繁育寄主对三种赤眼蜂个体大小及抱卵量的影响

【目的】繁育寄主及成蜂日龄均会影响赤眼蜂体内的抱卵量,为了解繁育寄主及育出赤眼蜂个体大小与赤眼蜂抱卵量的关系,我们在室内研究了米蛾 Corcyra cephalonica（Stainton）卵和亚洲玉米螟 Ostrinia furnacalis （Güenée）卵作为繁育寄主对3种赤眼蜂雌蜂大小、抱卵量的影响。【方法】在光周期14L:10D、温度25±1℃的室内条件下,以米蛾卵、亚洲玉米螟卵作为繁育寄主,解剖不同日龄（羽化后12-72 h）松毛虫赤眼蜂 Trichogramma dendrolimi Matsumura、玉米螟赤眼蜂Trichogramma ostriniae Pang et Chen以及稻螟赤眼蜂Trichogramma japonicum Ashmead,观察雌蜂抱卵量,测量成蜂的大小,分析雌蜂抱卵量与其日龄、个体大小以及繁育寄主的关系【结果】在羽化后48 h以内,3种蜂的抱卵量随雌蜂日龄的增长而增加。羽化后72 h,除米蛾卵繁育的玉米螟赤眼蜂及玉米螟卵繁育的松毛虫赤眼蜂的抱卵量比羽化后48 h时略高外,其他组合均出现下降。以亚洲玉米螟卵为繁育寄主时的玉米螟赤眼蜂的抱卵量显著高于对应日龄的以米蛾卵为繁育寄主时的抱卵量,而松毛虫赤眼蜂（除羽化后12和24 h外）和稻螟赤眼蜂则相反;以米蛾卵为繁育寄主时,相同日龄的赤眼蜂中,松毛虫赤眼蜂抱卵量最高,稻螟赤眼蜂的抱卵量最低;以亚洲玉米螟卵为繁育寄主时,玉米螟赤眼蜂抱卵量最高,稻螟赤眼蜂抱卵量最低。雌蜂抱卵量与雌蜂个体大小呈线性正相关,相关程度随雌蜂日龄增加而更加明显。【结论】后足胫节长度可以作为评价松毛虫赤眼蜂、玉米螟赤眼蜂和稻螟赤眼蜂质量的指标。赤眼蜂抱卵量受繁育寄主、赤眼蜂蜂种及雌蜂日龄的显著影响,寄主的适合性也会影响育出赤眼蜂的大小,筛选合适的繁育寄主有助于提高赤眼蜂的质量。     

Effects of size and fluctuating asymmetry on field fitness of the parasitoid Trichogramma carverae (Hymenoptera: Trichogrammatidae)

1. The effects of body size and asymmetry in morphological traits on field fitness were studied in the parasitoid Trichogramma carverae .
2. Significant fluctuating asymmetry was detected in four bristle counts and two wing measurements made on forewings. There was no evidence for directional asymmetry in any of the traits. An estimate of field fitness was obtained in grapevines by collecting released wasps arriving at oviposition sites consisting of egg rafts of the tortricid Epiphyas postvittana .
3. Comparisons of ovipositing and emergence samples indicated that wasps at oviposition sites were relatively larger and more variable in their size distribution. A non-parametric analysis of the relationship between fitness and size indicated that extremely large wasps had the highest fitness and suggested that small as well as large wasps may have had a fitness advantage.
4. For asymmetry, the only trait showing an association with field fitness was wing length. Wasps with a low length asymmetry were more likely to be collected at oviposition sites, although fitness curves indicated that wasps had a similar fitness once an intermediate length asymmetry was exceeded.
5. Mother–daughter comparisons for wasps from a genetically heterogeneous stock provided no evidence that size measures or asymmetries were heritable when wasps were reared on a factitious host.
6. These findings have implications for improving parasitism rates in inundative releases.     

Are wing size,wing shape and asymmetry related to field fitness of Trichogramma egg parasitoids?

The effects of wing shape, wing size, and fluctuating asymmetry in these measures on the field fitness of T. nr. brassicae and T. pretiosum were investigated. Trichogramma wasps mass-reared on eggs of the factitious host Sitotroga cerealella were released in tomato paddocks and those females ovipositing on Helicoverpa spp. eggs were recaptured. Comparisons of the recaptured group with a sample from the release population were used to assess fitness. Wing data were obtained by positioning landmarks on mounted forewings. Size was then measured as the centroid size computed from landmark distances, while Procrustes analysis followed by principal component analysis was used to assess wing shape. Similar findings were obtained for both Trichogramma species: fitness of wasps was strongly related to wing size and some shape dimensions, but not to the asymmetries of these measures. Wasps which performed well in the field had larger wings and a different wing shape compared to wasps from the mass reared population. Both size and the shape dimensions were linearly associated with fitness although there was also some evidence for non-linear selection on shape. The results suggest that wing shape and wing size are reliable predictors of field fitness for these Trichogramma wasps.     

