Effectiveness of hermetic containers in controlling paddy rice (Oryza sativa L.) storage insect pests

Naturally infested paddy rice was used to compare the effectiveness of polypropylene bags and hermetic storage containers over 12 months of storage in a warehouse. Insect pest identification as well as the infestation level, percentage of damaged grain, weight loss, and moisture content were evaluated. Five insect species associated with stored rice were identified during the storage period, namely lesser grain borer (Rhyzopertha dominica), red flour beetle (Tribolium castaneum), rice/maize weevil (Sitophilus spp.), angoumois grain moth (Sitotroga cerealella) and flat grain beetle (Cryptolestes ferrugineus). The lesser grain borer was the most predominant species with an average incidence above 70% after twelve months of storage, followed by the rice/maize weevil with an incidence of 17%. When compared to hermetic storage containers, polypropylene bag showed the highest mean infestation level with 233.3 individuals/kg after six months of storage, representing about 8-fold of the number of insects recorded in hermetic containers after six months of storage. In polypropylene container, the percentage of damaged grain and weight loss increased significantly achieving a maximum of 6.98% and 5.56% respectively, whereas using hermetic containers the highest percentage of damaged grain reached was 3.24% in polyethylene drum and the weight loss was 1.62% in GrainSafe bag. The results from the study show that the use of hermetic storage containers is a green alternative for safe storage of paddy rice, for 12 months without application of pesticides, bringing multiple advantages for smallholder farmers, lever food security and income generation for smallholder farmers and rice milling companies.     

An investigation of the extent of infestation of stored maize by insect pests in Rungwe District, Tanzania

Two hundred and sixty randomly selected subsistence farm households in Katumba ward, Rungwe District, Tanzania, were interviewed regarding methods that they use to prevent or control insect pests in stored maize. Maize samples were randomly collected from 130 out of 260 farm households and studied for infestation by insect pests, using incubation and inspection methods. About 93 % of the maize samples were found to be infested, either by weevils only (specifically Sitophilus zeamais and S. oryzae), by moths only (specifically Sitotroga cerealella), or by both weevils and moths. Both indigenous and improved varieties of maize were infested by the insect pests. The insect population density ranged from 0 to 210 per 120 maize kernels (or 51 g of maize), with an average of 80 insects per 120 maize kernels and a standard deviation of 51.44, amounting to 1,555 insects per kg of maize. Methods that farm households used to control the infestation of stored maize by insect pests were found to be inadequate. It was concluded that, with such high levels of infestation by insect pests, vulnerability of the subsistence farm households to food insecurity was inevitable. It was recommended that the government of Tanzania should make efforts to improve the resistance of maize grown in Rungwe district to Sitophilus and Sitotroga cerealella species, and that the affected farm households be encouraged to embrace new technologies, including genetic improvement of the resistance of maize to pests.     

Effect of paddy variety,milling status and aeration on the progeny emergence of Sitophilus oryzae L. (Coleoptera: Curculionidae)

In Sri Lanka, insects cause enormous losses in stored paddy; the rice weevil Sitophilus oryzae is a devastating insect. The magnitude of losses in stored paddy caused by insects varies with characteristics of paddy but has not yet been fully investigated. Due to the increased concerns on the use of synthetic chemicals, safer alternative pest management strategies for stored paddy are needed. Objectives of this study were to determine the effect of paddy variety, milling status and nature of aeration on the progeny emergence of S. oryzae. The experimental design was a three-factor factorial, completely randomized design (CRD).Freshly emerged S. oryzae adults were introduced to un-milled paddy or milled/polished rice belonging to traditional and improved varieties. The samples were maintained either open or airtight, and the progeny adults emerged was determined at monthly intervals. Progeny emergence was lower in the traditional varieties, un-milled paddy and under air-tight condition compared to improved varieties, milled/polished rice and aerated samples, respectively. Overall, the improved variety Bg 300 exhibited the maximum resistance to infestation by S. oryzae. Furthermore, white-colour and long-grain varieties produced lower progeny of S. oryzae than red-colour and short-grain varieties, respectively. It is concluded that the maximum protection in paddy/rice from insect infestation during storage can be achieved by using traditional varieties, stored as un-milled paddy (without dehusked) under airtight condition.     

