Stored grain pest prevalence and insecticide resistance in Egyptian populations of the red flour beetle Tribolium castaneum (Herbst) and the rice weevil Sitophilus oryzae (L.)

As a consequence of the widespread use of insecticides against insect pests in grain warehouses and in the food industry, insecticide resistance has greatly increased among these species all over the world. Nonetheless, insecticide resistance in stored grain insects in Egypt was little studied. Therefore, our study aimed to forecast infestation risks and determine the insecticide resistance level in Egyptian populations of the main insect pests of stored grains. To achieve this goal, we surveyed the populations of stored-product insects in wheat in two different sites in the Alexandria governorate (Egypt) between June and August 2017. Moreover, insecticide resistance levels in Egyptian populations of Tribolium castaneum (Herbst) and Sitophilus oryzae (L.) collected from wheat storage facilities (granaries and flour mills) in Alexandria governorate were also determined. Three contact insecticides, namely malathion, pirimiphos-methyl and cypermethrin, were tested. Tarsal contact bioassays on filter paper were carried out on adults following FAO methods and concentration-mortality lines were estimated to determine the resistance ratios for each insecticide and population. The data from the monitoring of insects revealed that T. castaneum and S. oryzae were the most common species infesting wheat in both Alexandria granaries and mills. Populations of S. oryzae were generally more resistant to malathion than the populations of T. castaneum. However, T. castaneum populations were more resistant to pirimiphos-methyl than the S. oryzae populations. Both populations of T. castaneum and S. oryzae were susceptible to cypermethrin. The detected levels of insecticide resistance indicate that this phenomenon takes place and should be a concern in Egyptian populations of T. castaneum and S. oryzae requiring monitoring and design of resistance management practices.     

Fitness in a malathion resistant Tribolium castaneum strain; feeding,growth and digestion

Extensive historical use of malathion in grain stores has led to the universal development of resistant strains of the red flour beetle, Tribolium castaneum Herbst. Adaptation to insecticide stress often reduces general fitness. To investigate non-defensive attributes physiological and biochemical properties (that may underlie fitness) of a field-derived malathion-resistant strain (larval resistance factor of 490) were measured against those of a susceptible strain and also with susceptible T. confusum. Further inhibition in vitro of gut proteolysis was determined for the resistant and susceptible strains of T. castaneum.The weights of whole gut tracts of the susceptible T. castaneum strain and T. confusum were similar but the resistant strain had significantly lower weight and width of whole gut tract. The gut of the resistant strain had more, and more intense, electrophoretic protein staining bands. Food consumed through the life cycle was significantly less for the resistant strain. Inhibitors for cysteine proteases had less effect in vitro in the resistant strain than in the susceptible strain. An inhibitor for serine proteases had almost no effect on proteolysis in the resistant strain.The reduced gut dimensions and food consumed, together with lower larval protein, appear to indicate a fitness cost that may be associated with malathion resistance. However, this may be offset by enhanced gut proteins and a relative greater protein content of the adult stage. The latter may be related to the reported increased reproductive capacity of the resistant adult and consequent superior fitness, compared to the susceptible. The lowered response of the resistant strain to cysteine and serine protease inhibitors may interact with adaptations to dietary inhibition in cases where resistant strains need managing, if this result is confirmed to be widespread.     

Assessment of eight rice cultivars flour for feeding resistance to Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae)

Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) is an important pest of processed stored grains worldwide. Study of life history, feeding efficiency and digestive function of an insect on different host cultivars can indicate their resistance for the insect's population increase. Due to the economic importance of T. castaneum on stored rice flour, this research was aimed to investigate the life history, feeding indices and digestive enzymatic activity of T. castaneum on flour of eight rice cultivars (Ali-Kazemi, Dom-Siah, Fajr, Gilaneh, Gohar, Hashemi, Khazar, and Neda). A delay in the developmental time of T. castaneum was detected on cultivar Gohar. The lowest fecundity and egg fertility were observed on cultivar Gohar. Feeding indices of fourth instar larvae were the lowest on cultivars Gohar and Neda. The amylolytic activity of fourth instar larvae was the highest on cultivars Hashemi, Dom-Siah, Ali-Kazemi and Gilaneh, and the lowest on cultivar Gohar. Also, the highest and lowest proteolytic activities of fourth instar larvae were on cultivars Khazar and Hashemi, respectively. Significant correlations were detected between tested parameters of T. castaneum with starch and protein value of examined cultivars flour. The results of cluster analysis indicate that Dom-Siah, Hashemi and Ali-Kazemi are relatively susceptible cultivars, and other tested cultivars, especially Gohar, are relatively resistant cultivars for feeding of T. castaneum. The resistant rice cultivars could be further evaluated to identify secondary biochemicals that contribute to T. castaneum resistance.     