The influence of previous host age on current host acceptance in Trichogramma

Trichogramma principium Sug. & Sor. females were sequentially offered two portions of the grain moth (Sitotroga cerealella Oliv.) eggs, either young (1-day old) or old (eggs that had developed 6 days at a temperature of 20 °C). The probability of host acceptance depended not only on current host age, but also on the age of the previously offered host. Particularly, Trichogramma females more often oviposited in old host eggs when previously offered young eggs (35–45% of Trichogramma females laid eggs) compared to females which were sequentially offered two portions of old eggs (15–20% of Trichogramma females laid eggs). In other words, parasitization by Trichogramma was stable even when transferred from young (preferred) to old (usually rejected) eggs. Dissections showed that refusing females had significantly more mature eggs than ovipositing females, independent of host age. Among ovipositing females, wasps provided with young hosts had fewer mature ovarial eggs than wasps provided with old hosts. Supposedly, Trichogramma females offered old hosts require a higher motivation to oviposit and have a correspondingly higher egg load than females offered young (preferred) hosts.     

逐日羽化的赤眼蜂品质的比较

本文报道了逐日羽化的赤眼蜂(Trichogramma maidis Pint.et Voeg)品质的比较结果.第1天羽化的雌蜂是群体中生活力最强的个体;第2和第3天羽化的雌蜂生殖力、寿命、个体大小和性比等4项指标逐渐下降;而第4天羽化的雌蜂质量最差.当逐日(第1—第4天)羽化的赤限蜂先分别用地中海粉斑螟卵繁殖1代,然后分别收集第1天内羽化的赤眼蜂试验时,子代(F₁)雌蜂的质量有了明显的提高.母代为第3和第4天羽化的赤限蜂,其子代雌蜂的质量分别超过母代.试验表明,通过实验室选择培养可以改进和提高大量培养赤眼蜂的质量.     

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.     

Carbohydrate Suppresses Parasitization and Induces Egg Retention in Trichogramma

The influence of carbohydrate (honey) on host acceptance and egg retention was studied in adult Trichogramma principium . The presence of honey reduced the percentage of ovipositing females and the mean number of eggs laid during 2 days. Consequently, in mass rearing, when Trichogramma is usually presented to factitious hosts for a short time, providing wasps with carbohydrate may decrease progeny production. The mean number of mature ovarial eggs in non-ovipositing females was much higher than in ovipositing females in both fed and starved wasps. The adaptive role of the positive correlation between food supply and egg retention in Trichogramma is discussed.     

Long-term egg retention and parasitization in Trichogramma principum (Hym., Trichogrammatidae)

Laboratory experiments with Trichogramma principium Sug. et Sor. females that were offered Sitotroga cerealella Oliv. eggs demonstrated that less than half of the ovipositing females started oviposition during the first 2 days of the experiment, whereas the rest of the ovipositing females showed a delay in parasitization ranging from 2 to 10 days after contact with the host. Almost 10% of the wasps refused to parasitize the grain moth eggs over 12 days. The delay in parasitization may be as long as 6–8 days without any significant decrease in the number of mature ovarial eggs, in the number of eggs laid during the first 48 h of oviposition, and in the total lifetime fecundity. This egg retention is responsible for the fact that in spite of a relatively short mean duration of the oviposition period in each individual female (approximately 4 days), host parasitization by a group of simultaneously emerged wasps was almost uniformly distributed over 8–10 days. When induced, the parasitization state (i.e. the tendency to parasitize sequentially offered portions of host eggs) was stable both in the presence of a host and under host deprivation extended up to 8 days. These data provide further evidence for our hypotheses that the stability of the parasitization state in Trichogramma is based on endocrine mechanisms.     

