Granary trial of protein-enriched pea flour for the control of three stored-product insects in barley

A granary trial was conducted to evaluate the efficacy of protein-enriched pea flour against three common stored-grain insects, Sitophilus oryzae (L.), Tribolium castaneum (Herbst), and Cryptolestes ferrugineus (Stephens). Six 30-t farm granaries were filled with approximately 11 t of barley. The barley was either not treated, treated with protein-enriched pea flour at 0.1% throughout the entire grain mass, or treated at 0.5% throughout the top half of the grain mass. Adult insects were released in screened boxes (two insects per kilogram barley for S. oryzae and T. castaneum 1.4 insects per kilogram barley for C. ferrugineus). Barley was sampled four times during the 70-d trial. The number and mortality of adults and emerged adults in the samples were noted. Four kinds of traps, flight, surface-pitfall, probe-pitfall, and sticky-bar, were placed at different locations in the granaries to estimate the movement of insects. The 0.1% protein-enriched pea flour treatment reduced adult numbers of S. oryzae by 93%, T. castaneum by 66%, and C. ferrugineus by 58%, and reduced the emerged adults by 87, 77, and 77%, respectively. Treating the top half of the barley with 0.5% protein-enriched pea flour had similar effects as treating the entire grain mass with 0.1% pea-protein flour. However, the top-half treatment failed to prevent insects from penetrating into the untreated lower layer. Differences between traps are discussed.     

Time-mortality relationships for Tribolium castaneum (Coleoptera: Tenebrionidae) life stages exposed to elevated temperatures

The use of elevated temperatures (> or = 40-60 degrees C) or heat treatments for managing insects in food-processing facilities is a viable alternative to space fumigation with methyl bromide. Quantitative data are lacking on the responses of life stages of the red flour beetle, Tribolium castaneum (Herbst), an important pest of food-processing facilities worldwide, to elevated temperatures used during heat treatments. We determined time-mortality relationships for eggs, young (neonate) larvae, old larvae, pupae, and adults of T. castaneum, exposed to constant temperatures of 42, 46, 50, 54, 58, and 60 degrees C. Generally, mortality of each stage increased with an increase in temperature and exposure time. Young larvae were the most heat-tolerant stage, especially at temperatures > or = 50 degrees C. Exposure for a minimum of 7.2 h at > or = 50 degrees C was required to kill 99% of young larvae, whereas the other stages required < or = 1.8 h. Heat treatments that control young larvae should control all other stages of T. castaneum, and young larvae should be used as test insects to evaluate efficacy against T. castaneum during an actual facility heat treatment. These results provide the basis for successful use of elevated temperatures for management of T. castaneum life stages associated with food-processing facilities.     

Susceptibility of Tribolium castaneum (Coleoptera: Tenebrionidae) life stages to flameless catalytic infrared radiation

The susceptibility of various life stages of the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), a pest of stored wheat, Triticum aestivum L., to flameless catalytic infrared radiation in the 3-7-microm range was evaluated in the laboratory. Immature stages were collected from flour infested with T. castaneum adults only for 1 d. Stages collected after 1 d represented eggs (collected on day 0); those collected after 7, 14, and 21 d from day 0 represented larvae in different developmental stages, whereas those collected after 24 d represented pupae. Adults (2 wk old) were collected after 42 d. Each of these stages was exposed for 45 or 60 s in 113.5 or 227.0 g of wheat at a distance of 8.0 or 12.7 cm from a bench top infrared emitter. The mean temperatures attained during exposures were measured continuously using a noncontact infrared thermometer connected to a computer. The mean grain temperatures attained increased with an increase in exposure time and were inversely related to distance from the emitter. Grain quantity least influenced mean temperatures attained. Pupae were the least susceptible stage and larvae collected after 7 d were the most susceptible stage. Variation in probability of death of various life stages decreased with an increase in mean grain temperatures attained. All life stages were killed after a 60-s exposure at a distance of 8.0 cm from the emitter in 113.5 g of wheat, where the mean +/- SE temperatures attained ranged from 107.6 +/- 1.2 to 111.4 +/- 0.5 degrees C. Our laboratory results using small grain quantities and short exposure times showed that flameless catalytic infrared radiation can be a valuable tool for managing insects in stored organic and nonorganic wheat.     

