Studies on three species of Trichogramma. I. Foraging behaviour for food or hosts

The foraging strategies for both food or hosts of three trichogrammatid species: Trichogramma evanescens, Trichogramma cacoecia and Trichogramma dendrolimi were compared using artificial patches of Sitotroga cerealella eggs. In all experiments, inexperienced and newly emerged wasps of < 1 h old were singly tested. When the females were allowed to land upon the hosts, the decision-making process for initial acceptance or rejection was species-dependent. The initial search in T. evanescens was for food, whereas T. dendrolimi or T. cacoeciae start to oviposit immediately after their emergence. When honey-deprived or undeprived females were each exposed to single patches for 20 or 60 min, variations in mean number of probing females 'drilling and ovipositing' were also species-dependent. Acceptance of host eggs by honey-deprived females and subsequent egg deposition were higher in both T. cacoeciae and T. dendrolimi than in T. evanescens . For all species, the probing of honey-undeprived females was higher than that of deprived ones. When the exposure period was prolonged to 24 or 48 h and the number of patches per female increased to three, most of the honey-deprived or undeprived T. evanescens females attacked one patch, and only a few of them attacked two patches. Foraging activity of honey-deprived females of T. cacoeciae was restricted to single patches, whereas most undeprived ones attacked more than one patch. In contrast, honey-deprived or undeprived T. dendrolimi females attacked more than one patch. The experiments showed that T. dendrolimi females have more powerful ovipositing urges than looking for food and that the opposite was the case for T. evanescens , with T. cacoeciae being intermediate.     

Comparison Between the Control Efficacy of Trichogramma evanescens Westwood (Hymenoptera: Trichogrammatidae) and Two Trichogramma cacoeciae Marchal Strains Against Grapevine Moth ( Lobesia botrana Den. & Schiff.), Depending on Their Release Density

In the first generation of the grape moth Lobesia botrana, Trichogramma evanescens spread to a greater extent than Trichogramma cacoeciae and parasitized most of the grape moth eggs. Reduction of damage to grapes was improved by doubling the number of T. evanescens release points in the first and second generations. In the second generation of the grape moth, T. cacoeciae was more efficient than T. evanescens . The highest proportion of individuals belonging to the reared and natural T. cacoeciae strains were found in the plot in which they were initially released. The total number of individuals emerging from parasitized eggs eggs was the same for each strain, which would suggest that neither predominated. Whichever T. cacoeciae strain considered, a density of 800 release points ha -1 did not induce greater parasitization than a density of 400 release points ha -1 .     

Do sympatric Trichogramma species parasitize the pest insect Helicoverpa armigera and the beneficial insect Chrysoperla carnea in different proportions?

Parasitism of two host species by five Trichogramma species (Hymenoptera, Trichogrammatidae) was studied in the laboratory. The host species were: i) the bollworm Helicoverpa armigera Hübner (Lepidoptera, Noctuidae), an important pest of many crops in the tropics and subtropics, and ii) one of its natural enemies, the lacewing Chrysoperla carnea Stephens (Neuroptera, Chrysopidae), a predator often used as a biological control agent. The proportion of H. armigera eggs parasitized from the total number of parasitized hosts differed between Trichogramma species. The average number of parasitized eggs per female in 24 h by Trichogramma pintoi and T. bourarachae was 10 of H. armigera and about 0.5 of C. carnea. For the other three Trichogramma species (T. cordubensis, T. evanescens and T. turkestanica) these averages varied from 6 to 11 H. armigera eggs and from 3 to 4 C. carnea eggs. Total adult offspring production, contacts with hosts, secondary clutch size and sex-ratio of each Trichogramma species were determined as well. The results show that sympatric Trichogramma may parasitize target and non-target species in different proportions. If this difference corresponds to the field situation, simple laboratory tests could be performed to select not only efficient biogical control agents, but also species which are the least detrimental to non-target hosts.     

