Insecticidal effect of thiamethoxam against seven stored-product beetle species

Bioassays were carried out in order to assess the insecticidal value of the neonicotinoid thiamethoxam in different concentrations against seven important beetle species that are major pests of stored grains. These species were Prostephanus truncatus (Horn), Rhyzopertha dominica (F.), Sitophilus oryzae (L.), Sitophilus granarius (L.), Oryzaephilus surinamensis (L.), Tribolium confusum Jacquelin du Val, and Cryptolestes ferrugineus (Stephens). Adults of these species were exposed to grains treated with thiamethoxam at dose rates of 0 (control), 0.01, 0.1, 0.5, 1, 2, 5 or 10 ppm. Our results indicate that with the increase of the insecticide concentration, there was also an increased adult mortality and a reduction in progeny production. To illustrate the relative sensitivity to thiamethoxam of the seven insects, starting with the most susceptible, we can classify them as P. truncatus > R. dominica = S. granarius = S. oryzae > T. confusum = O. surinamensis > C. ferrugineus. The findings of the present research show that thiamethoxam can be recommended for its efficacy at a rate of 10 ppm and duration of 14 days that could be used to control all insects and their progeny.     

Persistence and efficacy of indoxacarb against three stored product insect species on wheat and maize

In the present study, we investigated the insecticidal efficacy of indoxacarb on wheat and maize, against adults of three major stored-grain species, the rice weevil, Sitophilius oryzae (L.) (Coleoptera: Curculionidae), the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) and the confused flour beetle, Tribollium confusum Jacquelin Du Val (Coleoptera). For this purpose, bioassays were carried out with indoxacarb at the doses 0.1, 1 and 10 ppm. Moreover, the treated grains were left at the laboratory for a period of six months, in order to examine the residual effect of indoxacarb, by conducting bioassays at monthly intervals. For S. oryzae and R. dominica, adults were exposed in the treated grains for 7 and 14 d, while for T. confusum adults were exposed for 14 and 21 d, in order to estimate the mortality level. After the termination of this interval, the treated samples were left for an additional period of 65 days, on which progeny production was recorded. R. dominica was by far more susceptible than S. oryzae, given that mortality, in many cases, reached 100% even after 7 d of exposure, even at the lowest dose rate of 0.1 ppm. At the same time, for this species, progeny production was low. For S. oryzae, mortality was low at 0.1 ppm, with high levels of progeny production. T. confusum was the least susceptible of the species tested. Generally, during the experimental period, the efficacy of indoxacarb was decreased, but mortality was higher on wheat than on maize. Indoxacarb residues determination by GC-ECD indicated that after 6 months 33% of the insecticide remains in grains at 0.1 ppm dose, about 40–50% at 1 ppm and about 40–60% at 10 ppm dose. Based on the results of the present work, indoxacarb is an effective grain protectant, at least in the case of R. dominica and S. oryzae.     

Effects of zeolite formulations on the mortality and progeny production of Sitophilus oryzae and Oryzaephilus surinamensis at different temperature and relative humidity levels

The insecticidal potential of two natural zeolite formulations, Zeocem and Mycostop, was tested against the rice weevil Sitophilus oryzae (L.) and the sawtoothed grain beetle Oryzaephilus surinamensis (L.) on wheat, at the dose rates of 0.25, 0.50, 0.75, and 1 g/kg. The bioassays were carried out under laboratory conditions at three temperature levels (20, 25, and 30^οC) and two relative humidity (r.h.) levels (55, 75%). Mortality was recorded after 7, 14, and 21 d of exposure and progeny production was recorded 65 d later. Complete (100%) mortality was achieved only for O. surinamensis adults with Zeocem for most temperature and r.h. combinations tested. Progeny production for this species was extremely low. In contrast, mortality for S. oryzae was much lower and did not exceed 87% after 21 days at any of the combinations tested, while progeny production was high. For O. surinamensis exposed to Mycostop, mortality after 21 days did not exceed 97% for all temperature and r.h combinations, while overall progeny production was low. Moreover, S. oryzae mortality was generally low and did not exceed 56%, while progeny production for this species was high for most temperature and r.h. combinations. Despite the fact that some general trends were evident, the effect of temperarature and r.h. in zeolite efficacy was often found inconclusive. The results of the present study illustrated the insecticidal potential of zeolites for the contol of certain stored product insect species, which requires additional investigation.     