Effects of temperature and exposure time on mortality of stored-product insects exposed to low pressure.

The prospects of using low pressure that creates a low-oxygen atmosphere to control stored-product insects were investigated in the laboratory. Eggs, larvae, and pupae of Tribolium castaneum (Herbst), Plodia interpunctella (Hübner), and Rhyzopertha dominica (F.) were exposed to 32.5 mmHg in glass chambers at 25, 33, 37, and 40 degrees C for times ranging from 30 min to 144 h. Time-mortality data were subjected to probit analyses and lethal dose ratios were computed to determine differences in lethal time (LT) values among all species-life stage combinations across the four temperatures. Eggs of each species were the life stage most tolerant to low pressure. Pupae of T. castaneum and R. dominica were more tolerant to low pressure than larvae. In all life stages, mortality increased with increasing exposure time to low pressure and also with increasing temperature. Immature stages of R. dominica were more tolerant to low pressure than immature stages of the other two species. The LT99 for R. dominica eggs was 176.32 h at 25 degrees C and that for P. interpunctella eggs was 28.35 h at the same temperature. An increase in temperature to 33 degrees C resulted in a LT99 < of 85.98 h for R. dominica and 6.21 h for P. interpunctella. Higher temperatures resulted in further significant reduction in lethal time values. Low pressure represents a simple, nonchemical alternative to fumigants such as methyl bromide and phosphine for controlling pests of stored-products or other commodities.     

Cytogenetic effects of microwave irradiation on male germ cells of the mouse

Hybrid male mice were exposed to 2.45 GHz microwaves for 30 min/day, 6 days a week for two consecutive weeks at power densities of 1.0, 100 or 400 W m-2, with sham-exposed controls. Rectal temperatures before and after exposure were measured on days 1, 6 and 12. Measurements made on day 1 were treated with caution because of heterogeneity in rectal temperatures taken before exposure between the groups of mice given different treatments. On days 6 and 12, rectal temperatures rose by approximately 1 degree C in mice sham exposed, or exposed to 1 W m-2 or 100 W m-2. Only in the group of mice exposed to 400 W m-2 was the mean rise in rectal temperature during exposure (about 3 degrees C) significantly increased above the sham value. In groups killed 2-3 days after treatment (mainly meiotic exposure) frequencies of chromosome aberrations in spermatocytes showed no significant heterogeneity although the highest frequency of 1.5 per cent was at the highest (400 W m-2) power density. Another group killed 30 days after 100 W m-2 exposures (spermatogonial sampling) showed no significant increase over controls in chromosome aberration frequency. There was a small but significant increase in sperm count with increasing power density in mice killed 12-13 days after exposure, but a non-significant one in those exposed as spermatogonia (killed 41 days later). Thus effects were markedly less severe than those reported previously by Manikowska-Czerska et al. (1985) with a very similar radiation regime and were probably caused by the temperature enhancement.     

Comparative estimation of the effects of continuous and intermittent cyclical microwave radiation on the behavior of rats in the extraordinary situation

Research has been carried out to investigate the effects of pulsed microwave exposure without pause (7 GHz, 400 pps, 100 microseconds, 70-150 mW/cm2, exposure 10 min) and pulsed interrupted cyclical microwave exposure (5 min exposure--4 min pause--5 min exposure) on learned behaviors of rats in the paradigm of extraordinary situation (the rescue of the life). It was shown that reductions in conditioned behavior after acute pulsed microwave exposure occurred at SAR of 21 W/kg (100 mW/cm2) and after cyclical pulsed microwave exposure at SAR of 28.4 W/kg (135 mW/cm2).     