Survey of natural populations of Trichogramma (Hym., Trichogrammatidae) in the vineyards of Alsace (France)

Activity of Trichogramma , assessed by trapping with host-eggs, was observed as early as April and continued until October in the vineyards and their surrounding biotops. Trichogramma showed the greatest activity in April-May, July and September. Parasitized eggs were found before the main laying period of the first generation of the grapevine moths Lobesia botrana Den. and Schiff. and Eupoecilia ambiguella Hb. Four native species, Trichogramma cacoeciae Marchal, Trichogramma daumalae Dugast and Voegelé, Trichogramma evanescens Westwood and Trichogramma principium Sugonjaev and Sorokina were found.     

Use of tetracycline in larval diet to study the effect of Wolbachia on host fecundity and clarify taxonomic status of Trichogramma species in cured bisexual lines

Endosymbionts of the genus Wolbachia were efficiently cured from Trichogramma species by incorporating 0.02% tetracycline into the artificial diet used to rear larvae. Use of this technique yielded stable cured lines (bisexual and arrhenotokous lines) in which no Wolbachia organisms were detected by PCR for up to 14 generations after curing. Four cured strains of Trichogramma pretiosum showed a significantly lower total fecundity compared to their Wolbachia-infected counterpart. However, the fecundity of a single cured strain of Trichogramma evanescens was similar to its Wolbachia-infected counterpart. These differences in the effect on fecundity may be due to differences between the Wolbachia strains infecting T. pretiosum or T. evanescens, providing additional evidence for the hypothesis that a specific interaction exists between some Trichogramma species and their Wolbachia symbionts. Tetracycline in larval diet was also used to generate bisexual strains of Trichogramma oleae and Trichogramma cordubensis so that these species could be crossed with the closely related species, respectively, T. pretiosum and T. evanescens, to test their compatibility. These crosses showed a lack of compatibility, validating maintenance of these as distinct species.     

Parasitization of potato tuber moth eggs (Lep., Gelechiidae) from irradiated adults by Trichogramma (Hym., Trichogrammatidae) and control of moth population with combined releases of sterile insect and egg parasitoid

Abstract:  Eggs of the potato tuber moth (PTM) Phthorimaea operculella (Zeller) obtained from 150 or 300 Gy-irradiated moths, either inbred or out-crossed to untreated counterparts, were offered as host material to three generalist Trichogramma species; Trichogramma cacoeciae , Trichogramma evanescens , and Trichogramma principium , to determine the ability of these egg parasitoids to develop in F₁ sterile eggs. All eggs laid by the different parental crosses at 150 or 300 Gy, were acceptable and suitable for Trichogramma development. However, in no choice and paired comparison tests, eggs from 300 Gy-irradiated parents were significantly less preferred compared with eggs laid by non-irradiated moths. No intra-specific differences for PTM sterile eggs were recorded among the tested Trichogramma species. The mean number of wasps emerging from each egg types was not affected by an interaction between parental crosses and applied doses. Overall, this study demonstrates that release of irradiated and non-irradiated moths at a 5 : 1 over-flooding ratio and Trichogramma over potatoes in small plexiglass boxes, is complementary and more effective in reducing PTM F₁-emerged progeny than either technique used alone. The results provide baseline data for developing an integrated control approach by using inherited sterility technique in conjunction with Trichogramma for PTM population suppression.     

Temperature-dependent Development of Four Egg Parasitoid Trichogramma Species (Hymenoptera: Trichogrammatidae)