Modeling of the effect of relative humidity and temperature on proving rate of rice-flour-based dough

Proving is one of the key processes in bread making, where dough normally rests and grows under an environment of constant temperature and humidity. To better understand the effect of relative humidity (RH) and temperature on the kinetics of dough expansion during proving and be able to optimize the growth rate, rice-flour-based dough of same formulation was proved under various process conditions. Both RH and temperature showed significant effect on the dough expansion rate during proving. To describe the dough expansion, a first-order, non-Arrhenius kinetic model was developed. The influence of RH and temperature on the kinetic rate was described by an empirical model. Through verification, the model performance was proved to be reasonably good. The model was subsequently used to optimize the proving condition to maximize the kinetic rate constant therefore minimizing the proving time. The fastest proving condition for the rice-flour-based dough in this research was at 90% RH and 46.3 °C. According to the model, the kinetic rate constant under the optimal condition was estimated to be at 0.217 min⁻¹. From an initial height of 5 mm, the dough height could be increased to 11 mm within 6.4 min.     

Efficacy of layer grain treatment with thiamethoxam against adults of Rhyzopertha dominica (F.) and Sitophilus oryzae (L.)

The insecticidal effect of the neonicotinoid insecticide thiamethoxam, applied in layers of wheat, was studied in laboratory experiments, for the control of the lesser grain borer, Rhyzopertha dominica (F.) and the rice weevil Sitophilus oryzae (L.). In general, the increase of the size of the treated layer of wheat increased parental morality and decreased progeny production for both species. However, progeny production could not be totally avoided, even when the entire grain quantity was treated. Parental morality was lower for R. dominica than for S. oryzae, but the reverse was observed for progeny production for all treatments. Insect placement drastically affected thiamethoxam efficacy, since morality was generally higher when insects were forced to move downwards from the upper layer, as compared with insects that had been placed in the bottom part of the wheat column. Our study shows that thiamethoxam can reduce insect populations in partially treated wheat, at concentrations that are comparable with other, currently registered grain protectants.     

Influence of relative humidity on oxidation of the free and encapsulated oil fractions in freeze-dried microencapsulated oils

The objective of this work was to evaluate the effect of relative humidity (RH) on oxidation of the free and encapsulated oil fractions of dried microencapsulated oils (DMOs) during long-term storage at 30 °C. Sunflower and fish oils with different tocopherol content were encapsulated in a milk-based encapsulation matrix. The total non-volatile oxidation products and tocopherol were quantitated. Results showed that 0% and 32% RH were, respectively, the most unfavourable and favourable conditions against lipid oxidation. The 32% RH atmosphere exerted a great protective effect on the free oil as compared to 0% RH, while no or a negligible effect was found in the encapsulated oil. Except for the samples most susceptible to oxidation, the free oil remarkably oxidized more slowly than the encapsulated oil regardless of RH. Therefore, there were factors other than moisture that determined the oxidation rate in the free and encapsulated fractions of the DMOs.     

Influence of grain and relative humidity on the mortality of Sitophilus oryzae (L.) adults exposed to ethyl formate vapour

Ethyl formate (EF) is being investigated as an alternative to phosphine and methyl bromide, for the fumigation of stored products. The compound has been found to have a rapid action against stored-product insects and shows promise as a fast-acting disinfestant.The response of Sitophilus oryzae adults to EF in a sealed system was studied. Insects were exposed to a range of EF doses for 24 h at 25 °C, with a range of grain quantities and relative humidities (r.h.). It was found that rapid mortality of S. oryzae adults in a sealed system was obtained, with a range of applied concentrations required to achieve 99% mortality. Concentrations as low as 11.2 mg L⁻¹, for the exposures without wheat at 97% r.h., achieved 99% mortality, whereas 81.2 mg L⁻¹ EF was required for the exposures carried out on 1500 g wheat in 2.7 L at 60% r.h. Modelling studies of the mortality data revealed that, in general, the presence or absence of grain had the largest influence on mortality, where the larger the grain quantity, the higher the required EF dose to achieve 99% mortality. To a lesser degree, the r.h. also influenced the observed mortality, where the higher the r.h., the lower the required EF dose to achieve 99% mortality. In this experimental system, the factors that determined the level of mortality were a complex interaction of the initial dosage concentration (C₀), concentration×time product (Ct), grain quantity and r.h.     

