烟蚜茧蜂对烟蚜的选择性寄生及雌蜂年龄对后代性别的影响

烟蚜茧蜂寄生烟蚜后对烟蚜的产仔量和寿命影响较大,一龄若蚜至成蚜被寄生后的平均产仔量分别下降100.0%、97.3%、95.9%、92.7%、89.5%,平均寿命分别缩短65.6%、58.9%、57.9%、49.4%、38.3%;在各龄烟蚜数量比相同,雌蜂与烟蚜比为1:100的条件下,烟蚜茧蜂对二龄、三龄烟蚜有较强的嗜好性,这种嗜好性与雌蜂年龄无关;羽化并交配过的烟蚜茧蜂雌蜂,在前5 d内产卵寄生烟蚜,其后代的雌雄比大于1,寄主烟蚜的龄期对烟蚜茧蜂后代性别的影响不大。      

几种杀虫剂对烟蚜茧蜂搜索烟蚜行为的影响

利用Y形嗅觉仪观测了4种杀虫剂影响烟蚜茧蜂对烟叶及烟蚜复合体的选择行为.结果表明,在正常生长状况下,烟叶释放的挥发物对烟蚜茧蜂无明显引诱作用,而烟叶受到蚜虫为害后所释放的挥发性次生物质则对烟蚜茧蜂有明显的招引作用;在杀虫剂处理后,20％康福多、3％莫比郎乳油和40％氧乐果乳油会抑制烟蚜茧蜂的搜索行为,但氯氰菊酯则明显有...     

我国烟蚜茧蜂的研究进展

烟蚜茧蜂是烟蚜的一种重要寄生性天敌,对烟蚜的自然控制力较强。本文就烟蚜茧蜂的生物学、生态学及其应用等的研究进展作了较详尽的综述。生物学方面主要论述了烟蚜茧蜂的交配、寄生,发育,产卵,体色,性比,越冬,成蜂寿命及其对寄主生命活动的影响,生态学方面主要论述了烟蚜茧蜂的天敌以及气体因子、烟草长势和化学农药对其的影响。     

烟蚜茧蜂感器的扫描电镜观察

烟蚜茧蜂(Aphidius gifuensis)是蚜虫尤其是烟蚜(Myzus persicae)的常见重要寄生性天敌,烟蚜茧蜂感器的研究为其在寄生时的功能提供理论依据。本文运用扫描电镜技术,对烟蚜茧蜂的触角、复眼、口器、足上的重要感器形态与超微结构进行了系统研究。研究发现烟蚜茧蜂主要有 6种类型的感器:板形感器、刺形感器、毛形感器、锥形感器、Böhm氏鬃毛和膜状中垫。雌、雄蜂的感器差异不明显。触角鞭节上感器的种类和数量最多。毛形感器的数量最多且分布最广,Böhm氏鬃毛只分布在触角基节窝和足基节端部。      

烟蚜茧蜂规模繁殖中烟蚜越冬寄主筛选

烟蚜越冬种群保育对保障烟蚜茧蜂规模繁殖具有十分重要的意义。通过接种烟蚜与烟蚜茧蜂,对玉溪地区8种不同寄主植物上烟蚜的增长数量、烟蚜茧蜂寄生烟蚜后形成僵蚜的体重进行了比较。结果表明,接种后,油菜、白萝卜、红萝卜上烟蚜数量以及僵蚜体重均可达到烟蚜茧蜂繁殖技术指标要求,可作为烟蚜茧蜂规模化繁殖体系中烟蚜的理想越冬寄主。     

不同蜂蚜比的蜂蚜同接对规模化繁殖烟蚜茧蜂的影响

以漂浮育苗为载体,研究了不同蜂蚜比的蜂蚜同接后烟蚜茧蜂的繁殖效果。结果表明,蜂蚜比为1：100的蜂蚜作为蜂蚜同接的蚜源和蜂源,其初始寄生率为52.28%,按4头/株同接饲养25 d后,累计繁殖僵蚜量为261.66头/株,其寄生率高达97.3%,繁蜂效果最好。其次是蜂蚜比为1：200,再次是蜂蚜比为1：50。蜂蚜同接技术适用于烟蚜茧蜂的规模化繁殖,其繁蜂效果均优于先繁蜂再繁蚜的分接繁殖技术,在实际运用中蜂蚜比控制在1:100~1:200.     