Trichogramma species have been successfully utilized for biocontrol of several lepidopteran pests worldwide. The development, survival and progeny production of two Kenyan species' Trichogramma bournieri Pintureau & Babault and Trichogramma sp. nr. mwanzai Schulten & Feijen (collected from Kenya), Trichogramma evanescens Westwood (Germany) and Trichogramma chilonis Ishii (India) was studied at four constant temperatures (13, 18, 25 and 34°C) with the 011 aim of assessing the relative biotic potential of the two native species for 011 biocontrol of Helicoverpa armigera and Plutella xylostella in Kenya. The study was conducted at the Institute 011 for Biological Control (BBA), Darmstadt, Germany. The Trichogramma species tested showed variations 011 in fertility, developmental time, percent emergence, progeny production and sex ratio 011 at the four temperature regimes. Fertility decreased as temperature increased from 25 to 34°C. 011 T. chilonis and T. evanescens completed development at all temperatures tested, but T. 011 bournieri and T. sp. nr. mwanzai failed to complete development at 13°C. The developmental 011 period for all the species decreased as the temperature increased. The duration of development from 011 oviposition to adult emergence varied from 8 days to 12 weeks shorter at 34°C than at 011 13°C for T. chilonis and T. evanescens . For the various temperatures tested, a linear model was 011 satisfactory for egg to adult development at P = 0.05 for T. chilonis and T. evanescens . The 011 lower temperature thresholds for development and duration in degree-days were 8.83°C and 188 for 011 T. chilonis and 9.23°C and 192 for T. evanescens , respectively. For all temperatures tested, 011 T. sp. nr. mwanzai had the highest preimaginal survivorship. Adult emergence was lower at 13°C and 34°C than at 011 18 and 25°C. The highest fertility (mean ±SE) (50.37 ±2.32 adult 011 female -1 ) and progeny production (44.03 ±2.02 adult female -1 ) was recorded at 25°C for 011 T. evanescens . Sex ratio was biased towards female at all temperatures in T. bournieri and T. chilonis . 011 At all temperatures tested, T . sp. nr. mwanzai produced more males than females. For all species tested, 011 favourable parasitism was between 18 and 25°C. The results from this study will be useful for mass rearing purposes as well as for future field release programmes.     

Pattern of Egg Management by Trichogramma cacoeciae and T. dendrolimi (Hymenoptera: Trichogrammatidae)

The effect of temporary host deprivation on parasitization rates of Trichogramma cacoeciae Marchal and T. dendrolimi Matsumura was investigated. The study was conducted with females that we allowed to engage in 3 days of oviposition after various periods of host deprivation. It seems that the production and management of eggs by the two species is completely different. During the first day of oviposition, parasitization by T. cacoeciae was almost unaffected after 1 to 5 days of host deprivation. As deprivation time increased, however, the number of parasitized hosts decreased from an average of 28.6 ±2.0 hosts provided at emergence to an average of 12.5 ±2.3 hosts when the waiting time was 10 days. The number of hosts parasitized on the first day of parasitization by T. dendrolimi were not affected whatever the waiting test period. During the second or third days of oviposition, the lack of suitable hosts for T. cacoeciae did not depress egg-laying potentiality, whereas a strong reduction in parasitization rates by T. dendrolimi occurred in the next 2 days of oviposition whatever was the waiting period. This leads to ca. 50% reduction in total activity of 3 days of oviposition. Only in T. cacoeciae was it possible to distinguish between ageing and host deprivation. The data suggest that T. dendrolimi is a typical proovigenic species, while T. cacoeciae is neither definitely proovigenic nor synovigenic. A slight decrease in rate of emergence of offspring of T. cacoeciae females that had waited 8 to 10 days for their hosts was observed. As far as biological control is concerned, the efficiency of T. dendrolimi females may be more sensitive to host deprivation than T. cacoeciae.     

How does infection with parthenogenesis-inducing Wolbachia reduce the fitness of Trichogramma?

We analyzed the survival rate of the immature stages of Trichogramma species and lines that differed in their mode of reproduction. Specifically, we compared the mortality of arrhenotokous (W(-)), irrevertable thelytokous (W(-)), and Wolbachia-associated thelytokous (W(+)) forms. The embryonic mortality of the W(+) strains was significantly higher than that of the W(-) lines. The embryonic mortality was negligible for the arrhenotokous Trichogramma evanescens and the thelytokous Trichogramma cacoeciae, which is not infected with Wolbachia. Only 30% of the eggs of the Wolbachia-infected strains developed to adults, while the emergence rate of the Wolbachia-free strains was more than 78%, irrespective of the origin of the strains. More than 78% of the overall mortality in W(+) strains happened during the early stages of development. About 35% of embryos of W(+) strains remain in the mitotic stage even 48 h after oviposition. Most embryos of W(-) strains had already developed to cellular blastoderm after 6 h, regardless of strains. The mortality of immature stages in W(+) strains was mainly caused by the failure of the mitotic divisions.     