Response and genetic analysis of malathion-specific resistant Tribolium castaneum (Herbst) in relation to population density

Extensive use of malathion for pest control on stored cereals has resulted in worldwide resistance in red flour beetles, Tribolium castaneum. In this paper we investigate population density effects on the malathion-specific resistance in PRm, a strain from the Philippines, in an integrated resistance management framework. Two populations of malathion-specific resistant (PRm) and a malathion-susceptible strain of T. castaneum were bred at different densities: low (4 adults/g) and high (12 adults/g) density on wheat plus brewer's yeast in the laboratory. After eight generations, slopes of probit regression lines and LC₅₀ values were used to monitor the effect of insect rearing density on the progression of malathion-specific resistance. The LC₅₀ of the malathion-susceptible strain (Asm) did not change significantly during selection while LC₅₀s varied for both the high-density and low-density lines of PRm, the LC₅₀ of malathion ranged from 27.51 to 34.06 and from 21.14 to 29.39 μg malathion cm⁻² for high and low density, respectively.More than 33 generations were required to achieve a 10-fold increase of resistance for the low-density line compared to only 17 generations for the high-density line. Calculations from published formulae suggested that the malathion-specific resistance of both high- and low-density lines was under monofactorial control, with complete dominance.The data showed that environmental factors such as population density differences in insect rearing and development may influence the heritability of resistance. Furthermore, the variability in results published worldwide on resistance emphasises the need to standardize test conditions across laboratories.     

应用近红外光谱技术快速测定粳稻品种的直链淀粉含量

应用近红外光谱法以稻谷、糙米、精米、糙米粉和精米粉为扫描材料分别建立了粳稻直链淀粉含量的预测模型。结果表明采用光谱预处理的校正效果比不采用预处理的好,用偏最小二乘法(PLS)获得的粳稻稻谷、糙米、精米、糙米粉、精米粉的回归模型和交叉验证结果为:最优校正决定系数(R2)和交叉检验均方误差(RMSECV)分别为0.8136、2.74,0.8864、2.56,0.8915、2.59,0.9261、2.26,0.9505、1.83,粉碎性样品的误差比整粒样品的误差小。育种实践中,低世代可选用糙米、高世代可选用糙米粉或精米粉作为扫描样本测定稻米直链淀粉含量。     

Effect of Raw Material Preparation on Rice Vermicelli Quality

The physicochemical properties of high amylose rice flour prepared from wet milling and dry milling were examined and the rice vermicelli quality made from these flour samples was evaluated. The effect of flour particle size on rice vermicelli quality was also determined. The milling method affected chemical compositions and all physicochemical properties of the flour. A higher degree of starch damage occurred in drymilled flour. Rice vermicelli made from dry‐milled flour had higher cooking losses and softer texture than that made from wet‐milled flour and the commercial reference products. Flour particle size influenced both cooking and textural quality of rice vermicelli but did not influence the water absorption index. Flours with larger particle sizes gave vermicelli with higher cooking loss and less desirable texture than flours with smaller particle sizes. Flour with particle sizes less than 200 mesh produced acceptable vermicelli in terms of cooking and textural quality.     

