Age-specific dose-mortality effects of Beauveria bassiana (Deuteromycotina: Hyphomycetes) on the European corn borer,Ostrinia nubilalis (Lepidoptera: Pyralidae)

Three isolates of Beauveria bassiana were evaluated under laboratory conditions for pathogenicity against the European corn borer, Ostrinia nubilalis. Dose-mortality regressions and nonparametric statistical analyses revealed significant differences in pathogenicity between isolates and across O. nubilalis instars. First instars were found to be the most susceptible of the five larval stages. Little difference was noted for instars 2, 3, and 5 within any of the three B. bassiana isolates. Fourth instar larvae were found to be the most tolerant in all cases.     

Larval survival and development of susceptible and resistant Ostrinia nubilalis (Lepidoptera: Pyralidae) on diet containing Bacillus thuringiensis

Abstract 1 Larval survival and development of Dipel‐susceptible and ‐resistant strains of European corn borer, Ostrinia nubilalis (Hübner), were assayed using diets incorporating low doses of a commercial formulation of Bacillus thuringiensis var. kurstaki Berliner (Dipel ES). 2 Larval mortality, growth and development, pupation rate and pupal weight were not significantly different between Dipel‐susceptible and ‐resistant strains when larvae were reared on a nontoxic control diet. 3 Larval mortality of Dipel‐resistant larvae did not significantly change as Dipel concentration increased at the tested concentrations, whereas mortality of Dipel‐susceptible larvae increased dramatically as Dipel concentration increased. 4 Larval development was significantly delayed when larvae were fed diets containing low doses of Dipel. 5 Pupation rate and pupal body weight declined as Dipel concentration increased but it decreased faster for the susceptible strain than for the resistant strain.     

In vivo effect of mixtures of allelochemicals on the life cycle of the European corn borer, Ostrinia nubilalis

The phenylpropanoid, dillapiol, a compound capable of inhibiting the activity of cytochrome P-450 epoxidase in microsomal preparations of midguts of the European corn borer (ECB), Ostrinia nubilalis Hubner (Lepidoptera), did not enhance the toxicity of two insecticidal allelochemicals from the Asteraceae: the sesquiterpene lactone, tenulin or the phenylacetylene, phenylheptatriyne, when ingested simultaneously. Dillapiol alone was toxic to ECB larvae, and inhibited their growth. Possible reasons for the lack of synergism or potentiation by dillapiol of the insecticidal activity of the other allelochemicals are considered.

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Résumé Le dillapiole, un phénylpropanoide monomère d'un lignan et contenant un groupement méthylènedioxyhphényl (MDP), a la capacité d'inhiber in vitro les enzymes d'oxydations multiples à cytochrome P-450 (PSMO) utilisées par la pyrale du maïs (ECB), Ostrinia nubilalis, pour detoxifier les substances allélochimiques. Les composés contenant un groupe MDP comptent parmi les plus nombreux et puissants synergistes d'insecticides. Cependant, aucun synergisme n'est observé lorsque le dillapiole est ingéré par la pyrale en association avec l'une ou l'autre ou les deux substances secondaires insecticides des Astéraceae, la lactone sesquiterpène ténuline ou/et le polyacétylène phénylheptatriyne (PHT). Plutôt, le dillapiole est une toxine qui diminue la prise de poids des larves et retarde leur développement. Les effets toxiques sont plus importants avec le dillapiole seul que lorsque celui-ci est associé à la ténuline ou/et au PHT. Les expications possibles de ces résultats sont discutées.

     

Two multiplex sets of eight and five microsatellite markers for the European corn borer,Ostrinia nubilalis Hübner (Lepidoptera: Crambidae)

Primer sequence and polymorphism data are presented for 13 microsatellite loci isolated from the European corn borer moth, Ostrinia nubilalis, as part of a project to construct a linkage map for the two pheromone strains. Experimental conditions are described for polymerase chain reaction (PCR) multiplexing, which allows genotyping in two electrophoresis runs of eight and five markers each. In a sample of 27 individuals coming from one European locality, the number of alleles per locus ranged from one to 12, and gene diversity from 0 to 0.859. Seven loci showed a deficit of heterozygotes. Eleven loci cross‐amplify in the related Ostrinia furnacalis.     