Rice weevil management through application of silica nano particle and physico-chemical and cooking characterization of the treated rice

Nano technology is an alternative method for pest management and can be applied to minimize the post harvest storage losses due to insect infestation. A study was undertaken with an aim to control the stored grain pests, particularly rice weevil using silica nano particle (SNP). The nano-silica of 30 nm size was taken for the experiment. Entomotoxic effect of five different doses of SNP was tested against rice weevil Sitophilus oryzae. The effects of SNP mixing with grain at the rate of 0.25, 0.5, 0.75 and 1.0 g/kg of rice, stored in glass jars and gunny bags were examined. The cumulative mortality rate was studied at 1, 2, 4, 7 and14 days of exposure. Mortality rate of 80 and 97.4% were achieved after 7 and 14 days of storage by application of SNP at the rate of 0.5 g per kg of rice. Residual persistency of samples treated with optimum dose of SNP was studied by washing with distilled water at the ratio of 1:2 (sample to water ratio) for three times and the samples were studied under Scanning Electron Microscope (SEM). Single washing prior to cooking was found to be sufficient enough for removing the SNP from treated rice and can be recommended safe for cooking and consumption. This process can also prove to be an eco-friendly and efficient pest management technology. The technology is suitable for industrial application in large scale warehouses and storage godowns to control stored grain insect pests.     

Feeding substrate and temperature interplay determining infestations and losses by the sawtoothed grain beetle (Oryzaephilus surinamensis)

Sawtoothed grain beetle, Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae), is a secondary pest of stored products and one of the serious insect pests of cereal grains, commodities and packaged food throughout the world. However, this species is a concern beyond cereal grains, what may be differentially affected by temperature. Therefore, insect developmental time, larva and pupa survival, and adult emergence of O. surinamensis were assessed on different substrates (rice, sesame and date palm) at different temperatures (20, 25, 30 and 35 °C and 65% r.h). The substrate loss incurred by this insect infestation was also recorded. The larval stage was the main determinant for the overall developmental time of the sawtoothed grain beetle, regardless of the substrate and temperature tested. Adult emergence was affected by substrate (F_2,48 = 4.50, P = 0.02) and particularly temperature (F_3,48 = 24.94, P < 0.001), but not their interaction (F_6,48 = 0.40, P = 0.87), exhibiting little variation until reaching 30 °C, but with a quick decline at 35 °C. The performance of the insects in rice was better, and worse in dry date. Furthermore, the survival was inversely related to substrate loss, regardless of the substrate used for rearing the sawtoothed grain beetle. Thus, substrate and temperature range are major determinants of sawtoothed grain beetle infestation with consequences for this species management.     

Cumulative oxygen consumption during development of two postharvest insect pests: Callosobruchus maculatus Fabricius and Plodia interpunctella Hübner

Insect pests such as Callosobruchus maculatus Fabricius and Plodia interpunctella Hübner cause substantial losses to grain during postharvest storage. In the last few years, hermetic storage technologies have been successfully used by smallholder farmers in Africa and Asia to protect their harvested grain against insect pests. Hermetic technologies owe much of their effectiveness to restricting oxygen availability to insects confined in the containers. There is a need to better understand the biology of specific storage insect pests and their responses to hypoxia. We employed a novel and non-invasive analytical technology, the OxySense 5250i, to measure oxygen levels in closed containers, and evaluated its effectiveness in measuring the total oxygen consumption of two insect pests during their development: C. maculatus and P. interpunctella. The total amount of oxygen consumed by C. maculatus during its larval development period determined with the OxySense apparatus was not different from that previously recorded using another instrument, the Mocon Pac Check 325 gas analyzer. Using the OxySense 5250i, we found that P. interpunctella consumes nearly three times as much oxygen per insect over its larval-to-adult developmental period compared to C. maculatus. Information on the lifetime oxygen consumption of insects provides relevant information to the effectiveness and ability of hermetic technologies to protect stored products against insect pests.     

