Modelling damage on maize by the European Corn Borer, Ostrinia nubilalis

The European Corn Borer (ECB), Ostrinia nubilalis Hbn. (Lepidoptera: Pyralidae), is a major pest of maize in many countries. Yield losses caused by larvae of this insect depend mainly on the extent of cavity damage, the timing of tunnelling, and their within-plant distribution. To describe these factors, a mechanistic model of cavity appearance is proposed here. It takes into account the main biological processes which determine damage. These are the development, mortality and within-plant distribution of the ECB larvae. The model has been estimated and tested on field data collected at INRA-Versailles in France. Model fittings showed that (i) creation and lengthwise extension rates of cavities per larva depend on location and instar of the larvae, and that (ii) only instars 4 and 5 make cavities. This model described, with a high precision level, the appearance and lengthwise extension of cavities over time and their within-plant distribution for two maize varieties, several infestation dates and levels, and various climatic sequences.     

Genomic Basis of Circannual Rhythm in the European Corn Borer Moth

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Antifeedant and insecticidal properties of azadirachtin to the European Corn Borer, Ostrinia nubilalis

Azadirachtin, a triterpenoid substance from the neem tree, Azadirachta indica A. Juss., Meliaceae, was evaluated for its antifeedant and insecticidal properties to the European corn borer Ostrinia nubilalis Hübner. The 50% protective concentration for larval feeding on treated corn disks (PC₅₀) was 3.5 ppm for neonate larvae and 24 ppm for third instar larvae. Azadirachtin severely reduced larval growth at 1 and 10 ppm in a meridic diet and eventually caused 100% mortality at 10 ppm and 90% at 1 ppm. At 0.1 ppm azadirachtin showed no significant effect on larvae but altered the sex ratio in favor of male moths during adult emergence and arrested oviposition of female moths.Nutritional indices for naive and habituated third instar larvae suggested that reduction of growth was due to toxicity as shown by a lowered efficiency of conversion in the azadirachtin treated groups, rather than changes in digestibility. No clear evidence of tolerance was observed in the habituated group. The data suggest that at 10 ppm azadirachtin is an effective botanical insecticide for control of O. nubilalis.

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Résumé On a examiné les propriétés anti-appétantes et insecticides de l'azadirachtine, une substance triterpénoïde provenant d'Azadirachta indica envers la pyrale du maïs Ostrinia nubilalis. La concentration effective pour causer 50% d'inhibition de l'alimentation larvaire (PC₅₀) sur des disques foliaires a été de 3.5 ppm pour les larves de premier stade et de 24 g/8 pour celle de troisième stade. L'azadirachtine a sévèrement réduit la croissance larvaire à des concentrations de 1 et 10 ppm dans une diète méridique et, éventuellement, a causé 100% de mortalité à 10 ppm et 90% à 1 ppm. A 0.1 ppm l'azadirachtine n'a pas eu d'effet significatif sur les larves maïs a modifié l'indice de masculinité en faveur des mâles au moment de l'émergence et a empêché l'oviposition chez les femelles. Les indices nutritionnels pour les larves naïves de troisième âge et celles ayant subi une accoutumance suggèrent que la réduction de croissance est le résultat d'une intoxication comme le démontre une efficacité réduite de transformation chez les groupes traités à l'azadirachtine, plutôt que des changements de digestibilité. Il n'y a pas d'évidence claire de tolérance dans le groupe ayant subi l'accoutumance. Les résultats suggèrent qu'à 10 ppm l'azadirachtine est un insecticide botanique efficace envers O. nubilalis.

     

Toxicity of Bacillus thuringiensis Spo Cr Mutants for the European Corn Borer Ostrinia nubilalis

Inclusion bodies isolated from Spo Cr mutants of Bacillus thuringiensis were toxic for larvae of the European corn borer. Probit analysis revealed comparable toxicity between wild-type crystals (isolated from B. thuringiensis subsp. kurstaki) and crystals produced from two spore-free mutants of the same subspecies. Death of the larvae was due to starvation, presumably through delta-endotoxin-induced gut paralysis. Inclusion bodies pretreated with alpha-chymotrypsinogen were equally as toxic as native crystals for the insect larvae.     

Toxicity of Bacillus thuringiensis Spo− Cr+ Mutants for the European Corn Borer Ostrinia nubilalis

Inclusion bodies isolated from Spo⁻ Cr⁺ mutants of Bacillus thuringiensis were toxic for larvae of the European corn borer. Probit analysis revealed comparable toxicity between wild-type crystals (isolated from B. thuringiensis subsp. kurstaki) and crystals produced from two spore-free mutants of the same subspecies. Death of the larvae was due to starvation, presumably through δ-endotoxin-induced gut paralysis. Inclusion bodies pretreated with α-chymotrypsinogen were equally as toxic as native crystals for the insect larvae.     

