储藏小麦粉中害虫发生与温湿度变化的关系研究

研究了不同初始虫口密度(0、2、15头/kg小麦粉)的不同储粮害虫(锈赤扁谷盗成虫、赤拟谷盗成虫、赤拟谷盗成虫与锈赤扁谷盗成虫混合)发生对储藏小麦粉温度及环境湿度变化的影响。结果表明,在全部实验观察期间,随着实验时间延长,害虫为害引起小麦粉温度升高,初始感染害虫虫口密度越高小麦粉温度也越高;不同起始虫口密度的不同虫种害虫为害的小麦粉温度均表现出上升趋势,相互之间差异不显著。在全部实验观察期间,未受害虫感染的小麦粉温度变化在22.27～28.70℃,感染2头/kg赤拟谷盗的小麦粉温度变化在22.23～29.53℃,感染15头/kg赤拟谷盗的小麦粉温度变化在22.03～29.55℃。感染2头/kg锈赤扁谷盗的小麦粉温度变化在21.67～29.43℃,感染15头/kg锈赤扁谷盗的小麦粉温度变化在22.13～29.63℃。感染2头/kg混合虫种的小麦粉温度变化在22.30～29.63℃,感染15头/kg混合虫种的小麦粉环境变化在22.20～29.37℃。在实验观察期间,不同虫种、不同起始虫口密度害虫为害对小麦粉环境湿度变化影响差异不显著。     

控温气调技术在海南地区储粮中的应用研究

本研究在海南地区某粮仓进行控温充氮气调储粮技术试验。结果显示:实现常年控制粮堆温度,平均粮温21℃,最高粮温24.83℃;储藏2年的稻谷,色泽气味正常,最高脂肪酸值24.8mgKOH/100 g≤30 mgKOH/100 g,最高黄粒米率为0.53%≤1%;粮食储藏期间,最高虫口密度4.79头/kg≤5头/kg,主要害虫密度≤2头/kg,达到基本无虫水平。试验结果表明:在海南地区采用控温气调储粮技术能延缓储粮品质劣变,降低害虫及微生物感染率。     

入仓期玉米象感染不同时期小麦重量损失的研究

研究了粮食入仓过程中小麦感染玉米象造成的小麦重量损失.主要研究结果为:7月份入仓的小麦,小麦中的玉米象的虫口密度在2头/kg以上,小麦的水分在12%以上,在20 d后小麦重量将发生明显的变化.玉米象(米象)的虫口密度在1头/Kg以内,或小麦的水分在11%以内,小麦的重量损失发生明显变化推迟至一个月.8月份入仓的小麦,小麦中的玉米象的虫口密度在2头/kg以上,重量损失发生在15d内.9月初入仓的小麦,小麦中的玉米象虫口密度在2头/kg以上,小麦发生明显重量损失提前至10d.研究表明不同的玉米象虫口密度、小麦水分和不同的害虫感染时间可造成不同的粮食重量损失.因此,在发生明显的重量损失之前必须做出相应的防治措施.     

海南省农村小规模储粮技术研究

正采用新型PE仓为储具,结合植物源杀虫剂为储粮防护剂,稻谷储藏240天后,水分变化≤0.4%,与储粮前水分无显著差异。在0.5%香茅草、0.5%花椒处理条件下,储粮虫口密度为2头/kg,达到基本无虫水平,虫蚀粒率≤2.8%,霉变粒率≤0.3%,粮食损失率≤0.73%,干物质损失率≤1.11%。粮食品尝评分值变化≤4分,与储藏前评分值无显著差异。因此,采用PE仓与植物源杀虫剂配合使用的方法不仅能减少海南地区因高温、高湿带来的农户储粮质量损失,也能有效保证     

