Immediate and delayed mortality of the larger grain borer,Prostephanus truncatus (Horn), on different surfaces treated with thiamethoxam and alpha-cypermethrin

In this study, we evaluated efficacy of alpha-cypermethrin and thiamethoxam on concrete, linen and plastic surfaces, against adults of the larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae), which is an important pest of stored maize in the tropics. Insect mortality was recorded after 1, 3 and 7 days of exposure. Then, separately for each initial exposure, the surviving individuals were transferred to untreated surfaces and delayed mortality was assessed again 1, 3 and 7 days later. Adult mortality on both insecticide treated linen surface was significantly lower than those on the other surfaces. Regarding delayed mortality, for adults that had been initially exposed for 7 d, complete control was detected 7 d later on plastic and concrete surfaces treated with thiamethoxam, while for alpha-cypermethrin complete mortality was detected only on plastic surface. Overall, there was a noticeable delayed mortality of P. truncatus adults, for all exposures and surfaces, which indicates that even if the insects are removed from the substrate that with either alpha-cypermethrin or thiamethoxam, delayed mortality is more likely to occur than recovery.     

Aerosol concentration,deposition, particle size,and exposure interval as mortality factors Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae)

A series of trials was conducted for an experiment. In the first trial, adults of Tribolium confusum Jacquelin du Val, the confused flour beetle, were exposed on concrete arenas and treated with a combination aerosol of pyrethrin + methoprene dispensed for 5, 10, and 20 min at particle sizes of 4, 8, 12, and 16 μm, inside an aerosol exposure chamber. Nearly all adult T. confusum were knocked down when immediately removed from the chamber. Among all the exposure time and particle size combinations, recovery increased as the post-exposure holding period increased from one to seven days and when adults were transferred to untreated dishes with flour. A second experiment evaluated the residual effect of the aerosol on concrete arenas at 1, 3, and 6 weeks using 3-4-week-old larvae of T. confusum. Adult emergence of exposed larvae decreased with increasing particle size and exposure time. A biological index that assessed development of exposed larvae to the pupal and adult stages was also related to particle size and exposure interval, and this index was correlated with adult emergence. A third set of experiments investigated effects of particle size on adult fecundity for the 10-min exposure time. Male and female adults were cross-mated: exposed female with exposed male, exposed female with unexposed male, exposed male with unexposed female, and unexposed female and unexposed male. Progeny production was reduced as particle size increased, and there were indications that females were affected more than males by the aerosol treatment. This research could be used to improve insect pest management programs by adjusting application equipment to dispense aerosols at particle sizes that give optimum control of exposed adults and residual control of immatures and would also benefit pest management programs.     

Immediate and delayed mortality of Oryzaephilus surinamensis (L.) exposed on wheat treated with diatomaceous earth: effects of temperature, relative humidity, and exposure interval

Adult Oryzaephilus surinamensis (L.), the sawtoothed grain beetle, were exposed for 4-72 h on wheat treated with diatomaceous earth (Protect-It(TM)), then removed and held for 1 week on untreated wheat. Beetles were exposed and held at 22, 27, and 32 degrees C, 40, 57, and 75% r.h. (nine combinations). Mortality after the initial exposures increased as exposure interval and temperature increased, but humidity effects were inconsistent with temperature. Mortality after the one-week holding period was greater than initial mortality, and also increased as the original exposure interval and the temperature increased. At 22 and 27 degrees C, mortality of beetles exposed from 4 to 24 h at 75% r.h. was significantly lower than mortality of beetles exposed for the same time intervals at 40 and 57% r.h. Nearly all of the beetles exposed for 72 h at all three relative humidities were dead after 1 week. The relationship between exposure interval and mortality was described by sigmoidal and linear regression for both the initial mortality and mortality 1 week after being transferred to untreated wheat. Results indicate that O. surinamensis is susceptible to the Protect-It(TM) formulation of diatomaceous earth, and will continue to suffer from the effects of exposure even after they are removed from the treated environment.     

