Selectivity of neem to Trichogramma pretiosum Riley and Trichogrammatoidea annulata De Santis (Hymenoptera: Trichogrammatidae)

Trichogramma pretiosum Riley and Trichogrammatoidea annulata De Santis are commonly found in avocado and persimmon orchards in northern Parana state. However, their abundance depends on whether insecticides are used or not to control the key lepidopteran pests Stenoma catenifer (Wals.) (Lepidoptera: Elachistidae) and Hypocala andremona (Stoll) (Lepidoptera: Noctuidae), respectively. The aim of this work was to evaluate the effects of an aqueous neem seed extract (ANSE) at 15, 3 and 1.5%, and of an emulsifiable concentrate neem oil (ECNO) at 2.5, 0.5 and 0.25% on lifetime parameters of these trichogrammatids as a way of testing the feasibility of integrating the biological and chemical control methods. Chemicals were applied on Anagasta kuehniella (Zeller) (Lepidoptera: Pyralidae) eggs before or after parasitization (one, three or five days). ANSE was more deleterious to both parasitoid species than ECNO, regardless of the concentration and the time of application. The chemicals acted on a concentration and time dependent manner. Treating the host with neem before parasitism was less deleterious to wasp emergence, especially for T. annulata. Pre-treatments (24h) of the host eggs with ECNO at concentrations varying from 0.5% to 0.25% did not affect T. pretiosum longevity, but 2.5% reduced T. annulata survival. Feeding wasps with honey mixed with 0.25% ECNO negatively affected T. annulata survival.     

Ultrastructure of the natural and factitious host eggs of Trichogramma galloi Zucchi and Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae)

The surface and structure of the chorion of eggs of Diatraea saccharalis (F.) (Lepidoptera: Crambidae), Anticarsia gemmatalis (Huebner), Heliothis virescens F., Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae), Sitotroga cerealella (Oliver) (Lepidoptera: Gelechiidae), Ephestia kuehniella Zeller and Corcyra cephalonica Stainton (Lepidoptera: Pyralidae), that are hosts of Trichogramma galloi Zucchi and Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) were studied on SEM and TEM. Other characteristics of these eggs, such as changes in their color during embryonic development, size and volume were also recorded. Sculpturing and texture of the surface of the chorion greatly varied among the species studied, as well as the number of layers of the chorion and their thickness. Eggs of the factitious hosts were among the smallest and their volume was very close to each other. All these characteristics would provide basic information for a better understanding of the host selection behavior and are useful for the development of a suitable artificial host egg for the in vitro rearing of these egg parasitoids.     

Structure and ultrastructure of the spermatozoa of Trichogramma pretiosum Riley and Trichogramma atopovirilia Oatman and Platner (Hymenoptera: Trichogrammatidae)

Lino‐Neto, J., Báo, S. N. and Dolder, H. 2000. Structure and Ultrastructure of the Spermatozoa of Trichogramma pretiosum Riley and Trichogramma atopovirilia Oatman and Platner (Hymenoptera: Trichogrammatidae). —Acta Zoologica (Stockholm) 81 : 205–211 Spermatozoa of the Trichogramma pretiosum and T. atopovirilia are very slender and long, about 0.35 µm in diameter and 283 µm and 106 µm in length, respectively. Under light microscopy, they appear wavy along their entire length. The head contains a small acrosome which, together with the initial nuclear region is surrounded by an ‘extracellular sheath’, from which innumerable filaments irradiate. The nucleus is filled with homogeneous, compact chromatin and is attached to the flagellum by an electron dense centriolar adjunct, which extends anteriorly from the nuclear base. The flagellum consists of an axoneme with the 9 + 9 + 2 microtubule arrangement pitched in a long helix, as well as a pair of spiralling mitochondrial derivatives which coil around the axoneme. Based on these characteristics, the sperm of these Trichogramma are very similar to the chalcidoids studied to date and differ from non‐chalcidoid Hymenoptera. They differ widely from the sperm of T. dendrolimi and T. ostriniae studied, where no helically twisted structure is shown. However, based on these results we argue that the spiralling of the flagellar structures is a synapomorphy for Trichogrammatidae as well as for Eulophidae + Eurytomidae + Pteromalidae.     

