Phototactic behaviour of the parasitoid Encarsia formosa (Hymenoptera: Aphelinidae)

We investigated the spectral sensitivity and response to light intensity of Encarsia formosa (Hymenoptera: Aphelinidae), which is a key natural enemy of the greenhouse whitefly, Trialeurodes vaporariorum, and the tobacco whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae). To do so, we used 15 monochromatic lights (emitting various specific wavelengths from 340 to 649?nm) and white light. E. formosa adults, which are diurnal insects, showed a positive phototaxis to a broad spectrum of light, with peaks of sensitivity at 414, 340, 450, and 504?nm. These results show that this parasitoid is generally more sensitive to short wavelength lights than long wavelength lights across all spectral ranges tested. Furthermore, E. formosa adults showed an increased phototactic response at low intensities and a decreased response at high intensities, for both ultraviolet light and violet light. Thus, E. formosa showed both colour and intensity preferences. This experiment provides a scientific basis for the development of colour traps for insect pest management and improves understanding of the ecological significance of colour vision by E. formosa.     

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。     

烟蚜茧蜂随寄主有翅桃蚜迁飞而被携带扩散的模拟实验

蚜虫寄生蜂的广泛分布可能与有翅蚜的迁飞有关。为了证明这一假说, 本研究利用微小昆虫飞行磨系统, 分数十批(≤16头/批)对被烟蚜茧蜂Aphidius gifuensis Ashmead单头寄生后的有翅桃蚜Myzus persicae (Sulzer)进行模拟飞行并系统观察了飞行后有翅桃蚜的单头定殖情况。对实验观察数据按飞行时间和飞行距离进行归类, 采用单因素方差分析方法分析飞行时间和飞行距离对有翅桃蚜定殖后的存活和生殖力、烟蚜茧蜂发育等变量的影响; 采用多项式回归分析对所有变量和归类的数据进行统计和分析。结果表明: 成功飞行并定殖的有翅桃蚜有378头, 其中239头有翅桃蚜定殖后形成僵蚜。形成僵蚜的有翅桃蚜在飞行实验时平均飞行时间和飞行距离分别为2.63 h和2.16 km, 定殖后平均存活了6.11 d, 定殖第6天和第14天平均产若蚜累计数量分别为8.5头和162头。形成僵蚜和未形成僵蚜的有翅蚜的模拟飞行数据和定殖观察数据无显著差异。形成僵蚜的239头有翅桃蚜中, 最终成功育出烟蚜茧蜂205头, 僵蚜出蜂率为85.8%。雌雄性比为1∶5.2。结论认为, 专性寄生蚜虫的烟蚜茧蜂可以利用有翅蚜的迁飞而被携带扩散传播, 有翅蚜迁飞在蚜虫寄生蜂扩散中具有重要作用。     

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     

Storage techniques of mummies and adults of Aphidius gifuensis

Technology for mass storage is one of the most important issues facing the use of parasitoids for biological control programmes. The emergence rate, the proportion of females, adult longevity, parasitism rate of Aphidius gifuensis after cold storage of mummies at 5°C for different time periods, and the effect of different diets on their longevity were assessed. The results indicated that 10–30 days was a suitable period for cold storage at 5°C, but that 20 days was optimal. The 5% glucose solution was a successful food supplement for A. gifuensis. These results are important to the commercial exploitation of this economically important parasitic wasp.     

Functional responses of aphid parasitoids,Aphidius colemani (Hymenoptera: Braconidae) and Aphelinus asychis (Hymenoptera: Aphelinidae)

We evaluated the functional responses of two aphid parasitoids: Aphidius colemani on the green peach aphid Myzus persicae (Hemiptera: Aphididae), and Aphelinus asychis on M. persicae and the potato aphid, Macrosiphum euphorbiae (Hemiptera: Aphididae). Parasitoid oviposition occurred at host densities of 5, 10, 20, 30, 50, 80 or 100 aphids for A. colemani and 5, 10, 20, 30 or 50 aphids for A. asychis. More M. persicae were parasitized by A. colemani than by A. asychis at an aphid density of 50. Among the three types of functional response, type III best described the parasitoid response to the host densities both in A. colemani and A. asychis. The estimated handling time was shorter for A. colemani than for A. asychis (0.017 and 0.043 d, respectively). The proportion of aphids that were parasitized exhibited the same characteristic curve among the three host-parasitoid combinations: a wave form that appeared to be a composite of a decelerating (as in type II) response at low host density and an accelerating-and-decelerating (as in type III) response at medium to high host density. We hypothesize that the novel host species (and its host plant), density-dependent superparasitism, and/or density-dependent host-killing may have induced the modified type III response.     

