滞育烟蚜茧蜂的亲代效应评价

【目的】烟蚜茧蜂Aphidius gifuensis Ashmead是可持续防控蚜虫的优良内寄生蜂,适宜的低温短光照可诱导其进入滞育,滞育后产品货架期长达120 d,对害虫生防意义重大。为深入探索滞育烟蚜茧蜂的亲代效应,分析滞育机理,提高滞育诱导效率,指导该天敌产品的贮存实践,开展本项研究。【方法】在室内测试了滞育烟蚜茧蜂F1代的羽化率、性比、成蜂寿命、滞育率、寄生力以及F2代的羽化率、性比等生物学指标,综合评价滞育烟蚜茧蜂的亲代效应。【结果】滞育经历对烟蚜茧蜂子代的部分生物学性状具有显著性影响,F1代雌蜂比例显著增加,滞育维持30 d后子代雌蜂比例由0.59上升至0.65;F2代雌蜂比例与CK无差别,维持在0.58左右;F1代滞育率显著升高,可由对照的44.75%提高至74.01%,滞育维持30 d后子代滞育率具升高趋势;F1代寄生力略增加,各处理形成的僵蚜数在117~129头间,但无显著性差异;F1代羽化率、子代成蜂寿命与CK相比无差异。【结论】烟蚜茧蜂具有较显著的滞育亲代效应,亲代滞育经历可显著提高子一代的滞育率,利于子代抵御不良环境胁迫,提高种群存活率。     

温度对烟蚜茧蜂发育、生殖的影响

在恒汨１０、１５、２０、２５和３０℃实验条件下,测定了云南省玉溪地区烟蚜茧蜂（Ａｐｈｉｄｉｕｓ ｇｉｆｕｅｎｓｉｓ Ａｓｈｍｅａｄ）的发育历期和生殖力等生物学参数。结果显示,烟蚜茧蜂发育速率与温度的关系符合逻辑斯蒂曲线,即２５℃从卵至习化所需历期最短（１０．６７ｄ）,３０℃发育历期稍有延长（１１．６ｄ）。卵至羽化的发育起点温度为３．３℃,有效积温为２６６．０日度。烟蚜茧峰雌蜂羽化当天即可产卵,在产     

烟蚜茧蜂寄生对烟蚜生长发育和繁殖的影响

【目的】为探究烟蚜茧蜂Aphidius gifuensis对烟蚜Myzus persicae寄生后烟蚜生长发育和繁殖影响及其在烟蚜防控中的作用。【方法】采用室内叶片培养皿法,测定了不同龄期烟蚜(1-4龄若蚜及成蚜)被烟蚜茧蜂寄生后烟蚜当代(F₀)及后代(F₁)的发育历期、寿命、产仔量。【结果】烟蚜1龄若蚜被烟蚜茧蜂寄生后,1龄若蚜历期受到显著影响,较未被寄生对照缩短了0.65 d (33.00%),而2-4龄若蚜期和成蚜历期未受显著影响; 2龄若蚜被寄生后,4龄若蚜和成蚜历期均受到显著影响,较未被寄生的对照分别缩短了1.50 d (100.00%)和0.83 d (100.00%),而2和3龄若蚜期未受显著影响; 3龄若蚜被寄生后,4龄若蚜和成蚜期均受到显著影响,较未被寄生对照分别缩短了1.50 d (100.00%)和0.83 d (100.00%),而3龄若蚜期未受显著影响。2龄若蚜被寄生后烟蚜的寿命和产仔量均受到显著影响,寿命较未被寄生对照缩短了8.39 d(54.00%),每雌产仔量较未被寄生对照减少了48.67头(100.00%)。...     