Parasitism capacity of Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) reared under different temperatures on Bonagota salubricola (Meyrick) (Lepidoptera: Tortricidae) eggs

The parasitism capacity of Trichogramma pretiosum Riley strain bonagota on Bonagota salubricola (Meyrick) eggs was studied under the temperatures of 18, 20, 22, 25, 28, 30 and 32 degrees C. The number of days with parasitism, accumulated parasitism, total number of eggs parasitized per female and parasitoid longevity was evaluated. In the first 24h, parasitism ranged from 1.6 (32 degrees C) to 8.8 (22 degrees C) eggs of B. salubricola. Accumulated egg parasitism of B. salubricola reached 80% in 1st to 4th day at 20 degrees C to 32 degrees C, respectively, and in the 7th day at 18 degrees C. Temperatures from 18 degrees C to 22 degrees C were the best suited for the total eggs parasitized for female, resulting in 35.4 and 24.6 eggs/male respectively. T. pretiosum female longevity ranged from 7.8 to 2.5 days, at 18 degrees C and 32 degrees C, respectively. The results showed that T. pretiosum strain bonagota is better adapted to temperatures from 18 degrees C to 22 degrees C.     

四种杀菌剂对玉米螟赤眼蜂酚氧化酶活性的影响

为明确杀菌剂对玉米螟赤眼蜂Trichogramma ostriniae Pang et Chen毒性大小及其成蜂体内酚氧化酶（phenoloxidase, PO）活性影响, 本实验通过测定三唑酮（triadimefon）、 肟菌脂（trifloxystrobin）、 咪鲜胺（prochloraz）、 申嗪霉素（phenazino-1-carboxylic acid）4种杀菌剂对玉米螟赤眼蜂的急性毒性, 并分别测定活体和离体条件下各杀菌剂处理后酚氧化酶的比活性。结果表明, 各药剂对赤眼蜂的急性毒性大小为： 三唑酮＞咪鲜胺＞肟菌酯＞申嗪霉素, 其LC₅₀值分别为3.27, 6.46, 4.06和 9.72 mg/L, 其安全系数依次为0.07, 0.10, 0.20和1.47, 其中申嗪霉素为中等风险性, 其余3种药剂为高风险性, 且杀菌剂明显激活了PO的活性。活体条件下亚致死剂量处理得到的PO比活力高于离体处理, 且三唑酮处理组具有明显的剂量效应。本实验为研究杀菌剂对赤眼蜂的毒性及对PO的影响作了初步的探索, 为进一步研究赤眼蜂对杀菌剂的抗性及免疫能力奠定基础。     

Influence of Diaphania hyalinata (L.) (Lepidoptera: Crambidae) egg density on the parasitization capacity of Trichogramma exiguum Pinto & Platner and Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae)

The effects of the egg density of Diaphania hyalinata (L.) on several biological parameters of Trichogramma exiguum Pinto & Platner and T. pretiosum Riley were investigated. For that, 24h-old egg masses were isolated in glass tubes (15 replicates; 1 egg mass = 1 replicate), and offered to parasitization by a newly-emerged female of T. pretiosum or T. exiguum 24h at the proportion of one female to 5, 10, 15, 20, 25, 30, 35 and 40 eggs of D. hyalinata. The following parameters were evaluated: number of parasitized eggs, number of individuals per egg, viability and sex ratio. Trichogramma exiguum parasitized more eggs than T. pretiosum when more than 25 eggs were available per female. The percentage of emergence was satisfactory to T. pretiosum in densities up to 15 eggs/female and up to 20 eggs/female for T. exiguum. The number of individuals per egg was not statistically different in both species except in the density of 25 eggs/female. It can be concluded that T. exiguum performed better than T. pretiosum at larger clutch sizes, as T. exiguum parasitization capacity increased as a result of the size of the host clutch size.     

