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The European corn borer (ECB, Ostrinia nubilalis Hbn.) is a major pest in temperate regions of Europe and North America. Fifth instar ECB larvae enter diapause before winter and gradually develop cold hardiness. Here we investigated the combined influence of diapause phase and low temperature on sugar and polyol content in ECB larvae. Larvae in mid-diapause or diapause termination were acclimated at 5 °C, −3°C or −16 °C, and sugar and polyol content was measured using GC–MS. Control GC–MS measurements were conducted on untreated non-diapausing larvae. We detected differences in polyol (glycerol, sorbitol, myo -inositol) and sugar (trehalose, fructose, glucose) levels in diapausing versus non-diapausing larvae. Glycerol and trehalose were the most abundant of all analyzed cryoprotective compounds in diapausing larvae. Exposure of diapausing larvae to decreasing temperatures induced changes in polyol and sugar levels that depended on the phase of diapause. In mid-diapause larvae, decreasing temperatures induced a significant increase in glycerol and a decrease in sorbitol and myo -inositol. In larvae at diapause termination, polyol content was lower and less influenced by decreasing temperatures. In contrast, sugar levels were lower in larvae at mid-diapause versus diapause termination. Exposure of larvae to −16 °C induced a significant increase in the levels of all detected sugars. In particular, glucose levels were significantly higher in larvae at diapause termination following exposure to −16 °C. We propose that this shift toward sugar synthesis following low temperature exposure in larvae at diapause termination is a consequence of NADPH dependent polyol synthesis, and may be a mechanism for preservation of carbon reserves needed for post-diapause development. [ABSTRACT FROM AUTHOR]

Maize can be competitively colonized by several fungi that are capable of producing a variety of mycotoxins, mainly fumonisins B (FBs), with a negative impact on maize safety and quality. The aim of this study was to investigate the impact of the insecticide application against European Corn Borer on the contamination of “emerging” mycotoxins and other fungal metabolites co-occurring with the legislated ones in maize for human consumption in North-West Italy from 2009 to 2015. The insecticide application on average significantly increased the yield by 5%, and significantly reduced the ECB incidence and severity and the fungal ear rot incidence and severity compared to the untreated control. Overall, 25 Fusarium mycotoxins and metabolites were detected. The results underline that the use of the insecticide, the most common FBs control practice in temperate areas on food maize, also resulted in significant reductions of other mycotoxins produced by Fusarium spp. of the Liseola section. However, this practice was not generally able to reduce the contents of Fusarium spp. section Discolor and Roseum mycotoxins. In environmental and agronomic conditions that favor deoxynivalenol and other metabolites produced by the previous mentioned Fusarium spp., the insecticide treatment could even increase their contamination. [ABSTRACT FROM AUTHOR]

The processing snap bean industry views European corn borer, Ostrinia nubilalis (Hübner), larvae as contaminates in beans and has established a near zero tolerance. Currently, growers in New York (USA) apply 1–2 pyrethroid insecticide treatments for O. nubilalis control in snap bean. The objective of this study was to compare the residual efficacy of diamide and traditional pyrethroid insecticides at various foliar application timings against O. nubilalis . Insecticides were tested at four different timings (1, 7, 10, and 14 days before snap bean pod formation) in field trials performed in western New York in 2015 and 2016. Treatments were evaluated for O. nubilalis plant and pod damage and yield. Bioassays using snap bean leaves collected from the treated field plots were used to assess larval mortality. All materials exhibited excellent control of O. nubilalis when applied 1 day before pod formation, reducing pod and plant damage to ∼0%. However, for applications 14 days before pod formation, chlorantraniliprole and chlorantraniliprole + lambda-cyhalothrin consistently had lower pod and plant damage and higher larval mortality compared with the other materials. Chlorantraniliprole applied at 7, 10, and 14 days before pod formation also resulted in higher yields than the untreated control in 2015. Our results indicate that chlorantraniliprole-containing insecticides could be applied only once per season, eliminating the need for multiple applications, and could also be co-applied with fungicides or herbicides, which are applied earlier than standard pyrethroid insecticides. These results indicate that the anthranilic diamides, especially chlorantraniliprole, exhibit longer-term efficacy than pyrethroids, increasing the flexibility of spray timing by growers. [ABSTRACT FROM AUTHOR]

Blending Bacillus thuringiensis ( Bt ) corn and non- Bt corn seeds in the same bag is a convenient and easier compliance solution to satisfy refuge regulations. However, there has been considerable debate and concern about larval movement of the target insects in a seed blend because of its potential effect on the development of resistance. Reported here are studies to determine the larval movement of European corn borers, Ostrinia nubilalis (Hübner), in a seed blend compared to a structured refuge and their effects on survival, feeding injury and larval fitness. Also evaluated is the relative performance of a purple-seeded corn hybrid as a surrogate host plant for tracking gene flow. Seed blend and structured refuge arrangements of Agrisure GT/CB/LL Bt corn expressing Cry1Ab and isoline plants were evaluated at two locations in 2013 and 2014 by manually infesting refuge plants with first and second generation corn borer larvae. The majority of leaf and stalk injury was recorded on the refuge plant, which amounted to 66–83% of the total tunnel length. In both refuge arrangements, plant injury and the number of larvae recovered significantly decreased on neighboring plants with increasing distance away from the refuge plant in the same row. The relative decline in injury was much more pronounced in the seed blend, with neighbor Bt plants experiencing very minor tunneling or no injury at all due to the high dose trait. Eighty-nine percent fewer live larvae were also found on neighbor Bt plants in the seed blend compared to those found in the structured refuge plots. Larvae that moved to Bt plants as well as older instars that were manually placed on Bt plants failed to complete development. Comparison of the number of tunnels and larvae recovered per refuge plant indicated that the seed blend may not produce as many susceptible individuals as those produced in a structured refuge arrangement. Although the purple-seeded hybrid showed lower levels of ear and stalk injury, it could serve as an appropriate surrogate refuge plant to track gene flow. [ABSTRACT FROM AUTHOR]

