Wolbachia infection and an all-female trait in Ostrinia orientalis and Ostrinia zaguliaevi

Sex ratio distortion toward females (SR trait), induced by a Wolbachia bacterium, has been reported in two species of the Ostrinia furnacalis group, viz., O. furnacalis, and O. scapulalis (Lepidoptera: Crambidae). In addition, an SR trait caused by abacterial, unidentified agent(s) is known in O. scapulalis. Here we examined the SR trait in four other species of the furnacalis group, viz., O. orientalis, O. zaguliaevi, and O. zealis from Japan, and O. nubilalis from central and eastern Europe. Wolbachia infection was detected in three O. orientalis females and in one O. zaguliaevi female, and the infection was always associated with the SR trait. In terms of wsp and ftsZ gene sequences, Wolbachia strains in O. orientalis and O. zaguliaevi were indistinguishable from each other, or from those in O. furnacalis and O. scapulalis. These findings suggest that Wolbachia strains in the four Ostrinia species are probably identical. In addition, one O. zealis female, which was negative in diagnostic PCRs for Wolbachia and general bacteria, produced an all‐female brood. This trait was very similar to the SR trait caused by abacterial agent(s) in O. scapulalis.     

Study of the genetics of female sex pheromone production and male behavioral response in a moth, Ostrinia orientalis

Inheritance patterns of female sex pheromone production and male behavioral response were studied in Ostrinia orientalis. Results showed that the production of the female sex pheromone in O. orientalis was mainly controlled by a single autosomal factor, while the male behavioral response was controlled by a sex‐linked major gene.     

Sex pheromone of Ostrinia sp. newly found on the leopard plant Farfugium japonicum

Recently, larvae of Ostrinia were found feeding on the leopard plant Farfugium japonicum (Asteraceae), previously unrecorded as a host plant of this genus. The adult moths that developed from these borers were morphologically similar to, but distinct from, Ostrinia zaguliaevi, a monophagous species specialized for feeding on another Asteraceae plant, the butterbur Petasites japonicus. Although the taxonomical status of the moth feeding on F. japonicum is to be determined, distinct morphological differences in the adults strongly suggest this to be a new species (hereafter referred to as O. sp.). To gain an insight into the reproductive isolation between O. sp. and other members of the genus Ostrinia, the female sex pheromone and the males’ response to it were investigated using samples collected from F. japonicum. (Z)‐9‐tetradecenyl acetate (Z9‐14:OAc), (Z)‐11‐tetradecenyl acetate (Z11‐14:OAc), (E)‐11‐tetradecenyl acetate (E11‐14:OAc), tetradecyl acetate, and (Z)‐11‐hexadecenyl acetate were identified as candidates for sex pheromone components by analyses using gas chromatographs coupled to a mass spectrometer (GC‐MS) and electroantennographic detector (GC‐EAD). A series of bioassays of male responses in a wind‐tunnel and a field cage indicated that the former three compounds are essential for attracting males, and the latter two have no synergistic effect on the attraction. We therefore concluded that Z9‐14:OAc, Z11‐14:OAc and E11‐14:OAc are the sex pheromone components of O. sp. Although the same three compounds are used as the sex pheromone components of O. zaguliaevi and another congener, Ostrinia zealis, the blend proportions differed greatly among the three (Z9‐14:OAc/Z11‐14:OAc/E11‐14:OAc = 18/76/6 in O. sp., 45/50/5 in O. zaguliaevi and 70/6/24 in O. zealis). Differences in sex pheromones could contribute to the reproductive isolation between O. sp. and the other two Ostrinia species if males of each species exhibit a narrow window of response to their own blend ratio.     

Identification of the sex pheromone of Ostrinia palustralis

By means of gas chromatography with electroantennographic detection, gas chromatography-mass spectrometry and a series of bioassays, (E)-11-tetradecenyl acetate (E11-14:OAc) and (Z)-11-tetradecenyl acetate (Z11-14:OAc) at a ratio of 99:1 were identified as female sex pheromone components of Ostrinia palustralis. The average amounts of E11- 14:OAc and Z11-14:OAc in a single sex pheromone gland were 37.2±24.4 ng and 0.3±0.2 ng, respectively. In a wind-tunnel bioassay, the binary blend of E11- and Z11-14:OAc elicited the same male behavioral responses as did virgin females.     