Susceptibility of Ethiopian wheat varieties to granary weevil and rice weevil infestation at optimal and sub-optimal temperatures

Integrating varietal resistance with temperature manipulation during storage may provide a better option for protection of stored grains and may decrease reliance on the use of synthetic chemicals. The current study was conducted to determine the susceptibility of different varieties of wheat seed to the infestation by the granary weevil, Sitophilus granarius (L.), and rice weevil, Sitophilus oryzae (L.), at optimal (30 °C) and sub-optimal (19 °C) temperatures. Kernels of six wheat varieties namely, Danda'a, Digalu, ET-13-A2, Kakaba, Millennium, and Pavon-76 were examined over a period of 90 d. Significant interactions were detected between wheat varieties and storage temperature for progeny emergence, percentage of insect damaged kernels, grain weight loss, and amount of powder produced per gram of wheat. Kernels of Danda'a, infested with S. oryzae at 30 °C exhibited significantly lower mean progeny counts (13.3 live insects), lower percentage of grain weight loss (4.2%) and insect-damaged kernels (6.4%), and powder production (1.5 mg/g). Kernel weight and hardness index were negatively associated with percentage of insect damaged kernels and grain weight loss. Kernel diameter was positively associated with both of percentage of insect damaged kernels and grain weight loss. Wheat varieties with high Zeleny sedimentation values had lower percentage of insect-damaged kernels and grain weight loss. These results indicated that kernel weight, hardness index, and protein content are predominant factors contributing to wheat resistance against S. granarius and S. oryzae. The varieties Millennium and Danda'a can be considered with other integrated pest management approaches to reduce stored grain losses of wheat in Ethiopia.     

Effects of PICS bags on insect pests of sorghum during long-term storage in Burkina Faso

The PICS bags, originally developed for cowpea storage, were evaluated for sorghum (Sorghum bicolor) preservation. Batches of 25 kg of sorghum grain were stored in 50 kg PICS or polypropylene (PP) bags under ambient conditions for 12 months and assessed for the presence of insect pests and their damage, seed viability and, oxygen and carbon dioxide variations. The grain was incubated for 35 days to assess whether any insects would emerge. After six months of storage, oxygen levels decreased in the PICS bags compared to polypropylene bags. After 12 months of storage, only two pests, Rhyzopertha dominica and Sitophilus zeamais were found in the PICS bags. However, in PP bags there were additional pests including Tribolium castaneum and Oryzeaphilus mercator and Xylocoris flavipes. Grain weight loss and damage caused by these insects in the PP bags were significantly higher compared to those stored in PICS bags. Germination rates of sorghum grains stored in PP bags decreased significantly while no changes were observed in grains stored in PICS bags when compared to the initial germination. After the incubation post storage period, there was a resurgence of R. dominica in sorghum grains from PICS bags but the population levels were significantly lower compared to polypropylene bags. PICS bags preserved the quality and viability of stored sorghum grains and protected it from key insect pests. The PICS technology is effective for long-term sorghum storage but the potential resurgence of insects in low-oxygen environment calls for further research.     

稻谷储藏条件及储藏技术分析

稻谷储藏过程中其品质的变化深受外界条件的影响,外界因素包括温度、水分、空气比例以及虫害和微生物等,尤其是在储粮温度较高且稻谷水分偏大的条件下,稻谷霉菌生长较快,导致稻谷品质下降。综述储粮条件对稻谷品质的影响以及稻谷储藏期间储粮害虫和有害微生物和对稻谷的危害,讨论现有的稻谷储藏技术以及新型储粮技术的研究,目前低温储粮、气调储粮、利用CO2法检测稻谷霉菌以及天然防霉剂的研发等新型技术的开发为我国稻谷的安全储藏提供了更有效的技术保障,只是一些新型技术对粮仓的要求较高,实现全国性推广,存在一定的困难。     