Mortality and progeny production of four stored-product insect species on three grain commodities treated with Beauveria bassiana and diatomaceous earths

Laboratory bioassays were conducted to estimate the effectiveness of the entomopathogenic fungus Beauveria bassiana (Bals.-Criv.) Vuill. (Hypocreales: Cordycipitaceae) at 1.5 × 10⁸ and 1.5 × 10¹⁰ conidia/kg grain alone or mixed with the diatomaceous earths (DEs) Protect-It at 150 ppm and DEBBM at 50 ppm against adults of the rusty grain beetle, Cryptolestes ferrugineus Stephens (Coleoptera: Laemophloeidae), the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae), the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) and the psocid, Liposcelis paeta Pearman (Psocoptera: Liposcelididae). The adult insects were exposed to treated grains for 7, 14 and 21 days. For progeny emergence data, the treated units were remained under the same conditions for 62 days for all beetles and 30 days for psocids. The results revealed significant differences in mortalities of insect species among treatments and grains. The combined use of B. bassiana, at the highest dose, and DE increased adult mortalities of all species. In general, the treatments were least effective against T. castaneum and most effective against L. paeta. More numbers of dead insects were found on wheat than on rice or maize. The emergence of progeny was considerably reduced on grains treated with B. bassiana, at the highest dose, plus DE. The results of the present study suggest that the effectiveness of B. bassiana is fortified by the addition of DEs, but it varies among exposed insect species and commodities.     

Influence of temperature and relative humidity on the efficacy of thiamethoxam for the control of three stored product beetle species

Laboratory bioassays were carried out in order to evaluate the effectiveness of thiamethoxam in different levels of temperature and relative humidity (r.h.) against three major stored-grain beetle species, the lesser grain borer Rhyzopertha dominica (F.), the rice weevil, Sitophilus oryzae (L.) and the confused flour beetle, Tribolium confusum Jacquelin du Val. Adults of the three species were exposed on wheat treated with thiamethoxam at 0.1, 1 and 5 ppm and under six different combinations of temperature (20, 25 and 30 °C) and r.h. levels (55 and 75%). Our study showed that the increase in temperature increased mortality in all insect species, particularly at the lowest concentration. For some of the combinations tested, the low r.h. seemed to play a significant role in thiamethoxam efficacy in the case of R. dominica. Moreover, of the species tested, T. confusum was found to be the least susceptible, while R. dominica the most susceptible. In general, thiamethoxam was found to be effective against all three species, at concentrations that are comparable with most commercially available grain protectants.     

A wild strain of Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) from farm-stored maize in South Carolina: Effect of temperature on mating, survival, and fecundity

The purpose of this study was to develop age-specific survivorship and fecundity schedules for adult Plodia interpunctella (Hübner) relevant to maize storages, with special reference to the southeastern states (USA). Laboratory cultures were established with moths collected from farm-stored maize in South Carolina and maintained on cracked maize at 30 °C and 60% r.h. Age-specific schedules of survivorship and fecundity, the length of the oviposition period, mating success, and mating frequency were determined at 20, 25, 30, and 35 °C and about 75% r.h. The maximum oviposition period was longest (18 d) at 20 and 25 °C, and shortest (8 d) at 35 °C. The optimum temperatures for reproduction (mating frequency and fecundity) were 25–30 °C, but mean life-span was longest (13.2 d) at 20 °C and declined linearly with increasing temperature. Mean total (lifetime) fecundity ranged from 16.9 eggs at 35 °C to 227.7 eggs at 25 °C.     