繁育寄主对稻螟赤眼蜂寄生行为及寄生能力的影响

【目的】繁育寄主影响赤眼蜂的生物学特性,为明确米蛾 Corcyra cephalonica (Stainton)卵繁育的稻螟赤眼蜂 Trichogramma japonicum Ashmead是否和二化螟Chilo suppressalis (Walker)卵繁育稻螟赤眼蜂在防治二化螟上有差别,及田间用米蛾卵作为稻螟赤眼蜂续代寄主的可行性,本实验观察了羽化自不同寄主的稻螟赤眼蜂的寄主选择和寄生行为,研究了两种繁育寄主对稻螟赤眼蜂寄生能力的影响,为田间防治水稻螟虫提供参考信息。【方法】室内利用选择试验观察了由米蛾卵和二化螟卵繁育出的稻螟赤眼蜂对两种寄主的选择趋性及在两种寄主上的寄生行为和寄生能力,统计了羽化子代蜂的寿命。【结果】由二化螟卵繁育的稻螟赤眼蜂表现出了对二化螟卵的选择偏好,而米蛾卵繁育的稻螟赤眼蜂在米蛾卵和二化螟卵间没有表现出寄主选择偏好。寄主搜寻时间不受繁育寄主及供试寄主的影响,卵表探测时间和穿刺及产卵时间不受繁育寄主的影响,但同一寄主繁育的稻螟赤眼蜂在米蛾卵上的卵表探测时间显著长于在二化螟卵上的卵表检测时间。除二化螟卵繁育蜂寄生二化螟卵时的寄生率（36.95%）和羽化率（45.68%）较低外,米蛾卵繁育蜂寄生米蛾卵或二化螟卵以及二化螟卵繁育蜂寄生米蛾卵等3组处理间的寄生率、羽化率均无显著差异,各处理组间子代蜂寿命也无显著差异。【结论】繁育寄主影响稻螟赤眼蜂的寄主选择和寄生能力,但不影响寄生蜂搜寻寄主的能力和寄生行为。     

Effects of various insecticides on the development of the egg parasitoid Trichogramma dendrolimi (Hymenoptera: Trichogrammatidae).

The toxicity of six insecticides, acephate, methomyl, ethofenprox, cartap, chlorfluazuron, and Bacillus thuringiensis (Bt) was tested on different developmental stages of the egg parasitoid, Trichogramma dendrolimi (Matsumura). Each of the insecticides tested showed different degrees of toxicity to the parasitoid, Ethofenprox showed the highest toxicity and cartap showed relatively higher toxicity compared with the other insecticides. The development of the parasitoids treated with these two insecticides was normal, similar to that of the control group. Only the emergence of adult wasps from host eggs was disturbed. Emergence of the host, Mamestra brassicae larva was reduced following treatment with ethofenprox, cartap and methomyl. However, adult female wasps, which emerged from host eggs treated with the insecticides had the ability to oviposit normally.     

利用柞蚕卵繁殖的松毛虫赤眼蜂的适宜冷贮虫期和温度

我国普遍利用柞蚕Antheraea pernyi卵大量繁殖和释放赤眼蜂防治多种农林害虫。对赤眼蜂进行冷贮有助于其商品化生产、运输和释放应用。为了全面评价冷贮对柞蚕卵繁殖赤眼蜂的影响,作者采用柞蚕卵为寄主,以贮存温度（4℃、7℃、10℃和13℃）、贮存虫期（卵、幼虫、预蛹和蛹期）和贮存时间（2周、4周、6周和8周）为参试因子,研究了冷贮对松毛虫赤眼蜂Trichogramma dendrolimi羽化出蜂率、单卵出蜂数、单卵雌蜂比的影响。结果表明,3个因素均可单独或互作显著影响羽化出蜂率和单卵出蜂数,尤以贮存虫期的影响更为明显;但3个因素对单卵出蜂性比影响不大。综合各冷贮虫期对低温的反应,松毛虫赤眼蜂对10℃反应最敏感,各虫期羽化出蜂率和单卵出蜂数明显降低,不适宜长期冷贮;对7℃反应相对较不敏感,最适宜长期贮存。在适宜长期冷贮温度（4℃和7℃）条件下,适宜贮存虫期有所不同,4℃下为幼虫期和蛹期,7℃下为卵期和蛹期,在这些虫期和贮存温度条件组合下羽化出峰率和单卵出蜂数相对于其他虫期受冷贮的不利影响较小。从对羽化出蜂率的影响来看,于卵期7℃下冷贮为最适宜;从对单卵出蜂数的影响来看,于蛹期在4℃和7℃冷贮为适宜。     

Oviposition and offspring survival within eggs of European corn borer: discrimination of the host embryo by female Trichogramma nubilale

Oviposition preference and offspring survival relative to the location of the host embryo was tested in the egg parasitoid Trichogramma nubilale on European corn borer host eggs. Females preferentially oviposited near to the embryo on hosts about 24 h old. Survival of Trichogramma was lower when females oviposited far from the embryo, and a higher proportion of host embryos hatched. Females did not show preferences for drilling or oviposition within very young hosts relative to where the embryo would develop, and these eggs did not produce wasps or host larvae. Female behavior was apparently adaptive in day-old hosts, not to very young hosts.     