粮仓储粮霉变CO2法监测值主要影响因素

利用检测粮堆二氧化碳(CO_2)浓度变化的方法对储粮霉变进行监测,但该方法为间接测定,需对影响粮堆CO_2检测值的粮堆相关因素及传感器相关参数进行全面分析。试验结果表明,不同温度下储粮中霉菌生长早期阶段的霉菌增长量均与CO_2浓度变化同步,两者相关性系数0.99;较低的温度可使霉菌生长产气量显著降低,在霉菌生长量相当的状态下,30℃比20℃条件下测得的粮堆CO_2浓度值高4.7倍。粮食颗粒间空隙度等多种因素均可显著影响CO_2气体扩散,稻谷粮堆比小麦粮堆的孔隙度高约30%,稻谷粮堆在相距CO_2发生源50cm的监测点比小麦粮堆测得的峰值浓度高50%,峰值时间提前4d。对粮堆不同深度发生的霉变(距粮面1,2m),监测点设在粮面下3m可减少外界气体交换的影响,监测效果优于深度为1m的监测点。CO_2气体检测过程中,高的取样气流速度可显著降低检测值;对于各种规格的输气管道,适宜的检测气体取样量为管道内部理论体积的1.5倍。通过合理设定参数,CO_2法可灵敏地监测储粮霉菌活动。     

海南省农村小规模储粮技术研究

采用新型PE仓为储具,结合植物源杀虫剂为储粮防护剂,稻谷储藏240 d后,水分变化≤0.4%,与储藏前水分无显著差异。分别在0.5%香茅草、0.5%花椒处理条件下,储粮虫口密度为2头/kg,达到基本无虫水平,虫蚀粒率≤2.8%,霉变粒率≤0.3%,粮食损失率≤0.73%,干物质损失率≤1.11%。粮食品尝评分值变化≤4分,与储藏前评分值无显著差异。因此,采用PE仓与植物源杀虫剂配合使用不仅能减小海南地区因高温、高湿带来的农户储粮质量损失,也能有效的保证粮食在储藏过程中的品质。     

海南低温储粮仓储实验研究

本研究对海南地区的某仓库进行了实验测试,研究其在太阳能低温储粮方式下三年内仓储粮温的变化规律、稻谷品质变化情况、虫口密度变化等情况。结果显示:粮堆全年平均温度≤20℃;平均脂肪酸值(KOH)≤24.00mg/100 g;平均黄粒米率为0.32%≤1.00%;害虫密度≤5头/kg,主要害虫≤2头/kg;年平均磷化氢熏蒸次数≤1次/年;水分含量保持均匀平缓下降。由此得出太阳能低温储粮技术在海南切实可行。     

谷蠹侵害稻谷后其储藏品质变化研究

以粳稻谷为研究对象,选择不同的虫口密度(0、10、20、50、100和200头/500 g),在(30±1)℃与(75%±1%)RH条件下,对稻谷进行侵害实验,测定不同感染时间稻谷的水分、脂肪酸值、电导率、过氧化物酶、丙二醛等储藏品质指标,探讨不同虫口密度和感染时间下谷蠹对稻谷储藏品质的影响。结果表明:随着虫口密度的增加和侵害时间的延长,稻谷中的水分和过氧化物酶(POD)逐渐增加,而脂肪酸值、丙二醛和电导率逐渐降低,其中感染50 d时,各虫口密度感染的稻谷其过氧化物酶无明显变化,而50d后,迅速下降;水分和POD与感染时间呈极显著负相关,脂肪酸值、丙二醛和电导率与感染时间呈极显著正相关;脂肪酸值与虫口密度呈极显著正相关,电导率和丙二醛与虫口密度呈显著正相关,POD与虫口密度相关性不显著;脂肪酸值、POD、电导率、丙二醛各指标之间均呈极显著相关,水分除与POD呈显著正相关外,与其它各指标均呈极显著负相关;当虫口密度为50头/500 g时,感染稻谷30d后其品质便开始发生变化,因此,当稻谷中谷蠹虫口密度较大时,需要在30d内进行杀虫处理,以避免其品质遭受到大的影响。     