Hermetic storage for control of common bean weevil,Acanthoscelides obtectus (Say)

This study evaluated hermetic storage as a method of controlling Acanthoscelides obtectus (Coleoptera: Chrysomelidae: Bruchinae) in stored beans. Recently harvested “vermelhinho” cultivar of the common red bean was used, which had already been infested by A. obtectus in the field. Beans with a moisture content of 15.0% wet basis were stored in silo bags (3 kg), plastic bottles (1.5 L), or non-hermetic glass containers (3 L) (control) for 120 days. The packages were stored in an acclimatized chamber at 25 °C with a relative humidity of 70 ± 5%. At time intervals of 0, 30, 60, 90, and 120 days, three packages of each treatment were opened, and analyses were performed to assess the infestation percentage by insect pests, moisture content, density, electrical conductivity, germination percentage, and cooking time. There was no increase in infestation by A. obtectus in the grains stored in the silo bags and plastic bottles during the 120 days of storage; however, there was a significant increase in infestation in the grains in non-hermetic storage (control). The quality of the beans correlated with infestation; it was not altered in the hermetic storage systems and decreased in the control sample. Hermetic storage of common beans is an effective tool in the control of A. obtectus.     

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.     

Effect of radio frequency heating on the mortality of Rhizopertha dominica (F.) and its impact on grain quality

The use of radio frequency (RF) heating to reach temperatures lethal to stored product pests has significant potential. We examined the lethal effects of RF on the stored grain pest, Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae), under four different RFs, three types of grain, and different moisture contents of rice. The quality of two rice cultivars, after RF heating, was also tested. When heated to 58 °C by RF, R. dominica adult mortality reached 100%. The mortality of R. dominica adults reached 100%. The fastest mortality rate occurred at 50–52 °C. With an increase in RF, the time needed to attain a lethal temperature decreased. The heating time to reach 100% mortality differed among the three types of grain; for example, the heating time of wheat was faster than corn or rice. Kernel size and chemical composition was the main factor influencing the RF lethal rate in the different types of grain under the same experimental conditions. There was a significant linear relationship between moisture content (m.c.) and heating time (Y = −38.05 X + 15.501, R = 0.9803) in rice. RF heating of rice to 58 °C did not significantly affect milling quality, storage quality, or seed quality. Thus, heating time, types of grain, and the m.c. of the grains are three important factors that should be considered in RF heating to control stored product pests. These results indicate that RF heating could be an effective physical method for killing stored grain pests.     

Field trials to control insect pests of farm-stored maize in Zambia

Severe infestations of Sitophilus zeamais Motsch and Sitotroga cerealella Oliv. occur in maize cobs stored under farm conditions in Zambia causing up to 92% damaged grains 8 months after harvest. Shelling the maize reduced S. cerealella damage to low levels and also stabilized the moisture content of the grain providing a more suitable substrate for insecticide application and c control of S. zeamais. Malathion at 12 ppm a.i., tetrachlorvinphos (12 ppm), and jodfenphos (12 ppm), applied as dust admixtures to shelled maize in traditional mud-walled, timber and thatch storage cribs, all kept damaged grains below 10% up to 10 months after harvest. Pirimiphos-methyl (4 ppm) and fenitrothion (2 ppm) maintained these low damage levels up to 8 months after harvest, but there was evidence of continued S. cerealella infestation with these two insecticides.     