Acceptability and suitability of Tuta absoluta eggs from irradiated parents to parasitism by Trichogramma nerudai and Trichogramma pretiosum (Hymenoptera: Trichogrammatidae)

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Development of a continuous cell line from the insect egg parasitoid,Trichogramma pretiosum (Hymenoptera; Trichogrammatidae)

Summary A cell line (IPLB-TpE1) was established from embryos of the hymenopteran parasitoid,Trichogramma pretiosum Riley. Cultures contain a mixture of attached, elongate spindle-shaped cells and large aggregates of suspended cells. Chromosomes of the cells were typical ofTrichogramma species and isozyme characterization showed patterns similar toT. pretiosum adults, but distinctly different fromHeliothis zea, the lepidopteran host from which parasite eggs were obtained. The cells are capable of growth over a wide range of osmotic pressures with equal growth between 350 and 600 mOsm/kg. Optimal growth was obtained with a pH of 6.5. Doubling time at the 40th passage was 72 h and cultures are currently subcultured at weekly intervals. The mention of a commercial product does not constitute an endorsement by the U. S. Department of Agriculture.     

Behavior of Trichogramma atopovirilia Oatman & Platner and T. pretiosum Riley (Hymenoptera: Trichogrammatidae) on Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) egg masses.

In this study we analyzed the impact of physical barriers of Spodoptera frugiperda (J. E. Smith) egg-masses on the behavior of Trichogramma atopovirilia Oatman & Platner and Trichogramma pretiosum Riley. The duration of drumming, drilling, oviposition, period spent over the egg-mass, and interval between parasitized eggs were timed, and the number of parasitized eggs were recorded. The presence of scales on the egg-masses caused a significant increase in the time spent by both parasitoids on each process and a decrease in the residence time over the egg-mass and in the number of parasitized eggs, with an increase in the number of egg layers. There was a significant decrease in the number of parasitized eggs in relation to egg-masses with one layer and no scales. We observed that the physical barriers in fall armyworm egg-masses changed the behavior of T. atopovirilia and T. pretiosum, affecting their parasitization capacity.     

Experience acquisition by Trichogramma australicum Girault (Hymenoptera: Trichogrammatidae)

We investigated experience acquisition (alpha-conditioning) by females of the parasitoid Trichogramma australicum using host eggs of the noctuid moth Helicoverpa armigera (Hübner). We compared the acceptance of a host egg by females with different levels of ovipositional experience. The level of experience was designated using the standard oviposition sequence: (1) host contact (C); (2) host examination (E); (3) drilling (D); (4) full insertion (FI); and (5) oviposition (O). Each treatment consisted of a single experience level, but together these consituted a qualitative behavioural continuum of oviposition experience from naive (N) to experienced wasps. We found that host experience by adult T. australicum females can modify their behaviour. Mean duration of host finding was: N = C > E = D > FI = O. Mean duration of host examination and full insertion were: N = C > E = D = FI = O. Drilling was constant for all experience levels. Experience in drilling of the chorion during the previous host-exposure process represents a critical experience for a female and results in efficient handling and more ready acceptance of a subsequently encountered host egg.     

Wolbachia在玉米螟赤眼蜂内的三重感染

Wolbachia是一类广泛存在于节肢动物体内的共生菌。玉米螟赤眼蜂Trichogramma ostriniae是我国玉米田间的优势赤眼蜂种, 据报道, 赤眼蜂种内有Wolbachia感染。本文利用Wolbachia的16s rDNA和wsp基因引物通过PCR方法对玉米螟赤眼蜂的野生种群进行了调查, 发现以wsp基因为鉴定依据, 检测的所有个体都感染了3种Wolbachia ［wOstGDAa (GenBank accession no. EU157103), wOstGDAb (GenBank accession no. EU157104) 和 wOstGDB (GenBank accession no. EU157105)］。本文首次报道了野生赤眼蜂种群内Wolbachia的三重感染率几乎为100%。根据本研究的结果, 可以推测当不同种赤眼蜂寄生同一寄主时, Wolbachia可能会在不同赤眼蜂种间进行横向传播。     

Laboratory Performance Predicts the Success of Field Releases in Inbred Lines of the Egg Parasitoid Trichogramma pretiosum (Hymenoptera: Trichogrammatidae)