蛀食害虫对小麦淀粉酶及过氧化物酶活性的影响

探讨玉米象(Sitophilus zeamais)、米象(Sitophilus oryzae)和谷蠹(Rhyzopertha dominica)三种蛀食性害虫不同感染程度对小麦淀粉酶及过氧化物酶活性的影响及变化规律,为小麦科学储藏量化指标提供依据。选用河南产储藏2年的商用小麦,按不同虫种分组,设定不同的虫口密度和感染时间,检测小麦样品降落数值和过氧化物酶(POD)活性,并与虫口密度和感染时间作相关性分析。结果表明,随着虫口密度增加和感染时间延长,样品的降落数值呈波动上升趋势,POD活性呈下降趋势;三种害虫侵害后的样品降落数值与感染时间均存在极显著正相关,POD活性与感染时间均存在极显著负相关,降落数值与POD之间呈极显著负相关,而二者与虫口密度的相关性均不显著。     

小麦受蛀食性害虫侵害后其粉质特性动态变化

为探讨玉米象、米象和谷蠹3种蛀食性害虫不同感染程度对小麦出粉率和粉质特性的影响及其变化规律。选用河南产储藏2 a的商用小麦为材料,按不同虫种分组,设定不同的虫口密度,检测不同感染时间小麦的出粉率和制粉后面团的稳定时间和粉质指数,并与虫口密度和感染时间之间作相关性分析。结果表明:玉米象,米象和谷蠹侵害后样品出粉率与虫口密度和感染时间均呈极显著负相关;且随虫口密度增加和感染时间延长,出粉率总体呈下降趋势,样品的稳定时间和粉质指数呈下降趋势。     

不同初始虫口密度赤拟谷盗成虫为害对小麦粉挥发性物质的影响研究

本文采用顶空固相微萃取结合GC-MS研究了起始虫口密度分别为0、6、12、18 头/kg赤拟谷盗成虫为害小麦粉不同时间后挥发性物质种类、含量及成分的变化情况。研究结果表明,被赤拟谷盗成虫为害后的小麦粉挥发性物质主要为烃类、醇类、醛类和其他物质,随着为害时间的延长,小麦粉挥发性物质总含量增加,烃类、酯类和酸类物质含量随虫口密度的增加逐渐降低,醇类物质含量先增加后降低,起始虫口密度为12 头/kg赤拟谷盗成虫为害小麦粉40 d时出现了酮类物质。不同初始虫口密度赤拟谷盗成虫为害后的小麦粉主要特征挥发性物质为1,2-15,16-二环氧十六烷、(E)-3-二十碳烯、1-十二烯、环十二烯、1-十五醇、4-异丙基-1,3-环己烷二酮、羟甲基环丙烷、1-十三烯、(Z)-2-庚醛、戊醛、17-十八炔酸和甲基苯醌。本研究结果为通过检测储粮环境挥发物变化预测害虫发生提供了科学依据。     

Movement and distribution of Sitophilus zeamais adults and relationship between their density and trapping frequency in wheat bulks under different grain temperatures and moisture contents

Movement and distribution of Sitophilus zeamais adults and relationship between their trapping frequency and insect density were determined in one tonne wheat with 11.5 ± 0.2, 12.5 ± 0.1 and 13.5 ± 0.2% moisture contents (wet basis) inside cylindrical bins at 20, 25 and 30 °C. The introduced adult densities were 0.5, 1.0, and 2.0 adults/kg wheat (A/kg). Inside each bin, 15 probe traps were vertically installed in three layers. In each layer, five traps were installed at the center and half radii of the bin individually. The trapped adults were counted daily up to 7 d, and then 15 kg wheat was sampled at each trap location. The insect number in each sample was counted.The recovered adults in the top layer were less than that in the middle layer, while no significant difference between at middle and bottom layers. In each layer, adults preferred the center location at 0.5 A/kg, while this trend was unidentified at other densities. There was an autocorrelation of insect densities at adjacent locations at ≥ 1.0 A/kg, while no autocorrelation in the vertical direction. The adults had an aggregation distribution at any temperature, moisture content and adult density. The normal and Poisson model could not be used to describe the distribution of the count frequency of the adults in the samples, while the negative binomial model could describe this distribution in 18 out of 27 sampling sets at ≤ 1.0 A/kg. The trapping frequency was strongly influenced by the trapping period and increased with the increase of insect densities. The relationship between adult densities and trapping frequencies at the sampling locations had a significant difference at different grain temperatures, while no difference at different moisture contents, grain depths, and locations.     