Toxicity of propylene oxide at low pressure against life stages of four species of stored product insects

The relative toxicity of propylene oxide (PPO) at a low pressure of 100 mm Hg to four species of stored product insect at 30 degrees C over a 4-h exposure period was investigated. PPO at 100 mm Hg was toxic to all four species tested: Tribolium castaneum (Herbst), Plodia interpunctella (Hübner), Ephestia cautella (Wlk.), and Oryzaephilus surinamensis (L.). There were differences in susceptibility between the life stages of the tested insect species. Mortality tests on all life stages of the insects resulted in LD99 values ranging from 4.7 to 26.1 mg/liter. The pupal stage of E. cautella, O. surinamensis, and T. castaneum was the most tolerant stage with LD99 values of 14.4, 26.1, and 25.7 mg/liter, respectively. For P. interpunctella, the egg stage was most tolerant, with a LD99 value of 15.3 mg/liter. Generally, PPO at 100 mm Hg was more toxic to P. interpunctella and E. cautella than to O. surinamensis and T. castaneum. A 99% mortality of all life stages of the tested species was achieved at a concentrations x time product of 104.4 mg h/liter. These findings indicate that a combination of PPO with low pressure can render the fumigant a potential alternative to methyl bromide for rapid disinfestation of commodities.     

Different effects of microwave energy and conventional heat on the activity of a thermophilic beta-galactosidase from Bacillus acidocaldarius

The effect of microwave (f = 10.4 GHz) irradiation on a thermostable enzyme was experimentally tested, showing that irreversible inactivation is obtained. Enzymatic solutions (500 microliters, with concentrations between 10-100 micrograms/ml) were exposed at 70 degrees C, at SAR levels of 1.1 and 1.7 W/g for 15, 30, 45, or 60 min, and their activity was compared to that of a sample heated in a water bath at the same temperature. The residual activity of the exposed samples depends on enzyme concentration, microwave power level, and exposure time; activity was reduced to 10% in 10 micrograms/ml solutions treated at 1.7 W/g for 60 min. Microwave effects disappeared at concentrations above 50 micrograms/ml. These results were not found following water bath heating at the same temperature and durations.     

The effects of microwave radiation on avian dominance behavior

Seventeen birds from 12 flocks were exposed to microwave radiation under various combinations of power density and duration; three birds from two additional flocks served as sham-exposed controls. Experiments were conducted outdoors at Manomet, Massachusetts (41°56′N, 70°35′W) under normal winter ambient temperatures. Although irradiated birds maintained their positions within a flock hierarchy with one exception, some appeared to have a change in their level of aggression after exposure.     

Autoimmune processes after long-term low-level exposure to electromagnetic fields (experimental results) part 5. Study of the influence of blood serum from rats exposed to low-level electromagnetic fields on pregnancy and fetal and offspring development

The work evaluates the possible adverse effects on pregnancy and fetal and offspring development arising from the injection of blood serum from rats exposed to microwaves at a power density of 500 μW/cm² into intact female rats. The study is performed on 59 pregnant Wistar rats. Intrauterine mortality, embryo and fetal body weights, and placenta weight are used for the evaluation of embryo and fetal development. Generally accepted integral and specific parameters are used for the evaluation of the postnatal development of offspring during the first 30 days of life. It is shown that injection of blood serum from rats subjected to long-term RF exposure at 500 μW/cm² into intact rats on the tenth day of pregnancy results in adverse effects on fetal and offspring development. Higher total in utero and postnatal mortality, as well as delayed offspring development, are recorded.     

Enhanced efficacy of Beauveria bassiana for red flour beetle with reduced moisture

Red flour beetle, Tribolium castaneum (Herbst), is a major pest of stored and processed grains that is tolerant of Beauveria bassiana (Balsamo) Vuillemin under most conditions. Laboratory assays demonstrated that desiccating conditions improved the efficacy of the fungus. For T. castaneum larvae exposed to B. bassiana at different vapor pressure deficits (VPDs), the LC50 potency ratios were 2.3 for 2.42 kPa and 3.9 for 3.31 kPa compared with 1.06 kPa. There were significant effects of moisture on B. bassiana-associated mortality even with brief exposure to low VPD before or at the beginning of exposure to fungus. When T. castaneum larvae were held at 3.31 kPa 1 d before exposure to B. bassiana and/or in the first 1 or 2 d of exposure to the fungus, there was significantly greater mortality for all of the low moisture treatments than occurred with continuous incubation at 1.06 kPa. B. bassiana efficacy for adult T. castaneum was significantly better for VPDs of 3.56 or 3.78 than 1.06 kPa. Weight gain over 4 d of incubation with moisture held constant was significantly less at a VDP of 3.31 kPa than at 1.87 or 1.06 kPa. Treatment with fungus did not affect weight gain significantly. There was no significant difference in larval water content among treatments.     