Reconsidering the taxomony of several Ostrinia species in the light of reproductive isolation: a tale for Ernst Mayr

We reconsider the taxonomy of a group of closely related Ostrinia spp., illustrating how useful Mayr's biological species concept remains for studying speciation patterns and processes. We review and re-analyse recent data on Ostrinia scapulalis , Ostrinia nubilalis , Ostrinia narynensis and Ostrinia orientalis , along with those obtained over > 45 years in the former Soviet Union. The ten species of the 'trilobed uncus' group in the Ostrinia genus are classified into subgroups according to male mid-tibia morphology. However, none of the characters that further discriminate between them (female sex pheromones, male genitalia and calling time) varies together with male mid-tibia morphology, and neither do molecular markers. Moreover, male mid-tibia morphology appears to depend on only two diallelic loci and seems to be unrelated to reproductive isolation between Ostrinia taxa. By contrast, reproductive isolation is strongly related to host-plant type. In accordance with Mayr's species concept, we thus propose a revision of the trilobed uncus Ostrinia spp. based primarily on host-plant type. We propose that O. narynensis Mutuura & Munroe, 1970 ( syn. nov. ) and O. orientalis Mutuura & Munroe, 1970 ( syn. nov. ) be synonymized with O. scapulalis (Walker, 1859). We further demonstrate that O. nubilalis auctt. pro parte feeding on mugwort, hop, and several other dicotyledons (previously called the ' O. nubilalis mugwort-race' in France) also belongs to O. scapulalis . Consequently, we propose that only O. nubilalis specimens feeding on maize (the former French ' O. nubilalis maize-race') belong to O. nubilalis (Hübner, 1796). The implications of this revision are discussed.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 49–72.     

Genetic analysis and population survey of sex pheromone variation in the adzuki bean borer moth, Ostrinia scapulalis

Sexual communication in many moths occurs between females emitting a sex pheromone and males responding to it. Females of Ostrinia scapulalis (Lepidoptera: Crambidae) show a large variation in blend ratios of the two sex pheromone components (E)‐ and (Z)‐11‐tetradecenyl acetates. E type females produce a pheromone with a high percentage of (E)‐11‐tetradecenyl acetate, whereas Z type females produce the opposite blend. We established laboratory cultures of E and Z types. Females of the F₁ generation produced an intermediate blend (I type) in both reciprocal crosses of the E and Z cultures. Results of further crossing experiments suggested that the three pheromone types are primarily controlled by a single autosomal locus with two alleles. Also, analyses of the variation in pheromone blend within F₁, backcross and F₂ families suggested that other genetic factors modify the pheromone blend of the I and Z types. Investigation of the pheromone variation in natural populations at 14 localities in Japan has shown that the E type was predominant in northern Japan, whereas the pheromone was highly polymorphic in central Japan. At a locality in central Japan, the pheromone was constantly polymorphic for several years, and the pheromone type frequencies did not deviate from Hardy–Weinberg expectations, providing no evidence of selection or assortative mating between the pheromone types. Analyses of pheromone variation within families derived from feral females indicated that matings between a pair with different genotypes for pheromone production was occurring in natural populations. Overall, this study showed that the genetic basis of the pheromone variation in O. scapulalis is very similar to that in its sibling species Ostrinia nubilalis although the state of pheromone polymorphisms in natural populations appears to differ between the two species. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 84 , 143–160.     

General biology of Ostrinia palustralis memnialis (Walker), a potential biological control agent of Rumex spp. in Korea

Ostrinia palustralis memnialis is an oligophagous insect that feeds on the species of the genus Rumex. Continuous rearing of O. palustralis memnialis was carried out from 2004 to 2005, and its general biology was studied. The preliminary host specificity test showed a promising result for O. palustralis memnialis as a potential biological control agent for Rumex spp.     