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.     

Does the Polyphagous Egg Parasitoid <Emphasis Type="Italic">Trichogramma platneri</Emphasis> Nagarkatti (Hymenoptera: Trichogrammatidae) Display Behavioral Plasticity When Parasitizing Different Hosts?

Trichogramma platneri oviposition behavior on Amorbia cuneana egg masses was investigated under laboratory conditions. No relationship was detected between host surface area, number of edge turning on host eggs, and parasitoid clutch size. It was also observed that females parasitized the egg mass randomly by drilling into the egg mass and parasitizing individual eggs without using stereotypical behaviors to assess individual hosts (i.e. drumming and turning). However, clutch size did change due to ovipositional experience as naïve wasps with little or no ovipositional experience (<6 eggs parasitized), allocated significantly more progeny per host than wasps with longer ovipositional experience (24-h oviposition experience on a single egg mass). Moreover, naïve wasps parasitized significantly more eggs on the outer edge of the egg mass than experienced wasps. We contend that the physical characteristics of A. cuneana eggs and egg masses preclude T. platneri from completely discriminating between individual eggs. However, because T. platneri may be using kairomones from the egg mass, this described oviposition strategy remains effective.     

Development of a new attract‐and‐kill technology for Oriental fruit moth control using insecticide‐impregnated fabric

Various physiological effects of Wolbachia infection have been reported in invertebrates, but the impact of this infection on behavior and the consequences of these behavioral modifications on fitness have rarely been studied. Here, we investigate the effect of Wolbachia infection on the estimation of host nutritive resource quality in a parasitoid wasp. We compare decision‐making in uninfected and Wolbachia‐infected strains of Trichogramma brassicae Bezdenko (Hymenoptera: Trichogrammatidae) on patches containing either fresh or old host eggs. For both strains, fresh eggs were better hosts than older eggs, but the difference was smaller for the infected strain than for the uninfected strain. Oviposition behavior of uninfected wasps followed the predictions of optimal foraging theory. They behaved differently toward high‐ vs. low‐quality hosts, with more hosts visited and more ovipositions, fewer high‐quality hosts used for feeding or superparasitism, and a sex ratio that was more biased toward females in patches containing high‐quality hosts than in patches containing low‐quality ones. Uninfected wasps also displayed shorter acceptance and rejection times in high‐quality hosts than in hosts of lower quality. In contrast, infected wasps were less efficient in evaluating the nutritive quality of the host (fresh vs. old eggs) and had a reduced ability to discriminate between unparasitized and parasitized hosts. Furthermore, they needed more energy and therefore engaged in host feeding more often. This study highlights possible decision‐making manipulation by Wolbachia, and we discuss its consequences for Wolbachia fitness.     

Biological Control Potential of Wolbachia -infected Versus Uninfected Wasps: Laboratory and Greenhouse Evaluation of Trichogramma cordubensis and T. deion Strains

The effects of thelytoky-inducing Wolbachia ( &#102 -proteobacteria) on Trichogramma cordubensis and T. deion (Hymenoptera, Trichogrammatidae) were studied in laboratory and greenhouse conditions. One infected (thelytokous, all female) line of each wasp species was compared with its conspecific uninfected (arrhenotokous, sexual) counterpart for several fecundity and dispersal traits. Arrhenotokous lines had a higher fecundity than their thelytokous counterparts, which suggests that Wolbachia negatively affect the fecundity of Trichogramma females. The arrhenotokous females dispersed more in the laboratory than their thelytokous counterparts. In the greenhouse, the opposite effect or no difference between lines was found, indicating that the laboratory set-up used to measure dispersal is not useful to predict relative dispersal of the females in the greenhouse. Calculations show that by releasing 100 adult wasps of both lines, thus including arrhenotokous males in the sexual line, more eggs are parasitized by the thelytokous wasps. Therefore, in spite of their lower individual female fecundity, thelytokous lines have a better potential for biological control than their arrhenotokous counterparts.     