Increasing the maize plant population has undergone a constant evolution over the years, with the purpose of enhancing the crop yield. Field trials, in which 2 different experiments were considered, have been conducted in NW Italy in order to analyze the yield benefit of high plant density on recent hybrids, considering both intra-row and inter-row plant spacings. The first experiment, which was carried out during the 2013 and 2014 season, evaluated the effects of 4 growing plant densities (from 7.5 to 12 plants m −2 ) combined with 2 row widths (the traditional 0.75 m and a narrow inter-row spacing of 0.50 m) on plant architecture and grain yield. Two hybrids, with different ear developments (fixed and flex), were taken into account. The higher plant density led to a decrease in the stalk area (−20%), leaf greenness (−5.2%) and cob length (−10.8%). It also negatively affected the kernel weight (−7.1%) and the number of kernels per row (−10%). The grain yield only increased significantly, for both hybrids (+7.4%), if a density of 10.5 plants m −2 was reached when the inter-row spacing was reduced (0.50 m). In the second study, an innovative system (narrow inter-row spacing combined with a plant population of about 10.5 plants m −2 ) was compared with a standard planting system (7.5 plants m −2 sown on 0.75 m wide rows), considering 32 different production situations (PS) over 4 growing seasons (2011–2014). This study has confirmed that even though the single plant yield potential was reduced in terms of ear weight and thousand kernels weight by 18% and 6%, respectively for a high planting density, the final grain yield increased on 90% of the PS with an average gain of 11.7%. This work has proved that, in the conditions in which the experiments were conducted, a high planting density of up to 10.5 plants m −2 can lead to a significant yield increase, but only when it is combined with narrow inter-row spacing. These conditions increase plant stresses, and modify plant morphology and development to the detriment of the single plant yield. However, the lower yield per plant is fully compensated by the higher plant population. [ABSTRACT FROM AUTHOR]

The European Corn Borer (ECB), Ostrinia nubilalis (Hübner), plays an important role in promoting Fusarium infection and fumonisin production in maize kernels. Moniliformin (MON) is a mycotoxin that is usually found in association with fumonisins (FB), and as a consequence ECB is also expected to play a role in MON contamination. The aim of the current study was to investigate the influence of ECB activity on MON contamination and on the fungi responsible for its contamination. A comparison has been made between maize infected naturally by insect larvae and protected maize, from 2008 to 2010 in North–West Italy; the latter was obtained by positioning an entomological net at the end of maize flowering. The Fusarium proliferatum infection of the maize grain was higher in each growing season than that caused by Fusarium subglutinans , although both species were significantly increased due to the ECB damage to the maize ears. The ECB activity significantly increased the MON content 26-fold in 2008 from 43 to 1137 μg kg −1 , 25-fold in 2009 from < LOQ to 77 μg kg −1 and 94-fold in 2010 from 6 to 564 μg kg −1 . The relationship between the MON content and the Fusarium species producers of MON was closer for F. proliferatum ( r = 0.96, P < 0.001) than for F. subglutinans ( r = 0.83, P < 0.001). An in vitro assay was carried on in order to assess the toxigenic capacity of different F. proliferatum and F. subglutinans strains isolated from a field experiment and artificially inoculated on a maize substrate. On average, the F. proliferatum isolated strains showed a significantly higher ( P < 0.001) toxigenic capacity than the F. subglutinans strains. In conclusion, the combination of the high toxigenic capacity of F. proliferatum , and its more frequent occurrence and greater intensity in the field make it possible to state that the production of MON in maize temperate areas, such as North Italy, is mainly due to F. proliferatum infections and is closely linked to the injury caused by ECB larvae. [ABSTRACT FROM AUTHOR]

Diapause is a state of arrested development during which insects cope with many external and internal stressful factors. European corn borer, Ostrinia nubilalis , overwinters as a fifth instar freeze-tolerant diapausing larva. In order to explore diapause-linked stress tolerance processes, the expression of selected genes coding for stress-related proteins—glutathione S-transferase ( Gst ), thioredoxin ( Trx ), glutaredoxin ( Grx ), ferritin ( Fer ), metallothionein ( Mtn ), and heat shock proteins Hsp90 , Hsc70 , Hsp20.4 , and Hsp20.1 —was assessed in the fat body of diapause-destined, warm (22 °C) and cold (5 °C) acclimated diapausing larvae using the quantitative real-time PCR. Gene expression was normalised to mRNA transcripts for Actin and Rps03, and relative expression was calculated using non-diapausing larvae as a control group. During the initiation phase of diapause, the abundance of mRNA transcripts of Grx , Hsp90 , Hsc70 , and Hsp20.1 was significantly upregulated, Trx , Fer , Mtn , and Hsp20.1 were unchanged, while only Gst was clearly downregulated in comparison to non-diapause control. Later, in the early phase of diapause, the expression of most genes (except Trx and Hsp20.1 ) was upregulated in warm-acclimated larvae, while only Trx and Hsp90 were upregulated in cold-acclimated larvae. Furthermore, the relative expression of all genes (except Trx ) increased gradually throughout the diapause in cold-acclimated larvae. This result indicates that the half-life of mRNAs is prolonged during diapause at low temperature, which may lead to a gradual accumulation of mRNA transcripts. Our results show that both diapause programming and temperatures affect the expression of stress-related genes in Ostrinia nubilalis . [ABSTRACT FROM AUTHOR]