Naturally occurring Trichogramma species in olive farms in Egypt

A survey of two-year studies (2001-2003) was carried out in two olive groves sited at two representative olive growing areas, namely Paradise Park (arid area) and Burg E1-Arab farm (semi-arid area) to monitor the frequency of endemic Trichogramma species on olive moth (Prays oleae) and jasmine moth (Palpita unionalis). The suspended host bait traps were found to be a more practical and effective tool for collecting Trichogramma wasps than the attached ones. Four naturally occurring Trichogramma species were collected for the first time in Egypt from the olive groves, where releases have never been conducted. T.bourarachae was collected exclusively from Burg El-Arab farm. It seems that this wasp species adapts well to the semi-arid area. Three species, namely T. cordubensis, T. nr.pretiosum and T. cacociae were isolated from Paradise Park farm. All of these wasps were also bred from naturally parasitized host eggs during favorable and even at unfavorable temperature conditions of June-August. However, these endemic species did not occur naturally in sufficient numbers to keep the pest populations from reaching damaging levels.The excessive usage of insecticides and the oophagous predators (e.g., ants and lacewing larvae) are some factors that affect the performance of Trichogramma wasps in olive farms.The presence of warm weather wasp strains suggests the existence of well-adapted wasp species or swains which may be appropriate candidates for the control of target pests in olive groves. Additional study is required to determine the best “habitat-specific” species/strains of Trichogramma for augmentative release of naturally occurring wasps and to incorporate them into integrated pest management programs. Efforts should be made to conserve these endemic species from oophagous predators, hot weather and insecticides.The olive and jasmine moth-larvae and pupae found under tree canopies were bred and emerged parasitoids were listed.     

卷蛾赤眼蜂体内共生菌Wolbachia对寄主产雌孤雌生殖行为的影响

在30℃的条件下,连续饲养卷蛾赤眼蜂Trichogramma cacoeciaeMarchall10代,观察每代蜂的生物学特性,并进行Wolbachia的wsp基因的分子检测,以研究卷蛾赤眼蜂产雌孤雌生殖行为与其体内共生菌Wolbachia的关系。结果表明,高温下卷蛾赤眼蜂体内的Wolbachia被抑制,4代以后wsp基因的PCR检测结果变为阴性;同时赤眼蜂的产雌孤雌生殖行为的改变程度也随着世代的增加呈递增趋势。这显示卷蛾赤眼蜂的产雌孤雌生殖行为与其体内的共生菌Wolbachia具有一定程度的相关性。     

Efficacy of Trichogramma wasps for controlling tomato leaf miner Tuta absoluta

Tomato is considered as one of the most essential vegetables after potato in Egypt. Tomato is infested by many insects; one of these serious insects is tomato leaf miner Tuta absoluta, which causes yield losses up to 100%. T absoluta is attacking leaves, flowers, stems and fruits. Trichogramma species is playing an important role in reducing this insect infestation. Efficiency of Trichogramma evanescens alone and in combination with insecticides were assessed against T. absoluta in tomato fields. Three release rates 500, 1000 and 1500 parasitized egg/card as well as 2 insecticides (Dimilin and Corgen) were applied. Number of normal and parasitized eggs, live and dead larvae and tunnel numbers were recorded. The results revealed that T. absoluta eggs were higher in control plots than those counted in Trichogramma plots. Among Trichogramma release rates, higher release rates, obtained higher parasitism rates of Tuta eggs (reached to 50%). Companying Trichogramma with IGR Dimilin had a little side effect on parasitism rate which it was smaller compared to plots of Trichogramma alone. Dimilin (IGR) caused reducing in Tuta larval population, which it differed significantly compared to control plots. Another IGR, Coragen resulted increasing the mortality of Tuta larvae than other treatments. In Trichogramma release rates, higher release rates, lower number of tunnels were found. In plots of companying Trichogramma with Coragen, the lowest tunnel numbers were recorded. Field release of T. evancences would be a promise biocontrol agent to suppress T. absoluta. These findings may encourage using T. evancences as a favorable strategy for integrated management of T. absoluta to produce safe tomato.     