Patterns of fluctuating asymmetry in flowers: Implications for sexual selection in plants

Characters in animals used in signalling and subjected to strong directional selection often demonstrate (i) an elevated level of fluctuating asymmetry (small random deviations from bilateral symmetry) and (ii) a negative relationship between the degree of individual fluctuating asymmetry and the size of a given character. We tested these two predictions in plants since flowers are subjected to strong directional selection and are involved in signalling to pollinators, whereas leaves are supposed not to be directly involved in signalling. The overall level of fluctuating asymmetry in a number of plant species with bilaterally or radially symmetric flowers was not generally higher in floral traits than in leaves. The level of fluctuating asymmetry in plants was sometimes significantly consistent within individuals. The absolute degree of individual fluctuating asymmetry in floral traits was generally negatively related to the size of the trait, while there was a positive relationship for leaves. The degree of individual fluctuating asymmetry in floral traits was marginally negatively related to the degree of individual fluctuating asymmetry in leaf traits. These patterns of fluctuating asymmetry in plants suggest that (i) the degree of asymmetry in flowers signals different aspects of quality than does the degree of asymmetry in leaves, and that (ii) fluctuating asymmetry in flowers often reflects the phenotypic quality of individual plants.     

The effect of host size on quality attributes of the egg parasitoid,Trichogramma pretiosum

In a study of the quality ofTrichogramma pretiosum Riley (Hymenoptera: Trichogrammidae), we compared female wasps emerging from natural hosts, parasitized in the laboratory or the field with those emerging from factitious hosts used for commercial mass production. Females from the natural hosts were larger, more fecund, and longer lived than those from the factitious hosts. Compared to small females, large female wasps are substantially more fecund when honey (carbohydrate) is available but marginally more fecund when honey is unavailable. The size of a femaleT. pretiosum depends on two factors: the size of the host egg from which it emerges even when the wasp was gregarious, and the number of conspecifics that emerge with it. The similarities in the size distribution of female wasps emerging from natural hosts, in conjunction with the mechanism by whichTrichogramma measure host size and allocate eggs accordingly, suggests the hypothesis that size related components of fitness in femaleT. pretiosum are under strong selection in the field.     

Host color preferences and short-range searching behavior of the egg parasitoid Trichogramma ostriniae

The color of lepidopteran eggs often varies by species or egg condition, and parasitoids that attack lepidopteran eggs could therefore potentially use color to obtain information about host identity or quality. The objective of our study was to determine whether females of the egg parasitoid Trichogramma ostriniae Pang & Chen (Hymenoptera: Trichogrammatidae) showed differential responses to egg color when searching for hosts over short distances and when evaluating the suitability of encountered eggs. We examined the wasps’ host‐selection behavior in a Petri dish arena using white, yellow, green, and black clay beads as egg models presented against a green background (to mimic leaf color). In no‐choice tests, bead color had a significant effect on the proportion of tested wasps that accepted a bead for further examination, on the time it took wasps to find and begin examining a bead, and on the time that wasps spent examining the beads. However, bead color had only a marginally significant effect on the proportion of wasps attempting to drill into a bead with their ovipositors, and no significant effect on the amount of time they spent drilling. The wasps also showed significant color preferences when given a choice between two adjacent beads of different colors. The results of the no‐choice and choice trials taken together indicated a color preference ranking of yellow > white > green > black. The wasps’ higher preference for the yellow and white egg models generally corresponds to the white or yellowish‐white egg color of T. ostriniae's target host, the European corn borer moth, Ostrinia nubilalis Hübner (Lepidoptera: Crambidae). The wasps’ strong rejection of black egg models is likely to be an adaptive response that reflects the fact that eggs that are wholly or partially black are often unsuitable for parasitization due to advanced caterpillar development, damage to the egg, or previous parasitization.     

The use of oviposition‐induced plant cues by Trichogramma egg parasitoids

1. Female parasitoids have evolved various foraging strategies in order to find suitable hosts. Egg parasitoids have been shown to exploit plant cues induced by the deposition of host eggs. 2. The tiny wasp Trichogramma brassicae uses oviposition‐induced cues from Brussels sprouts to locate eggs of the cabbage white butterflies Pieris brassicae and Pieris rapae that differ in their egg‐laying behaviour. These plant cues are elicited by male‐derived anti‐aphrodisiac pheromones in the accessory reproductive gland (ARG) secretions of mated female butterflies. However, the closely related generalist species Trichogramma evanescens does not respond to Brussels sprout cues induced by the deposition of P. brassicae egg clutches. 3. Here we showed in two‐choice bioassays that T. evanescens wasps respond to Brussels sprout cues induced by (i) the deposition of single eggs by P. rapae, and (ii) the application of ARG secretions from either mated P. rapae females, or from virgin female butterflies in combination with P. rapae's anti‐aphrodisiac compound indole. The wasps only associatively learned to respond to Brussels sprout cues after applying indole alone by linking those cues with the presence of P. rapae eggs. 4. Our results indicate that Trichogramma wasps more commonly exploit oviposition‐induced plant cues to locate their host eggs. Generalist wasps show less specificity in their response than specialists and employ associative learning.