Seasonal changes in the FA composition of triacylglycerols and phospholipids prepared from the whole bodies of non-diapausing and diapausing fifth instar larvae of Ostrinia nubilalis , Hubn. (Lepidoptera: Crambidae) were determined to evaluate the role of these lipids in diapause. Substantial changes in the FA composition of triacylglycerols and phospholipids were triggered by diapause development. This led to a significant increase in the overall FA unsaturation (UFAs/SFAs ratio), attributable to an increase in the relative proportion of MUFAs and the concomitant decrease in PUFAs and SFAs. In triacylglycerols, the significant changes in the FAs composition are the result of an increase in the relative proportions of MUFAs, palmitoleic acid (16:1n-7) and oleic acid (18:1n-9), and a concomitant reduction in the composition of SFAs and PUFAs, mainly palmitic acid (16:0) and linoleic acid (18:2n-6), respectively. Changes in the composition of phospholipids were more subtle with FAs contributing to the overall increase of FA unsaturation. Differential scanning calorimetry (DSC) analysis revealed that the melt transition temperatures of total lipids prepared from whole larvae, primarily attributable to the triacylglycerol component, were significantly lower during the time course of diapause compared with non-diapause. These observations were correlated to the FA composition of triacylglycerols, most likely enabling them to remain functional during colder winter conditions. We conclude that O. nubilalis undergoes remodeling of FA profiles of both energy storage triacylglycerols and membrane phospholipids as an element of its overwintering physiology which may improve the ability to cold harden during diapause. [ABSTRACT FROM AUTHOR]

Maize grain yields and profitability are enhanced in temperate growing areas as a result of an early sowing. However, cool conditions may constrain the uptake of nitrogen (N) and phosphorus (P) by the root system during the early and more susceptible growth stages. The application of starter fertilizers near the plant roots could ensure better N and P availability and improve early vigor of the crop. The aim of this study has been to quantify the overall benefits of a localized starter fertilization with N or P, or their combination, on maize (early development, grain yield, grain quality and sanitary traits). A 4-year field experiment was conducted in NW Italy during the 2014–17 growing seasons. The trial compared the sub-surface placement of N, P and NP in bands close to the maize seed furrows, as a starter fertilization strategy, with unfertilized controls on sandy silt loam (SSL), silt loam (SL) and silty clay loam (SCL) soils. These soils were placed side by side, and were characterized by low, high and medium N and plant-available P contents, respectively. The results showed that when N and P were applied together, the early vigor (plant height) and canopy development (NDVI values) of the maize were significantly enhanced, compared to both the controls and to the application of the single elements in all the soils. The positive growth responses to starter NP fertilization were combined with accelerated crop phenological development, so that anthesis occurred 2.4–3.1 days earlier. Thus, the grain yield was enhanced following the NP sub-surface placement (+7%, +15% and +11%, in SSL, SL and SCL, respectively), mainly due to an increase in the number of kernels per ear (+10%), while the grain moisture content was reduced, compared to the controls, in all the soils (−2.2%). The application of N or P alone did not consistently affect either the grain yield or the moisture content in any of the three soils. The starter fertilization strategy also affected both the qualitative and sanitary grain traits. NP and N both resulted in an increase in the grain hardness in the SL and SCL soils, but when P was applied alone, no significant effects were observed. The use of NP starter fertilization significantly reduced the ear injuries caused by European Corn Borer in all three soils (−44%), and reduced ear rot severity in the SSL and SL soils and the fumonisin content (−72%) in the SL and SCL soils, compared to the untreated controls. The synergistic effect of N and P applied as a sub-surface band at sowing had a consistent positive effect on the advancement of the flowering dates at different sites in different years, even in soils that have tested high to P or N. Thus, the application of NP starter fertilizer is a crop practice that should be considered in North Italy and for similar soils and environments. [Display omitted] • NP starter fertilization in a temperate climate increased maize early vigor. • Earlier anthesis dates with starter application led to yield and qualitative benefits. • N or P alone did not consistently benefit yield or grain moisture content. • NP starter fertilization together increased yield and quality in all soils and years. [ABSTRACT FROM AUTHOR]

Transgenic expression of Bacillus thuringiensis (Bt) crystalline (Cry) toxins by crop plants result in reduced insect feeding damage, but sustainability is threatened by the development of resistance traits in target insect populations. We investigated Bt toxin resistance trait in a laboratory colony of the European corn borer, Ostrinia nubilalis, selected for increased survival when exposed to Cry1Ab and correlated survival on Cry1Ab toxin with a constitutive ∼146.2 ± 17.3-fold reduction in midgut aminopeptidase N1 (apn1) transcript levels. A 7.1 ± 1.9-fold reduction apn3 transcript level was also correlated with Cry1Ab resistance. Quantitative trait locus (QTL) mapping identified a single major genome region controlling Cry1Ab resistance on linkage group 24 (LG24), and a minor QTL on LG27. Both QTL were independent of apn1 and apn3 loci on LG02. Positional mapping identified genetic markers that may assist in the identification of causal gene(s) within QTL intervals. This study indicates that genetic factor(s) may act in trans to reduce both apn1 and apn3 expression in Cry1Ab resistant O. nubilalis larvae, and suggest that gene regulatory pathways can influence Bt resistance traits. These findings show that gene interactions (epistasis) may influence Bt resistance in target insect populations. [ABSTRACT FROM AUTHOR]