The effect of repeated microwave irradiation on the frequency of sex-linked recessive lethal mutations in Drosophila melanogaster

The effect of repeated microwave irradiation (2375 MHz, CW) on mutagenic changes in Drosophila melanogaster was investigated. Oregon-R males were exposed to sublethal doses of microwaves (15 W/cm2 for 60 min, 20 W/cm2 for 10 min, and 25 W/cm2 for 5 min) for 5 days. The Muller-5 cross was used to detect sex-linked recessive lethal mutations. 4 lethals were found in treated groups but their frequency was not significantly different from that of the control group. No cumulative effect of repeated exposures on the mortality of the treated males was observed; on the contrary, their mortality decreased with the number of exposures. Irradiation did not affect the sex ratio of the F1. A significant decrease in the number of F1 offspring was noted in the group exposed to the power density of 15 W/cm2. A negative thermal effect of microwaves on male germ cells was probably manifested by this long exposure.     

Thermal and Nonthermal Effects of Discontinuous Microwave Exposure (2.45 Gigahertz) on the Cell Membrane of Escherichia coli

The aim of this study was to investigate the effects on the cell membranes of Escherichia coli of 2.45-GHz microwave (MW) treatment under various conditions with an average temperature of the cell suspension maintained at 37°C in order to examine the possible thermal versus nonthermal effects of short-duration MW exposure. To this purpose, microwave irradiation of bacteria was performed under carefully defined and controlled parameters, resulting in a discontinuous MW exposure in order to maintain the average temperature of the bacterial cell suspensions at 37°C. Escherichia coli cells were exposed to 200- to 2,000-W discontinuous microwave (DW) treatments for different periods of time. For each experiment, conventional heating (CH) in a water bath at 37°C was performed as a control. The effects of DW exposure on cell membranes was investigated using flow cytometry (FCM), after propidium iodide (PI) staining of cells, in addition to the assessment of intracellular protein release in bacterial suspensions. No effect was detected when bacteria were exposed to conventional heating or 200 W, whereas cell membrane integrity was slightly altered when cell suspensions were subjected to powers ranging from 400 to 2,000 W. Thermal characterization suggested that the temperature reached by the microwave-exposed samples for the contact time studied was not high enough to explain the measured modifications of cell membrane integrity. Because the results indicated that the cell response is power dependent, the hypothesis of a specific electromagnetic threshold effect, probably related to the temperature increase, can be advanced.     

Rhesus monkey behavior during exposure to high-peak-power 5.62-GHz microwave pulses

Limits on the exposure to high-peak-power, short-duration microwave pulses have only recently been adopted. Additional data, however, are needed to understand the effects that may be produced by exposure to high-peak-power pulsed microwaves. Four male rhesus monkeys (Macaca mulatta) were trained on an operant task for food pellet reward to investigate the behavioral effects of very high-peak-power 5.62 GHz microwaves. The operant task required monkeys to pull one plastic lever on a variable interval schedule (VI-25 s) and then respond to color signals and pull a second lever to obtain food. The monkeys were conditioned to perform a color discrimination task using one of three colors displayed by a fiber-optic cable. A red signal was the discriminative stimulus for responding on the first lever. A response on the second lever when a green signal was presented (1 s duration) delivered a food pellet. If a response on the second lever was made in the presence of a white signal, a 30-s timeout occurred. While performing the behavioral task, the monkeys were exposed to microwave pulses produced by either a military radar (FPS-26A) operating at 5.62 GHz or the same radar coupled to a Stanford linear energy doubler (SLED) pulse-forming device (ITT-2972) that enhanced peak power by a factor of nine by adding a high power pulse to the radar pulse. The effects of both types of pulses were compared to sham exposure. Peak field power densities tested were 518, 1270, and 2520 W/cm² for SLED pulses and 56, 128, and 277 W/cm² for the radar pulses. The microwave pulses (radar or SLED) were delivered at 100 pps (2.8 μs radar pulse duration, ≈ 50 ns SLED pulse duration) for 20 min and produced averaged whole-body SARs of 2,4, or 6 W/kg. Compared to sham exposures, significant alterations of lever responding, reaction time, and earned food pellets occurred during microwave exposure at 4 and 6 W/kg but not 2 W/kg. There were no differences between radar or SLED pulses in producing behavioral effects. ©1994 Wiley-Liss, Inc.