End-use quality characteristics of hermetically stored paddy

Four paddy varieties (Bg 352, Bg 300, Bg 358 and Bg 360) were stored in hermetic IRRI bags and common woven polyethylene bags (polybags) at room temperature either uninfested or infested with rice weevils (Sitophilus oryzae (L.)). After 9 months of storage, samples were tested for insect mortality, gas contents, moisture content (m.c.), thousand grain mass (TGM), porosity, hardness, whiteness, total milled rice yield (TMR), head rice yield (HRY), gelatinization temperature, amylose (AC), crude protein (CP), crude fat, free fatty acid (FFA), thiamine and niacin contents and sensory characteristics. These properties after storage were compared with their initial condition. The oxygen content dropped from 21% to 7% and 13.8% for infested and uninfested IRRI bag samples, respectively. The results showed that m.c., of the IRRI bag samples increased significantly (P < 0.05) by 5% when compared to the initial sample but it increased by 15% in polybag stored samples. After 9 months, dry matter loss (DM) was 65% higher in polybag than IRRI bag samples. Highest DM loss was observed in Bg 300 and the lowest DM loss was observed in Bg 358 and Bg 360. Paddy samples stored in IRRI bags showed reduced whiteness compared to polybag stored samples. Storage in IRRI bags significantly increased (P < 0.05) TMR, HRY, AC and sensory values compared to polybag samples. However, paddy samples stored in polybags significantly increased (P < 0.05) their CP and FFA contents while decreasing sensory values, thiamine and niacin contents. The FFA value of polybag samples was 2.5 times higher than IRRI bag samples. Hermetic storage of dry paddy improved overall paddy quality but different end-use quality parameters were observed in the two paddy grain types of short round (Bg 352 and Bg 300) or intermediate bold (Bg 358 and Bg 360).     

Predicting Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) populations and associated grain damage in smallholder farmers’ maize stores: A machine learning approach

Prostephanus truncatus is a notorious pest of stored-maize grain and its spread throughout sub-Saharan Africa has led to increased levels of grain storage losses. The current study developed models to predict the level of P. truncatus infestation and associated damage of maize grain in smallholder farmer stores. Data were gathered from grain storage trials conducted in Hwedza and Mbire districts of Zimbabwe and correlated with weather data for each site. Insect counts of P. truncatus and other common stored grain insect pests had a strong correlation with time of year with highest recorded numbers from January to May. Correlation analysis showed insect-generated grain dust from boring and feeding activity to be the best indicator of P. truncatus presence in stores (r = 0.70), while a moderate correlation (r = 0.48) was found between P. truncatus numbers and storage insect parasitic wasps, and grain damage levels significantly correlated with the presence of Tribolium castaneum (r = 0.60). Models were developed for predicting P. truncatus infestation and grain damage using parameter selection algorithms and decision-tree machine learning algorithms with 10-fold cross-validation. The P. truncatus population size prediction model performance was weak (r = 0.43) due to the complicated sampling and detection of the pest and eight-week long period between sampling events. The grain damage prediction model had a stronger correlation coefficient (r = 0.93) and is a good estimator for in situ stored grain insect damage. The models were developed for use under southern African climatic conditions and can be improved with more input data to create more precise models for building decision-support tools for smallholder maize-based production systems.     