Age- and density-related oviposition behavior of the European corn borer,Ostrinia nubilalis (Lepidoptera: Pyralidae)

Age-related oviposition patterns ofOstrinia nubilalis were studied at three population densities in the laboratory by releasing newly eclosed adults in wire-screened cages and analyzing their oviposition throughout the adult stage with digital analysis. Oviposition sequences of individual females depositing egg masses were documented on the third and seventh nights after eclosion with a video camcorder. During a sequence, a female produced an egg in an average time of 15 or 26 s on the third and seventh nights, respectively, and completed depositing an egg mass the size of 20–39 eggs in an average time of 316 and 525 s, respectively. Females were not easily disturbed during egg mass deposition and pulsated their abdomen before deposition of each egg. Females produced few egg masses the first night after eclosion. Oviposition increased on nights 2 and 3 but declined steadily thereafter as females matured. Females older than 6 nights produced fewer egg masses; the proportion of egg masses with fewer than 20 eggs increased gradually. By the end of the adults' lifetime, nearly 100% of the egg masses had fewer than 20 eggs. The data are fundamental to our research to define the role of phytochemicals in modifying oviposition behavior of the European corn borer.     

Intercrop effects on the distribution of populations of the European corn borer, Ostrinia nubilalis, in maize

Field investigations conducted from 1982 to 1984 to assess intercrop effects on the distribution of Ostrinia nubilalis (Hübner), Lepidoptera, Pyralidae, in maize revealed that the incidence of damage by O. nubilalis was influenced significantly by the proximity of maize to potato. Maize fields adjacent to potato fields had a lower incidence of early season damage by O. nubilalis and a higher incidence of late-season damage than maize isolated from potato.     

Characterization of six antibacterial response genes from the European corn borer (Ostrinia nubilalis) larval gut and their expression in response to bacterial challenge

Six cDNAs encoding putative antibacterial response proteins were identified and characterized from the larval gut of the European corn borer (Ostrinia nubilalis). These antibacterial response proteins include four peptidoglycan recognition proteins (PGRPs), one β-1,3-glucanase-1 (βglu-1), and one lysozyme. Tissue-specific expression analysis showed that these genes were highly expressed in the midgut, except for lysozyme. Analysis of expression of these genes in different developmental stage showed that they were expressed in larval stages, but little or no detectable expression was found in egg, pupa and adult. When larvae were challenged with Gram-negative bacteria (Enterobacter aerogenes), the expression of all six genes was up-regulated in the fatbodies. However, when larvae were challenged with Gram-positive bacteria (Micrococcus luteus), only PGRP-C and lysozyme genes were up-regulated. This study provides additional insights into the expression of antibacterial response genes in O. nubilalis larvae and helps us better understand the immune defense response in O. nubilalis.     

Sex pheromone gland of the female European corn borer moth,Ostrinia nubilalis (Lepidoptera,Pyralidae): ultrastructural and biochemical evidences

The sex pheromone gland of the female European corn borer moth, Ostrinia nubilalis was studied using light and electron microscopy. The pheromone gland is formed by hypertrophied epidermal cells at the mid-dorsal region of the intersegmental membrane between abdominal segments 8 and 9/10. Active glandular cells contain extensive apical membrane foldings, a single nucleus, many free ribosomes, numerous mitochondria, microtubules and lipid droplets. Smooth endoplasmic reticulum is scanty. In young moths, the glandular cells are smaller in size, the microvilli at the apical membrane are poorly developed and the cytoplasm contains fewer mitochondria, microtubules, and no lipid droplets. The surrounding unmodified epidermal cells are small cuboidal or squamous cells. These cells have ill-defined apical membrane foldings and do not contain lipid droplets in the cytoplasm and the overlying cuticle. Fatty acids analyses revealed the presence of the sex pheromone components, (E)-11-tetradecenyl acetate, and their immediate precursors, methyl (E)-11- and methyl (Z)-11-tetradecenoate, only in the dorsal portion of the cylindrical intersegmental membrane. Results of the present study show that the sex pheromone gland of O. nubilalis is restricted to the dorsal aspect of the intersegmental membrane between segments 8-9/10 and is not a ring-gland.     

Changes in calling behaviour and mating success in the European corn borer (Ostrinia nubilalis), caused by relative humidity

We examined the calling behaviour of O. nubilalis virgin females, held at three different constant conditions of relative humidity from the time of emergence through their sixth night of calling, as well as the incidence of mating over time at low or high relative humidity conditions. The mean age at which females initiated calling in their life was independent of relative humidity conditions, although more variable at low humidity. On successive nights of calling, fewer virgin European corn borer females called under low compared with high humidity conditions, and those that did began later in scotophase, had fewer calling bouts, and spent less time calling. These changes in the female prereproductive behaviour were reflected on the incidence of mating which, in the first two days following emergence, was significantly less at low than at high humidity conditions. The ecological significance of these results is discussed in relation with the susceptibility of O. nubilalis to desiccation.