1 This is a US Government work and, as such, is in the public domain in the United States of America.

     

Heat transfer analysis of Staphylococcus aureus on stainless steel with microwave radiation

Staphylococcus aureus (NCTC 6571; Oxford strain) on stainless steel discs was exposed to microwave radiation at 2450 MHz and up to 800 W. Cell viability was reduced as the exposure time increased, with complete bacterial inactivation at 110 s, attaining a temperature of 61.4 degrees C. The low rate of temperature rise, RT, of the bacterial suspension as compared with sterile distilled water or nutrient broth suggests a significant influence of the microwave sterilization efficacy on the thermal properties of the micro-organisms. The heat transfer kinetics of thermal microwave irradiation suggest that the micro-organism has a power density at least 51-fold more than its surrounding liquid suspension. When the inoculum on the stainless steel disc was subjected to microwave radiation, heat conduction from the stainless steel to the inoculum was the cause of bacteriostasis with power absorbed at 23.8 W for stainless steel and 0.16 W for the bacteria-liquid medium. This report shows that the microwave killing pattern of Staph. aureus on stainless steel was mainly due to heat transfer from the stainless steel substrate and very little direct energy was absorbed from the microwaves.     

Toxicity of diatomaceous earth to red flour beetles and confused flour beetles (Coleoptera: Tenebrionidae): effects of temperature and relative humidity

Red flour beetles, Tribolium castaneum (Herbst), and confused flour beetles, Tribolium confusum (DuVal), were exposed for 8-72 h to diatomaceous earth (Protect-It) at 22, 27, and 32 degrees C and 40, 57, and 75% RH (9 combinations). Insects were exposed to the diatomaceous earth at 0.5 mg/cm2 on filter paper inside plastic petri dishes. After exposure, beetles were held for 1 wk without food at the same conditions at which they were exposed. Mortality of both species after initial exposure was lowest at 22 degrees C but increased as temperature and exposure interval increased, and within each temperature decreased as humidity increased. With 2 exceptions, all confused flour beetles were still alive after they were exposed at 22 degrees C, 57 and 75% RH. Mortality of both species after they were held for 1 wk was greater than initial mortality for nearly all exposure intervals at each temperature-humidity combination, indicating delayed toxic effects from exposure to diatomaceous earth. For both species, the relationship between mortality and exposure interval for initial and 1-wk mortality was described by linear, nonlinear, quadratic, and sigmoidal regression. Mortality of confused flour beetles was lower than mortality of red flour beetles exposed for the same time intervals for 46.7% of the total comparisons at the various temperature-relative humidity combinations.     

Effects of whole body microwave exposure on the rat brain contents of biogenic amines.

The effects of whole body microwave exposure on the central nervous system (CNS) of the rat were investigated. Rats weighing from 250 to 320 g were exposed for 1 h to whole body microwave with a frequency of 2450 MHz at power densities of 5 and 10 mW.cm-2 at an ambient temperature of 21-23 degrees C. The rectal temperatures of the rats were measured just before and after microwave exposure and mono-amines and their metabolites in various discrete brain regions were determined after microwave exposure. Microwave exposure at power densities of 5 and 10 mW.cm-2 increased the mean rectal temperature by 2.3 degrees C and 3.4 degrees C, respectively. The noradrenaline content in the hypothalamus was significantly reduced after microwave exposure at a power density of 10 mW.cm-2. There were no differences in the dopamine (DA) content of any region of the brain between microwave exposed rats and control rats. The dihydroxyphenyl acetic acid (DOPAC) content, the main metabolite of DA, was significantly increased in the pons plus medulla oblongata only at a power density of 10 mW.cm-2. The DA turnover rates, the DOPAC:DA ratio, in the striatum and cerebral cortex were significantly increased only at a power density of 10 mW.cm-2. The serotonin (5-hydroxytryptamine, 5-HT) content in all regions of the brain of microwave exposed rats was not different from that of the control rats. The 5-hydroxyindoleacetic acid (5-HIAA) content in the cerebral cortex of microwave exposed rats was significantly increased at power densities of 5 and 10 mW.cm-2.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mortality of eggs of stored-product insects held under vacuum: effects of pressure, temperature, and exposure time