杀虫剂对烟蚜茧蜂不同发育阶段的毒性

【背景】烟蚜茧蜂是控制烟蚜田间种群的重要寄生蜂。施用化学杀虫剂防治烟蚜及其他害虫时,也会对烟蚜茧蜂产生毒性,影响对烟蚜种群的自然控制效果。了解杀虫剂对烟蚜茧蜂不同发育阶段的毒性,可为田间选择合理施药时间提供参考。【方法】在室内用试管药膜法和饲喂法测定了5%阿维菌素、5%啶虫脒、10%顺式氯氰菊酯和10%吡虫啉对烟蚜茧蜂成蜂的毒性,并在烟蚜茧蜂各虫期使用亚致死浓度药剂处理,研究这些杀虫剂对其羽化的影响。【结果】阿维菌素的触杀和胃毒作用最强,烟蚜茧蜂24 h死亡率分别为87.78%和94.44%;吡虫啉的触杀和胃毒作用最弱,烟蚜茧蜂24 h死亡率分别为41.11%和61.11%;啶虫脒(烟蚜茧蜂24 h死亡率分别为81.11%和86.66%)、顺式氯氰菊酯(烟蚜茧蜂24 h死亡率分别为64.44%和67.78%)的触杀和胃毒作用居中。在寄生蜂卵期用药,阿维菌素和啶虫脒可显著降低当代成蜂羽化率;在幼虫期用药,4种杀虫剂均显著降低了成蜂的羽化率;在蛹期用药,4种杀虫剂对成蜂的羽化率均没有显著影响。在寄生蜂幼虫期使用阿维菌素会使雌蜂比例显著高于对照,其余3种杀虫剂对雌蜂比例均无显著影响。【结论与意义】在烟蚜茧蜂成虫期使用这些杀虫剂,死亡率均较高,因此在成蜂较多时应禁止使用杀虫剂。     

栽培措施对烟田前期烟蚜和烟蚜茧蜂种群数量的影响

通过设置 5种类型烟田 ,研究了栽培措施对烟田前期烟蚜Myzuspersicae(Sulzer)和烟蚜茧蜂Aphidiusgifuehsis(Ashmead)种群数量的影响。地膜和耕作方式对烟田前期烟蚜种群数量均有显著影响。不同类型烟田烟蚜种群数量大小依次为桃园附近、纯作未覆膜、间作未覆膜、纯作覆膜、间作覆膜烟田。其中 ,桃园附近烟田烟蚜种群数量显著高于其它烟田 ,未覆膜烟田高于覆膜烟田 ,纯作烟田又高于间作烟田。地膜对烟田前期烟蚜茧蜂种群数量有显著影响。覆膜烟田烟蚜茧蜂种群数量高于未覆膜烟田。因此 ,烟田覆膜有利于降低烟蚜种群数量、增大烟蚜茧蜂种群数量 ;间作也能在一定程度上抑制烟蚜种群增长。     

烟蚜茧蜂寄生对烟蚜生长发育和繁殖的影响

【目的】为探究烟蚜茧蜂Aphidius gifuensis对烟蚜Myzus persicae寄生后烟蚜生长发育和繁殖影响及其在烟蚜防控中的作用。【方法】采用室内叶片培养皿法,测定了不同龄期烟蚜(1-4龄若蚜及成蚜)被烟蚜茧蜂寄生后烟蚜当代(F₀)及后代(F₁)的发育历期、寿命、产仔量。【结果】烟蚜1龄若蚜被烟蚜茧蜂寄生后,1龄若蚜历期受到显著影响,较未被寄生对照缩短了0.65 d (33.00%),而2-4龄若蚜期和成蚜历期未受显著影响;2龄若蚜被寄生后,4龄若蚜和成蚜历期均受到显著影响,较未被寄生的对照分别缩短了1.50 d (100.00%)和0.83 d (100.00%),而2和3龄若蚜期未受显著影响;3龄若蚜被寄生后,4龄若蚜和成蚜期均受到显著影响,较未被寄生对照分别缩短了1.50 d (100.00%)和0.83 d (100.00%),而3龄若蚜期未受显著影响。2龄若蚜被寄生后烟蚜的寿命和产仔量均受到显著影响,寿命较未被寄生对照缩短了8.39 d(54.00%),每雌产仔量较未被寄生对照减少了48.67头(100.00%)。此外,2-3龄若蚜被寄生后其后代(F₁)1龄若蚜历期受影响最大,较未被寄生烟蚜后代1龄若蚜期缩短了0.80 d(40.00%),其F₁代平均寿命较未被寄生烟蚜后代平均寿命延长了5.72 d(41.20%),但其产仔量与对照差异不显著。【结论】不同龄期烟蚜被烟蚜茧蜂寄生后,其发育历期和寿命比未被寄生的缩短,产仔量比被未寄生的少,但其F₁代平均寿命比未被寄生后代烟蚜的长且其产仔量未受显著影响。当代2龄若蚜期是控制烟蚜增长的关键时期。这些结果对确定烟蚜茧蜂防治烟蚜适期及认识其机理具有重要参考意义。     