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Résumé Nous avons étudié le comportement d'appel des femelles vierges d'Ostrinia nubilalis maintenues sous trois conditions constantes d'humidité relative, depuis l'émergence jusqu'à la sixième nuit d'appel, ainsi que l'incidence d'accouplement d'individus placés en milieu sec ou humide pour diverses périodes de temps. Les conditions d'humidité n'ont pas significativement affecté l'âge moyen auquel les femelles ont commencé à appeler au cours de leur vie, bien qu'il ait été plus variable à 53% h.r. Les nuits subséquentes, le comportement d'appel des femelles maintenues à basse humidité a débuté plus tard dans la nuit, s'est exprimé pour une période de temps plus courte avec moins de séquences d'appel que celui de leurs congénères placés en milieu humide, et la proportion de femelles en appel a toujours été plus faible à 53% h.r. Ces changements du comportement préreproducteur des femelles se sont répercutés sur l'incidence d'accouplement qui, les deux premiers jours suivant lémergence, a été significativement plus faible à basse humidité qu'elle ne l'a été en milieu humide. Ces résultats seront discutés en relation avec l'écologie de O. nubilalis et associés à sa susceptibilité à la dessication.

     

Development of European corn borer larvae on Event 176 Bt corn: influence on survival and fitness

European corn borer larvae, Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae) that have completed development on Event 176 Bt corn hybrids have survived exposure to sublethal doses of the Cry1Ab Bt toxin or are exploiting plant tissues that do not express the toxin. To evaluate the impact of such exposure, diapausing larvae were collected from Event 176 and conventional hybrids and compared for rates of pupation, parasitism, fitness (pupal weight, longevity, and fecundity) and susceptibility to the Cry1Ab toxin. Larvae completing development on Event 176 corn exhibited approximately 10% higher survival rates and correspondingly lower parasitism rates than larvae completing development on conventional hybrids. No significant differences were detected in pupal weight, fecundity, longevity or susceptibility to the Cry1Ab Bt toxin. These results indicate that survival on Event 176 corn are not adversely affect fitness and does not cause increased tolerance to the Cry1Ab toxin in subsequent generations.     

On the relationship between the electroantennogram and simultaneously recorded single sensillum response of the european corn borer,Ostrinia nubilalis

Electrical responses of the whole antenna (electroantennogram) and that of the single sensillum trichodeum (electrosensillogram) of male moth of the European corn borer, Ostrinia nubilalis, to their two pheromone components, (Z)- and (E)-11-tetradecenyl acetates, were recorded simultaneously. The configuration characteristics of both responses resemble each other, and demonstrate an interaction between sensilla trichodea. The typical difference in the response pattern between London (Ontario) and New York strains of this moth seems to be a property of the sensillum trichodeum.     

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.     

Adult dispersal of Ostrinia nubilalis Hübner (Lepidoptera: Crambidae) and its implications for resistance management in Bt-maize

Abstract:  Dispersal of European corn borer, Ostrinia nubilalis Hübner was examined by release and recapture of the dye marked adults and by capture of the feral adults in and around the large 50 ha center pivot irrigated fields of Bacillus thuringiensis (Bt) maize. Pheromone and black light traps were used to catch the adults. In 1999, 15 094 marked males and 7993 marked females were released, and in 2001, 13 942 marked males and 9977 marked females were released. In 1999, maximum mean recapture beyond the release point was 1.95 and 1.67% for males and females, but in 2001, the recapture rate was 9.97 and 4.37% for males and females. Few males (3.8%) and females (2.07%) were recaptured in neighbourhood maize fields. An exponential decay function explained recapture of marked adults across the dispersal distance. More than 90% of marked adults were recaptured within 300 m of the release point. Large numbers of feral adults were captured throughout the study fields. Feral adult dispersal could be fitted to a linear model. Virgin females (20% marked and 8% feral) were captured throughout the study fields. The recapture of marked insects suggests that the dispersal was limited. However, capture of feral adults throughout Bt-maize fields indicate that the actual dispersal may be more extensive than indicated by recapture of marked adults. Potential refuge sources for the feral adults were 587–1387 m from the edge of the study fields. It is not clear if the dispersal recorded in this study is extensive enough to support the current resistance management strategy for corn borers. There appears to be some dispersal of corn borers from the non-transgenic 'refuge' fields into the transgenic fields that allows some genetic mixing of the two populations.     