Effect of diet on phosphine toxicity,rate of development and reproduction of the rice weevil Sitophilus oryzae (Linnaeus)

One of the loci responsible for strong phosphine resistance encodes dihydrolipoamide dehydrogenase (DLD). The strong co-incidence of enzyme complexes that contain DLD, and enzymes that require thiamine as a cofactor, motivated us to test whether the thiamine deficiency of polished white rice could influence the efficacy of phosphine fumigation against insect pests of stored grain. Three strains of Sitophilus oryzae (susceptible, weak and strong resistance) were cultured on white rice (thiamine deficient), brown rice or whole wheat. As thiamine is an essential nutrient, we firstly evaluated the effect of white rice on developmental rate and fecundity and found that both were detrimentally affected by this diet. The mean time to reach adult stage for the three strains ranged from 40 to 43 days on brown rice and 50–52 days on white rice. The mean number of offspring for the three strains ranged from 7.7 to 10.3 per female over a three day period on brown rice and 2.1 to 2.6 on white rice. Growth and reproduction on wheat was similar to that on brown rice except that the strongly resistant strain showed a tendency toward reduced fecundity on wheat. The susceptible strain exhibited a modest increase in tolerance to phosphine on white rice as expected if thiamine deficiency could mimic the effect of the dld resistance mutation at the rph2 locus. The strongly resistant strain did not respond to thiamine deficiency, but this was expected as these insects are already strongly resistant. We failed, however, to observe the expected synergistic increase in resistance due to combining thiamine deficiency with the weakly resistant strain. The lack of interaction between thiamine content of the diet and the resistance genotype in determining the phosphine resistance phenotype suggests that the mode of inhibition of the complexes is a critical determinant of resistance.     

Development of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) on rice milling components and by-products: Effects of diet and temperature

Development of Tribolium castaneum (Herbst), the red flour beetle, was assessed on different rice components and their various by-products (i.e., diets) commonly found in rice mills, in two separate experiments. In the first experiment, eggs did not develop through to the adult stage on rough rice hulls, paddy rice dust, and milled rice dust, while eggs developed to the adult stage to some extent on rice flour, milled whole kernels, brown rice, milled broken kernels, and bran. For the diets where development occurred, the lowest percentage was on brown rice, and adults that emerged on brown rice had smaller elytra compared to adults emerging on the other diets. In the second experiment, 1–2-day old neonates were exposed on the diets listed above and held at 22, 27, 32, and 37 °C. At all temperatures, development to the pupal and adult stages was slowest on rice flour. At 22 °C, development to those stages took about twice as long compared to development at 27 °C. As temperature increased developmental times were reduced. Even though neonates developed slowest on rice flour adult emergence rates were not affected. Predictive models were used to estimate potential population development on the diets. At 22 and 27 °C, adult size as measured by elytra length was greatest when they developed on bran, while body weight was generally lowest for adults that developed on brown rice. Results show that T. castaneum can utilize rice components and by-products produced during the rice milling process, although not all components or by-products were optimal for development, and emphasis should be placed on cleaning and sanitation to remove food sources to limit infestations. Mill managers can use these results to show the importance of sanitation, and potentially improve overall pest management programs inside the mill.     

Effects of milling on functional properties of rice flour

ABSTRACT:  A commercial long-grain rice flour (CRF) and the flours made by using a pin mill and the Udy mill from the same batch of broken second-head white long-grain rice were evaluated for their particle size and functional properties. The purpose of this study was to compare the commercial rice flour milling method to the pin and Udy milling methods used in our laboratory and pilot plant. The results showed that pin milled flour had more uniform particle size than the other 2 milled flours. The chalky kernels found in broken white milled rice were pulverized more into fines in both Udy milled flour and CRF than in the pin milled flour. The excessive amount of fines in flours affected their functional properties, for example, WSI and their potential usage in the novel foods such as rice breads (RB). The RB made from CRF collapsed more than loaves made from pin milled Cypress long-grain flours.     