In this study we assessed the relationship between the laboratory and field performance of different isofemale lines of Trichogramma pretiosum Riley. In comparative assays, we used three rare mitochondrial haplotypes as genetic markers of the isofemale lines, and by introgressing these mitochondrial haplotypes into each of 15 genetically different nuclear lines, also tested the assumption that mitochondria are neutral markers. In a laboratory trial, 45 isofemale lines (15 nuclear genotypes x three mitochondrial haplotypes) were ranked in three categories (best, intermediate and worst) according to the mean offspring production and the proportion of female offspring. Subsequently, lines from each of the three categories were selected for field releases to quantify field parasitism on Ephestia kuehniella. Temporally separate releases were done in a transgenic Bt cornfield, with four plots, each with 50 points of recapture. The points of recapture consisted of trap cards with eggs of E. kuehniella collected daily. The trap cards were maintained in the laboratory at 25°C until the adult wasps emerged, and the maternal identity of the wasps was determined using qPCR and high-resolution melt curve analysis to determine the mitochondrial haplotype. The results showed that these measures of laboratory performance (fecundity and offspring sex ratio) were good predictors of field success in T. pretiosum. We also report strong evidence discrediting the assumption that mitochondria are neutral, in view of the correlation between performance and mitochondrial haplotype.     

Selectivity evaluation of insecticides used to control tomato pests to Trichogramma pretiosum

The effects of the insecticides abamectin, acetamiprid, cartap and chlorpyrifos on larvae, pupae (within the host egg) and adults of the egg parasitoid Trichogramma pretiosum Riley (Hym.: Trichogrammatidae) were evaluated under laboratory conditions, using three standard tests described by IOBC. When sprayed on the immature stages of this parasitoid, cartap and chlorpyrifos proved to be the most harmful insecticides, affecting both the emergence success and parasitism capacity of this parasitoid, whereas abamectin and acetamiprid were selective. Abamectin was harmful to adults (residue test on glass plates), slightly harmful to larvae, and moderately harmful to pupae (sprayed on the immature stages within host eggs Anagasta kuehniella (Zeller)); acetamiprid was moderately harmful to adults, harmless to larvae, and slightly harmful to pupae; cartap was harmful to adults, moderately harmful to larvae and harmful to pupae; chlorpyrifos to adults, harmless to larvae and harmful to pupae.     

The Effectiveness of Trichogramma chilonis,Trichogramma pretiosum and Trichogramma brasiliense (Hymenoptera: Trichogrammatidae) as Parasitoids of Helicoverpa armigera (Lepidoptera: Noctuidae) on Sunflower (Helianthus annuus) and Redgram (Cajanus cajan)

The performance of three species of trichogrammatids on the pest, Helicoverpa armigera was evaluated in the laboratory and screenhouse conditions in Karnataka, India during 1996-97. Laboratory studies indicated that Trichogramma chilonis and Trichogramma pretiosum were more effective parasitoids of H. armigera than Trichogramma brasiliense. In screenhouse conditions, T. chilonis was the most effective parasitoid of H. armigera eggs on sunflower plants in comparison to the other two trichogrammatid species. When releasing 50?000 per ha on sunflower and redgram, T. chilonis parasitised 50.1 and 11.4% H. armigera eggs, respectively. The position of H. armigera eggs on different plant parts of sunflower had no effect on parasitism by T. chilonis. However, parasitism by the same trichogrammatid among different plant parts of redgram varied significantly. It parasitized 43.4 and 18.7% H. armigera eggs on leaves and flowers, respectively, and significantly fewer, 3.9%, on pods (P<0.05). The growth stage of redgram plants also had an effect on parasitism by T. chilonis, parasitism being extremely low on plants with pods.     

Strategic ejaculation in the egg parasitoid Trichogramma turkestanica (Hymenoptera: Trichogrammatidae)

Abstract.  1. Several parameters influence sperm allocation by males, including their size and sperm stock, intra-specific variability, quality of females', as well as the risk and intensity of sperm competition.
2. Models predict that males should invest the maximum ejaculate size when sperm competition intensity is low. As sperm competition intensity increases, males should decrease the number of sperm transferred during mating.
3. This decrease in sperm transfer to females occurs because the benefits gained by males with each extra unit of expenditure on sperm decrease. When sperm supply is not unlimited, males could expect a better return by keeping some or all sperm for mating under lower competition intensity.
4. In this study, the ejaculate size of males that were kept in groups of one, five or 10 males prior to mating, has been investigated in the haplodiploid egg parasitoid Trichogramma turkestanica Meyer (Hymenoptera: Trichogrammatidae).
5. As predicted by theory, the number of sperm transferred decreased significantly with an increase in the number of rivals.
6. This is the first study showing strategic sperm allocation depending on sperm competition intensity in a parasitoid.     