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.     

Comparison of insect detection efficiency by different detection methods

Detection percentage of stored grain insects using different separation methods was determined. The stored grain insects tested were: Oryzaephilus surinamensis (L.), Rhyzopertha dominica (F.), Sitophilus oryzae (L.), and Tribolium castaneum (Herbst). To determine the detection percentage, 1 or 100 adults of the four insect species, and 1 or 100 young or old larvae of T. castaneum were introduced into wheat with 14 ± 1%, 16 ± 1%, or 18 ± 1% moisture content. The following four methods were used to separate the introduced insects from the infested wheat: Berlese funnel (Berlese), shaking grain on a metal sieve (Metal sieve), shaking grain on an acrylic device (Acrylic sieve), and microwave heating. For all detection methods, wheat moisture content did not influence the detection percentage. Detection method and insect species influenced the recovery percentage. For example, Metal sieve and Acrylic sieve methods had a higher recovery percentage of adults of O. surinamensis and T. castaneum than for S. oryzae and R. dominica. There was no significant difference in recovery percentage of the larvae and adults between the Metal sieve and Acrylic sieve methods, with the exception of weevils. The Berlese method had the lowest recovery percentage of introduced insects, with the exception of weevils, while the Microwave method had the highest or the second highest recovery percentage. Generally, the recovery percentage of the young larvae was lower than that of adults. The Microwave method could improve detection accuracy for larvae.     

Insect pests, Aspergillus flavus and aflatoxin contamination in stored wheat: A survey at North Bihar (India)

Fifty stored wheat samples (25 each of insect pest free and infested) were collected from North Bihar (India). Of the four major pests recorded, Sitophilus oryzae was the dominant insect, followed by Tribolium castaneum, Rhizopertha dominica and Trogoderma granarium. Aspergillus flavus was recorded in all samples: infection in insect-damaged samples was 87% and in insect-free samples 25%. Aflatoxin contamination was found in 19 and 2 of the insect-damaged and insect-free lots respectively. The role of insect pests in making wheat grains vulnerable to A. flavus infection and subsequent aflatoxin production is discussed.     

Evaluation of sampling units and sampling plans for adults of Cryptolestes ferrugineus (Coleoptea: Laemophloeidae) in stored wheat under different temperatures, moisture contents, and adult densities

Development and evaluation of optimum size and number of sample units is required for cost-effective management of stored grain beetles. In this study, we evaluated the sampling parameters and accuracy of insect density detection and estimation, developed the optimum size and number of sample units, and conducted a feasibility study of the insect detection and density estimation. The measured insect densities in 92% of random samples were less than the introduced insect densities and 67.4 ± 10.8% of random samples did not contain adults when the introduced insect density was 0.1 A/kg (adult/kg). If the random sampling technique was used and 15% of the stored wheat bulk was sampled, 72% of determined means of insect densities of the sampling sets were lower than the introduced insect densities. Increasing the size of sample units did not improve the accuracy of the estimation of insect densities; however, it did considerably increase the probability of insect detection when insect densities were lower than 1.0 A/kg. We recommend at least 7 kg per sample unit for insect detection (especially when insect densities < 0.1 A/kg) and the optimum number of sample units with 15 kg grain per unit should be >24 for a fixed precision of 0.35 when insect densities < 0.1 A/kg. This might be a challenge for grain storage practice. Therefore, using sampling technique to estimate insect densities and detect insects at low insect densities (<0.1 A/kg) might not be practicable.     