烟蚜茧蜂滞育诱导的温光周期反应

烟蚜茧蜂Aphidius gifuensis Ashmead是可持续防控蚜虫的优良内寄生蜂,在害虫生防中具有重要作用,研究其滞育对探索发育调控机制、延长产品货架期、提高防治效果意义重大。本文采用梯度变温法和光周期反应曲线法,系统研究了温度和光周期对烟蚜茧蜂滞育诱导的影响,研究结果表明:烟蚜茧蜂以老熟幼虫滞育,滞育类型属冬滞育型。低温、短光照是诱导烟蚜茧蜂滞育的主要环境因子,二者相互配合能诱导更多个体滞育。短光照(L∶D=8∶16)条件下,温度低于12℃可诱导烟蚜茧蜂进入滞育,8℃时滞育率可达54.35%。长光照(L∶D=14∶10)下,高温不能诱导烟蚜茧蜂滞育,低温下的滞育率较低,仅为1.79%。低温(10℃)下,短光照(8 h)可诱导50.70%的高滞育率,光照为14 h和6 h其滞育率均显著下降。25℃时,不同光照下滞育率均为0,光周期作用不显著。综合而言,温度和光周期均能显著影响烟蚜茧蜂的滞育,温度较光周期的滞育诱导效能更显著,二者互作配合能极显著的诱导烟蚜茧蜂进入滞育态。     

一种扩繁烟蚜茧蜂的载体植物适合性评价

为评估平卧菊三七作为载体植物扩繁烟蚜茧蜂的适合性,测试了烟蚜在平卧菊三七、以及常见寄主植物烟草、茄子和二年生萝卜共4种寄主植物上的发育历期和繁殖力等,获得了净增殖率、周限增长率、内禀增长率、平均世代周期、种群加倍时间等主要生命表参数,比对了不同载体植物上的烟蚜对烟蚜茧蜂个体发育的影响。结果显示:这4种寄主植物上烟蚜的发育历期为二年生萝卜(22.79 d)平卧菊三七(22.22 d)烟草(22.01 d)茄子(18.92 d),茄子上最短,其他三种寄主植物上无显著差异;单头烟蚜总产仔量为二年生萝卜(63头)平卧菊三七(52头)茄子(43头)烟草(41头);内禀增长率rm值为茄子(0.283)二年生萝卜(0.278)平卧菊三七(0.277)烟草(0.255)。表明相同条件下,相对于烟草,烟蚜偏好取食平卧菊三七;平卧菊三七作为载体扩繁出的烟蚜茧蜂僵蚜,体型与烟草、二年生萝卜扩繁者的差异不显著。平卧菊三七可用作大量扩繁烟蚜及烟蚜茧蜂的载体植物。     

烟草品种、育苗方式和烟蚜来源对烟蚜茧蜂寄生能力的影响

【目的】本研究旨在筛选出适合烟蚜茧蜂Aphidius gifuensis寄生烟蚜Myzus persicae的烟草品种、育苗方式和烟蚜来源,为烟蚜茧蜂人工繁殖和复壮提供科学参考。【方法】采用盆栽法,调查了不同烟草品种(云烟87、K326、翠碧1号和红花大金元)繁殖烟蚜若蚜、不同来源烟蚜(来自烟区、来自非烟区和室内繁殖种群)若蚜和烟草不同育苗方式(土壤育苗和湿润育苗)繁殖烟蚜若蚜时,烟蚜茧蜂成蜂对烟蚜若蚜的寄生率以及成蜂羽化率、寿命、体型大小和雌蜂比。【结果】结果表明,不同烟草品种繁殖烟蚜若蚜对烟蚜茧蜂成蜂寄生率存在显著影响。其中,在红花大金元和翠碧1号繁殖烟蚜上的烟蚜茧蜂成蜂寄生率分别比在K326繁殖烟蚜上的烟蚜茧蜂成蜂寄生率高19.00%和14.00%,但对烟蚜茧蜂的其他指标没有显著影响;不同烟蚜来源对烟蚜茧蜂寄生率也存在显著影响,其中,烟蚜茧蜂成蜂对非烟区烟蚜若蚜和烟区烟蚜若蚜的寄生率比对室内繁殖种群烟蚜若蚜的寄生率分别高20.25%和16.75%,但对烟蚜茧蜂成蜂的羽化率、寿命、体型大小和雌蜂比没有显著影响;烟草不同育苗方式对烟蚜茧蜂成蜂的寄生率无显著影响。【结论】烟蚜茧蜂对烟蚜...     