Long-term storage of sexual and asexual Trichogramma brassicae (Hymenoptera: Trichogrammatidae)

The effect of exposure duration to pre-storage (representing fall conditions) and storage (representing winter conditions) temperatures on the emergence rate in sexual and asexual Trichogramma brassicae Bezdenko (Hymenoptera: Trichogrammatidae) was studied under controlled laboratory conditions. Asexual T. brassicae was infected by Wolbachia, an endosymbiont bacterium. We considered 0, 30, 40, 50 and 60 days as exposure duration at 10°C and 0, 30, 60, 90 followed by 180 days as exposure duration at 4°C for both T. brassicae strains. Emergence rate was significantly affected by the presence of Wolbachia, the duration of exposure to 10°C, the duration of storage at 4°C and their interactions, but not by the interaction between strain × storage duration at 4°C. Emergence rate of adults was positively correlated with exposure duration at 10°C, but it gradually decreased as the cold storage duration (4°C) increased in both strains. In conclusion, we are able to store both asexual and sexual strains for longer periods of time at 4°C, but the emergence rate of sexual T. brassicae was greater than asexual in all the treatments. The presence of Wolbachia could have a negative effect on fitness of T. brassicae and reduces its emergence rate after long-term storage.     

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.     

Molecular identification of two Trichogramma species (Hymenoptera: Trichogrammatidae) in Korea

Trichogramma wasps parasitize eggs of various insect species. Several Trichogramma species have been commercialized to manage Lepidopteran agricultural pests. Correct species identification is essential for successful biological control. However, the microscopic size and morphological similarity of Trichogramma species makes correct identification very difficult. Internal transcribed spacer (ITS)-2 gene sequences have been used to identify Trichogramma species. Using this molecular marker, Trichogramma species that are commercially available in Korea were identified as Trichogramma ostriniae and Trichogramma brassicae. The latter has not previously been reported in Korea. Additionally, Cadra cautella and Sitotroga cereallela eggs (host eggs of the commercialized Trichogramma species in Korea) were infected with Wolbachia. However, Trichogramma were not infected with the bacterium. This indicates that horizontal transfer of Wolbachia does not occur from host to wasp.     

Maternal thermal effect on diapause in Trichogramma species (Hymenoptera: Trichogrammatidae)

Both direct thermal and maternal photoperiodic effects on diapause induction have been thoroughly investigated in many insect species, while maternal thermal effects have been infrequently studied. We studied the effect of temperature during development of maternal generation on the proportion of diapausing progeny in four species of the genus Trichogramma Westw., minute egg parasitoids, widely used for biological control of lepidopteran pests. The maternal generations were reared at day lengths of 12 and 18 h and temperatures of 17, 20, 25 and 30°C, and their progeny developed under day length of 12 h and temperatures of 13 and 14°C. In T. evanescens and T. piceum, the proportion of diapausing progeny decreased with increasing temperature under all tested photoperiods and thermal regimes of progeny development; the high temperature of 30°C totally averted diapause of progeny. In T. buesi and T. principium, low temperatures of 17 and 20°C resulted in relatively high proportion of diapausing progeny only when the maternal generation developed under short‐day conditions. The threshold of the maternal thermal response varied from 17–18 to 22–23°C. Under field conditions, Trichogramma females are exposed to such high temperatures only during summer, when diapause in their progeny is in any case prevented by the maternal photoperiodic response and by the thermal response of the larvae. We conclude that the maternal thermal effect on diapause induction, although to a different extent, is inherent to Trichogramma species but, at least as suggested by laboratory experiments, it does not play any role in the regulation of seasonal development under natural conditions. However, during mass rearing of Trichogramma wasps, it should be taken into account that high temperature, even when combined with short photoperiod, can avert diapause in the next generation.