Geographical variation in female sex pheromones of the rice leaffolder moth, Cnaphalocrocis medinalis: identification of pheromone components in Japan

Sex pheromone components of the Japanese rice leaffolder moth, Cnaphalocrocis medinalis Guenée (Lepidoptera: Pyralidae) were identified from ovipositor extracts of virgin females as (Z)-11-octadecenal, (Z)-13-octadecenal, (Z)-11-octadecen-1-ol and (Z)-13-octadecen-1-ol at a ratio of 11:100:24:36 by GC-EAD, GC, GC-MS. The total amount was estimated to be ca.0.9 ng/female. Field bioassays in Kagoshima, Japan, showed that the two aldehydes are essential for male attraction and the alcohols may have a synergistic effect on the aldehydes. A rubber septum containing 0.9 mg of the four components at the natural ratio was shown to be an effective lure for monitoring this pest in Japan. The above four components are quite different from the sex pheromone components reported previously for the same species of either Philippine or Indian origin; components were shown to be (Z)-11-hexadecenyl acetate and (Z)-13-octadecenyl acetate at a ratio of 98:2 in the Philippine blend and 1:10 in the Indian blend. Furthermore, in the field tests in Japan, neither the Philippine blend nor the Indian blend showed any attractive activity, while the Japanese blend attracted significant numbers of male moths. These results suggest that there are remarkable geographical variations in the sex pheromone composition of this species or there are several distinct species using different sex pheromone blends.     

Variability in virulence of Beauveria spp. soil isolates against Ostrinia nubilalis

European corn borer (Ostrinia nubilalis) is an important maize pest which is treated mainly by synthetic pesticides with many negative effects for ecosystem and human health. Soil borne entomopathogenic fungi of species belonging to Beauveria genus may provide an alternative strategy for biological control of this pest. In this article, we report results of virulence testing of 46 soil isolates of Beauveria spp. against O. nubilalis in relation to isolates origin and haplotype. All strains were collected from soil using Galleria mellonella bait method. Conidia suspension with concentration 10⁷ conidia in ml was used for virulence test against 4th instar larvae of O. nubilalis at temperature 25°C. After 14 days, mortality of larvae was in the range 34%–96%. Median lethal time LT50 was estimated to 5.5–21.3 days. Mortality was not in relation to habitat or any other environmental parameter of sites where isolates came from. Differences among species were insignificant. Isolates were divided into 8 genetic lineages and 14 haplotypes using sequencing of ITS and Bloc nuclear regions. None of the lineages showed higher mortality than others. Despite more or less virulent isolates being found in each lineage, the three most virulent isolates belonged to the same lineage Beauveria bassiana A3. The four most virulent isolates were compared to commercial isolate GHA to assess medium lethal concentration. LC50 were estimated in range 7.5 × 10⁴ to 9.5 × 10⁵. Three of the four isolates showed equal or greater efficiency than strain GHA.     

Specificity of sex pheromones, the role of host plant odour in the olfactory attraction of males, and mate recognition in the aphid Cryptomyzus

Abstract. Choice tests in an olfactometer showed that males of the aphid Cryptomyzus galeopsidis spent more time in the odour of conspecific females than of a sibling species or a more distantly related Cryptomyzus species, which all co-occur on red currant. Analysis of the pheromone-emissions of females showed the presence of a nepetalactol and a nepetalactone, two known aphid sex pheromone components. However, no interspecific difference in the ratio of the components ( c. 30:1) was found, and this ratio did not change as the females aged. Males were only slightly attracted by a synthetic 30:1 mixture of these two components, and in a choice test preferreď the odour of conspecific females. The sex pheromone of Cryptomyzus spp. must thus consist of more than two components, the first time this has been reported for aphids. Host plant odour did not attract males or enhance the activity of the pheromone.     

A male-specific odorant receptor conserved through the evolution of sex pheromones in Ostrinia moth species

In many moths, mate-finding communication is mediated by the female sex pheromones. Since differentiation of sex pheromones is often associated with speciation, it is intriguing to know how the changes in female sex pheromone have been tracked by the pheromone recognition system of the males. A male-specific odorant receptor was found to have been conserved through the evolution of sex pheromone communication systems in the genus Ostrinia (Lepidoptera: Crambidae). In an effort to characterize pheromone receptors of O. scapulalis, which uses a mixture of (E)-11- and (Z)-11-tetradecenyl acetates as a sex pheromone, we cloned a gene (OscaOR1) encoding a male-specific odorant receptor. In addition, we cloned a gene of the Or83b family (OscaOR2). Functional assays using Xenopus oocytes co-expressing OscaOR1 and OscaOR2 have shown that OscaOR1 is, unexpectedly, a receptor of (E)-11-tetradecenol (E11-14:OH), a single pheromone component of a congener O. latipennis. Subsequent studies on O. latipennis showed that this species indeed has a gene orthologous to OscaOR1 (OlatOR1), a functional assay of which confirmed it to be a gene encoding the receptor of E11-14:OH. Furthermore, investigations of six other Ostrinia species have revealed that all of them have a gene orthologous to OscaOR1, although none of these species, except O. ovalipennis, a species most closely related to O. latipennis, uses E11-14:OH as the pheromone component. The present findings suggest that the male-specific receptor of E11-14:OH was acquired before the divergence of the genus Ostrinia, and functionally retained through the evolution of this genus.     