Insecticidal efficacy of diatomaceous earth against Sitophilus oryzae (L.) (Coleoptera: Curculionidae) and Tribolium confusum du Val (Coleoptera: Tenebrionidae) on stored wheat: influence of dose rate, temperature and exposure interval

Laboratory experiments were conducted in order to assess the insecticidal effect of a diatomaceous earth formulation (Silicosec^®, Biofa GmbH, Germany) against Sitophilus oryzae and Tribolium confusum on stored wheat. Adults of the two species were exposed on wheat treated with diatomaceous earth at four dose rates: 0.25, 0.5, 1 and 1.5 g/kg of wheat, respectively. For each dose rate, the treated wheat was placed at 22°C, 25°C, 27°C, 30°C and 32°C. Dead adults were counted after 24 and 48 h, 7 and 14 d of exposure. After the 14-d interval, the live adults were removed and placed for 7 d in untreated wheat (in the case of S. oryzae) or untreated flour (in the case of T. confusum), and the production of F₁ was recorded. For both species, dose rate, temperature and exposure interval significantly affected mortality (P<0.001). Mortality was higher at longer exposure intervals. The efficacy of SilicoSec against S. oryzae increased with temperature, but for T. confusum mortality was lower at 32°C, compared to 30°C, for 24 and 48 h exposure intervals. Tribolium confusum proved less susceptible to SilicoSec than S. oryzae. In general, the rates of 1 and 1.5 g/kg of wheat provided a satisfactory level of protection against the two species examined. For S. oryzae, F₁ emerged only at 22°C, in wheat treated with 0.25 or 0.5 g/kg. However, for T. confusum, F₁ were recorded at 22°C for 0.5 g/kg and at 22°C, 25°C, 27°C and 30°C for 0.25 g/kg.     

六个品种小麦对玉米象的抗虫性比较研究

试验选用产自河北、河南、山东等省的6个小麦品种,分别是良星66、泛麦8号、西农979、郑麦7698、济麦22和矮抗58。从田间获取的样品分别将其水分含量调节为12.5%左右,每16 g粮食感染6头母代玉米象成虫(雌雄比为4∶2),之后检查其子代成虫羽化数量,羽化时间,并计算发育历期和敏感系数。主要结果为:济麦22中的玉米象平均发育历期最短(40.8 d),子代成虫数量最多(46头),对玉米象的敏感系数为9.40;西农979中的玉米象平均发育历期为42.6 d,子代成虫数量为8头,对玉米象的敏感系数为4.98。抗虫性最小的济麦22中玉米象子代成虫羽化初现时间、羽化高峰和终止时间都相应地是最短,抗虫性最大的西农979中害虫初现时间和终止时间有所延长,但并非最大值。良星66中的玉米象羽化终止时间最长,但其抗虫性却小于西农979。由样品感染卵至成虫初现的过程中小麦品种间的重量变化量差异不显著。结果表明:试验小麦品种间对玉米象的抗虫性差异显著,子代成虫出现数量多的小麦品种其敏感系数也相应地小,但羽化时间长短与小麦的敏感系数大小变化趋势不完全一致,小麦感染害虫后重量下降量与其敏感性相关性不明显。     

Persistence and activity towards Sitophilus zeamais (Coleoptera: Curculionidae) of pirimiphos-methyl sprayed at different temperatures on maize

The air temperature in storage units in tropical areas frequently exceeds 50°C during the warmest periods of the day. Since protectant insecticides are sprayed on grains under these conditions, such high temperatures may interfere with the insecticidal activity. To assess this possibility we sprayed maize grains with pirimiphos-methyl 500 EC (0.8 ml c.p./l and 1.5 l/t) at different temperatures (25°C, 30°C, 35°C, 40°C, 45°C, and 50°C) and 55% r.h. The grains were then maintained at 27±1°C and 55±5% r.h. throughout the experiment which lasted 90 days. Residues of pirimiphos-methyl on the sprayed grains were analyzed every 30 days. Grain samples were assessed every 15 days after the insecticide spraying for their effect on the maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae). Insect mortality was evaluated after 24 and 48 h of exposure to the treated grain. The level of pirimiphos-methyl residue on maize grains decreased with an increase in storage period and air temperature during the insecticide spraying (varying from 11.0±0.1 to 1.1±0.1 ppm, corresponding to the residue levels at 25°C on the day of the spraying and after spraying at 50°C and 90 days of storage). The same trend was observed for mortality of the maize weevil, which dropped from 95.4±13.3% to 2.5±2.5% after 90 days storage after insecticide spraying at 50°C. These results indicate that temperature at spraying can affect insecticide persistence and activity during storage.     