Endophytic beauveria bassiana (balsamo) vuillemin in corn: The influence of the plant growth stage and ostrinia nubilalis (hübner)

A conidial suspension of the entomopathogenic fungus Beauveria bassiana (Balsamo) Vuillemin, was injected into corn plants at anthesis to suppress populations of the European corn borer Ostrinia nubilalis (Hübner) (Lepidoptera: Pyralidae). The fungus colonized the plants and moved, primarily upward, within the pith, possibly along with plant photosyn‐thates. Beauveria bassiana injected into the corn plants significantly reduced the amount of European corn borer tunneling. Colonization of corn plants by B. bassiana was independent of European corn borer infestation. The impact of environmental conditions on the movement and colonization of the plants by B. bassiana is discussed.     

Free amino acids of the haemolymph of the southwestern corn borer and the European corn borer in relation to their diapause

The titres of free amino acids present in the haemolymph of diapausing larvae of the southwestern corn borer, Diatraea grandiosella and the European corn borer, Ostrinia nubilalis, were examined. High titres of serine were found in the haemolymph of both species. Serine may serve as a storage form of compounds that are required for the synthesis of uric acid and other purines. The high titres of proline found in the haemolymph of O. nubilalis during the fall and winter may contribute to the freezing tolerance of this species. Alanine accumulated in the haemolymph of both species during the winter.     

Morphological characteristics of antennal sensilla in the European cornborer Ostrinia nubilalis (Lepidoptera: Pyralidae)

The European cornborer antenna is filiform in both sexes, but exhibits a substantially larger diameter in the males. On the antenna of both sexes, the following sensillum types were characterized: sensilla trichodea, s. basiconica, s. auricillica, s. coeloconica, s. chaetica and s. styloconica. Long dorsal bristles were of a chaetic type. An intermediate trichoid/basiconic type was found in low numbers on the ventral part of the antenna. In the male, three different morphological types of s. trichodea were observed, having one, two or three sensory cells, correlated with different dimensions of the hair. The s. trichodea with three sensory cells are most common in the basal part of the antenna, while sensilla with two cells are mainly found distally. Trichodea with one sensory cell are more evenly distributed over the length of the antenna. All cells present in the different s. trichodea respond to sex pheromone components or to a behavioural antagonist in electrophysiological sensillum recordings. S. basiconica and s. auricillica had 2-3 sensory cells, and a probable olfactory function. Sensilla coeloconica, also with a putative olfactory function, contained 3-5 sensory cells. S. chaetica of the taste/tactile type possessed 4 + 1 sensory cells. S. styloconica comprised three sensory cells with possible functions as thermo- and hygroreccptors.     

Electroantennogram response gradient on the antenna of the European corn borer, Ostrinia nubilalis

The electroantennogram (EAG) response of male moths of the European corn borer (Ostrinia nubilalis) to their two pheromone components, (Z)- and (E)-11-tetradecenyl acetates, were studied. The EAG amplitude of the fast initial phase was approximately proportional to the antennal length. Local EAG responses were obtained along the length of the antenna with multiple electrodes. Response-interaction studies indicated a unique spread of the EAG response in a proximal direction in the antenna. A possible mechanism of the EAG summation was considered. The EAG response characteristic was similar for both (Z)- and (E)-11-tetradecenyl acetate along the length of the antenna.     

溴氰菊酯对亚洲玉米螟雄蛾感受雌性信息素的影响

为了探索溴氰菊醋对亚洲玉米螟雄蛾感受雌性信息素的影响,本文运用触角电位仪和风洞装置对亚洲玉米螟雄蛾进行了电生理和行为反应的测试．结果表明,处理雄蛾对不同比例雌性信息素的触角电位反应分别在E／Z;1／9、5／5和9／1处出现峰值,与对照相比无显著改变,但反应幅度为0．25—0．45mV,比对照下降0．15—0．35mV．对不同剂量的性信息素,引起可见触角电位反应的低限阈值为1ng,饱和反应剂量为10000ng,但反应幅度亦下降0．1—0．5mV,说明溴氰菊酯主要是影响雄蛾周缘感受系统的敏感性．但在风洞测试中,雄蛾除在反应率上比对照明显降低外,其峰值感受比例从E／Z＝1／1漂移到7／3以上．雄蛾对雌性信息素的低限反应剂量也从10ng漂移到100ng,并且高限反应剂量也从100000ng降低到50000ng,使有效作用剂量范围缩小．这说明溴氰菊酯对雄蛾的行为反应有较大影响,不仅使雄蛾对性信息素感受的敏感性降低,也影响到其感受的专化性。