烟蚜茧蜂对麦田蚜虫的防治效果

为发掘利用麦田麦蚜自然繁育烟蚜茧蜂的潜力,建立蚜虫生态区域联防联控体系,以麦田自然发生麦蚜为防控对象,在麦田中释放单位面积不同数量的烟蚜茧蜂,调查并分析了释放烟蚜茧蜂与化学药剂处理和空白对照田块烟蚜茧蜂对麦蚜的寄生率、麦蚜虫口减退率、防治效果以及小麦产量指数等参数.结果显示,在麦田中麦蚜平均数量达到300头/百株时,烟...     

利用蜂蚜同接技术规模饲养烟蚜茧蜂

利用蜂蚜同接技术饲养烟蚜茧蜂,结果表明,蚜源的寄生率控制在47％左右,平均每株接蚜2.8头/株,饲养18d后最高繁蚜量可达11万头/m2,饲养23d后单位面积可获得4.9万头/m2以上的僵蚜量,繁蚜和繁蜂效益较高.     

烟田常用杀虫剂对烟蚜茧蜂的毒力及其保护酶的影响

为了筛选对烟蚜茧蜂安全性高的药剂并明确烟田常用杀虫剂对烟蚜茧蜂保护酶的影响,测定了3种烟田常用杀虫剂对烟蚜茧蜂成虫的毒力以及不同浓度的吡虫啉对烟蚜茧蜂成虫体内超氧化物歧化酶、过氧化物酶和过氧化氢酶活性的影响。结果表明,杀虫剂对烟蚜茧蜂成虫的毒力大小顺序为:啶虫脒 > 高效氯氟氰菊酯 > 吡虫啉;从不同浓度的吡虫啉对烟蚜茧蜂生命活动和防御机制的影响来看,除LC₁₀浓度吡虫啉促进烟蚜茧蜂成虫体内POD活性提高和3个浓度处理后12 h成虫CAT活性显著提高外,其余处理浓度和时间对3种酶的活性呈现抑制作用。此结果为探明烟蚜茧蜂对杀虫剂的防御机制提供了一定的理论依据。     

烟蚜重寄生蜂种群动态初步研究

系统调查了烟田和繁蜂棚内烟蚜重寄生蜂的种类、数量组成和种群变动。结果表明,烟蚜重寄生蜂有蚜虫宽缘金小蜂、宽肩阿莎金小蜂和合沟细蜂3种。在烟田,重寄生蜂出现的时间较烟蚜茧蜂滞后25 d,但高峰期仅相差约5 d,这种在时间上滞后、数量上跟随紧密的效应是制约烟蚜茧蜂种群数量的重要因素之一。在全年繁蜂的繁蜂棚内,重寄生率最高达65.0%,烟蚜茧蜂的羽化率还不到1.0%,而在田间简易繁蜂棚内,重寄生率不超过10.0%。且均以接蜂后7～21 d内烟蚜茧蜂羽化率为最高,而重寄生率以接蜂后7～14 d的最低。因此,人工繁殖烟蚜茧蜂时,建议在田间繁蜂棚内进行短期的繁蜂,即以接蜂后7～14 d为最佳繁蜂周期。     

Influence of temperature on the functional response of Anisopteromalus calandrae (Hymenoptera: Pteromalidae), a parasitoid of Rhyzopertha dominica (Coleoptera: Bostrichidae)

The functional response of Anisopteromalus calandrae (Howard) parasitizing 4th-instar Rhyzopertha dominica (F.) on wheat was estimated over a range of temperatures and host densities. A functional response equation was used in which a quadratic component that included temperature was substituted for handling time. The instantaneous search rate increased with increasing temperatures. The maximum rate of parasitization was 13 larvae/24 h at 30°C and 35°C. Handling time was lowest at 30°C and highest at 20°C. The ability of A. calandrae to find and parasitize R. dominica over a broad range of temperatures makes it a good candidate for natural control of stored grain pests.     

Effects of three temperature regimes on rearing and biological activities of Bracon hebetor (Say) (Hymenoptera: Braconidae)

The body color of Bracon hebetor adults was either black, yellow with black spots, or completely yellow when development from egg to adult took place at 15–18°C, 25 or 35°C, respectively, and the wasps were reared on Ephestia cautella larvae. The longest adult life-span of both sexes occurred when adults reared and emerged at 25°C were held at 15–18°C. Female adults of all colors lived longer than males, especially at 25 and 35°C. The lowest parasitizing efficiency was at 35°C, whereas the highest number of eggs per female occurred at 25°C irrespective of the body color.In general, the parasitoid wasps have somewhat tolerated the three temperature levels and continued to reproduce in spite of their distinct variations in body color. Such variations might be of importance as a mechanism of survival for B. hebetor in date stores during the cold season as well as in the green date palm and cotton fields during warm seasons in Iraq.     

