Overwintering of Trichogramma ostriniae (Hymenoptera: Trichogrammatidae) within target and non-target host eggs

Trichogramma ostriniae was imported into the USA from China and it continues to be evaluated as a biological control agent against the European corn borer and other lepidopteran pest species. A natural enemy's ability to overwinter is a facet of its biology with important ramifications for biological control and non-target effects. Thus, studies were conducted to examine the ability of the introduced egg parasitoid to survive over winters in central New York State. Eggs of Ostrinia nubilalis, Ephestia kuehniella, Trichoplusia ni, Helicoverpa zea and Utetheisa ornatrix were subjected to parasitism by adult T. ostriniae and then placed out of doors and exposed to winter conditions. For trials initiated in 2003 and 2004, the adult parental wasps were exposed to a diapause-inducing photoperiod and temperature regime in the laboratory; in 2010, parental wasps were conditioned out of doors and prior to the onset of winter conditions. Emergence of their progeny was monitored over time by taking aliquots of parasitised eggs, and holding them under warm conditions until emergence was complete. The level of wasp emergence generally displayed a decline followed by gradual increase until spring. Levels of overwintering ranged from 1% for O. nubilalis to 76% for E. kuehniella, and logistic regression indicated that the odds of overwintering was dependent on the year, host species, time out of doors and varied over exposure time depending on host. The potential to overwinter in New York was further confirmed by positive identification of T. ostriniae from naturally occurring O. nubilalis eggs collected from field sites where augmentative releases had been made in previous years.     

室内外评价在黄淮海夏玉米区释放玉米螟赤眼蜂防治亚洲玉米螟的可行性

为了评价在黄淮海夏玉米区释放米蛾卵繁育的玉米螟赤眼蜂Trichogramma ostriniae防治亚洲玉米螟Ostrinia furnacalis的可行性,本试验在室内组建了玉米螟赤眼蜂在亚洲玉米螟卵上的实验种群生命表的基础上,在河南省鹤壁市滑县测定了玉米螟赤眼蜂对亚洲玉米螟的防治效果,筛选出了具有较好防治效果的释放密度和释放方法。结果显示,米蛾卵繁育的玉米螟赤眼蜂在亚洲玉米螟卵上的净生殖力R0为9.8240,单雌平均产雌率R0'为12.6256,2013年在河南省鹤壁市滑县释放玉米螟赤眼蜂能使亚洲玉米螟虫口密度减退73.91%,释放密度为2.25×105头/hm2。2014年在鹤壁市淇滨区钜桥镇采用传统的人工挂卡和新型的无人机释放玉米螟赤眼蜂,亚洲玉米螟虫口密度减退54.55%-68.16%。结果表明,在黄淮海夏玉米区释放米蛾卵繁育的玉米螟赤眼蜂防治玉米螟是可行的。     

温度对麦蛾卵繁育的玉米螟赤眼蜂发育和生殖的影响

玉米螟赤眼蜂Trichogramma ostriniae Pang et Chen是玉米螟的重要卵寄生性天敌,控制适宜的温度有利于室内大规模繁育。本试验以麦蛾卵为寄主,研究了不同温度(18℃、20℃、23℃、25℃、28℃、30℃、33℃、36℃)对玉米螟赤眼蜂的寿命、生殖力、子代羽化率和发育历期的影响。结果表明,20℃-25℃条件下雌蜂寿命最长,达7.9-9.0 d。在18℃-30℃亲代生殖力和子代羽化率无显著差异,亲代产卵量为40.9-61.7粒;羽化率为74.31%-84.22%。玉米螟赤眼蜂从卵到羽化的发育历期随温度的升高而显著缩短,由18℃时的22.6 d缩短至33℃的7.0 d。36℃时,雌蜂的寿命仅为0.56 d,且不能进行正常的生殖活动。因此,室内用麦蛾卵大规模繁育玉米螟赤眼蜂,适宜的温度为28℃-30℃;仅保存蜂种时,可选用温度18℃-20℃。     

Patch time allocation in male parasitoids

Abstract 1. Patch time allocation has been mostly studied in female parasitoids exploiting patches of hosts. Different parameters such as oviposition, host encounters, patch quality, etc. have been repeatedly shown to modify the time females invest on hosts. 2. Male parasitoids are expected to maximise their lifetime fitness by maximising the number of females inseminated during their life. Because they can be sperm and/or time limited, they should optimise their time allocation on emergence patches. 3. Patch time allocation thus appears to be an important question for both male and female parasitoids. 4. In this study, we determined the parameters used by males of the egg parasitoid Trichogramma turkestanica to decide when to leave the emergence patch. Among the different patch‐leaving parameters tested, only contacts with parasitised hosts and presence of virgin females significantly influenced the patch‐leaving tendency. 5. Our results suggest that males express behaviours that could enable them to optimise their patch exploitation time, as females do, but using different strategies.     