A wild strain of Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) from farm-stored maize in South Carolina: Development under different temperature, moisture, and dietary conditions

The purpose of this study was to determine the duration of immature development and survivorship of Plodia interpunctella (Hübner) on maize over a range of temperatures and grain moisture contents encountered in maize stored on farms in the southeastern states (USA). Laboratory cultures were established with moths collected from farm-stored maize in South Carolina and maintained on cracked maize at 30 °C and 60% r.h. The incubation period and percentage hatch of eggs was determined at 18 combinations of temperature and r.h. Hatch was <1% at 15 and 40 °C. In the range 20-35 °C, percentage hatch declined as temperature increased, and the mean incubation period ranged from 3.1 to 8.5 d. Neither percentage hatch nor incubation period were affected by r.h. between 43% and 76%. The relationship between mean developmental period (oviposition to adult eclosion) and temperature was well described by a quadratic polynomial that predicted a decline from 67.6 to 30.1 d as temperature increased from 20 to 31.1 °C, followed by an increase to 38.5 d as temperature increased further to 35 °C. The results suggest a lower temperature threshold for development near 15 °C and an upper limit slightly greater than 35 °C. Moisture content had a significant effect on developmental period at all the temperatures studied, but the pattern of variation with moisture depended upon the temperature.     

Occurrence of mycotoxins in maize,grass and wheat silage for dairy cattle in the Netherlands

The occurrence of mycotoxins in 140 maize silages, 120 grass silages and 30 wheat silages produced in the Netherlands between 2002 and 2004 was determined using a liquid chromatography coupled with tandem mass spectrometry detection (LC-MS/MS) multi-method. Deoxynivalenol (DON) was detected above the limit of quantification (LOQ) of 250 μg kg^?1 in 72% of maize and 10% of wheat silages. Average DON concentrations were 854 and 621 μg kg^?1, respectively, and maximum concentrations 3142 and 1165 μg kg^?1, respectively. Zearalenone was detected above the LOQ of 25 μg kg^?1 in 49% of maize and 6% of grass silages. Average zearalenone concentrations were 174 and 93 μg kg^?1, respectively, and maximum concentrations 943 and 308 μg kg^?1, respectively. The incidences and average concentrations of DON and zearalenone in maize silage were highest in 2004. The incidence of other mycotoxins was low: fumonisin B1 and 15-acetyl-DON were detected in 1.4 and 5% of maize silages, respectively, and roquefortin C in 0.8% of grass silages. None of the silages contained aflatoxins, ochratoxin A, T2-toxin, HT2-toxin, sterigmatocystin, diacetoxyscirpenol, fusarenon-X, ergotamine, penicillinic acid, or mycophenolic acid. This study demonstrates that maize silage is an important source of DON and zearalenone in the diet of dairy cattle. Since the carryover of these mycotoxins into milk is negligible, their occurrence in feed is not considered to be of significant concern with respect to the safety of dairy products for consumers. Potential implications for animal health are discussed.     

Movement of adult rusty grain beetles, Cryptolestes ferrugineus (Coleoptera: Cucujidae), in wheat in response to 5°C/m temperature gradients at cool temperatures

The direction and speed of movement of adult rusty grain beetles in 12 and 24 h at 2.5-27.5°C (standard error was ±0.2°C in all of the experiments) were determined in 100×100×1000 mm³ wheat (14.5±0.2% moisture content) columns with or without 5°C/m temperature gradients. At 5°C or less, adults could not move more than 5 cm in 24 h. At 7°C or less, 98% of adults could not move more than 5 cm in 24 h. Between 5°C and 27.5°C, the beetles preferred warmer areas and increasing temperature caused an increased number of insects to move towards the warmer areas both in vertical and horizontal columns. Insects moved faster in the vertical direction than in the horizontal direction and the maximum absolute speed of the beetles was <0.2 m/d at 7°C, 0.4 m/d at 10°C in the horizontal direction, 1 m/d at 10°C in the vertical direction and more than 1 m/d at 17.5°C or higher. When temperature at the top end of the vertical column was lower than that at the bottom, 98% of adults moved down; when temperature at the top end was higher than that at the bottom, 5% at 10°C, 7% at 15°C, 25% at 20°C, and 30% at 25°C moved up. The speed of the insect movement to the bottom was reduced by an opposing temperature gradient. The results of the factorial experiments showed that the speed and direction of insect movement were affected by temperature, temperature gradient, geotaxis, and the interaction between temperature gradient and geotaxis. Adults were more sensitive to geotaxis than to temperature gradient and the preference of geotaxis decreased with the increase of temperature.     