光周期和温湿度对烟蚜茧蜂寄生能力和繁殖的影响

【目的】烟蚜茧蜂Aphidius gifuensis对烟蚜Myzus persicae有着极高的寄生率,而被广泛用于烟田防治烟蚜。但在人工扩繁烟蚜茧蜂过程中,环境因素对烟蚜茧蜂的生长发育有一定影响。本研究旨在明确光周期、湿度和温度对烟蚜茧蜂在烟蚜上寄生力的影响。【方法】在室内分别调查温度25℃、相对湿度70%与4个光周期(9L∶15D,12L∶12D, 14L∶10D和19L∶5D)组合条件下,温度25℃、光周期14L∶10D与4个相对湿度(65%, 70%, 75%和80%)条件下,以及相对湿度70%、光周期14L∶10D与4个温度(10℃, 15℃, 25℃和35℃)组合条件下,烟蚜茧蜂成蜂对烟蚜若蚜的寄生率及成蜂羽化率、寿命、性比(雌性占比)和后足胫节长度。【结果】结果表明光照时间过长或过短均会对烟蚜茧蜂的生长发育造成负面影响。在温度25℃和相对湿度70%时,光周期14L∶10D下烟蚜茧蜂成蜂的体型最大,其成蜂后足胫节最长,为0.439 mm;光周期为12L∶12D下烟蚜茧蜂成蜂的体型最小,后足胫节长度只有0.345 mm;光周期14L∶10D下烟蚜茧蜂成蜂对烟蚜若蚜的寄生率、寿...     

Asymmetric size effect of sexes on reproductive fitness in an aphid parasitoid Aphidius ervi (Hymenoptera: Aphidiidae)

Most studies on size–fitness relationships focus on females and neglect males. Here, we investigated how body size of both sexes of an aphid parasitoid, Aphidius ervi Haliday, affected the reproductive fitness. Reproductive fitness was generally positively correlated with body size for both sexes in this species. Large individuals of both sexes had greater longevity, large males fathered more progeny, and large females had higher fecundity, parasitism, and greater ability in host searching and handling. We demonstrated in this study that size effects of males and females were asymmetric on different reproductive fitness parameters. With increasing body size females gained more than males in longevity and fecundity while males gained more than females in the number of female progeny. Regardless of female size, large males sustained a female-biased population longer than small males. These results suggest that male body size should also be considered in the quality control of mass-rearing programs and the evaluation of parasitoid population growth.     

Interactions among the entomopathogenic fungus, Beauveria bassiana (Ascomycota: Hypocreales), the parasitoid, Aphidius matricariae (Hymenoptera: Braconidae), and its host, Myzus persicae (Homoptera: Aphididae)

The effect of the entomopathogenic fungus Beauveria bassiana on the biological characteristics and life table of Aphidius matricariae, a parasitoid of the green peach aphid, Myzus persicae, was studied under laboratory conditions. Aphids were first infected with twice the LC₉₅ of B. bassiana for third-instar M. persicae (2 × 10⁸ conidia/ml). Subsequently, at different intervals they were exposed to 1-day-old mated parasitoid females for 24 h. The number of mummies produced per female and the percentage emergence of the F1 generation differed significantly as a function of the time interval between application of the fungus and exposure to the parasitoid. The interference of B. bassiana on parasitoid development was also studied by first exposing the aphid hosts to the parasitoid for 24 h and subsequently applying B. bassiana. The number of mummies produced by a female A. matricariae varied from 11.8 to 24.8 and was significantly different when the aphids were first exposed to the parasitoids and then treated with B. bassiana 24, 48, 72, and 96 h after exposure. There were no significantly different effects of B. bassiana on net reproductive rate (R₀), mean generation time (T), intrinsic rate (r_m) and the finite rate of increase (λ) of A. matricariae as a result of development in hosts exposed to low or high conidial concentrations (1 × 10², 2 × 10⁸ conidia/ml). The parasitoids developed in infected hosts had lower r_m, λ, T and DT (doubling time) values compared with those that developed in uninfected hosts but no differences were observed in R₀ values. With proper timing, A. matricariae and B. bassiana can be used in combination in the successful biological control of M. persicae.     