Abstract: Aminopeptidase N (APN) isoforms from Lepidoptera are known for their involvement in the mode of action of insecticidal Cry proteins from Bacillus thuringiensis. These enzymes belong to a protein family with at least eight different members that are expressed simultaneously in the midgut of lepidopteran larvae. Here, we focus on the characterization of the APNs from Ostrinia nubilalis (OnAPNs) to identify potential Cry receptors. We expressed OnAPNs in insect cells using a baculovirus system and analyzed their enzymatic activity by probing substrate specificity and inhibitor susceptibility. The interaction with Cry1Ab and Cry1Fa proteins (both found in transgenic insect-resistant maize) was evaluated by ligand blot assays and immunocytochemistry. Ligand blots of brush border membrane proteins showed that both Cry proteins bound mainly to a 150 kDa-band, in which OnAPNs were greatly represented. Binding analysis of Cry proteins to the cell-expressed OnAPNs showed that OnAPN1 interacted with both Cry1Ab and Cry1Fa, whereas OnAPN3a and OnAPN8 only bound to Cry1Fa. Two isoforms, OnAPN2 and OnAPN3b, did not interact with any of these two proteins. This work provides the first evidence of a differential role of OnAPN isoforms in the mode of action of Cry proteins in O. nubilalis. [Copyright &y& Elsevier]

Abstract: The genetically modified maize MON89034 × MON88017 expresses different crystal (Cry) proteins with pesticidal activity against the European corn borer (Cry1.105; Cry2Ab2) and the Western corn root worm (Cry3Bb1). Non-target organisms, such as soil nematodes, might be exposed to the Cry proteins that enter the soil in course of crop growing. Therefore, the risk of those proteins for nematodes was assessed by testing their toxic effects on Caenorhabditis elegans. All three insecticidal Cry proteins showed dose-dependent inhibitory effects on C. elegans reproduction (EC50: 0.12–0.38 μmol L−1), however, at concentrations that were far above the expected soil concentrations. Moreover, a reduced toxicity was observed when Cry proteins were added jointly. A C. elegans mutant strain deficient for receptors for the nematicidal Cry5B was also resistant against Cry1.105 and Cry2Ab2, suggesting that these Cry proteins bound to the same or similar receptors as nematicidal Cry proteins and thereby affect the reproduction of C. elegans. [Copyright &y& Elsevier]

Abstract: The phenological development of insects is simulated predominantly via models based on the response of the organisms to air temperature. Despite of a large body of literature supporting the evidence that the organism physiological response to temperature is nonlinear, including a declining phase, most of these models calculate the rate of development using a linear approach, implying that air temperatures mostly does not fall outside of the linear region of response to temperature of the organism. Another simplification is represented by the calculation of the rate of development using daily mean air temperature, which has already been demonstrated being a reliable method only in limited conditions. It can be hypothesized that the use of developmental models based on linear developmental rates, which can be successfully applied under climate conditions to which organisms are well adapted, could be inadequate under either future climatic scenarios or when extreme events occur (e.g., heat waves). In such contexts, linear responses might lead to interpretations of climate effects not consistent with the real organism physiological response to temperature. In this work the case of Ostrinia nubilalis Hübner (European corn borer, ECB) development was taken as an example to compare (i) a nonlinear approach with hourly air temperature as input (HNL approach), (ii) a linear based approach with hourly air temperature as input (HL approach), (iii) a linear based approach with daily air temperature as input (averaging method, DL approach), and (iv) a linear based approach using a cutoff temperature with daily air temperature as input (DLcutoff approach). The comparison was performed under the IPCC (Intergovernmental Panel for Climate Change) emission scenario A1B, and three time frames in Europe: 1995–2004 (baseline–2000s), 2015–2024 (2020s), and 2045–2054 (2050s). The SRES A1B was selected as one of those for which the projected raise of temperature is estimated to be one of the highest, although the projected difference comparing to the other SRES is estimated as evident in the 2050s time frame, among the ones considered. Using degree-days as a proxy for the rate of development, results showed that the DL approach predicts more than the HNL in all the time frames in almost all Europe with the exception of Southern Italy and the Mediterranean coasts of France and Spain where the differences were negligible. These effects were due (i) to the linear relationship used by the DL approach, and partially (ii) to the averaging operation that decrease the effects of high temperatures in regions with high (but not extreme) warm temperatures. The HNL and HL approach predicted the same pattern of degree-days accumulation in all Europe with the exception of the regions of Southern Iberian peninsula (across all the timeframes), Balkans, and Turkey (under the 2050 scenario). This effect was due to the different HNL and HL accumulation of degree-days at temperatures higher than the ECB optimum temperature. The comparison between the DLcutoff and the HNL approaches showed similar results to the DL vs HNL approach in central and Northern Europe, while in Southern Europe a negative difference (more DD accumulated for the HNL approach) were observed: in regions characterized by high temperatures, the cutoff temperature, setting a limit to the maximum temperatures diminished the calculated average temperature and as a consequence the calculated degree-days. The results of this work showed that according to the method chosen for simulations, different results can be obtained, hence leading to different conclusions about the effect of a warming climate on pest development. These results stress the need of reconsidering the appropriateness of models to be used, which cannot be assumed as correct on the basis of their effectiveness under current conditions. [Copyright &y& Elsevier]