Laboratory evaluation of two insect juvenile hormone analogues against Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae)

The insect juvenile hormone analogues methoprene and fenoxycarb have been tested against larval stages of the lesser mealworm, Alphitobius diaperinus. Methoprene completely prevented the formation of adult insects at a concentration of 5.0 ppm in food medium. The same effect was achieved with only 0.05 ppm fenoxycarb. There was no evidence that sub-lethal levels of methoprene decreased the fecundity of insects that successfully completed adult development. The results of these laboratory tests are discussed in relation to the potential use of these compounds for control of A. diaperinus in intensive poultry production units.     

Effects of cold storage, rearing temperature, parasitoid age and irradiation on the performance of Trichogramma evanescens Westwood (Hymenoptera: Trichogrammatidae)

In this study, the effects of cold storage, rearing temperature, parasitoid age, and irradiation on the performance of the egg parasitoid Trichogramma evanescens were investigated. Pupae of T. evanescens can be stored at 4 °C for up to 3 weeks without much loss of performance. The longevity and walking speed of adults emerging from chilled pupae significantly decreased after longer storage periods. The F₁ generation of adults which emerged from pupae stored up to 3 weeks was able to parasitize as well as the control. The parasitization rate was similar at 24, 27, and 30 °C, but significantly decreased at 33 and 36 °C. Although T. evanescens developed to the pupal stage at 36 °C, no adult emergence was observed at this temperature. Developmental periods were longer at 24 °C than at higher temperatures. The optimum age for T. evanescens to successfully parasitize host eggs ranged from 24 to 90 h. The parasitization frequency of the 56-78 h aged females was higher than for the other age groups. The daily egg laying pattern of female T. evanescens adults was similar when they were reared on Ephestia kuehniella or Plodia interpunctella eggs. Gamma- or ultraviolet-irradiated and unirradiated host eggs were equally preferred by adult females.     

Antennal olfactory responses to individual cereal volatiles in Theocolax elegans (Westwood) (Hymenoptera: Pteromalidae)

Theocolax elegans (Westwood) is a pteromalid wasp that parasitizes immature stages of stored-grain insect pests. In a previous study, uninfested wheat kernels and their hexane extracts were shown to be attractive to the adult wasps. To contribute to the understanding of the olfactory basis of the host-habitat recognition, the electroantennographic (EAG) responses of both sexes of T. elegans to a range of volatile compounds previously identified from grains of various cereals were recorded. All compounds tested elicited measurable EAG responses. The largest EAG amplitudes were evoked by 2-octanone, 1-hexanol, 2-heptanone, (E)-2-nonenal, decanal, (E)-2-hexenal, propionic acid, (E)-2-octenal and hexanoic acid in males, and by propionic acid, 2-hexanone, (E)-2-heptenal, 2-heptanone, hexanal, (E,E)-2,4-heptadienal, butanal, hexanoic acid and octanal in females. Aromatic compounds were the weaker antennal stimulants in both sexes. Sexual differences in the EAG amplitude to some compounds were found, with males being significantly more responsive to 13 of the 34 compounds tested. Comparison of EAG responses to various chemicals indicated a strong antennal capability to differentiate in respect to structure (aliphatics and aromatics), carbon chain length, functional group (acid, alcohol, aldehyde, ketone) and absence/presence of double bonds (saturated, mono- and di-unsaturated compounds). Possible roles of cereal volatiles in host-habitat location of T. elegans are discussed in relation to the possible future implementation of T. elegans-based biological control strategies.     