Effect of temperature and relative humidity on yellowing rate of paddy

The effects of temperature and relative humidity (or water activity) in storage chambers on yellowing rate of paddy were investigated and then an empirical equation for predicting the yellowing rate was developed. Paddy was conditioned using saturated salt solutions at relative humidities ranging from 0.80 to 0.95 and temperatures of 35, 45, 55, 60 and 65°C. The yellowing rate was found to follow the zero order kinetics. The yellowing constant value (k) increased exponentially with temperature and increased linearly with water activity. The magnitude of apparent activation energy varied from 130–145 kJ/mol. A predictive equation for determining yellowing rate was ln k=−δa_w−/T+(γa_w)/T where a_w was water activity (valid from 0.80 to 0.95), T was absolute temperature (valid from 308 to 338 K) and , δ, and γ were constants. The results of variance analysis showed that temperature, water activity and their interaction significantly influenced the yellowing rate of paddy.     

醒发温湿度对馒头感官评定影响

选择对馒头醒发起关键作用两个关健因素:温度和相对湿度,以感官评分作为指标,找出较佳醒发温度和醒发相对湿度;结果表明,馒头醒发时最佳条件为:醒发温度40℃,醒发相对湿度85%。     

Effect of the relative humidity of drying air during the resting period on the composition and appearance of dry-cured ham surface

This study evaluates the effect of three different relative humidities (RH) during the resting period on the composition of the external part of Semimembranosus muscle (2 mm thick) and the appearance of the surface of the dry-cured ham after resting and ageing. Forty-eight hams stored after salting for 40 days at 4±1 °C and three different RH (52±3, 78±3 and 85±3%) were studied. Half of the hams in each treatment were sampled after the resting period and the rest were aged for 8 additional months at the same temperature and RH. Storage of hams at 52% RH during resting produced a white appearance in some parts of the rind and increased the surface covered with oil drip. Hams stored at 78% showed a similar composition to those stored at 52%, except for the higher moisture content and lower Na/moisture ratio at the end of the resting period, and potassium content (on dry matter, dm) at the end of the process. At the end of resting no white rind was observed, and at the end of the process the surface covered with oil drip was slightly lower than at 52%. Storage of hams at 85% RH increased the surface pH, Na2HPO4.12H2O crystallisation, Mg (dm), Mg/moisture, K (dm) and NPN/NT at the end of the resting period, and increased the pH and Mg (dm), Mg/moisture, Na/moisture, K/moisture, the ash (dm) and ash/moisture contents and decreased the a_w and the surface covered with oil drip at the end of the process.     

Symptoms of dry eye related to the relative humidity of living places

PurposeTo investigate the impact of relative humidity (RH) and climate variables of the place of residence on symptoms of dry eye disease (DED) in primary eye care practice.MethodsA cross-sectional analysis of the Ocular Surface Disease Index (OSDI) dry eye classification of 1.033 patients [classified as non-DED (OSDI ≤22) and DED (OSDI >22)] was conducted in a multicentre study in Spain. Participants were classified according to the 5-year RH value (data from the Spanish Climate Agency -www.aemet.es) into two groups: those who lived in low RH (<70%) places and those who lived in high RH (≥70%) places. Additionally, differences in daily climate records (EU Copernicus Climate Change Service) were assessed.ResultsThe prevalence of DED symptoms was 15.5% (95% CI 13.2%–17.6%). Participants who lived in places with <70% RH showed a higher prevalence of DED (17.7%; 95% CI 14.5%–21.1%; P < 0.01 adjusted for age and sex) than those who lived in places with ≥70% RH (13.6%; 95% CI 11.1%–16.7%) and a closer, but not statistically significant, risk for DED (OR = 1.34, 95% CI 0.96 to 1.89; P = 0.09) than previously described DED risk factors [age older than 50 years (OR = 1.51, 95% CI 1.06 to 2.16; P = 0.02) and female sex (OR = 1.99, 95% CI 1.36 to 2.90; P < 0.01)]. Some climate data showed statistically significant differences (P < 0.05) between participants with DED and non-DED (mean wind gusts; atmospheric pressure; mean and minimum relative humidity); these variables did not significantly increase DED risk (OR close to 1.0 and P > 0.05).ConclusionThis study is the first to describe the impact of climate data on dryness symptomatology in Spain, confirming that participants who live in locations with RH <70% have a higher prevalence (corrected for age and sex) of DED. These findings support the use of climate databases in DED research.     