Mass Rearing of Aphidius gifuensis (Hymenoptera: Aphidiidae) for Biological Control of Myzus persicae (Homoptera: Aphididae)

The green peach aphid, Myzus persicae, is a major pest of tobacco, Nicotiana tabacum, in Yunnan province, China, where its control still depends on the use of insecticides. In recent years, the local government and farmers have sought to improve the biological control of this tobacco pest. In this paper, we present methods for mass rearing Aphidius gifuensis, a dominant endoparasitoid of M. persicae on tobacco plants in this region. The tobacco cultivar K326 (N. tabacum) was used as the host plant and M. persicae as the host insect. In the greenhouse, we collected tobacco seedlings for about 35 days (i.e., until the six-true-leaf stage), transferred them to 7.5-cm diameter pots, and kept these plants in the greenhouse for another 18 days. These pots were then transferred to an insectary-greenhouse, where the tobacco seedlings were inoculated with five to seven wingless adult M. persicae per pot. After 3 days, the infested seedlings were moved to a second greenhouse to allow the aphid population to increase, and after an additional 4±1 days when 182±4.25 aphid adults and nymphs were produced per pot, they were inoculated with A. gifuensis. With this rearing system, we were able to produce 256±8.8 aphid mummies per pot, with an emergence rate of 95.6±2.45%; 69% were females. The daily cost of parasite production (recurring costs only) was US$ 0.06 per 1000 aphid mummies. With this technique, we released 109 800 parasitoids in 1998, 196 000 in 1999, 780 000 in 2000, and 5 600 000 in 2001 during a 2-month period each year. This production method is discussed with respect to countrywide usage in biological control and integrated control of M. persicae.     

Isolation and characterization of microsatellites in Aphidius ervi (Hymenoptera: Braconidae) and their applicability to related species

Aphidius ervi (Hymenoptera: Braconidae) is an important biological control agent of aphids, and a model organism for the study of host–parasitoid ecology and evolution. We isolated microsatellite loci from A. ervi to examine the genetic effects of its introduction from Europe to North America. We present primers for 11 microsatellites from A. ervi. We have assayed six of these loci for variability and found from two to 37 alleles. These six primer pairs were tested on 17 related species and appear broadly applicable. These microsatellite loci provide a new tool for research on A. ervi and its relatives.     

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。     

Olfactory responses of Aphidius gifuensis to odors of host plants and aphid‐plant complexes

Abstract The olfactory responses of Aphidius gifuensis to odors from two host plants (Nicotiana tabacum and Brassica napus ssp.) and their complexes with different infestation levels of two host aphids (Myzus persicae and Lipaphis erysimi) were respectively examined in an olfactometer. The results showed that female A. gifuensis did not respond to odors of undamaged or mechanically damaged host plants, but significantly responded to odors of aphid/plant complexes. Moreover, A. gifuensis responded significantly to odors of both M. persicae and L. erysimi/plant complexes when host plants were infested by high levels of aphids, suggesting that quantity of aphid‐induced volatiles could be important for attracting A. gifuensis. When tested between aphid/plant complexes, A. gifuensis did not show its preference for either complex. The efficiency of A. gifuensis against aphids in open fields potentially could be improved by using its olfactory response to aphid/plant complexes.     

变温贮藏僵蚜对烟蚜茧蜂耐寒能力的影响

为明确变温贮藏以麦二叉蚜为寄主的僵蚜对烟蚜茧蜂耐寒能力的影响,探究其体内的生化物质变化规律,测定了变温处理后羽化的烟蚜茧蜂雌雄成虫过冷却点、结冰点、体内含水量、脂肪、蛋白质和总糖含量的变化.结果表明:与对照(20℃)相比,经4℃22 h/20℃2h和4 ℃ 46 h/20℃2h处理1周后烟蚜茧蜂的耐寒能力显著增强.经变温处理后,烟蚜茧蜂雌雄个体的过冷却点、结冰点均出现不同程度的下降,雌蜂经4℃22 h/20℃2h处理后过冷却点和结冰点最低,分别为-26.38和-25.51 ℃;雄蜂经4 ℃ 46 h/20℃2h处理后过冷却点和结冰点最低,分别为-26.82和-26.38℃.经变温处理后烟蚜茧蜂僵蚜雌雄个体体内糖和蛋白质含量上升而脂肪和体内含水量下降,尤以经4℃22 h/20 ℃ 2 h和4℃46h/20℃2h处理后的变化最为明显.变温可以提高烟蚜茧蜂僵蚜的低温抵抗能力,且其耐寒能力的增加与其体内生化物质含量的变化密切相关.僵蚜经4℃22h/20℃2h和4℃46h/20℃2h贮藏1周后更有利于烟蚜茧蜂的生存和实践应用.     