Genetic structure of European and Mediterranean maize borer populations on several wild and cultivated host plants

Target pests may become resistant to Bacillus thuringiensis (Bt) toxins produced by trangenic maize (Zea mays L.). Untreated refuge areas are set aside to conserve high frequencies of susceptibility alleles: a delay in resistance evolution is expected if susceptible individuals from refuges mate randomly with resistant individuals from Bt fields. In principle, refuges can be toxin‐free maize or any other plant, provided it hosts sufficiently large pest populations mating randomly with populations from Bt‐maize fields. Our aim was to examine the suitability of several cultivated or weedy plants [pepper (Capsicum frutescens L.), sorghum (Sorghum spec.), sunflower (Helianthus annuus L.), cocklebur (Xanthium spec.), cantaloupe (Cucumis melo L.), and hop (Humulus lupulus L.)] as refuges for Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae) and Sesamia nonagrioides Lefebvre (Lepidoptera: Noctuidae), two major maize pests in southern Europe. Larvae of both species were collected on these plants. Their genetic population structure was examined at several allozyme loci. We found little or no evidence for an influence of geographic distance, but detected a significant host‐plant effect on the genetic differentiation for both species. Ostrinia nubilalis populations from sunflower, pepper, cocklebur, and sorghum appear to belong to the same genetic entity as populations collected on maize, but to differ from populations on hop. Accordingly, females from pepper and cocklebur produced exclusively the ‘Z’ type sexual pheromone, which, in France, characterizes populations developing on maize. Qualitatively, these plants (except hop) could thus serve as refuges for O. nubilalis; however, they may be of little use quantitatively as they were found much less infested than maize. Sesamia nonagrioides populations on maize and sorghum reached comparable densities, but a slight genetic differentiation was detected between both. The degree of assortative mating between populations feeding on both hosts must therefore be assessed before sorghum can be considered as a suitable refuge for this species.     

蛾类性信息素生物合成途径及其调控

蛾类通过产生和识别物种特异性性信息素来引发后续交配行为,因此它在两性交配行为中至关重要.它们具有不同碳链长度、末端官能团、不同双键位置和构型等化学结构特征,本文详细讨论了不同蛾类性信息素的合成途径以及催化每一步反应的相关酶系,列举了15种夜蛾科不同亚科常见物种的性信息素组分及其比例,总结了产生特定比例性信息素的可能原因,查阅了夜蛾科不同物种已经鉴别的性信息素,并按照不同亚科、不同官能团和碳链长度对其进行分类,归纳了同一物种及其亲缘物种性信息素组分和比例的变异,总结了产生变异的分子机理,讨论了性信息素变异和物种进化的关系.最后以生物合成激活神经肽(PBAN)为主, 介绍了其调控途径和机制.本文旨在以不同的蛾类性信息素合成途径为线索,从共有合成途径出发深入了解其规律和共性,从特异合成途径出发探究物种间的进化和变异,展望未来的研究方向及其应用.     

Field observations of Ostrinia nubilalis eclosion and post‐eclosion activity of females around their natal plants

Abstract The early part of the post‐eclosion, pre‐mating period were examined under field conditions for Ostrinia nubilalis. Post‐eclosion behavior of 25 and 21 females during the first and second flight periods were observed until they left their natal site. Summer generation larvae were reared under field conditions and the timing of adult eclosion was observed. Eclosion occurred at two times during the day, peaking before dawn and before dusk; 46% of females and 56% of males eclosed during the morning period and the rest eclosed during the evening period. After eclosion, females spent 30–60 min expanding their wings. Their typical behavior was to remain calmly on their natal site. None of the females exhibited calling behavior before leaving. All females left their natal sites sometime before dawn. The probability of leaving increased with time. Leaving rates were not significantly different between females of the first and second flight. These field observations indicate that females have several possibilities for pre‐mating movement, which might allow females to move out from their natal field before mating. In addition, we also discuss the influence of pre‐mating movements in relation to the rate of Bacillus thuringiensis (Bt) resistance evolution.     