Abstract: Bacterial isolates from the European Corn Borer (ECB) Ostrinia nubilalis and the coleopteran Colorado Potato Beetle (CPB) Leptinotarsa decemlineata midguts were identified and characterized. Twenty-four colonies, selected on solid media with cellulose as the sole carbon source and pH values ranging from 5 to 12, were identified through 16S sequencing as members of the genera Acinetobacter, Comamonas, Klebsiella, Microbacterium, Micrococcus and Sphingobacterium. A complete enzymatic characterization revealed widespread – albeit moderate – cellulase properties in all but one isolate and high xylanase activity in the four CPB isolates. Different enzymatic patterns in terms of optimal pH, substrate use and degradation times were observed, and several isolates were selected as promising cellulase producers at extreme (pH 12) conditions. Implications of the results for the biotechnological industry are discussed. [Copyright &y& Elsevier]

Abstract: (3S,5S,6S)-Tetrahydro-6-isopropyl-3,5-dimethylpyran-2-one, a C5-epimer of a component of the natural sex pheromone of the wasp Macrocentrus grandii, the larval parasitoid of the European corn borer Ostrinia nubilalis, was synthesized starting from methyl l-valinate. The transformation includes a Kulinkovich cyclopropanation reaction, a cationic cyclopropyl-allyl rearrangement of cyclopropyl methanesulfonate, a diastereoselective alkylation of Oppolzer’s (N-propionyl)-(2R)-bornane-10,2-sultam and a diastereoselective hydrogenation using Wilkinson’s catalyst as the key steps. [Copyright &y& Elsevier]

Abstract: Most moth species in the genus Ostrinia use varying ratios of (Z)-11- and (E)-11-tetradecenyl acetate as their main sex pheromone components. The Asian corn borer is unique within the genus having evolved to use pheromone components with a shift in the location of the double bond, (Z)-12- and (E)-12-tetradecenyl acetate. We identified cDNAs representing five pheromone binding proteins (PBPs) and two sensory neuron membrane protein genes from an antennal transcriptome. The coding regions of the orthologous genes were cloned from the Asian corn borer and the (E) and (Z) sex pheromone races of the European corn borer. Their nucleotide sequences and transcript expression levels were analyzed to identify candidate genes from the Asian corn borer that may have evolved specificity to the 12-tetradecenyl acetate ligand. PBP2 and PBP3 transcripts were expressed at high male-biased levels. PBP3 had the most nonsynonymous nucleotide substitutions resulting in ten amino acid changes. Based on the predicted three-dimensional structure of PBP3, six of these ten amino acid changes occur in domains that may interact with the pheromone ligand. Future studies will determine whether PBP3 has evolved specificity to the Asian corn borer sex pheromone. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: Chitinases belong to a large and diverse family of hydrolytic enzymes that break down glycosidic bonds of chitin. However, very little is known about the function of chitinase genes in regulating the chitin content in peritrophic matrix (PM) of the midgut in insects. We identified a cDNA putatively encoding a chitinase (OnCht) in European corn borer (ECB; Ostrinia nubilalis). The OnCht transcript was predominately found in larval midgut but undetectable in eggs, pupae, or adults. When the larvae were fed on an artificial diet, the OnCht transcript level increased by 4.4-fold but the transcript level of a gut-specific chitin synthase (OnCHS2) gene decreased by 2.5-fold as compared with those of unfed larvae. In contrast, when the larvae were fed with the food and then starved for 24h, the OnCht transcript level decreased by 1.8-fold but the transcript level of OnCHS2 increased by 1.8-fold. Furthermore, there was a negative relationship between OnCht transcript level and chitin content in the midgut. By using a feeding-based RNAi technique, we were able to reduce the OnCht transcript level by 63-64% in the larval midgut. Consequently, these larvae showed significantly increased chitin content (26%) in the PM but decreased larval body weight (54%) as compared with the control larvae fed on the diet containing GFP dsRNA. Therefore, for the first time, we provide strong evidence that OnCht plays an important role in regulating chitin content of the PM and subsequently affecting the growth and development of the ECB larvae. [Copyright &y& Elsevier]