阿维菌素对广赤眼蜂（Trichogramma evanescens）不同发育阶段的毒性和实验种群动态的影响

研究了阿维菌素对广赤眼蜂不同发育阶段的毒性和实验种群动态的影响.结果表明,阿维菌素田间推荐剂量喷雾处理可显著降低米蛾卵内广赤眼蜂的羽化率;除卵期外,其它3种发育阶段经该药处理,羽化后的雌蜂寿命显著缩短,其中预蛹和蛹期处理雌蜂前翅畸形率高达43.3%～47.2%,影响程度随着其生长发育的进行呈增大趋势.根据药膜法剂量与效应测定结果,广赤眼蜂成蜂对阿维菌素比较敏感,LC50值为2.1991mg·L-1.温室盆栽试验表明,1.8%阿维菌素乳油对广赤眼蜂成蜂的持效期为10d,具有一定程度的残留毒性.广赤眼蜂的蛹经阿维菌素亚致死剂量LC35处理后,发育至成蜂,除羽化后的雌蜂产卵量显著减少外,雌蜂寿命、子代羽化率和子代性比与对照并无显著差异.生命表参数显示,LC35处理后的广赤眼蜂净增值率和世代平均历期明显地低于对照,但内禀增长率、周限增长率和种群倍增时间与对照差异不明显.可以认为阿维菌素亚致死剂量对广赤眼蜂的种群没有重要影响.     

赤眼蜂体外培育产卵增效剂的研究(英语)

七种物质(聚乙烯醇、明胶、白乳胶、琼脂、木薯粉、米粉和淀粉一定浓度的水溶液或悬液用作松毛虫赤眼蜂Trichogramma dendrolimi拟澳洲赤眼蜂T.con fusum及广赤眼蜂T.euanescens人工体外培育的产卵增效剂以吸引这些蜂在人工卵上产卵.这七种溶液都能提高三种赤眼蜂在人工卵内的产卵量,不同的赤眼蜂对不同的增效剂有不同的产卵行为反就,我们可利用其中最有效而经济的增效剂以增强体外培育赤眼蜂的效率.     

几种赤眼蜂对灰白蚕蛾寄生能力的影响

通过室内功能反应试验,测定松毛虫赤眼蜂T.dendrolimiMatsumura、短管赤眼蜂T.pretiosumRiley、暗黑赤眼蜂T.pintoiVoegele、玉米螟赤眼蜂T.ostriniaePangetChen、卷蛾分索赤眼蜂Trichogrammatoidea bactraeNagaraja、拟澳洲赤眼蜂T.confusumViggiani、舟蛾赤眼蜂T.closteraePangetChen、广赤眼蜂T.evanescensWestwood对广州地区重要园林害虫灰白蚕蛾的寄生能力。结果表明,除卷蛾分索赤眼蜂外,其它7种赤眼蜂对灰白蚕蛾的寄生作用均能用HollingⅡ型功能反应模型拟合。松毛虫赤眼蜂对灰白蚕蛾的寄生能力为最强,短管赤眼蜂和暗黑赤眼蜂次之,最大寄生卵量分别为25.8粒/雌、19.0粒/雌和18.6粒/雌,且在灰白蚕蛾卵内都能发育成功和正常羽化,可进一步进行筛选。虽然玉米螟赤眼蜂和舟蛾赤眼蜂对灰白蚕蛾有较强的寄生能力,但其后代雌蜂率都较低,且玉米螟赤眼蜂不能正常羽化,因此不适宜用来防治灰白蚕蛾。卷蛾分索赤眼蜂、广赤眼蜂和拟澳洲赤眼蜂的最大寄生量都较低,均不超过15.0粒,对灰白蚕蛾卵的寄生潜能不大。     