蚜虫雄蚜与雌性母对性信息素及植物挥发物的田间反应

田间观察了桃蚜Myzus persicae (Sulzer)、绣线菊蚜Aphis spiraecola Patch 、山楂圆疣蚜Ovatus crataegarius (Walker)等3种蚜虫对性信息素[(4aS,7S,7aR)-荆芥内酯和 (1R,4aS,7S,7aR)-荆芥醇]的反应,并且调查了性信息素与植物挥发物对桃蚜的田间引诱活性的相互作用.在有冬寄主或夏寄主植物的田中,性信息素诱捕器诱捕到桃蚜雄蚜与雌性母的数量显著多于对照诱捕器的诱捕数;但在非寄主植物的田中,却引诱不到桃蚜.苯甲醛(冬寄主植物桃树Prunus persica的主要挥发物组分之一)能够增强桃蚜雄蚜的引诱作用.绣线菊蚜雄蚜和雌性母对植物中提取的荆芥内酯有反应,而山楂圆疣蚜雄蚜和雌性母对植物中提取的和人工合成的荆芥内酯都没有反应,但对荆芥醇有反应.并且在荆芥醇中添加荆芥内酯之后对山楂圆疣蚜雄蚜引诱活性显著提高.还讨论了雌性蚜产生化合物被雄蚜作为性信息素、被雌性母作为聚集信息素以及性信息素与寄主植物挥发物的相互作用.     

多胚发育寄生蜂腰带长体茧蜂在寄主亚洲玉米螟幼虫体内的发育

多胚发育的幼虫内寄生蜂腰带长体茧蜂Macrocentrus cingulum的卵、胚胎和幼虫在寄主亚洲玉米螟Ostrinia furnacalis幼虫血腔内发育,通常1枚卵可以分裂增殖为数百只胚胎。本文通过定时解剖寄生的寄主幼虫,初步了解了腰带长体茧蜂多胚的形成过程及其在寄主体内的发育情况。结果表明：以4龄末期亚洲玉米螟幼虫为寄主时,寄生蜂卵产入寄主体内10 min左右开始卵裂,1天左右,初级胚胎从卵壳中被释放出来。之后胚胎在胚外膜内持续分裂产生大量二级胚胎形成桑葚胚。寄生后3天左右,二级胚胎从胚外膜中被释放出来,进入胚胎发育阶段。寄生后6天左右,胚胎进入胚带形成阶段。寄生后8天左右,胚带伸长,头尾形成。寄生后9天左右,身体分节完成,部分幼虫孵化,蜕去胚外膜。寄生后13天左右,蜂幼虫从寄主体内啮出。胚胎在发育初期体积变化不大,但从胚带形成开始,体积则迅速增大。腰带长体茧蜂与另一多胚发育寄生蜂佛州点缘跳小蜂Copidosoma floridanum在胚胎发育进程上明显不同,体现了它们对各自寄主的适应。     

Sex pheromone blend discrimination in two races and hybrids of the European corn borer moth, Ostrinia nubilalis

Abstract. The response specificity of males of two races, and hybrids, of the European corn borer moth, to a large series of doses/ratios of E- and Z11-14:OAc, was determined in a sustained-flight tunnel. For both races an area of peak response was determined, which included the natural ratio eliciting peak levels of source contact, and other treatments eliciting response profiles over the behavioural sequence not significantly different from the peak. Consistent with studies on other moth species response specificity was controlled by two threshold effects, one affecting locking-on to odour plumes of lower doses and off-ratios containing lower proportions of the E or Z isomer than the natural blend, and the other resulting in arrestment of upwind flight to higher doses and off-ratios containing higher proportions of the E or Z isomer man the natural blend. A comparison of the size of the areas of peak response showed that males of the univoltine Z race (UZ) using a 3:97 E:Z mix displayed greater specificity and sensitivity than did males of the bivoltine E race (BE) responding to a 99:1 E:Z pheromone mix. At doses higher than those eliciting peak response (<100 μg) response specificity was lower for both races, but especially for the BE race, with increased levels of upwind flight and source contact occurring to off-ratios. Finally, consistent with a previous behaviour/genetic study on this species, F₁ hybrid males displayed peak levels of source contact not only to their natural isomer ratio (65:35 E:Z), but also to an expanded range of doses of ratios ranging from 2% to 98% E.     