Abstract: This experiment determined the chemical composition, rumen degradability (aNDF in stalks and starch in kernels) and in vitro gas production of kernels from three corn hybrids treated (TT) or not treated (control, CTR) with insecticides against the European corn borer (ECB, Ostrinia nubilalis). Two whole-plant silage hybrids belonging to the FAO rating 600 and 700 maturity class (S600 and S700, respectively) and one selected for grain production (G600, FAO rating 600, Dekalb-Monsanto Agricoltura S.p.A., Lodi, Italy) were sown in two main plots (TT and CTR) of an experimental field. Two subsequent treatments of pyrethroids (25 and 1.2g/ha of cyfluthrin and deltamethrin, respectively) were applied to the TT plots. The insecticide treatment reduced the number of damaged plants (4.5 broken plants/plot versus 0.3 broken plants/plot, P<0.01) and increased the total grain yield by 11% (13.8t/ha versus 12.4t/ha), while hybrids did not differ. ECB larvae which bored into the stalk tunnels modified the chemical composition of stalks and kernels. In stalks, total sugars content (i.e. glucose, fructose, sucrose) was about twice that in TT versus CTR plants (123g/kg versus 60g/kg DM, P<0.01), while aNDF content was higher in CTR stalks (765 versus 702g/kg DM, P<0.01). DM degradability after 48h of incubation of stalks was higher in TT than in CTR, both in vitro (0.360 versus 0.298, P<0.01) and in situ (0.370 versus 0.298, P<0.05), while there were no differences in aNDF degradability. Kernels from TT plots contained less DM (615g/kg versus 651g/kg, P<0.01) and more CP (84g/kg and 78g/kg DM, P<0.05) than those from CTR plots, while in situ rumen starch disappearance and in vitro gas production were similar. Corn hybrid selected for yield of grain (G600) differed from S600 and S700 due to a higher (P<0.01) content of aNDF, ADF and lignin(sa) in the stalks, and a higher starch content (696g/kg versus 674 and 671g/kg DM, P<0.01) and CP (87g/kg versus 77 and 76g/kg DM, P<0.05) in grain. The G600 hybrid produced stalks with a lower (P<0.01) aNDF rumen degradability than the S600 and S700. On field ECB insecticide treatment improved corn grain yield, reduced broken plants and increased stalk sugars content at harvesting, but did not change the rumen degradation of either stalks or grain. [Copyright &y& Elsevier]

Abstract: First generation hybrid males from crosses between the Asian corn borer (ACB), Ostrinia furnacalis, and the “univoltine Z-strain” European corn borer (ECB), Ostrinia nubilalis, were examined with respect to behavioral and physiological responses to ACB and ECB pheromones. The hybrid males often flew to the pheromone of ECB Z-strain, but very rarely to the ACB pheromone. We mapped the tuning profiles of each ORN of the F1 hybrids with respect to the relevant pheromone components and a common behavioral antagonist by employing differential cross-adaptation and varying doses of the ligands. In the trichoid sensilla of F1 hybrid males, the three co-compartmentalized ORNs produced spikes that were very difficult to distinguish by size, unlike the parental populations. Comparing the responses to ACB and ECB components at different doses reveals overlapping profiles similar to males of both parental types, but more responsiveness to the ECB pheromone components. We were unable to detect any differences in the ORN tuning profiles when comparing males with different behavioral phenotypes. While the two ECB pheromone races have similar ORN tuning properties that are different from those in ACB, the spike-amplitude patterns of ECB E-strain and ACB have greater homology when compared to ECB Z-strain. [Copyright &y& Elsevier]

Abstract: DAS-Ø15Ø7-1xDAS-59122-7 (1507×59122) is a genetically modified (GM) maize hybrid that was produced by crossing of two GM maize inbreds; DAS-Ø15Ø7-1 and DAS-59122-7. This hybrid cross expresses four transgenic proteins: Cry1F and PAT (from DAS-Ø15Ø7-1) and Cry34Ab1/Cry35Ab1 and PAT (from DAS-59122-7) that confer resistance to lepidopteran and coleopteran pests and tolerance to the herbicidal active ingredient glufosinate-ammonium. The current subchronic feeding study was conducted in Sprague-Dawley rats to evaluate the potential health effects of long-term consumption of a rodent diet containing 1507×59122 maize grain compared with a diet containing maize grain from its near-isogenic control (091). Diets formulated with three unrelated non-GM commercial hybrids (3573, 35P12, 36G12) were also included for within study reference data. All diets contained 34% (w/wt) maize grain and were prepared according to the specifications of PMI® Nutrition International, LLC Certified Rodent LabDiet® 5002 (PMI® 5002). Diets were fed ad libitum to rats for at least 92days. OECD 408 response variables from rats fed the 1507×59122 diet were compared with those from rats fed the 091 control diet. No toxicologically significant differences were observed in nutritional performance variables, clinical and neurobehavioral signs, ophthalmology, clinical pathology (hematology, clinical chemistry, coagulation, and urinalysis), organ weights, and gross and microscopic pathology between rats in the 091 and 1507×59122 treatment groups. The results from this study demonstrate that 1507×59122 maize grain is as safe and nutritious as non-GM maize grain and support the concept that crossing of two safe GM maize events results in production of a safe stacked GM event. [Copyright &y& Elsevier]

Abstract: Fusarium verticillioides is a common maize pathogen which causes diseases on ears and synthesis of the mycotoxins, fumonisins, in kernels. Fumonisin production is influenced by both environmental conditions and agricultural inputs during growth and maturation of the maize plant. The aim of this research was to evaluate the effect of crop management techniques on fumonisin contamination in maize kernels. Experiments were conducted in Northern Italy during 2006 and 2007 using two maize hybrids with different precocity. Factors evaluated were seed planting time (March versus May), plant density (65,000 plants versus 80,000 plants per ha), N fertilization (200kg N versus 400kg N per ha), and chemical treatment to control European maize borer (ECB) (yes versus no). These factors were analyzed were as follows: (T1) May sowing, high plant density and N fertilization, (T2) March sowing time, high plant density and N fertilization, (T3) March sowing time, low plant density and balanced N fertilization, (T4) the same agronomic techniques as T3 plus a chemical treatment to control European maize borer. Ears were analyzed morphologically for ECB incidence and severity. Subsequently, kernels were analyzed chemically for fumonisins. Fumonisin contamination was reduced by 57%, 69% and 86% for T2, T3 and T4, respectively, compared to T1. This study clearly underlines that the application of good agricultural practices (GAP) in crop management strategies can effectively control fumonisin contamination of maize kernels. [Copyright &y& Elsevier]