Comparison between protein functional properties of two rice cultivars

The functional properties of proteins from a high-protein–content rice cultivar (Nutriar) were analyzed and compared with those from a usual Latin-American cultivar (El Paso 144). Isolates from brown and milled flours were prepared and their emulsifying, foaming, and hydration properties studied. The four isolates displayed a very low solubility within a wide range of moderate pH, but demonstrate a significantly higher solubility at extreme pHs (either high or low). Nutriar isolates had a significantly higher solubility and greater surface properties than El Paso 144 isolates. The Nutriar isolate from brown flour was more soluble at pH 9 than the other isolates and moreover showed the highest capacity for forming and stabilizing foams and emulsions. In contrast, the Nutriar isolate from milled rice exhibited a higher solubility and greater foaming properties at an acid pH. The surface properties and solubility were significantly correlated among the four samples. All four isolates exhibited good water-imbibition and water-holding capacities.     

The effect of oil content and insecticides on insects attacking rice bran

Ephestia cautella (Walker) was unable to survive on rice bran of less than 5 per cent oil content and even on bran with 10 per cent oil it developed slowly and mortality was high. Tribolium castaneum (Herbst) survived on rice brans with oil contents of 0–10 per cent but the mortality and time taken for development increased as the oil content decreased. Latheticus oryzae Waterhouse survived and bred better on de-oiled rice bran than T. castaneum.Adult T. castaneum and L. oryzae were placed on batches of de-oiled rice bran treated with 20 or 16 ppm malathion, 8 or 4 ppm pirimiphos methyl, 8 or 4 ppm phoxim or 6 or 3 ppm fenitrothion, and mortality assessments were made over a period of 8 weeks after treatment. In general L. oryzae was more susceptible to the insecticides than was T. castaneum. Phoxim at 8 ppm gave highest mortality of T. castaneum and phoxim and pirimiphos methyl, both at 8 ppm, were equally effective in causing the highest mortality of L. oryzae. Malathion at 20 ppm or 16 ppm gave high mortality of both insects initially but began to lose effectiveness after 31 days. Fenitrothion did not give adequate control of either species. Phoxim at 8 ppm was the most successful treatment in preventing breeding of both species.The highest level of insecticide residue found 50 days after treatment was 13·7 ppm for malathion initially at 20 ppm, and by this time the other insecticides had lost about 60 per cent of their initial residue levels.     

Susceptibility of varieties of stored rough rice to losses caused by storage insects

Losses caused by Sitophilus oryzae (L.), Rhyzopertha dominica (F.), and Sitotroga cerealella (Olivier) in 6 commercial varieties of rough rice from the Southern United States were assessed as weight loss of rough rice, loss of milling yield, and loss of monetary value. Over 3 insect generations, S. oryzae caused the least damage, probably because this species requires grains with gross hull defects and the proportion of such grains was relatively small. Damage attributable to S. cerealella or R. dominica was approximately equal. The varieties Vista and Lebonnet were the most susceptible and the variety Dawn the most resistant after 3 generations.     

Growth and development of Tribolium castaneum (Herbst) on rice flour and brown rice as affected by time and temperature

Tribolium castaneum (Herbst), the red flour beetle, is a cosmopolitan stored product insect that infests a variety of raw grains and processed grain products. Although this pest is prevalent in rice mills, there is a comparative lack of data on growth and development on rice by-products and fractions compared to other grains. In this study, ten mixed-sex adults were exposed on 200 g of either rice flour or brown rice, and populations were assessed after 2, 4, 6, 8, and 10 months at 22, 27, or 32 °C. At 22 °C, the number of adults, pupae and larvae on rice flour and brown rice remained low throughout the 12-month storage period. At 27 °C, the number of adults on rice flour increased to a maximum at 8 months, while adult populations on brown rice remained relatively constant from 2 to 10 months, with few pupae or larvae in the samples. At 32 °C, adult populations on rice flour and brown rice were constant after month 2, with low numbers of pupae and larvae. Adult predation could have accounted for low numbers of pupae and larvae. Using the original 10-month data, populations were projected for an additional 14 months to predict population patterns. Adult numbers showed an increase over time at all temperatures on rice flour and brown rice at 22 °C but numbers seemed to stabilize at 27 and 32 °C. For both diets at 27 and 32 °C, projected pupae and larvae numbers remained steady but low compared to adults. However, populations would not be expected to increase indefinitely because at some point the resources would become limited and populations would crash or decline. Results show T. castaneum can deplete fixed resources such as bags of rice flour or brown rice when temperatures equal or exceed 27 °C.     