Heterospecific larval competition and host discrimination in two species of aphid parasitoids: Aphidius ervi and Aphidius smithi

Females of the solitary aphid parasitoids Aphidius ervi Haliday and A. smithi Sharma & Subba Rao (Hymenoptera: Aphidiidae) discriminated between unparasitized pea aphids and those parasitized by the other species. Oviposition restraint varied with the attack sequence and the length of the interval between successive attacks. The tendency to reject a previously parasitized host increased with interval length; A. smithi females rarely oviposited in aphids that had been parasitized 30 h earlier by A. ervi. Early first-instar larvae of A. ervi physically attacked and killed older A. smithi larvae, and older A. ervi larvae killed younger A. smithi, possibly by physiological suppression. Neither species appeared to have a competitive advantage when their eggs hatched at the same time. The evolution of heterospecific host discrimination in A. ervi and A. smithi is discussed. It is suggested that avoidance of multiparasitism is adaptive for both parasitoid species: for A. smithi because it is the inferior larval competitor, and for A. ervi because immatures develop more slowly in multiparasitized than in initially unparasitized hosts.

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Compétition interspécifique et discrimination des hôtes chez deux parasitoïdes de pucerons: Aphidius ervi et A. smithi

Résumé Les femelles des parasitoïdes de pucerons: Aphidius ervi Haliday et A. smithi Sharma & Subba Rao (Hyméno. Aphidiidae) distinguent les pucerons du pois sains des parasités par d'autres espèces. La rétention de la ponte dépend de la séquence de l'attaque et du temps écoulé entre des attaques successives. La tendance au rejet d'un puceron précédemment parasité augmente avec l'importance du délai; A. smithi a rarement pondu dans des pucerons qui avaient été parasités 30 h avant par A. ervi. Les jeunes larves de premier stade de A. ervi ont attaqué physiquement et tué les larves plus âgées de A. smithi, et les larves plus âgées de A. ervi ont tué des larves plus jeunes de A. smithi par élimination physiologique. Aucune espèce ne semble avoir un avantage quand les oeufs ont éclos en même temps. L'évolution de la discrimination interspécifique de l'hôte chez A. ervi et A. smithi est discutée. On estime que la tendance à éviter le multiparasitisme est adaptative chez les 2 espèces: pour A. smithi parce qu'il est dominé dans la compétition larvaire et pour A. ervi parce que les larves se développent plus lentement dans un hôte multiparasité que dans un hôte initialement sain.

     

The role of natural enemy guilds in Aphis glycines suppression

Generalist natural enemy guilds are increasingly recognized as important sources of mortality for invasive agricultural pests. However, the net contribution of different species to pest suppression is conditioned by their biology and interspecific interactions. The soybean aphid, Aphis glycines (Hemiptera: Aphididae), is widely attacked by generalist predators, but the relative impacts of different natural enemy guilds remains poorly understood. Moreover, low levels of A. glycines parasitism suggest that resident parasitoids may be limited through intraguild predation. During 2004 and 2005, we conducted field experiments to test the impact of different guilds of natural enemies on A. glycines. We contrasted aphid abundance on field cages with ambient levels of small predators (primarily Orius insidiosus) and parasitoids (primarily Braconidae), sham cages and open controls exposed to large predators (primarily coccinellids), and cages excluding all natural enemies. We observed strong aphid suppression (86- to 36-fold reduction) in treatments exposed to coccinellids, but only minor reduction due to small predators and parasitoids, with aphids reaching rapidly economic injury levels when coccinellids were excluded. Three species of resident parasitoids were found attacking A. glycines at very low levels (<1% parasitism), with no evidence that intraguild predation by coccinellids attenuated parasitoid impacts. At the plant level, coccinellid impacts resulted in a trophic cascade that restored soybean biomass and yield, whereas small natural enemies provided only minor protection against yield loss. Our results indicate that within the assemblage of A. glycines natural enemies in Michigan, coccinellids are critical to maintain aphids below economic injury levels.     