Low pressure applied to a commodity creates a low-oxygen atmosphere that can be effective to control stored-product insects. Previous work determined that eggs of several species of stored-product insects were among the most tolerant life stages to low pressure. The current study was conducted to determine the mortality of eggs in response to various pressures, temperatures, and exposure times. An initial experiment determined that the sensitivity of eggs to vacuum varied with their age. Eggs of Plodia interpunctella (Hübner) were most sensitive to low pressure when they were 3 or 48 h old, whereas those of Rhyzopertha dominica (F.) were most sensitive at 12 and 120 h of age. In subsequent experiments, eggs of Cadra cautella (Walker), P. interpunctella, R. dominica, and Tribolium castaneum (Herbst) were exposed to pressures of 50, 75, 100, 200, and 300 mmHg in glass chambers at 5, 15, 22.5, 30, and 37.5 degrees C for times ranging from 12 to 168 h. Time-mortality data were subjected to probit analyses and lethal dose ratios were computed to determine differences in lethal time values among species across the 25 low pressure-temperature combinations for each species. In all four species the mortality of eggs increased with increasing exposure time and temperature. Low temperatures and high pressures were the least effective conditions for killing eggs, compared with high temperatures combined with low pressures in all species investigated. These results provide important guidelines for developing treatment schedules for disinfestation of commodities on a commercial scale.     

Effect of microwave radiation on inactivation of Clostridium sporogenes (PA 3679) spores.

Three techniques for studying effects of microwave radiation on microorganisms were introduced. Spores of Clostridium sporogenes (PA 3679) were chosen as a test organism because the kinetic parameters for thermal inactivation are well known and because of the importance of the genus Clostridium to the food industry. For the first technique, a specially designed kinetics vessel was used to compare inactivation rates of microwave-heated and conventionally heated spores at steady-state temperatures of 90, 100, and 110 degrees C. Rates were found to be similar at the 95% confidence level. The second and third techniques were designed to study the effect of relatively high power microwave exposure at sublethal temperatures. In the second approach, the suspension was continuously cooled via direct contact with a copper cooling coil in a well-mixed vessel, outside the microwave oven. The suspension was pumped through a Teflon loop in the oven, where it continuously absorbed approximately 400 W of microwave power. Inactivation occurred in both irradiated and unirradiated samples. It was suspected that copper ions entered the suspension from the copper coil and were toxic to the spores. The fact that the results were similar, however, implied the absence of nonthermal microwave effects. In the third approach, the copper coil was replaced with a silicone tubing loop in a microwave transparent vessel. The suspension was continuously irradiated at 150 W of microwave power. No detectable inactivation occurred. Results indicated that the effect of microwave energy on viability of spores was indistinguishable from the effect of conventional heating.     

Fluorescence depolarization studies of the phase transition in multilamellar phospholipid vesicles exposed to 1.0-GHz microwave radiation

The phase transition in multilamellar dimyristoylphosphatidylcholine (DMPC) vesicles was studied during exposure to continuous wave 1.0-GHz microwave radiation. Fluorescence depolarization measurements using a lipid-seeking molecular probe, diphenylhexatriene (DPH). were performed as a function of temperature. Semilog plots of microviscosity versus temperature illustrate the phase transition which shows a 5°C shift when the vesicles are treated with chloroform as a positive control. No shift of the phase transition was found during exposure to microwave radiation at specific absorption rates between 1 and 30 W/kg. Samples were exposed in a rectangular transmission line (TEM cell), and specific absorption rates were calculated from electrical measurements of incident, reflected, and transmitted power. Samples were exposed to increasing intensities of radiation, while the temperature was maintained at either 23.5 or 25.5 °C; these temperatures represented the two ends of the phase transition region for these vesicles. No statistically significant difference was found between exposed and control samples. These results are in contrast to those of others using laser Raman spectroscopy to measure the phase transition in similar multilamellar vesicles exposed to microwave radiation.