Effects of artificial and natural diets on success in tip recording and on galeal chemosensillum morphology of European Corn Borer larvae

Abstract. Larvae of Ostrinia nubilalis (Hübner) (Lepidoptera: Pyralidae) were reared on artificial diet, fresh cut corn, or switched from diet to corn for 5 days prior to tip recording. Electrophysiological responses to a standard mixed chemical stimulus were obtained from the galeal uniporous chemosensilla of the early fifth-stadium larvae. Mouthparts of some larvae were briefly treated with protease, then recorded again. Larvae were then processed for scanning electron microscopy (SEM) of chemosensilla terminal pores. Spike:noise ratios were significantly higher for corn-reared, switched-to-corn, and protease- treated larvae, relative to diet-reared larvae. Morphology of the chemo- sensilla terminal pores, as assessed by SEM, reveals that apparent occlusion of the pore tip is significantly greater for diet-reared larvae relative to the other groups. The data suggest an association between quality of the electrophysiological recordings and physical blockage of the terminal sensillum pore. These data should serve as a caveat for those engaged in chemosensory studies of insect herbivores.     

A fly in the ointment: evaluation of traditional use of plants to repel and kill blowfly larvae in fermented fish

Introduction

In rural areas in Laos, fly larvae infestations are common in fermenting fish. Blowflies (Chrysomya megacephala, Diptera: Calliphoridae) are attracted to oviposit (and/or larviposit) onto fermenting fish which results in infestations with fly larvae. Knowledge of traditional use of plants to repel larvae during the production of fermented fish is common and widespread in Lao PDR.

Research Questions

How effective are the most salient species in repelling, and killing fly larvae in fermenting fish?

Material and Methods

The three plant species most frequently reported to repel fly larvae during an ethnobotanical survey throughout Lao PDR were tested for repellence and larvicidal activity of fly larvae infesting fermented fish. The lethality and repellence of Tadehagi triquetrum (L.) H. Ohashi (Fabaceae), Uraria crinita (L.) Desv. ex DC. (Fabaceae) and Bambusa multiplex (Lour.) Raeusch. ex Schult. & Schult. f. (Poaceae) were tested in an experimental design using fermenting fish in Vientiane, Lao PDR.

Results

The repellent effect of fresh material of T. triquetrum and U. crinita, and the larvicidal effect of fresh B. multiplex, is significantly more effective than that of dried material of the same species, and the total effect (repellence and larvicidal effect combined) for each of the three species was significantly more effective for fresh than for dry material. Fresh material of T. triquetrum, U. crinita, or B. multiplex added on top of the fermenting fish repelled 50%, 54%, 37%, and killed 22%, 28%, and 40% of fly larvae. The total effect was not significantly different per species at 72%, 82%, and 77%, respectively.

Discussion and Conclusions

The three most salient species are effective in repelling and killing fly larvae in the production of fermented fish, and may be essential to augment food safety during traditional fermentation in open jars.     

Development and Harmfulness of the European Corn Borer,Ostrinia nubilalis Hb. (Lepidoptera,Pyralidae), in the Central Chernozem Region

Long-term observations have revealed the factors responsible for periodic rises in abundance of the European corn borer Ostrinia nubilalis Hb. in the Central Chernozem Region of Russia. These factors are sufficient precipitation during several consecutive years and the current decline in agrotechnical soil treatment. The host specialization, biology, and phenology of the corn borer in the region have been clarified. Corn is damaged most intensely among the cultivated plants, and the yellow foxtail Setaria glauca, among the weeds. The effects of precipitation on seasonal development and harmfulness of the corn borer have been demonstrated. Low precipitation during the pest pupation period leads to mass pupal mortality, a shift of the seasonal development onto later dates, and a lower proportion of damaged stems in the crops. Insufficient precipitation during the larval feeding period enhances the effect of pest damage on the plant productivity and results in heavier yield loss. During the corn borer outbreaks the yield loss reached 15% in corn and 11.4% in millet. Depending on the weather conditions, the loss of millet yield due to this pest may be as great as 39% or as low as 3%.

     

Moniliformin and the European Corn Borer (<Emphasis Type="Italic">Ostrinia nubilalis</Emphasis>)

A representative survey was made of maize ears of the 1988 and 1989 crop in Austria to establish the influence of corn borer injuries onFusarium species involved in ear fusariosis andFusarium toxin production.TheFusarium species most frequently isolated from rot-damaged ears wereFsacchari var. subglutinans (about 50 %) andF. graminearum (about 30 %). There was a striking difference between theFusarium species of the Liseola and the Discolor section concerning their occurrence on corn borer-damaged ears. More than 80 % of the ears infected withF. sacchari var. subglutinans andF. verticillioides, but less than 15 % of the ears infected withF. graminearum, F. crookwellense andF. culmorum showed corn borer injuries.Toxin analyses of the infected ears corresponded to the known toxigenicity of the respectiveFusarium species. Ears infected withF. sacchari var. subglutinans contained moniliformin (up to 20 mg/kg), those infected withF. verticillioides fumonisin B₁ and B₂ (up to 15 mg/kg). In ears infected withF. graminearum, F. culmorum andF. crookwellense zearalenone (up to 40 mg/kg) and deoxynivalenol (up to 500 mg/kg) or nivalenol (up to 10 mg/kg), respectively, could be detected. Hence measures to combat the European corn borer will mainly reduce moniliformin and fumonisin contamination, but will affect zearalenone, deoxynivalenol and nivalenol contents of the ears to a much lesser extent.     