Host-associated kairomones used for habitat orientation in the parasitoid Lariophagus distinguendus (Hymenoptera: Pteromalidae)

Males and females of the parasitic wasp Lariophagus distinguendus respond to volatiles emitted by the larval faeces of one of their hosts, the granary weevil Sitophilus granarius. Previous studies have shown that attractive chemicals are emitted by astigmatid mites living in the host faeces and that these cues are attractive only to experienced parasitoids. In the present study we demonstrate that larval faeces of the host and headspace extracts of the faeces are attractive for both sexes of the parasitoid even when the mites were experimentally excluded from the beetle rearings. The response to volatiles from mite-free host faeces is innate. In order to elucidate the chemistry of this odor, headspace extracts were fractionated by adsorption chromatography. Tests using combinations of fractions of different polarities revealed that both the non-polar pentane and the polar methanol fractions were necessary to maintain the attractiveness. This indicates that the attractive odor is composed of a complex blend of components with different polarities. The composition of the polar fraction was analyzed by gas chromatography-mass spectrometry, whereas elucidation of the structure of non-polar components has not been possible so far. By orientating toward the same host-related volatiles used by females for host finding, L. distinguendus males may be arrested in patches of potentially high female density and thus increase their chance of mating.     

Effect of temperature on reproductive parameters and the longevity of Acarus farris (Acari: Acaridae)

Reproductive parameters and the longevity of Acarus farris were examined at six constant temperatures, ranging from 7 to 29 °C, and a relative humidity of 90±5%. As temperature increased, the preoviposition period rapidly decreased to a minimum, above 25 °C. Fecundity was adversely affected by extreme temperatures while the oviposition period increased as temperature was reduced. The relationship between reproductive parameters and temperature was fitted using different polynomial and non-linear models. Male and female longevity increased as temperature decreased, except for the males at 7 °C, which showed significantly lower longevity than at 10 °C. Moreover, males showed significantly greater longevity than females. The effect of temperature on the capacity for increase of A. farris populations was also established. The non-linear Lactin model provided a reliable fit of the relationship between intrinsic rate of increase and temperature (R²>0.99). The optimum temperature for development was calculated to be 25 °C. At this temperature, the population doubling time was 2.8 days. The lower and upper thermal thresholds for A. farris populations were established at 6.4 and 29.9 °C, respectively.     

Effects of time/temperature treatments on potato (Solanum tuberosum) starch: a comparison of isolated starch and starch in situ

Previously, time/temperature treatments of starch have been performed mainly on starch/water systems. In this study the same time/temperature treatments were applied to starch/water systems and to potato starch in situ. Two potato varieties (Solanum tuberosum cultivars Asterix and Bintje) were used. The effect of time/temperature treatments on gelatinisation behaviour was evaluated using differential scanning calorimetry (DSC). A blanching process was simulated by heating samples to 74 °C and then cooling them to 6 °C. A DSC scan showed that starch was completely gelatinised after this treatment. Retrogradation of amylopectin increased during storage at 6 °C from 0 to 24 h after blanching. Annealing of starch, with the aim of altering cooking properties, was performed by heating samples to temperatures below the gelatinisation onset temperature. Treating samples at 50 °C for 24 h caused a shift in gelatinisation onset temperature of 11–12 °C for isolated starch and 7–11 °C for in situ samples. The extent of the annealing effect depended on the difference between onset and annealing temperatures, and prolonged treatment time increased the effect. Starch/water systems and tissue samples behaved similarly when exposed to time/temperature treatments. The most apparent difference was the shift of gelatinisation to higher temperatures in tissue samples. Copyright © 2003 Society of Chemical Industry     

Effects of seed roasting temperature and time on the quality characteristics of sesame (Sesamum indicum) oil

The quality characteristics and composition of sesame oils prepared at different roasting temperatures (160–250°C) from sesame seeds using a domestic electric oven were evaluated as compared to an unroasted oil sample: only minor increases (P<0·05) in characteristics, such as peroxide value, carbonyl value, anisidine value and thiobarbituric acid reactive substances, of sesame oils occurred in relation to increasing roasting temperature and time between 160 and 200°C, but colour units of oils increased markedly over a 220°C roasting temperature. Significant decreases (P<0·05) were observed in the amounts of triacylglycerols and phospholipids in the oils prepared using a 250°C roasting temperature. The amounts of γ-tocopherol and sesamin still remained over 80 and 90%, respectively, of the original levels after roasting at 250°C. In the oil prepared using a 250°C roasting temperature, sesamol was detected at 3370 mg per kg oil, but sesamolin was almost depleted after 25 min of roasting. Burning and bitter tastes were found in the oils prepared at roasting temperatures over 220°C. The results suggested that a high-quality product would be obtained by roasting for 25 min at 160 or 180°C, 15 min at 200°C and 5 min at 220°C when compared with the other samples. © 1997 SCI.