Efficacy of methoprene for multi-year protection of stored wheat,brown rice,rough rice and corn

Hard red winter wheat, brown rice, rough rice, and corn were treated with the insect growth regulator (IGR) methoprene at rates of 1.25 and 2.5 ppm, held for 24 months at ambient conditions in buckets on the floor of a grain bin, and sampled every two months. Bioassays were done by exposing 10 mixed-sex adults of Rhyzopertha dominica (F.), the lesser grain borer, and Tribolium castaneum (Herbst), the red flour beetle, on wheat, R. dominica and Sitotroga cerealella (Oliver), the Angoumois grain moth, on brown rice and rough rice, and T. castaneum and S. cerealella on corn. Sample size for all commodities was about 80 g, and these samples were held for 3 months at 27°C-60% r.h. Both rates of the IGR completely suppressed adult progeny development of R. dominica with little resulting feeding damage, sample weight loss, or insect damaged kernels (IDK). Some adult progeny production of S. cerealella and resulting IDK occurred at both rates on rough rice, brown rice, and corn, but was far less than in untreated controls. There was little adult progeny production but some feeding damage caused by larval T. castaneum in the treated wheat and corn but again far less than in untreated control. Allowing continual exposure of parental adults on grains treated with an IGR, rather than exposing those parental adults for a short time period, may give more accurate evaluations of residual efficacy. Results show that methoprene used as a grain protectant will give residual control of stored product beetles for 24 months, but complete control of S. cerealella may require inclusion of a contact insecticide.     

小麦粉中虫卵的快速检测技术的研究与比较

为了建立一种快速检测小麦粉中昆虫虫卵的方法,比较研究了浮选法、尿酸检测法、几丁质检测法和染色法4种方法检测小麦粉中虫卵的效果及优缺点的比较。结果表明浮选法最高检出率为5.59%,不适用于虫卵检测;几丁质检测法只能证明虫卵中有几丁质,但无法定量;尿酸检测法中检测出的尿酸浓度与虫卵数成正相关,相关系数R2为0.998 6,最低检出限为0.1粒卵/g;利用溴甲酚绿和酸性品红将小麦粉染色的结果是溴甲酚绿将虫卵染成黄橙色,小麦粉染成褐绿色;酸性品红将虫卵和小麦粉都染成紫色,但小麦粉被染颜色更深。染色法虫卵检测率约为75%,初步可以用于小麦粉中虫卵的快速检测。随机取样的小麦粉检测与实际发生虫量比较发现尿酸检测法的检测率为73.3%,染色法的检测率为85%。说明了尿酸法和染色法可以初步用于小麦粉中昆虫虫卵的检测,其灵敏度和操作规范有待进一步优化和研究。     

Effect of damaged starch on acrylamide formation in whole wheat flour based Indian traditional staples, chapattis and pooris

Variation in acrylamide content of two Indian traditional products, chapatti and poori was observed with respect to the damaged starch content in whole wheat flour of different wheat varieties from which these products were prepared. Wheat cultivar ‘lokwan’ was milled by altering mill aperture, feed rate and moisture content to obtain whole wheat flour with damaged starch contents ranging from 6.23% to 28.12%. Acrylamide content of the chapatti and pooris prepared from such flours ranged from 12.5 to 65.5 μg/kg in chapatti, and 25.5 to 130.5 μg/kg in pooris. Impact of several additives showed 10 μmol/g flour citric acid, and 100 μmol/g flour calcium chloride to reduce acrylamide in pooris by approximately 54% and 72%, respectively, without altering the sensory analysis of the products.     

Detection of eggs of stored-product insects in flour with staining techniques

Chemical stains were investigated with the aim of developing a method for detecting eggs of stored-product insects in refined wheat flour (white flour), so that eggs and flour particles could be distinguished easily. Eggs of the rust-red flour beetle, Tribolium castaneum, the saw-toothed grain beetle, Oryzaephilus surinamensis and the rice moth, Corcyra cephalonica were detected by staining with 0.1% bromocresol green or 1:1 mixture of bromocresol green+0.5% orange G solution after acid digestion of the flour particles. In contrast to the standard AACC method of staining with iodine solution where both eggs and flour particles were stained brownish-yellow or yellow, bromocresol green alone or in mixture with orange G, differentially stained the insect eggs and the flour particles distinct orange and green, respectively. Eggs in flour could also be detected using 0.05% acid fuchsin but both eggs and flour particles were stained uniformly pink.     

