Intraguild interactions between the predator Macrolophus pygmaeus and the parasitoid Eretmocerus mundus,natural enemies of Bemisia tabaci

The native parasitoid Eretmocerus mundus Mercet and the predator Macrolophus pygmaeus Rambur are widely used to control Bemisia tabaci (Gennadius) in Mediterranean tomato greenhouses. An optimal biological control strategy for B. tabaci should take into account intraguild interactions between these natural enemies. In this study, predator's prey preferences and prey consumption were studied when offered different parasitoid and whitefly stages. The effect of the host plant on the adults of both natural enemies was also examined. M. pygmaeus preferred to consume B. tabaci over E. mundus when immature stages and adults of B. tabaci and E. mundus were offered. They consumed a larger amount of healthy B. tabaci nymphs and adults than of parasitised nymphs or E. mundus adults. The predator M. pygmaeus interfered with the reproduction of E. mundus females on cotton but not on tomato. However, B. tabaci nymphal mortality on tomato associated with parasitoid host feeding was also lower when the adult parasitoids coexisted with the predators. The joint release of M. pygmaeus and E. mundus adults did not increase the control of the whitefly B. tabaci.     

三种杀虫剂对烟粉虱优势寄生蜂海氏桨角蚜小蜂的安全性评价

为评价噻虫嗪、阿维菌素和氟啶虫胺腈对烟粉虱优势寄生蜂海氏桨角蚜小蜂Eretmocerus hayati的安全性,采用琼脂保湿浸叶法分别测定了3种杀虫剂对烟粉虱成虫和海氏桨角蚜小蜂成蜂的室内毒力以及对海氏桨角蚜小蜂蛹羽化率的影响.结果表明,噻虫嗪、阿维菌素和氟啶虫胺腈对烟粉虱的LC50分别为453.76 mg/L、2.00 mg/L和29.47 mg/L,对海氏桨角蚜小蜂成蜂的LC50分别为0.23 mg/L、1.07 mg/L和0.64 mg/L.通过风险系数评估,表明阿维菌素对海氏桨角蚜小蜂成蜂安全,而噻虫嗪和氟啶虫胺腈对该蜂成蜂具有轻微到中度毒性.3种杀虫剂在烟粉虱和寄生蜂之间的选择性毒力指数表明噻虫嗪对海氏桨角蚜小蜂的负向选择性最强,其次是氟啶虫胺腈,阿维菌素最弱.3种杀虫剂均可显著降低海氏桨角蚜小蜂蛹的羽化率,对蛹的毒性为轻微有害,风险等级为2级.本研究结果将为烟粉虱综合治理中协调使用寄生蜂和化学药剂奠定理论基础.     

两种蚜小蜂对烟粉虱寄主的产卵选择性(英文)

双斑恩蚜小蜂和桨角蚜小蜂是华南地区烟粉虱的两种优势种寄生蜂。本文研究了两种寄生蜂对不同龄期烟粉虱寄主的产卵选择特性。结果表明:两种寄生蜂均可寄生烟粉虱的1~4龄若虫。当只有1个龄期的烟粉虱若虫存在时,双斑恩蚜小蜂更多地寄生3龄和4龄若虫,较少寄生1龄和2龄若虫;而桨角蚜小蜂则更多地寄生3龄和2龄若虫,较少寄生1龄和4龄若虫。在4个龄期若虫同时存在时,双斑恩蚜小蜂会明显增加对3龄和4龄若虫的产卵寄生,降低对1龄和2龄若虫的寄生;而桨角蚜小蜂则增加对2龄和3龄若虫的寄生,减少对1龄和4龄若虫的寄生。寄主植物的差异不影响这二种蚜小蜂对各龄期烟粉虱若虫的产卵选择倾向。结果提示,烟粉虱若虫3龄和4龄是双斑恩蚜小蜂最适宜的寄主,而桨角蚜小蜂最适宜的寄主是烟粉虱2龄和3龄若虫。     

两种蚜小蜂对烟粉虱寄主的产卵选择性（英文）

双斑恩蚜小蜂和桨角蚜小蜂是华南地区烟粉虱的两种优势种寄生蜂。本文研究了两种寄生蜂对不同龄期烟粉虱寄主的产卵选择特性。结果表明: 两种寄生蜂均可寄生烟粉虱的1～4龄若虫。当只有1个龄期的烟粉虱若虫存在时,双斑恩蚜小蜂更多地寄生3龄和4龄若虫,较少寄生1龄和2龄若虫;而桨角蚜小蜂则更多地寄生3龄和2龄若虫,较少寄生1龄和4龄若虫。在4个龄期若虫同时存在时,双斑恩蚜小蜂会明显增加对3龄和4龄若虫的产卵寄生,降低对1龄和2龄若虫的寄生;而桨角蚜小蜂则增加对2龄和3龄若虫的寄生,减少对1龄和4龄若虫的寄生。寄主植物的差异不影响这二种蚜小蜂对各龄期烟粉虱若虫的产卵选择倾向。结果提示,烟粉虱若虫3龄和4龄是双斑恩蚜小蜂最适宜的寄主,而桨角蚜小蜂最适宜的寄主是烟粉虱2龄和3龄若虫。     