赤拟谷盗对小麦粉品质的影响

赤拟谷盗是小麦粉加工及储存过程中的重要害虫之一。选用普通小麦粉180g,向其中投入赤拟谷盗成虫,研究小麦粉在感染头数分别为0、10、30、60、100、200,感染时间为0、15、25、35、45d时的品质变化。实验表明:随着虫口密度的增大和感染时间的延长,小麦粉的水分稍有上升,灰分变化不大;粗淀粉含量降低,粗蛋白质含量升高,湿面筋含量和面筋指数则呈现不规律的波动;清蛋白、球蛋白、谷蛋白含量下降,醇溶蛋白的含量上升;降落数值下降明显。在较低虫口密度下时,小麦粉的峰值黏度、最低黏度、黏度破损值和最终黏度有升高趋势,但随着虫口密度的增大又逐步降低。     

Damage potential of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) on cocoa beans: Effect of initial adult population density and post infestation storage time

The effect of different initial adult population densities of Tribolium castaneum (Herbst) at several post infestation storage times on the final adult population density, the percentage of damaged beans, the percentage of weight loss, and the weight of insect feeding residues on cocoa beans was investigated in laboratory experiments. Both factors interactively had highly significant (P < 0.01) effects on variables assessed. The highest mean final adult population density of 129.7 ± 4.6 was recorded in samples infested with the highest initial adult population density and stored for 150 d, while the least mean adult population density of 10.8 ± 0.54 was recorded on samples infested with the lowest initial adult population density in samples stored for 30 d. The highest percentage damaged cocoa beans 51.0 ± 1.21% was recorded in samples infested with the highest initial adult population density, while the least mean percentage damaged beans of 16.9 ± 1.26% was also recorded on samples infested with the lowest initial adult population density. Similar trends of means were recorded for all the remaining variables. Correlation between factors was significant and positive. Multiple and simple linear regressions analyses were also significant (P < 0.01) and all equations fitted the regression models and perfectly described the relationship between the independent and the dependent variables. Our results show that T. castaneum can impact negatively on both the quantity and quality of stored cocoa within just 30 days of infestation, with the impact increasing with increasing population density and post infestation storage time.     

Evaluations of the new deltamethrin-treated all-in-one hermetic bag for the control of the Khapra beetle,Trogoderma granarium (Everts)

The khapra beetle, Trogoderma granarium (Everts), is a highly destructive stored product insect that presents a significant threat to stored bagged grain. Hermetic packaging is designed to maintain the quality and safety of stored grain, while continually protecting the grain from insect infestations during storage. The objective of this research was to evaluate a prototype deltamethrin, all-in-one treated hermetic bag on contact efficacy, larval mobility, and the control of T. granarium in artificially infested wheat. The insecticidal activity of the deltamethrin-treated packaging was tested against larvae and adults of T. granarium through contact bioassays. There was a significant reduction in responsive adults after 5 day and >86% of larvae were unresponsive after 9 d of exposure on the treated bag. Trogoderma granarium movement toward a food bait was <10% after a 24 h exposure on the treated bag compared to ~45% of larvae on untreated bag. Lots of 15 kg of wheat were artificially infested with 100 T. granarium larvae and placed inside treated and untreated storage bags, sealed, and stored in a semi-field warehouse, and observed after 2, 6, and 8-weeks for T. granarium survival and grain quality attributes. The weight and number of insect damaged kernels was lower across all storage intervals for grain held in the treated bags, as compared with control bags. Live adult T. granarium were observed at 2-weeks in treated and untreated bags, but there were no live adults observed after 8-weeks of storage in both bags. The new prototype hermetic bags maintained positive grain qualities, however more information on the hermetic parameters are needed to understand how some individuals survived.