Population level effects of cadmium and the insecticide imidacloprid to the parasitoid, Aphidius ervi after exposure through its host, the pea aphid, Acyrthosiphon pisum (Harris)

The objective of this study was to assess the influence of toxic substances with different modes of action on a two-species system: an aphid-specific parasitoid, Aphidius ervi Haliday, feeding on the pea aphid, Acyrthosiphon pisum (Harris). The instantaneous rate of population increase (r_i) was used as a measure of population level toxic effect in this study. The toxicants evaluated were imidacloprid, a nonpersistent neurotoxic insecticide, and cadmium, a chronic pollutant with a tendency to accumulate. We evaluated the effects of cadmium and imidacloprid on A. pisum and A. ervi because both toxicants can occur together in polluted areas where crops are grown. Cadmium (200 or 400 mg kg⁻¹ dry weight soil) and imidacloprid (4 or 40 g a.i. ha⁻¹) were applied to soil contained in plastic pots in which broad bean plants, Vicia faba L., were grown. Results of this study indicated that cadmium at the concentrations tested, reduced population growth rate of the pea aphid. Imidacloprid also reduced aphid growth rate, but only at the highest concentration tested (40 g a.i. ha⁻¹). Combinations of cadmium and imidacloprid had the greatest impact on aphid growth rate. Imidacloprid alone had no effect on population growth rate of the parasitoid. However, cadmium alone or in combination with imidacloprid had a negative impact on A. ervi by reducing population growth rate 77%. These results indicate that negative impacts on parasitoids may occur in areas where cadmium contamination is present and imidacloprid is used to control aphids.     

Effects of feeding frequency and sugar concentration on behavior and longevity of the adult aphid parasitoid: Aphidius ervi (Haliday) (Hymenoptera: Braconidae)

The effectiveness of the predatory mite, Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseidae), as a suppressive agent of the twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), was evaluated on greenhouse ivy geraniums at predator:prey release ratios of 1:60, 1:20, and 1:4. Releases at each predator:prey ratio were made at moderate and high T. urticae densities to determine if initial pest population size influenced the suppressive ability of the predator. At ratios of 1:4 and 1:20, P. persimilis significantly reduced T. urticae populations 1 week after release and kept them at low levels thereafter. Plant damage also was significantly reduced at these densities. After 4 weeks, the P. persimilis that were released at a ratio of 1:4 consistently reduced T. urticae populations from densities as high as 30 T. urticae per leaf to fewer than 0.6 per leaf. We found no interaction between release ratio and T. urticae density, indicating that predator effectiveness remains constant, at least within the range of T. urticae densities used. Our work demonstrates the potential of P. persimilis to provide effective control of T. urticae on a greenhouse-grown floricultural crop at a moderately low predator:prey ratio (1:20) and over a range of initial pest densities. However, we recommend that P. persimilis be released at a ratio of 1:4 for greatest reliability and successful control of T. urticae on ivy geraniums.     

Aphelinus albipodus(Hymenoptera: Aphelinidae) andDiaeretiella rapae(Hymenoptera: Braconidae) Parasitism onDiuraphis noxia(Homoptera: Aphididae) Infesting Barley Plants Differing in Plant Resistance to Aphids

Russian wheat aphid,Diuraphis noxia(Mordvilko), as a pest of small grains, has prompted research into biological control and host plant resistance. In the presence of Russian wheat aphid, leaves of a susceptible barley (Morex) are curled and chlorotic and sustain large densities of this aphid, while leaves of a resistant barley (STARS-9301B) remain flat and green and sustain fewer aphids. Might parasitism of Russian wheat aphid byAphelinus albipodusHayat & Fatima andDiaeretiella rapaeMcIntosh be affected differently by these plant types? When presented the plants separately and based on parasitism rate relative to aphid density, the largerD. rapaewas more effective in parasitizing relatively high densities of aphids within curled leaves of Morex than relatively low densities of aphids on uncurled leaves of STARS-9301B. Parasitism byA. albipodusdid not significantly differ among the plants. When given a choice of plants, approximately equal rates of parasitism occurred on the two plant lines for both parasitoid species, and parasitism byD. rapaewas greater thanA. albipodus.These data indicate that using parasitoid size as an indicator of success in a physically restricted environment may be misleading, when considered in a plant environment responsive in several manners to aphids (chlorosis, curling, and ability to sustain Russian wheat aphid). We expect that use of resistant barley will result in decreased parasitoid abundance as aphid densities decrease. However, parasitism rates are expected to be approximately equal on resistant and susceptible barley. In this system, plant resistance and biocontrol are compatible management strategies.     