通风过程中进风相对湿度对仓储粮堆温度和水分的影响研究

温度和水分含量是两个重要的物理变量,在研究谷物储存时品质变化起到很大作用。通风用于冷却粮堆并保持温度恒定,以防止水分迁移。良好的通风条件对粮仓内存储安全有显著影响。目前,通风空气相对湿度对粮堆水分影响的研究相对较少。采用数值模拟和实验研究相结合的方式,探索和比较因不同进风相对湿度而引起的通风过程中仓储的小麦温度和水分变化规律。结果表明:进风相对湿度较低时冷却干燥效率更高,小麦粮堆降温更快速,并将昆虫和霉菌的活动保持在较低水平。     

Influence of storage conditions on the quality properties of wheat varieties

Effects on the quality properties in real storage conditions and galvanized steel silos for wheat varieties (cv. Bezostaya and Lancer) in the 180 day storage period were investigated. The wheat quality properties including grain moisture, crude protein, hectoliter weight, thousand grain weight, Zeleny sedimentation, wet gluten, dry gluten, and falling number were monitored in the laboratory in three replicates at regular intervals. From these results, crude protein, hectoliter weight, and thousand grain weight of Bezostaya and Lancer wheat varieties decreased with an increase in storage period. Grain moisture, Zeleny sedimentation, wet gluten, and dry gluten increased with storage period until the first two months and subsequently decreased. However, grain moisture for Lancer wheat increased until the third month of storage, after which it decreased. Falling number increased with increase in storage period.     

烘茧温湿度连续动态测量系统的研制及应用

针对现行烘茧工艺中温度的定点测量及没有湿度测量的问题,自行研制出了烘茧温湿度连续动态测量系统。利用该系统对CL-100型循环式热风烘茧机内部温湿度进行了实际测量,并分析了烘茧机内温湿度的变化情况。结果表明,该系统完全适合于烘茧机内的温湿度测量,系统的应用将有助于烘茧人员制订合适的烘茧工艺,提高烘茧质量。     

Effect of relative humidity and temperature on absorption kinetics of two types of oxygen scavengers for packaged food

To investigate the effect of temperature and relative humidity (RH) on the absorption kinetics of self‐activated and moisture‐activated O₂ scavengers for packaged food, kinetic parameters of each O₂ scavenger were evaluated at 43%, 75% or 100% RH and at 10, 25 and 40 °C respectively. Absorption kinetics was well described by a first‐order reaction with an Arrhenius type behaviour. For moisture‐activated O₂ scavengers, a proper high RH was needed to ensure a high O₂ absorption capacity, as average O₂ absorption capacity was 3.82 mL at 43% RH and 43.40 mL at 75% RH. When the temperature increased, O₂ absorption rate constant ascended from 10 °C to 40 °C on an average of 0.153 and 0.306 h^?1 in moisture‐activated and self‐activated O₂ scavengers respectively. We could take the effect of temperature and RH into account when we chose different types of iron‐based O₂ scavengers for packaged food.     

Susceptibility of stored-product beetles on wheat and maize treated with thiamethoxam: effects of concentration, exposure interval, and temperature

Sitophilus zeamais Motschulsky, the maize weevil, Oryzaephilus surinamensis (L.), the saw-toothed grain beetle, and Tribolium castaneum (Herbst), the red flour beetle, were exposed for 1, 2, 3, and 6 d at 22°C, 27°C, and 32°C on maize treated with 0, 0.5, 1.0, 2.0, or 4.0 ppm thiamethoxam, a new-generation neonicotenoid insecticide. A second series of tests was conducted on hard winter wheat using S. oryzae (L.), the rice weevil, Rhyzopertha dominica (F.), the lesser grain borer, and T. castaneum. Mortality of all species on both commodities generally increased with insecticide concentration, exposure interval, and temperature, and data were described by linear and non-linear regressions with concentration as the independent variable. Mortality of S. zeamais ranged from 58% to 90% on maize treated with 0.5 ppm thiamethoxam, and approached 95–100% as concentration increased to 4 ppm. Oryzaephilus surinamensis appeared to be slightly less susceptible than S. zeamais; mortality ranged from about 18% to 80% at 5 ppm and there was a more gradual increase in mortality as concentration increased. Mortality of T. castaneum generally did not exceed 40% at any concentration unless the beetles were exposed for 6 d. Mortality of R. dominica and S. oryzae was less than 60% when exposed on treated wheat for 1 and 2 d, but increased to nearly 100% when exposed for 6 d at 27°C and 32°C. Mortality of T. castaneum did not exceed 20% at the 1- and 2-d exposures, and approached 100% only when beetles were exposed for 6 d at 32°C. Few F₁ adults of any species were found in treated maize or in treated wheat but the number of F₁ T. castaneum in untreated maize and untreated wheat was very low compared with the other species. Results show that thiamethoxam would be an effective protectant of stored maize seed and stored wheat seed.     