Abstract: Transgenic corn expressing Cry1Ab (a Bacillus thuringiensis toxin) is highly effective in the control of Ostrinia nubilalis. For its toxic action, Cry1Ab has to bind to specific insect midgut proteins. To date, in three Lepidoptera species resistance to a Cry1A toxin has been conferred by mutations in cadherin, a protein of the Lepidoptera midgut membrane. The implication of cadherin in the resistance of an Ostrinia nubilalis colony (Europe-R) selected with Bacillus thuringiensis Cry1Ab protoxin was investigated. Several major mutations in the cadherin (cdh) gene were found, which introduced premature termination codons and/or large deletions (ranging from 1383 to 1701bp). The contribution of these major mutations to the resistance was analyzed in resistant individuals that survived exposure to a high concentration of Cry1Ab protoxin. The results indicated that the presence of major mutations was drastically reduced in individuals that survived exposure. Previous inheritance experiments with the Europe-R strain indicated the involvement of more than one genetic locus and reduced amounts of the cadherin receptor. The results of the present work support a polygenic inheritance of resistance in the Europe-R strain, in which mutations in the cdh gene would contribute to resistance by means of an additive effect. [Copyright &y& Elsevier]

Abstract: Fusarium verticillioides, a known producer of fumonisins, has been reported to be the most common pathogen of maize causing Fusarium ear rot and grain fumonisin contamination. Field tests were carried out in 2004 and 2005 growing seasons in two sites located in the North of Italy to determine the effects of sowing date and insecticide treatment against European corn borer (ECB, Ostrinia nubilalis Hübner) on maize susceptibility to Fusarium ear rot and fumonisin contamination under natural infection conditions. Two sowing dates (at about 25–30 day intervals) and two insecticide application treatments with lambda–cyhalothrin (at 7 and 14 days after the ECB flight peak) were compared with the untreated control in each year/site. Ears were rated for both incidence and severity of ECB damage and Fusarium ear rot at harvest. Harvested kernels were analyzed for fumonisin B1 (FB1) and B2 (FB2) contents. Insecticide treatments significantly reduced the ECB infestation compared to the untreated control. The insecticide treatments applied 7 days after the ECB flight peak controlled insect damage significantly better than those applied later. The ECB damage severity was also higher for the later than the earlier sowing date (14%) compared to the earlier one. A significant effect of sowing date and insecticide application on Fusarium ear rot was evidenced. For the earlier sowing date treatments, ear rot incidence and severity reductions of 13% and 16%, respectively, compared to those of later sowing dates were noted. Insecticide applications to plants resulted in lower ear rot severity than the untreated control (up to 29%). Maize sowed earlier and treated with insecticide 7 days after the ECB flight peak resulted in a significantly lower grain fumonisin concentration (up to 67%), compared to those of untreated and late sowed maize. In Mediterranean areas, the choice of an early sowing date and appropriate treatments with pyrethroid insecticides against ECB might represent a useful tool to limit raw maize fumonisin concentration to levels below the EU maximum admissible level recently fixed by the Commission. [Copyright &y& Elsevier]

Predicting the potential distribution of agricultural pests, both indigenous and introduced, plays a key role in determining the impact of global change on agricultural, horticultural and forestry ecosystems. This study investigates changes in the climatic niche of one of the most important agricultural pests, the European Corn Borer (Ostrinia nubilalis, Hubner), using the multi-generational phenology model ECAMON. The model enables us to predict the development of the European Corn Borer (ECB), to estimate the risk of its establishing a permanent population, and to give an indication of climate-related stress factors affecting the species. The evaluation of ECAMON demonstrated that it provides accurate predictions of the onset and duration of the key phenological stages over a broad range of sites. It explains over 70% of the variation in the timing of key developmental stages based only on daily weather data. ECAMON simulations correctly predicted the presence/absence of the ECB over the study region during the 1961–1990 reference period. It also helped to explain the sudden increase in the maize infestation over the territory of the Czech Republic during the unusually warm period of 1991–2000. The ECAMON results demonstrated that the effect of climate will be significant and complex. According to our estimates, the extent of the climate niche will expand within the next 20–30 years to cover almost the entire area suitable for agriculture by 2040–2075. The establishment of a bivoltine population is not imminent within the next decade, but it is likely to take place during the period of 2025–2050. The timing and extent of these changes will be affected not only by changes in the means of key meteorological parameters, but also in their variability. These shifts will be clearly accompanied by an earlier onset of key developmental stages of the pest. The study demonstrated that the level of uncertainty caused both by emission scenarios and by differences in global circulation models (GCMs) are of the same order of magnitude. Thus, only the combination of a wide range of emission scenarios and GCMs can provide insight into the potential effect of climate change on any particular species. Under future climate conditions, grain maize is expected to partly replace traditional cereals (e.g. winter wheat, rye, etc.); thus the establishment of a national or international monitoring scheme is desirable, and an ECAMON-like tool might serve as the basic modeling platform for such an effort. [Copyright &y& Elsevier]