The Effect of Abiotic Factors on the Male Mate Searching Behavior and the Mating Success of Aphidius ervi (Hymenoptera: Aphidiidae)

The effect of wind speed and distance from the source on the male response of the aphid parasitoid, Aphidius ervi (Hymenoptera: Aphidiidae), to a pheromone source was studied in a wind tunnel. The number of males taking flight, entering the plume and successfully reaching the source, decreased at wind speeds >50 cm/s. Furthermore, the proportion of those attempting upwind flight that fell to the ground increased with increasing wind speed. In contrast, distance from the source had no significant effect on any of the parameters examined. While male flight behavior was significantly reduced at 70 cm/s, some males walked to the source when there was a bridge connecting the pheromone source and the release platform. This suggests that ambulatory behavior could be a significant component of male mate searching in A. ervi when wind conditions are too strong for upwind flight. The possible effects of variation in atmospheric pressure on male flight behavior to the long distance pheromone, as well as to the short distance one, were also investigated. No significant effects of atmospheric pressure were observed. These findings differ significantly from those previously reported for another aphid parasitoid, A. nigripes, and the reasons for such differences are discussed.     

Foreign exploration for Scirtothrips perseae Nakahara (Thysanoptera: Thripidae) and associated natural enemies on avocado (Persea americana Miller)

Scirtothrips perseae Nakahara was discovered attacking avocados in California, USA, in 1996. Host plant surveys in California indicated that S. perseae has a highly restricted host range with larvae being found only on avocados, while adults were collected from 11 different plant species. As part of a management program for this pest, a “classical” biological control program was initiated and foreign exploration was conducted to delineate the home range of S. perseae, to survey for associated natural enemies and inventory other species of phytophagous thrips on avocados grown in Mexico, Guatemala, Costa Rica, the Dominican Republic, Trinidad, and Brazil. Foreign exploration efforts indicate that S. perseae occurs on avocados grown at high altitudes (>1500 m) from Uruapan in Mexico south to areas around Guatemala City in Guatemala. In Costa Rica, S. perseae is replaced by an undescribed congener as the dominant phytophagous thrips on avocados grown at high altitudes (>1300 m). No species of Scirtothrips were found on avocados in the Dominican Republic, Trinidad, or Brazil. In total, 2136 phytophagous thrips were collected and identified, representing over 47 identified species from at least 19 genera. The significance of these species records is discussed. Of collected material 4% were potential thrips biological control agents. Natural enemies were dominated by six genera of predatory thrips (Aeolothrips, Aleurodothrips, Franklinothrips, Leptothrips, Scolothrips, and Karnyothrips). One genus each of parasitoid (Ceranisus) and predatory mite (Balaustium) were found. Based on the results of our sampling techniques, prospects for the importation of thrips natural enemies for use in a “classical” biological control program in California against S. perseae are not promising.     

多杀菌素对天敌昆虫白蛾周氏啮小蜂的毒力评估

[目的] 生物防治与化学防治相结合是害虫综合防治的重要策略,蛹寄生蜂白蛾周氏啮小蜂是一种重要的天敌昆虫,在美国白蛾的生物防控中起关键作用。本研究旨在评估农林生产中常用的广谱、低毒杀虫剂多杀菌素对白蛾周氏啮小蜂的安全性。[方法] 采用药膜法检测多杀菌素对小蜂的毒力,并检测亚致死浓度多杀菌素处理后,小蜂体内解毒酶活性的变化。[结果] 多杀菌素对小蜂无短期（1 h）触杀作用,但随施药时间延长,其对小蜂的毒杀作用增强,25 mg·L^-1多杀菌素施药2 h后,可诱导约18.67%小蜂个体死亡。施药4 h后,不同浓度多杀菌素对小蜂的毒杀作用差异最明显,低浓度（5 mg·L^-1）多杀菌素可诱导11.33%小蜂死亡,而中、高浓度多杀菌素（≥ 15 mg·L^-1）可诱导77.33%~88.00%个体死亡。施药6 h后,LC₅₀值达7.44 mg·L^-1,安全系数为0.31,属高风险性农药。此外,亚致死浓度多杀菌素可明显诱导小蜂羧酸酯酶活性提高,对乙酰胆碱酯酶与谷胱甘肽-S-转移酶活性具有剂量效应。[结论] 多杀菌素对白蛾周氏啮小蜂的毒力作用较强,在美国白蛾生防区需慎用。