马尾松毛虫及其寄主松属植物的地史初步考证

初步考证了我国重要的森林害虫———马尾松毛虫DendrolimuspunctatusWalker及其寄主松 (科 )属植物的化石起源 ,认为马尾松毛虫衍生为一个新的物种的时间 ,不应早于中生代的侏罗纪 ,很可能是侏罗纪与白垩纪早期的某个时期 ;并初步探讨了第三纪以来中国古地质、古气候变化对现今马尾松毛虫的分布、遗传多样性的空间格局及其历史成因的可能影响 ,文史还涉及许多重要的生物地质历史事件 ,对于理解马尾松毛虫在同样的地质时期的动态等具有重要的参考意义     

亚洲玉米螟交配率和交配次数与其日龄、性比和精巢大小的关系

【目的】昆虫交配行为与其日龄和生殖系统发育密切相关。本研究旨在明确亚洲玉米螟Ostrinia furnacalis交配行为与其日龄、性比和雄蛾精巢大小的关系,为性信息素群集诱杀和交配干扰防控亚洲玉米螟提供理论依据。【方法】通过室内交配实验测定了不同配对晚数、日龄、性比亚洲玉米螟的交配率和交配次数,通过雄蛾精巢解剖分析了交配次数与精巢体积的关系。【结果】亚洲玉米螟的交配率随配对晚数增加而增加,但第1-5晚的增加速度大于第6-7晚的;1-4日龄蛾的交配率随日龄增加而增加,5日龄蛾的交配率显著降低;1-3日龄蛾配对1晚的交配率与新羽化蛾配对2～4晚的均无显著差异。亚洲玉米螟可以交配1～3次,但是交配3次的比例极低。雌性数量从1增为2时,雄蛾的交配率显著增加;从2增为3时,雄蛾的交配率显著降低、死亡率显著增加,交配1次的雄蛾进行二次交配的比例也增加,并且雄蛾更愿意与处女雌蛾进行第2次交配;交配1次雄蛾的精巢体积总是显著大于同期未交配雄蛾的,交配1次稍降低了雄蛾精巢的衰退速度,交配2次则明显增加雄蛾精巢的衰退速度。【结论】本研究明确了亚洲玉米螟交配与日龄、性比和雄蛾精巢体积之间的关系,从理论上证...     

The effect of stem diameter on European corn borer behavior and survival: potential consequences for IRM in Bt-corn

The ability of non‐crop plants to support complete development of insect pests is an important factor for determining the impact of those plants on resistance management programs for transgenic crops. We assessed the effect of one physical factor, plant stem diameter, on the ability of plants to support full development of the European corn borer (ECB), Ostrinia nubilalis Hübner (Lepidoptera: Crambidae), the target pest of transgenic Bt‐corn. In the field, European corn borer larvae were significantly more likely to tunnel and survive in plants with larger stem diameters. Larvae were 40× more likely to survive on corn, the largest plant tested, compared to many of the smaller plants. In the laboratory, larvae were more likely to survive in and less likely to abandon the largest diet‐filled artificial stems that varied only in stem diameter. In conditions simulating those that an ECB larvae would encounter upon abandoning a host, larvae survived up to three weeks and were able to locate corn as a new host with a significantly higher frequency than would be expected if they were foraging randomly. These results indicate that the probability of ECB larval survival to maturity on a plant other than corn is relatively low and thus these smaller stemmed non‐corn plants may not make a substantial contribution to the pool of susceptible adults. Conversely, since more mature larvae are not as susceptible as neonates, any larvae that partially develop on non‐corn plants and subsequently colonize Bt‐corn may not be exposed to a lethal dose of the toxin. Since some proportion of the individuals that survive could be partially resistant heterozygotes the presence of non‐corn host plants could facilitate the development of resistant ECB populations.