Genetic Variation in the Strongly Canalized Sex Pheromone Communication System of the European Corn Borer, Ostrinia Nubilalis Hubner (Lepidoptera; Pyralidae)

The major difference in pheromone production between the so-called E and Z strains of the European corn borer Ostrinia nubilalis is controlled by two alleles at a single autosomal locus. E-strain females produce an (E)-11-tetradecenyl acetate pheromone with 1-3% of the Z isomer, whereas Z-strain females produce the opposite blend. In laboratory-reared insects we found that F(1) females produced, on average, a 71:29 E/Z ratio, but the distribution was clearly bimodal. The variability in pheromone blend produced by heterozygous females could be explained by the existence of two different alleles in the Z strain which in combination with the E-strain allele for the major production locus cause the production of a component mixture either high or low in the E isomer. In addition, evidence was found for an independently inherited factor, existing in the E strain, with a dominant effect on the amount of E isomer produced by females homozygous for Z-alleles at the major production locus. Thus, the low variability normally found in the pheromone mixture produced by O. nubilalis and other moth females may, by canalization, hide a considerable amount of underlying genetic variation.     

玉米种质资源对六种重要病虫害的抗性鉴定与评价

在2003-2005年间,对604份玉米种质进行了抗弯孢菌叶斑病和玉米螟鉴定,筛选出抗弯孢菌叶斑病的材料93份,抗玉米螟材料22份。2006-2009年间,对836份玉米种质进行了抗大斑病、茎腐病、穗腐病和瘤黑粉病的鉴定与评价,筛选出一批高抗和多抗的资源。在836份资源中,对大斑病1、2和N号3个生理小种具有抗性的材料均为50%左右;抗茎腐病材料为41.3%,高抗和抗性种质分别为264和81份;穗腐病高抗和抗性种质分别为5和171份,占比为21.1%;瘤黑粉病高抗和抗性种质各261和14份,占总鉴定材料的32.9%。上述结果表明抗大斑病、茎腐病和瘤黑粉病的种质资源较为丰富。通过对抗性结果进行对比分析,发现不同生态区玉米种质的抗性强弱以及抗性多样性存在明显差异,黑龙江和内蒙古的种质对病虫害的抗性强弱及多样性程度明显高于四川种质。此外,玉米自交系对病虫害的抗性强弱以及多抗性程度高于农家种。     

Non-Randomness of Fluctuations in the European Corn Borer Ostrinia nubilalis (Hbn.) (Lepidoptera,Crambidae) Long-Term Population Dynamics in Krasnodar Territory

Entomological Review - The paper presents the results of analysis of long-term (1994–2017) data on the population dynamics of the local bivoltine European corn borer population developing on...     

A field test of the use of pop‐off data storage tags in freshwater fishes

In the present study, pop‐off data storage tags (pDST) without any transmitting capabilities were attached to 118 adult salmonids in a 19 000 km² freshwater system (Lake Ontario). The 9·3 cm long cylindrical tags were externally attached to fishes using a backpack‐style harness, set to record pressure (dBar ≈ depth in m) and temperature every 70 s (and at some key times, every 5 s) and programmed to release from the harness and float to the surface after c. 1 year. Recapture of the bright‐orange tags for data retrieval relied on members of the public finding tags on shore, or on anglers capturing fishes with tags attached and using the contact information displayed on each tag to mail tags to the research team in exchange for a monetary reward. Thirty‐seven tags were found and returned from the 118 released (31%), while 26 of the 118 tags (22%) remained scheduled to pop‐off in summer 2017. Of the 37 tags returned, 23 were from wild‐caught fishes (out of 88 wild‐caught and tagged fishes; 26%) and yielded useful data whereas 14 were from hatchery‐reared fishes that were opportunistically tagged and appear to have been unable to acclimate to life in the wild and died days to weeks after release. The field study described here thus demonstrated that pDSTs can be a viable option for collecting large amounts of high‐resolution depth and temperature data for salmonids in freshwater systems. Technical challenges, limitations and unknowns related to the use of pDSTs with freshwater fishes are discussed. In addition, pDSTs are compared with alternate electronic tagging technologies and assessed for their potential as a more widespread tool in research on freshwater fishes.