Effects of the Host Species and the Number of Parasitoids per Host on the Size of Some Trichogramma Species (Hymenoptera: Trichogrammatidae)

The size of some Trichogramma spp. adults and especially the ovipositor length depends on the species, but is also related to the host species and to the number of parasitoids per host. The length is greater in T. evanescens than in T. pretiosum itself greater than in T. exiguum, but the width is similar in the three species. For T. evanescens, the size obtained in Mamestra brassicae host when three or four insects emerged is similar to that obtained in Ephestia kuehniella host when singly parasitized. The size of the ovipositor is important because it may influence the possibility of in vitro egg laying in artificial host eggs. A shorter or a narrower ovipositor could cause difficulties in egg-laying into artificial host eggs composed of a membrane of unsuitable thickness.     

Comparative biology and life tables of Trichogramma evanescens and T. cacoeciae with Ephestia elutella as host at four constant temperatures

The age-specific fecundity of Trichogramma evanescens Westwood and T. cacoeciae Marchal (Hymenoptera: Trichogrammatidae) with Ephestia elutella (Hübner) (Lepidoptera: Pyralidae: Phycitinae) as host and the life span of the adults with and without hosts was determined at 20, 26, 30 and 35 °C and 75 ±5% r.h. in the laboratory. At 35 °C, no progeny emerged. The availability of hosts prolonged the longevity in both species. Longevity, percentage of parasitism, fecundity, and the intrinsic rate of natural increase were higher in T. evanescens than in T. cacoeciae. Trichogramma evanescens is expected to be more effective than T. cacoeciae for use in biological control of Ephestia spp., especially at low and high temperatures.     

Are Trichogramma bourarachae and the perkinsi species group really distinct from Trichogramma buesi and the pintoi group,respectively?

Abstract:  The two Trichogramma species T. bourarachae and T. buesi belonging to two closely related groups, perkinsi and pintoi , were compared. The inter-species crossings did not result in hybrids and, therefore, the two species show complete genetic isolation. Eleven morphometric characteristics (eight from male genitalia and three from male antennae) and seven ratios between the latter characters confirmed the validity of these species. Significant differences (P < 0.01) actually exist for 56% of the measured characters and the calculated ratios. Among the morphometric characters analysed, five contribute to the definition of the perkinsi and pintoi groups and allow for comparisons to be made. However, only two of them (40%) show a difference between the groups (P< 0.01). Such a result, in accordance with those from other studies, has led to the combination of the two groups synonymously, under the name of perkinsi .     

赤眼蜂生物学与繁殖技术研究及应用——广东省生物资源应用研究所(原广东省昆虫研究所)赤眼蜂研究50年

本文介绍了广东省生物资源应用研究所(原广东省昆虫研究所)50多年来有关赤眼蜂生物学与繁殖技术及应用研究工作。内容包括赤眼蜂种质资源挖掘、寄生生态学、药剂敏感性、滞育贮存和体外培育技术等应用基础研究。研究的赤眼蜂近20种(品系),重点研究了使用范围广的松毛虫赤眼蜂、拟澳洲赤眼蜂、广赤眼蜂以及可用米蛾卵繁殖并对南方水稻、甘蔗和玉米等作物螟虫有较好防控效果的稻螟赤眼蜂、欧洲玉米螟赤眼蜂和亚洲玉米螟赤眼蜂。     

Wolbachia在我国广赤眼蜂种群内的感染

Wolbachia是广泛分布于节肢动物生殖组织内的一类细胞内共生菌,它属于原细菌的α亚类,能够通过调控寄主的生殖活动而促进其在寄主种群中的扩散。通过对wsp 基因的克隆及PCR-RFLP分析确定了Wolbachia在我国广赤眼蜂种群内的存在,并发现有2种Wolbachia 菌系的感染,命名为wEvaA和wEvaB。经过克隆分离得到了这2种Wolbachia的wsp基因序列,在GenBank的登录号为AY390279和 AY390280 ,并由基于wsp基因的聚类树中发现,这两种Wolbachia菌系均属于A组。