Suitability of Bemisia tabaci (Hemiptera: Aleyrodidae) instars for the parasitization by Encarsia bimaculata and Eretmocerus sp. nr. furuhashii (Hymenoptera: Aphelinidae) on glabrous and hirsute host plants

The host instar preferences of Encarsia bimaculata and Eretmocerus sp. nr. furuhashii parasitizing Bemisia tabaci and their development on four host plants, collard, eggplant, cucumber and tomato, were studied in the laboratory. Both of the parasitoids accepted all nymphal stages of B. tabaci, but E. bimaculata preferred third and fourth instars while Er. sp. nr. furuhashii preferred second and third instars under both choice and no choice conditions. Regardless of host stage parasitized, adults of parasitoids emerged only from fourth instars. When given the simultaneous choice of all instars, E. bimaculata reduced parasitization of first and second instars (3.73 and 4.76%, respectively) while increasing parasitization of third and fourth instars (5.44 and 6.93%, respectively), in contrast Er. sp. nr. furuhashii increased its parasitization of second and third instar nymphs (1.27 and 3.17%, respectively) and decreased that of first and fourth instars (7.0 and 3.06%, respectively). Host plants did not significantly influence instar preference for either parasitoid. Developmental periods of both the parasitoids from egg to adult emergence were longest when first instars were parasitized and shortest when fourth instars were selected. Parasitoid developmental time was generally shorter on glabrous plants than on hirsute plants.     

When host choice is a problem for a generalist herbivore: experiments with the whitefly, Bemisia tabaci

1. Experiments with adult females of the whitefly, Bemisia tabaci, demonstrated that when mixtures of host plants were present, performance was reduced relative to that on the best of the host plants when presented alone. 2. Behavioural observations indicated that in the presence of a variety of plants, individuals moved more, switched between plants more frequently, and stayed feeding in one place for shorter periods of time, compared with the situation when single plant species were available. 3. The data are interpreted as a constraint on attentiveness in the presence of complex, mixed-sensory stimuli.     

寄主植物对双斑恩蚜小蜂的发育、存活和繁殖的影响

研究了茄子和扶桑两种不同寄主植物对烟粉虱寄生性天敌双斑恩蚜小蜂Encarsia bimaculata发育、存活和繁殖等特性的影响。在26±0.5℃的条件下,在扶桑上,双斑恩蚜小蜂卵至成虫的发育历期为13.6天,2龄幼虫至成虫的存活率为93.2%;而在茄子上双斑恩蚜小蜂卵至成虫的发育历期和2龄幼虫至成虫的存活率分别为12.1天和91.1％。扶桑上双斑恩蚜小蜂雌性成虫的平均寿命为8.0天,平均单雌产卵量为35.9粒;而在茄子上雌性成虫的平均寿命为6.6天,平均单雌产卵量为27.6粒。双斑恩蚜小蜂在扶桑和茄子植物上的种群内禀增长率分别为0.2081和0.892。两种不同寄主植物对双斑恩蚜小蜂在若虫发育历期和存活率、成虫寿命和平均产卵量以及内禀增长率等方面均存在着显著差异。研究结果表明,寄主植物对双斑恩蚜小蜂的发育、存活和繁殖有较大的影响。     

番茄感染双生病毒对叶毛密度和海氏桨角蚜小蜂搜寻行为及适合性的影响

植物病毒可通过影响植物形态和生理特性从而对媒介昆虫和寄生性天敌产生作用。然而, 在植物 媒介昆虫 寄生蜂三营养级关系研究中有关植物病毒的影响很少被考虑。本研究测定和分析了番茄植株感染番茄黄化曲叶病毒（tomato yellow leaf curl virus, TYLCV)后叶毛密度的变化及对烟粉虱Bemisia tabaci (Gennadius)重要寄生性天敌海氏桨角蚜小蜂Eretmocerus hayati Zolnerowich and Rose行为与适合性的影响。结果表明： 携带TYLCV病毒番茄植株叶毛密度显著增加, 为健康植株叶毛密度的1.8倍。海氏桨角蚜小蜂在带毒植株叶片上的寄主处置时间和寄主块停留时间显著长于其在健康植株叶片上的时间, 分别为其2倍和1.5倍, 但寄生蜂的寄生率、 羽化率及发育历期差异不显著(P>0.05)。本文首次报道了双生病毒侵染可引起叶毛密度的增加, 对理解植物-双生病毒-烟粉虱-寄生蜂四方关系提供了新的数据。