松毛虫赤眼蜂对被害与未被害马尾松的趋性选择

分别利用培养皿和“Y”形嗅觉仪的测定方法,研究了松毛虫赤眼蜂Trichogramma dendrolimiMatsumura对马尾松毛虫Dendrolimus punctatusWalker危害的马尾松针(Pinus massoniana)与未被害马尾松针的趋性选择反应。发现未被害松针和被害松针对松毛虫赤眼蜂均具显著的引诱作用,但是在被害与未被害松针两者之间,松毛虫赤眼蜂明显选择被害松针;对于不同被害程度而言,松毛虫赤眼蜂倾向于选择被害程度严重的松针,而与松针是否被马尾松毛虫连续危害的关系不明显。即松毛虫赤眼蜂可以通过马尾松毛虫被害后的寄主植物(马尾松)所散发的气味以对寄主栖息地定向,跟踪、寻找马尾松毛虫。     

Host suitability and preference studies of Trichogramma cordubensis (Hymenoptera: Trichogrammatidae)

Studies of host suitability and preferences of Trichogramma cordubensis Vargas and Cabello (Hymenoptera: Trichogrammatidae) were performed with eggs of six Lepidoptera (Noctuidae) species: Thysanoplusia orichalcea Fabricius, Peridroma saucia (Hübner), Xestia c-nigrum L., Phlogophora meticulosa (L.), Noctua pronuba (L.), and N. atlantica (Warren). Host suitability was studied by analysing separately the effects of the attacked host species and the influence of the rearing host species on different biological parameters of T. cordubensis. Host preference was analysed by offering eggs of two host species simultaneously to a single female wasp without previous oviposition experience (dual-choice tests). Results show that P. saucia, followed by P. meticulosa were the least suitable hosts for T. cordubensis, since on these species the preimaginal development of the parasitoids was significantly longer and, the number of parasitized eggs as well the number of offspring per female were significantly lower. Contrarily, T. cordubensis parasitized at a higher rate the eggs of the endemic non-target species, N. atlantica. Dual choice tests showed that the option of the first host to be accepted by the wasp was random; however, the mean number of parasitized eggs differed significantly when two host species were offered simultaneously to T. cordubensis, always being the host species with heavier eggs the most parasitized.     

M-PCR： a powerful method for rapid molecular identification of Trichogramma wasps （Hymenoptera： Trichogrammatidae）

Two species-specific primers were designed depending on ITS2 sequence variation of 37 Trichogramma wasps, and these primers were applied to establish an assay,multiplex PCR (M-PCR), for molecular diagnosis of two important Trichogramma wasps,T. confusum and T. dendrolimi, in China. Multiplex-PCR results showed that only target species produced two PCR products, one product of ITS2 region species-specific amplification and one product of its ITS 1 region universal amplification, but other species produced only one ITS1 universal PCR product. Using this method, the target Trichogramma species can be distinguished from other Trichogramma species. Molecular identification based on M-PCR has particular value over morphological technology and other approaches, such as normal molecular and biochemical methods. Furthermore, because M-PCR assay can avoid false negative results, which frequently happen in PCR reaction, this method will be much more accurate and useful for Trichogramma identification, and can be developed as an easy and rapid diagnostic kit applied in the identification and quality monitoring of Trichogramma mass products both in the factory and in the field. Such an easy and rapid diagnostic kit will be valuable in the application of Trichogramma species as a biological control.     

Refinement of a cell line based artificial diet for rearing the parasitoid wasp, Trichogramma pretiosum

An artificial diet incorporating insect cells originally developed for Trichogramma australicum Girault (Hymenoptera: Trichogrammatidae) was successfully used to rear Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae). To refine the diet, individual components were removed. Chicken egg yolk and the insect cells were identified as the most important components for T. pretiosum development. Their removal resulted in few pupae and no adults. Removal of Grace’s insect medium, a common component of artificial diets, was found to markedly improve the development of T. pretiosum, producing 60% larva to pupa transition and 19% pupa to adult transition. There was no significant difference in T. pretiosum development on diets in which milk powder, malt powder or infant formula were interchanged, despite differences in nutrient composition. The use of yeast extract resulted in significantly higher survival to the adult stage when compared with yeast hydrolysate enzymatic and a combination of yeast extract and yeast hydrolysate enzymatic. Comparison of four antimicrobial agents showed the antibacterial agent Gentamycin and the antifungal agent Nystatin had the least detrimental effect on T. pretiosum development. The use of insect cell line diets has the potential to simplify artificial diet production and significantly reduce T. pretiosum production costs in Australia compared to diets using insect hemolymph or the use of natural or factitious hosts.