Determination of fusarium mycotoxins in wheat,maize and animal feed using on-line clean-up with high resolution mass spectrometry

An automated method involving on-line clean-up and analytical separation in a single run using TurboFlow? reversed phase liquid chromatography coupled to a high resolution mass spectrometer has been developed for the simultaneous determination of deoxynivalenol, T2 toxin, HT2 toxin, zearalenone and fumonisins B1 and B2 in maize, wheat and animal feed. Detection was performed in full scan mode at a resolution of R?=?100,000 full width at half maximum with high energy collision cell dissociation for the determination of fragment ions with a mass accuracy below 5?ppm. The extract from homogenised samples, after blending with a 0.1% aqueous mixture of 0.1% formic acid/acetonitrile (43:57) for 45?min, was injected directly onto the TurboFlow? (TLX) column for automated on-line clean-up followed by analytical separation and accurate mass detection. The TurboFlow? column enabled specific binding of target mycotoxins, whereas higher molecular weight compounds, like fats, proteins and other interferences with different chemical properties, were removed to waste. Single laboratory method validation was performed by spiking blank materials with mycotoxin standards. The recovery and repeatability was determined by spiking at three concentration levels (50, 100 and 200% of legislative limits) with six replicates. Average recovery, relative standard deviation and intermediate precision values were 71 to 120%, 1 to 19% and 4 to 19%, respectively. The method accuracy was confirmed with certified reference materials and participation in proficiency testing.     

小麦替代部分玉米对藏羊生长性能、表观消化率和血清生化指标的影响

本试验旨在研究小麦替代精料中部分玉米对藏羊生长性能、表观消化率、血清生化指标和脏器发育的影响。选取60只初始体重相近,健康无病的2~3月龄藏羊,随机分成2组,每组30只,每组5个重复。对照组饲喂玉米型基础日粮,试验组饲喂10%小麦替代精料中部分玉米。试验期100 d,其中预饲期10 d,正试期90 d。结果表明：1）试验组的终末体重、平均日增重、体长和体躯指数显著高于对照组（P<0.05）。2）试验组中粗蛋白、粗纤维、中性洗涤纤维、酸性洗涤纤维和粗灰分的表观消化率显著高于对照组（P<0.05）。3）试验组中谷草转氨酶显著低于对照组（P<0.05）。4）瘤胃重量和皱胃重量试验组显著高于对照组（P<0.05）。结论：在藏羊日粮中添加10%小麦粉替代精料中部分玉米能有效提高藏羊的表观消化率,从而使藏羊对其日粮的利用率增加提高其生长性能和脏器重量,同时还能降低血清中谷草转氨酶含量从而改善肝脏功能,以维持藏羊正常的消化代谢,本研究结果可为小麦替代玉米为绵羊饲料的推广提供理论依据。     

The effects of temperature,concentration and exposure time to acetylene on initiation of banana ripening

The initiation of ripening of bananas by acetylene was studied with various concentrations and times of exposure at a range of temperatures. Ripening was associated with loss in firmness of the pulp, change in peel colour, and increases in total soluble solids content of the pulp. An interaction between the pulp temperature of bananas and their response to acetylene was demonstrated over a temperature range of 14 to 35°C in that the higher the temperature the shorter the exposure time, or the lower the concentration required. The period of exposure to acetylene was also shown to affect initiation of fruit ripening, with longer exposures up to 24 h requiring less gas or a lower temperature to initiate ripening. Fruit exposed to acetylene gas at the lower temperatures (14 to 16°C) were shown to ripen normally with respect to pulp soluble solids and pulp rupture force, although the co-ordination of the degreening response was lost in some fruit exposed to acetylene for 72 h. The temperature at which bananas were initiated to ripen did not affect their flavour.     