Population dynamics of Myzus persicae on tobacco in Yunnan Province,China, before and after augmentative releases of Aphidius gifuensis

The population dynamics of Myzus persicae were investigated in the field in a year without releases of Aphidius gifuensis (1998–1999), in a year with A. gifuensis releases (2000–2001) and several years later (2005–2007). The results showed that both high mean population densities and damage rates did not differ between 1998 and 1999, but were significantly lower in 2000–2001 and 2005–2007. Moreover, farmers also reported the decrease of M. persicae populations and attributed the declines to augmentative releases of A. gifuensis in their own fields, indicating farmers’ recognition in the effectiveness of A. gifuensis for M. persicae control. In addition, compared with the historical data on pesticide use for M. persicae control, the number of insecticide applications and cost of M. persicae control was sustained at a low level in 2007 (several years after release of A. gifuensis). This suggests that the augmentative releases of A. gifuensis could be effective and sustainable in M. persicae control.     

Suitability of three aphid species for Aphidius gifuensis (Hymenoptera: Braconidae): Parasitoid performance varies with hosts of origin

Oviposition behavior and offspring fitness of the parasitoid Aphidius gifuensis (Ashmead) were compared on three aphid species, Sitobion avenae F., Myzus persicae (Sulzer), and Aphis gossypii Glover using wasps collected from both S. avenae and M. persicae. A. gifuensis produced more mummies and adults on S. avenae and M. persicae than on A. gossypii regardless of the host of origin. Mummy production was influenced by attack rate and percentage of aphids superparasitized. The F₁ generations from S. avenae and M. persicae were more female-biased and wasps were larger than those from A. gossypii. Although there were significant differences in development time of A. gifuensis in the three aphid species, the difference was generally shorter than one day. Fewer mummies were produced when A. gifuensis was transferred between S. avenae and M. persicae, but no significant difference was observed in emergence rate, percentage of female offspring, or body size. The effects of host species on A. gifuensis female performance and offspring fitness are discussed, along with the potential for using A. gifuensis to control M. persicae and A. gossypii.     

保幼激素类似物对烟蚜茧蜂生长发育、寄生率和蜕皮相关酶活性的影响

【目的】烟蚜Myzus persicae是烟草上重要的害虫之一,烟蚜茧蜂Aphidius gifuensis是烟蚜的一种优势寄生蜂。本研究旨在筛选出可延迟烟蚜茧蜂羽化时间的最佳保幼激素,解决规模化繁殖过程中出现的烟蚜茧蜂羽化不一致、不整齐,生产上急需烟蚜茧蜂防控烟蚜时所需烟蚜茧蜂数量不足而影响防蚜效果等严重问题。【方法】利用液浸法测定了不同浓度(5 000, 1 000, 200, 40和8 ng/μL)的5种保幼激素类似物包括稀虫乙酯(ZR-512)、稀虫炔酯(ZR-777)、稀虫酯(ZR-515)、苯氧威［(对苯氧乙基)氨基甲酸乙酯)］和保幼激素Ⅲ(2,6-壬二烯酸)处理后对烟蚜茧蜂羽化率、羽化时间、成蜂寿命、雌蜂比例和寄生率的影响;通过生物化学方法测定1 000 ng/μL这5种保幼激素类似物处理后烟蚜茧蜂蛹内与蜕皮相关酶含量和活性,筛选能延迟烟蚜茧蜂羽化时间的最佳保幼激素类似物。【结果】测试的不同浓 度的5种保幼激素类似物中200 ng/μL ZR-777和1 000 ng/μL ZR-512处理后能显著延迟烟蚜茧蜂羽化时间,分别比对照(10%丙酮处理)延迟了44.00和56.00 h;不同浓度的ZR-515和苯氧威处理后烟蚜茧蜂羽化率较对照组显著降低。与对照组相比,测试的不同浓度的5种保幼激素类似物对成蜂寿命均没有显著影响;1 000和40 ng/μL ZR-777处理显著降低了雌蜂比例。200 ng/μL ZR-777, 1 000 ng/μL ZR-512和5 000 ng/μL ZR-512处理对烟蚜茧蜂的寄生率无显著影响。5种保幼激素类似物以1 000 ng/μL浓度处理时,ZR-512处理组中烟蚜茧蜂蛹内酚氧化酶含量和活性以及几丁质酶活性均最低。【结论】生产上可用1 000 ng/μL ZR-512和200 ng/μL ZR-777处理烟蚜茧蜂,以达到调控烟蚜茧蜂羽化时间,取得足量、一致的烟蚜茧蜂。结果为烟蚜茧蜂规模化繁殖提供了理论依据。     