Spinosad: A new natural product for stored grain protection

Spinosad is a reduced-risk insecticide derived by fermentation from the soil actinomycete, Saccharopolyspora spinosa Mertz & Yao. Spinosad is currently registered in several countries as a grain protectant at a maximum labeled use rate of 1 ppm (1 mg a.i./kg of grain) and with the Maximum Residue Level (MRL) or tolerance on grains set at 1 or 1.5 ppm. Global launch of spinosad as a grain protectant is expected in the near future, pending final acceptance of international residue tolerances for spinosad by major grain importing and exporting countries. Spinosad effectively controls economically important beetle and moth pests associated with stored grain and is also effective against certain psocid species. Spinosad provides grain protection through control of adult and/or immature life stages of pest insects. The pest spectrum of spinosad under commercial grain storage conditions is still being defined, but it is clear from available laboratory and field evaluations on various grains that the lesser grain borer, Rhyzopertha dominica (F.); larger grain borer, Prostephanus truncatus (Horn); rusty grain beetle, Cryptolestes ferrugineus (Stephens); flat grain beetle, Cryptolestes pusillus (Schönherr); red flour beetle, Tribolium castaneum (Herbst); confused flour beetle, Tribolium confusum Jacquelin du Val; Indian meal moth, Plodia interpunctella (Hübner); rice moth, Corcyra cephalonica (Stainton); Angoumois grain moth, Sitotroga cerealella (Olivier); almond moth, Cadra cautella Walker; and the psocid species Lepinotus reticulatus Enderlein and Liposcelis entomophila (Enderlein) are susceptible to spinosad and complete control is to be expected. Other pest species such as the maize weevil, Sitophilus zeamais Motchulsky; rice weevil, Sitophilus oryzae (L.); and sawtoothed grain beetle, Oryzaephilus surinamensis (L.) are susceptible to spinosad to varying degrees, but their overall level of control remains to be verified under commercial grain storage conditions. Spinosad residues are highly stable on grains stored in bins, with a length of protection ranging from 6 months to 2 years. Numerous factors have been shown to impact the overall performance of spinosad, including insect pest species, pest life stage, grain type, grain variety, and formulation type. Spinosad possesses a unique mode of action in insects and controls insect strains resistant to other grain protectants. When launched globally, spinosad will represent a valuable new addition to the limited arsenal of grain protectants and can positively impact global food security. Its combination of high efficacy, broad insect pest spectrum, low mammalian toxicity, and sound environmental profile is unique among existing products currently used for stored-grain protection.     

Efficacy of phosphine and insect penetration ability in ZeroFly® bags

The deltamethrin incorporated woven polypropylene ZeroFly® storage bag is a promising novel technology for grain storage. However, if grain stored in ZeroFly bags gets infested and has to be fumigated using phosphine (PH₃), data on the effectiveness of such treatments are needed. Additionally, obtaining field data on ability of stored-product insect pests to breach ZeroFly bags would facilitate insect management. Therefore, efficacy of PH₃ in immature and adult Sitophilus zeamais (Motschulsky), Prostephanus truncatus (Horn), Rhyzopertha dominica (F.) and Tribolium castaneum (Herbst) in experimental cages in maize stored in 100-kg polypropylene (PP), jute and ZeroFly bags was investigated. Post-fumigation mortality of adults was recorded after 7 d, and after 7 wk for immatures. The ability of either S. zeamais or P. truncatus to penetrate fabric of PP, jute and ZeroFly bags was assessed. Phosphine efficacy was good in all the three types of bags and resulted in complete mortality of adults and immatures of the four species tested. Sitophilus zeamais and P. truncatus were more successful in penetrating the PP bag fabric and on average made 84 and 780 holes per bag over a 4 mo-period, respectively; this was followed by jute with 37 and 614 holes. The ZeroFly bag was harder to breach and ≤3 holes per bag were made for both species. This study shows that PH₃ is highly efficacious in insects that infest maize stored in ZeroFly bags, and that these bags are not easily penetrated by stored product insect pests. Hitherto, ZeroFly bags are a good technology for storing grain that is not infested, and fumigation using PH₃ can be effectively conducted if infestation occurs. Therefore, ZeroFly bags can be incorporated in integrated stored product insect management (IPM) programs for bagged grains.     