Effect of relative humidity and chlorophenol content on the fungal conversion of chlorophenols to chloroanisoles in fibreboard cartons containing dried fruit

The effect of relative humidity and chlorophenol content on the fungal conversion of 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol and pentachlorophenol to the corresponding chloroanisoles in fibreboard cartons was studied under temperature and humidity conditions similar to those that could occur in shipping containers during the transportation of packaged dried fruit. The conversion was studied in cartons manufactured from virgin Kraft fibreboard (total chlorophenol content 66 μg kg^?1) and fibreboard prepared from recycled waste paper (total chlorophenol content 1375 μg kg^?1). Positive correlations were established between both storage humidity and fungal population with chloroanisole production in the fibreboard. The concentration of the chloroanisoles in the packaged fruit increased with increasing relative humidity. The roles of relative humidity and chlorophenol content in fibreboard are discussed with respect to the development of chloroanisole-induced mustiness in packaged dried fruit.     

Residual efficacy of an insecticide-coated net for the control of stored product beetles

In the present study, the residual efficacy of an alpha-cypermethrin-coated net (Carifend®, BASF AG, Ludwigshafen, Germany) was evaluated in laboratory studies against four species of stored product insects. The insecticide-treated net was fitted into the bottom of plastic petri dishes, whereas two other sets of dishes (without net, with net without insecticide) served as controls. The insects used in the bioassays were Sitophilus oryzae, Tribolium confusum, Oryzaephilus surinamensis and Prostephanus truncatus. Adults of these species were exposed every 30 d for a total of 90 consecutive days in total. Based on the results, the insecticidal effect of the net remained at high levels during the entire experimental period, indicating its high residual effect. Among the species tested, T. confusum was the least susceptible. Carifend® can be a valuable tool for the protection of stored products against storage insects, and its use can be further examined towards this direction.     

Influence of technological conditions of sausage fermentation on the aminogenic activity of L. curvatus CTC273

The influence of technological factors (temperature and relative humidity of the manufacturing process and the diameter of the sausage) on the aminogenic activity of the strain Lactobacillus curvatus CTC273 was evaluated. Inoculation of sausages with L. curvatus CTC273 resulted in the accumulation of large amounts of biogenic amines (higher than 1000 mg/kg dry matter in some samples) during the manufacture of fuet and llonganissa sausages. Sausages produced via process ‘A’ (3 days at 20-23 °C and 90-95% RH followed by 20 days at 12-14 °C and 70% RH) contained significantly higher amounts (p < 0.05) of biogenic amines than those manufactured via process ‘B’ (23 days at 12-13 °C and 70-90% RH), specifically tyramine, cadaverine and phenylethylamine in llonganissa and phenylethylamine in fuet. The higher fermentation temperature and relative humidity during the fermentation stage in process ‘A’ promoted decarboxylase activity in L. curvatus CTC273 and thus favoured amine accumulation. The diameter of the sausages also influenced biogenic amine production. Higher amine levels were found (p < 0.05) in llonganissa than in fuet, regardless of the manufacturing conditions. The effect of the factors considered on the modulation of aminogenic activity is not necessarily linked to the effect of strain growth, but chiefly favouring proteolytic and decarboxylase reactions.     

蒸化工艺中高温高湿蒸汽温湿度测量仪的研制

基于蒸化工艺中蒸汽温湿度控制的重要性,针对蒸化过程中出现的过热现象和高温高湿气体温湿度难测量的问题,自行研制出蒸化机温湿度电子测量仪。该装置以瑞士Sensirion公司的SHT75高精度温湿度传感器和美国Microchip公司的PIC16F628单片机为核心元件,巧妙的汇编语言编程和电路设计,铜烧结网防护探头和特氟隆耐高温屏蔽信号线的运用,使其能在恶劣条件下使用,不但能自动加热防止结露,而且能准确测量出高温高湿蒸汽的温湿度。