggesting recovery when placed on food after insecticide exposure. β-Cyfluthrin was effective against R. dominica but ineffective against T. castaneum and O. surinamensis field strains. Chlorpyrifos-methyl plus deltamethrin was only partially effective against field strains of the three species. Reduced susceptibility in field strains may be due to inherent formulation deficiency and low levels of tolerance or resistance to β-cyfluthrin. No single insecticide provided adequate control of the three species tested.

Effect of gaseous ozone for control of stored product pests at low and high temperature

Gaseous ozone (O3) has shown potential for control of insects in stored grain. A previous laboratory study determined doses of ozone necessary to control freely exposed and internal stages of eleven stored product pest species at 20 °C. In this study the impact of temperature on the effect of ozone was tested on two species of stored product pests: Sitophilus granarius and Plodia interpunctella. Insects were exposed to continuous flows of ozone in doses of approximately 33 ppm for 6 d or approximately 131 ppm for 8 d at low temperatures between 7.3 and 7.9 °C and high temperatures between 29.6 and 31.6 °C, respectively. Results from the previous study conducted at 20 °C were used in the data analysis.The result of the treatments was unaffected by the temperatures used in the study. Treatment with a high dose of ozone for 8 d led to full mortality in all stages of S. granarius and all stages of P. interpunctella except eggs at the high temperature. At the low dose for 6 d some survival was found in both species at all three temperatures. Thus, in the temperature range studied, we could not confirm that the effect of ozone on S. granarius and P. interpunctella is related to temperature.

Sampling stored‐product insect pests: a comparison of four statistical sampling models for probability of pest detection

Developing sampling strategies to target biological pests such as insects in stored grain is inherently difficult owing to species biology and behavioural characteristics. The design of robust sampling programmes should be based on an underlying statistical distribution that is sufficiently flexible to capture variations in the spatial distribution of the target species. Comparisons are made of the accuracy of four probability-of-detection sampling models - the negative binomial model,(1) the Poisson model,(1) the double logarithmic model(2) and the compound model(3) - for detection of insects over a broad range of insect densities. Although the double log and negative binomial models performed well under specific conditions, it is shown that, of the four models examined, the compound model performed the best over a broad range of insect spatial distributions and densities. In particular, this model predicted well the number of samples required when insect density was high and clumped within experimental storages. This paper reinforces the need for effective sampling programs designed to detect insects over a broad range of spatial distributions. The compound model is robust over a broad range of insect densities and leads to substantial improvement in detection probabilities within highly variable systems such as grain storage.

Radio frequency selective heating of stored-grain insects at 27.12 MHz: A feasibility study

The feasibility of radio frequency (RF) selective heating as a disinfestation technique was investigated, considering rusty grain beetle in bulk wheat samples at 27.12 MHz. Although pesticides and fumigants are the most commonly used methods for controlling insects in postharvest products such as grains, nuts, and fruits, they pose a direct threat to human health and the environment. In this work, power dissipation factors and the rate of increase of temperature in the insect bodies and wheat kernels were considered to assess the effectiveness of the proposed method. Dielectric and other physical properties of the insect and wheat were measured, and the electric field intensities in the system were estimated using an electromagnetic model. The host grain at three levels of moisture contents, 12%, 15%, 18% wet weight basis, were included to cover a wide range of grain storage scenarios, and the dielectric properties were measured at temperatures between 15 °C and 75 °C. The ratios of electric field intensity (Ei2/Eg2) and dielectric loss factor (εi″/εg″) within the insect bodies to that in grain kernels ranged from 0.13 to 0.76 and from 8.61 to 169.93 respectively. The latter had a significant effect on insect-to-wheat power absorption factor, Pig, which varied between 5 and 40. The relative rate of increase of temperature for insect-to-wheat was directly related to Pig, but inversely related to the product of insect/grain specific heat and density, which varied between 0.89 and 1.33, and was therefore almost identical to Pig, and ranged from 6.47 to 29.6. This large relative rate of increase of temperature in insect bodies compared to wheat may have potential benefits in heating the insects selectively with radio frequency energy to their lethal temperature while keeping the host grain at moderate temperature, and therefore minimising or eliminating adverse effects on its physicochemical properties.

Can Ozone be a New Control Strategy for Pests of Stored Grain?

Ozone (O3) is a strong oxidant with a long history of safe use in many fields. Researches have been recently focused on the application of O3 as a fumigant to control stored-grain insects and microorganisms and to reduce mycotoxins. This review found the following facts: (1) O3 significantly suppressed insect populations at ≤50 ppm with 4 days treatment; (2) to eradicate insect infestation, >135 ppm with more than 8 days treatment would be required; (3) O3 at 50 ppm with 3 days treatment reduced 63 % of stored fungi; (4) O3 at 5–30 ppm could reduce mycotoxin contamination; however, high concentration and long treatment time were required to eliminate mycotoxins; (5) application of O3 at doses that were sufficient for the effective disinfestation of grain might affect qualities of grain; and (6) O3 at 47–106 ppm could noticeably damage equipment in 2 months by corrosion. Based on these facts, we recommended that ≤50 ppm O3 should be used in the stored-grain industry and its potential method of application was also analyzed.