Limitation of superparasitism by Aphidius rhopalosiphi: a consequence of aphid defensive behaviour

Abstract. 1. The behavioural mechanisms limiting superparasitism by Aphidius rhopalosiphi (DeStefani-Perez) are described.
2. A.rhopalosiphi did not discriminate between parasitized and unparasitized aphids, or avoid attacking and ovipositing in previously parasitized aphids.
3. Aphid defensive behaviour was increased for a short period after a parasite stabbing attack. In response to this behaviour the number of parasite stabbing attacks subsequently undertaken declined.
4. Once a stabbing attack had been initiated, parasite oviposition success was unaffected by aphid defensive behaviour.
5. It is concluded that applied defensive behaviour, by limiting the number of stabbing attacks undertaken by A.rhopalusiphi , effectively limits the number of parasite eggs laid and the extent to which super parasitism occurs.     

An 'artificial aphid' for Aphidius ervi (Hym., Braconidae)

Abstract:  An artificial aphid was developed by making parafilm^® bubbles filled with aphid haemolymph and its suitability for parasitoid oviposition was tested. Aphidius ervi accepted the parafilm^® aphid and laid eggs on it. By stretching, the thickness of the parafilm could be changed. The thicker the parafilm, the higher was the mean number of ovipositional stings and the lower the mean number of eggs released by A. ervi .     

Plant structure and the foraging success of Aphidius rhopalosiphi (Hymenoptera: Aphidiidae)

Abstract. 1. A study of searching behaviour on wheat and host preference of Aphidius rhopalosiphi (DeStefani-Perez) is described.
2. Parasitoids divided their time equally between the leaves but spent very little time on the ear.
3. After contact with honeydew or an aphid host, parasitoids were arrested in a particular area and increased the time spent searching.
4. Aphids feeding on the ear were parasitized less successfully, since their position between the grains protected them from parasitoid attacks.
5. A.rhopalosiphi exhibited no preference for Metopolophium dirhodum (Walker) or Sitobion avenae (Fabricius), although the handling time for the latter was significantly longer; this resulted in fewer S.avenae being parasitized when it was abundant. Parasitoids did not switch between hosts in these experiments.
6. As a result of its searching behaviour, A.rhopalosiphi will encounter and parasitize M.dirhodum feeding on the leaves more frequently than S.avenae, which feeds on the ear. This will limit the parasitoid's ability to regulate populations of the cereal aphid S. avenae.     

Stress intensity and fitness in the parasitoid Aphidius ervi (Hymenoptera: Braconidae): temperature below the development threshold combined with a fluctuating thermal regime is a must

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桃蚜对不同单色光趋性反应的测定

为了探讨蚜虫对不同色光选择反应的定量指标, 采用滤光片技术测定了有翅和无翅桃蚜Myzus persicae对不同波长单色光的趋性反应。结果表明: 有翅蚜对490~550 nm范围内的单色光表现出明显趋性, 其中对538.9和549.9 nm的绿偏黄色光趋性最强, 平均位移分别达25.29和22.97 cm, 其次为491.5 nm的蓝绿色光, 而对于波长576.0 nm的黄色光并没有表现出明显趋性。无翅蚜对不同单色光的趋性反应则没有明显的峰值, 最高相对平均位移仅1.41。行为测定结果与前人电生理测定的结果基本一致, 说明以位移作为小体昆虫趋光性强弱的指标是可靠的。