不同储藏温湿度对玉米中蛋白质的影响

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小麦/玉米垄沟套作条件下施肥部位对土壤水氮分布的影响--测试文章

通过旱棚小车模拟小麦/玉米垄沟套作种植试验,研究了3种不同垄沟部位（垄顶、垄底和沟中）施肥对小麦/玉米生长和产量及土壤水氮分布的影响。结果表明：相同灌水条件下,施肥部位对垄沟套作水分分布影响不显著,但土壤硝态氮的分布差异较大; 垄顶施肥和垄底施肥处理下,由于水肥异区,其垄上小麦生长带的硝态氮主要分布在0～30 cm土层,有效地减少了硝态氮向土壤深层淋溶,而后期沟内玉米生长带的水氮处理相同,因此其硝态氮分布差异较小; 在相同灌水条件下,垄沟套作可以有效降低水分流失,减少氮肥损失,因此较传统平作更有利于作物生长,提高小麦、玉米的产量,且以垄顶施肥和垄底施肥效果最显著,小麦产量较平作分别增加11.47%、10.81%,玉米产量较平作分别增加18.87%、22.70%。     

Cooking oils and “Triplex” in the control of Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) in farm-stored maize

The uses of some cooking oils viz., noug oil, soybean oil, sunflower oil, corn oil and olive oil, and the reputedly non-toxic botanical “Triplex”, were evaluated against maize weevil, Sitophilus zeamais, in stored maize grain under local Ethiopian storage conditions in 2003. For comparison, an untreated sample and the synthetic insecticides, malathion 5% dust and Actellic 2% dust, at the recommended rates of 0.05% (w/w) were included. All the cooking oils tested had a significant toxic effect on the weevils in stored grains. The oil treatments showed significantly higher mortality of adult weevils at each sampling period compared with the untreated grains. The cooking oil treatments also significantly reduced weight loss and grain damage as compared with the untreated control. The Triplex treatment was of comparable effectiveness to the synthetic insecticides, causing high mortality of adult weevils, low-percentage grain damage and low-percentage weight losses. These promising oils and Triplex could be recommended for use as part of an integrated pest management program in stored maize, particularly at low levels of pest infestation and, in the case of cooking oils, for grain intended for home consumption.     

The biology,ecology and management of the larger grain borer,Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae)

The invasive larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae), originating from Meso-America, is a devastating stored product pest of maize (Zea mays L.) and cassava (Manihot esculenta). This species can destroy up to 40% of stored maize within four months. Despite four decades of research, P. truncatus has spread throughout Africa, while decimating maize and cassava production. Given the continuing problems with P. truncatus, the likelihood for its continued range expansion under climate change, and its status as a species of concern in many countries, the objective of this review was to provide an updated and comprehensive freely accessible record of the distribution and spread, biology, development, and ecology, host preferences, chemical ecology, detection, and monitoring, and management of P. truncatus. We conducted a search of the literature from 1911 to 2021 using Google Scholar and Web of Science to find all papers related to key search terms. We found that P. truncatus has been recorded in 36 countries across the globe, including 21 now in Africa. A recent predictive model found that the insect has been limited to tropical and subtropical regions but could likely spread to temperate regions as temperatures rise with climate change. Conspecifics respond to their two component, male-produced aggregation pheromone early after eclosion, but quickly switch to other cues as older adults. At close-range, P. truncatus may use food cues, but host volatiles are not involved in long-range host finding of commodities. Research on managing P. truncatus has mostly focused on chemical control to the detriment of other tactics, with the most promising tactic likely to be the different hermetic storage technologies. Many outstanding areas of basic behavior and ecology remain to be assessed for P. truncatus. We highlight specific areas that should be prioritized for further work in order to better manage and reduce the impact of this invasive insect pest.