Effects of Cry1F and Cry34Ab1/35Ab1 on storage pests

Two crystalline protoxins from Bacillus thuringiensis (Bt), Cry1Fa1 and Cry34Ab1/Cry35Ab1 (Cry1F, Cry34/35Ab1), were evaluated for efficacy against lepidopteran and coleopteran storage pests. Cry1F was tested against the lepidopterans Sitotroga cerealella (Angoumois grain moth) and colonies of Plodia interpunctella (Indian mealmoth) that are susceptible or resistant to Bt Cry1Ab and Cry1Ac toxins, Bt subspecies entomocidus, and the commercial formulation Dipel^®. Cry1F was also tested against the coleopterans Cryptolestes pusillus (flat grain beetle) and Tribolium castaneum (red flour beetle). Cry34/35Ab1 was tested against S. cerealella, C. pusillus, and T. castaneum, and against additional coleopteran storage pests, including Tenebrio molitor (yellow mealworm), Trogoderma variabile (warehouse beetle), Oryzaephilus surinamensis (sawtoothed grain beetle), Rhyzopertha dominica (lesser grain borer), and Sitophilus oryzae (rice weevil). Strains of Bt-susceptible or -resistant P. interpunctella generally were more sensitive to Cry1A protoxin or toxin than either Cry1F protoxin or Dipel. Despite difficulties with the bioassay of S. cerealella larvae, the data suggest that Cry1F and Cry34/35Ab1 caused increased larval mortality, and a developmental delay was observed and no pupae emerged with 0.9% Cry1F. Neither Cry1F nor the corn rootworm-active toxin Cry34/35Ab1 significantly affected the biological parameters of the coleopteran species evaluated.     

A systemic approach to qualitative changes in the stored-wheat ecosystem: Prediction of deterioration risks in unsafe storage conditions in relation to relative humidity level, infestation by Sitophilus oryzae (L.), and wheat variety

A multidimensional laboratory trial was carried out to identify the primary causes of changes in quality traits in the stored-grain ecosystem to reveal critical storage condition boundaries that may endanger grain quality retention. Qualitative criteria were followed on grain batches from 3 wheat varieties which were stored for 160 d at temperature of 22-23 °C, at two different relative humidities, and with or without infestation by the rice weevil Sitophilus oryzae, to build a multivariate data matrix. The interactions between biotic deteriorative factors and qualitative trait changes were explored through a principal component analysis (PCA). From the Pearson’s product moment correlation matrix, it was observed that the variables that correlated significantly with insect and fungal species dynamics were: moisture content, hL mass, seed viability, and fat acidity of extracted whole flour. Four factors explained the major part of the variance: storage duration, moisture content, hidden insect infestation density, and fungal contamination level. The rate of increase of the insect population was significantly different between varieties. PCA revealed that the significant difference in qualitative deterioration pattern observed between the three varieties was not related to their hardness but rather to a different relationship between the grain and relative humidity. Germination rate was the first quality factor to decline during the storage period. The technological properties of flour extracted from each variety were not affected before insect population density exceeded 1000 adult insects per kg. The rate of qualitative changes induced by the biotic deterioration factors was processed into a “biodeterioration susceptibility index” (BSI) according to the safe storage time assessed in the present study. This index may be used in IPM approaches to predict the susceptibility of a particular wheat variety to insect and fungal damage during long-term storage.     

Research advance in gas detection of volatile organic compounds released in rice quality deterioration process

Rice quality deterioration will cause grievous waste of stored grain and various food safety problems. Gas detection of volatile organic compounds (VOCs) produced by deterioration is a nondestructive detection method to judge rice quality and alleviate rice spoilage. This review discussed the research advance of VOCs detection in terms of nondestructive detection methods of rice quality deterioration, applications of VOCs in grain detection, inspection of characteristic gas produced during rice spoilage, rice deterioration prevention and control, and detection of VOCs released by rice mildew and insect attack. According to the main causes of rice quality deterioration and major sources of VOCs with off-odor generated during rice storage, deterioration can be divided into mold and insect infection. The results of literature manifested that researches mainly focused on the infection of Aspergillus in the mildew process and the attack of certain pests in recent years, thus the research scope was limited. In this paper, the gas detection methods combined with the chemometrics to qualitatively analyze the VOCs, as well as the correlation with the number of colonies and insects were further studied based on the common dominant strains during rice mildew, that is, Aspergillus and Penicillium fungi, and the common pests during storage, that is, Sitophilus oryzae and Rhyzopertha dominica. Furthermore, this paper pointed out that the quantitative determination of characteristic VOCs, the numeration relationship between VOCs and the degree of mildew and insect infestation, the further expansion of detection range, and the application of degraded rice should be the spotlight of future research.