Characterisation of Brown and Milled Yellow Rice and Development of an Expanded Snack

Brown rice and yellow milled rice were characterised in relation to milling properties, cooking, processing quality and microbial testing, and utilised to develop an expanded snack. The extrusion process was done in a Mapimpianti single screw cooker-extruder. A flour sample feed rate of 70 g (dry matter) min⁻¹ was maintained by varying the force-feeder speed. A screw speed of 150 rev min⁻¹ and a die with 20 die-nozzle orifices (2 mm in dia) were used. The die zone was heated at 110°C by electrical resistance. Compressed air was circulate around the barrel to maintain precise control of the temperature. The moisture content of the samples was 120, 150 and 180 g kg⁻¹. The grains were classified as long-thin with an average size of 2·13 mm×6·79 mm. The milling yields obtained in the laboratory with paddy rice were 700 g kg⁻¹ brown rice and 600 g kg⁻¹ milled rice. Brown rice and yellow milled rice had similar amylose contents, 225 and 256 g kg⁻¹, respectively. Gel consistency was soft with low gelatinisation temperature (63–68°C) for both samples. Field fungi such as Helminthosporium oryzae and storage fungi as Aspergillus spp were present in paddy, yellow milled and commercial rice. Helminthosporium oryzae was not present in extruded products. The extruded products showed low density and a high degree of expansion, with the optimum degree of expansion obtained in flours processed with moisture at 150 g kg⁻¹ in both milled and brown rice. The highest values for water solubility index were obtained with flours from milled yellow rice and none of the extruded products showed significant differences on water absorption index. Sensory analyses carried out on the snack products showed them to be acceptable, with the bent acceptance for products made from milled yellow rice processed with 150 g kg⁻¹ moisture.     

Insect development in milled rice: Effects of variety,degree of milling,parboiling and broken kernels

Parboiled milled rice was less suitable than raw milled rice for progeny production by Plodia interpunctella (Hübner), Cadra cautella (Walker), Lasiodermaserricorne (F.), Tribolium confusum Jacquelin duVal, Rhyzopertha dominica (F.), Sitophilus oryzae (L.) and Oryzaephilus surinamensis (L.). The variety ‘Dawn’ was less suitable than ‘Belle Patna’, ‘Nato’ or ‘Bluebelle’ for all species except O. surinamensis and L. serricorne. An increase in milling rendered the rice less suitable for these seven species and for Tribolium castaneum (Herbst). Broken kernels did not significantly change the number of progeny from any of the species developing during a test period.     

Assessment of Rhyzopertha dominica (F.) progeny and feeding damage on rice dried with infrared radiation

Infrared radiation (IR) is a method of drying grains that eliminates insect and microbial pests. It is unknown if IR could cause grains to be more susceptible to insects. Thus, the effects of IR on Rhyzopertha dominica development and feeding damage using long-grain rice varieties, Clearfield XL745 (hybrid) and CL152 (pureline), were examined. Rough rice was dried with three IR intensities: 2.15, 2.83, and 10.84 kW/m². The number of progeny developed, feeding damage, and frass weight after IR-drying were compared with air-drying methods for rough rice and rice milled to brown rice after drying. Since R. dominica develop internally, X-ray technology was used to examine internal progeny and feeding damage. Progeny development and kernel damage appeared to be more affected by fraction (brown rice) than the cultivar of rice or intensity of IR used, with more progeny produced on brown rice than rough rice. An IR intensity of 10.84 kW/m² increased the number of overall progeny, the amount of adults, and frass produced on CL152 brown rice. An intensity of 10.84 kW/m² also increased the amount of larvae observed for both varieties and fractions. The intensity of 10.84 kW/m², under the conditions of this study, is not recommended for drying rice.