Abstract: Three percent of E-strain Ostrinia nubilalis males fly upwind in response to the Ostrinia furnacalis pheromone blend [a 40:60 ratio of (E)-12-tetradecenyl acetate to (Z)-12-tetradecenyl acetate (E12-14:OAc to Z12-14:OAc)], in addition to their own pheromone blend [a 99:1 ratio of (E)-11-tetradecenyl acetate to (Z)-11-tetradecenyl acetate) (E11-14:OAc to Z11-14:OAc)]. We assessed the olfactory receptor neuron (ORN) responses of these behaviorally “rare” males versus those of normal males. For the three ORNs housed within each sensillum, we tested responsiveness to Z12-14:OAc, E12-14:OAc, Z11-14:OAc, E11-14:OAc, and the behavioral antagonist (Z)-9-tetradecenyl acetate (Z9-14:OAc). Z11-14:OAc, E11-14:OAc, and Z9-14:OAc stimulated ORNs exhibiting distinct small, large, and medium spike sizes, respectively. For rare and normal males, both Z12-14:OAc and E12-14:OAc usually elicited responses from the largest-spiking ORN. In many ORNs of normal males, Z12-14:OAc or E12-14:OAc stimulated the smaller-spiking ORN that is responsive to Z11-14:OAc. In rare males, detectable ORN responses from the smaller-spiking ORN in response to Z12- and E12-14:OAc were virtually non-existent. These differences in ORN tuning in rare males will tend to create an ORN firing ratio between the large- and small-spiking ORNs in response to the O. furnacalis blend that is similar to that elicited by the O. nubilalis blend. [Copyright &y& Elsevier]

Three years (2000–2002) of field studies were conducted in mid-Missouri, USA, to assess the impact of various compositions of herbaceous field borders on populations of the European corn borer, Ostrinia nubilalis. Border treatments of: (1) a mixture of warm-season grasses and legumes, (2) a mixture of cool-season grasses and legumes, (3) tall fescue alone, and (4) a corn border control were planted around plots of field corn. Percent stalks infested with European corn borer and number and length of larval tunnels in stalks were analyzed. Warm-season vegetation-bordered corn had consistently lower percent stalks infested than corn bordered by cool-season vegetation, tall fescue or a corn control. The results indicate that the adoption of field border programs such as CP33 will have little or no impact on European corn borer management. [Copyright &y& Elsevier]

Abstract: Maize line 1507, containing event DAS-Ø15Ø7-1 (1507), is a genetically modified (GM) maize plant that expresses the cry1F gene from Bacillus thuringiensis (Bt) sbsp. aizawai and the phosphinothricin-N-acetyltransferase (pat) gene from Streptomyces viridochromogenes throughout the plant including in the grain expression of the Cry1F protein confers in planta resistance to the European corn borer (ECB; Ostrinia nubilalis Hübner: Crambidae) and other lepidopteran pests. Expression of the PAT protein confers tolerance to the herbicidal active ingredient glufosinate–ammonium. The current study evaluated the nutritional performance of rats fed diets containing 1507 maize grain in a subchronic rodent feeding study. The grains in this study, 1507, its near-isogenic control (33P66), and a non-GM commercial hybrid (33J56) contained similar amounts of proximates, amino acids, minerals, anti-nutrients, and secondary metabolites. The subchronic feeding study compared standard toxicology response variables in rats fed diets containing 1507 maize grain with those in rats fed diets containing non-GM maize grains. All diets were prepared according to the specifications of PMI® Nutrition International, LLC Certified Rodent LabDiet® 5002 (PMI® 5002). Diets were fed ad libitum to Sprague–Dawley rats for approximately 90 days. In-life response variables included indicators of dietary performance and weekly evaluations for clinical signs of toxicity. No toxicologically significant differences were observed in the nutritional performance variables, clinical and neurobehavioral signs, ophthalmology, clinical pathology (hematology, clinical chemistry, coagulation, and urinalysis), organ weights, and gross and microscopic pathology between any pair of treatment groups. These results demonstrate that 1507 maize grain is as safe and as nutritious as non-GM maize grain. [Copyright &y& Elsevier]

Summary: The application of transgenic crops has expanded enormously since their introduction to agriculture in the 1990s. Despite increased research activity in the area of non-target effects, the impact on many groups of soil organisms still remains unclear. In this study, laboratory feeding experiments were conducted to detect possible effects of Bt corn on the detritophagous Allajulus latestriatus (Diplopoda, Julidae). We tested the transgenic corn N4640Bt (expressing the Bt protein Cry1Ab), the corresponding non-transgenic isoline, and two further conventional corn varieties. Furthermore, a toxicity test was performed, in which purified Cry1Ab was added to a corn leaf diet in different concentrations. Cry1Ab concentrations in corn leaves, corn leaf diet, faeces and diplopods were quantified, applying an enzyme-linked immunosorbent assay (ELISA). We performed bioassays using the European Corn Borer Ostrinia nubilalis to test the insecticidal activity of different samples. No significant differences in mortality, consumption of corn leaves, or weight gain were found when animals were fed on N4640Bt compared to its isoline and the other two varieties. However, faeces production per diplopod was significantly increased when animals were kept on Bt corn compared to the isoline and to another corn variety. In the toxicity test, no significant differences were found for mortality, consumption, weight gain or faeces production between diets, not even at Cry1Ab concentrations more than 100 times higher than in Bt leaves. Bioassays proved that the Bt protein in transgenic leaves and in faeces of diplopods was still insecticidal. The toxicity test indicated that Cry1Ab excretion in the faeces is linearly correlated to the Cry1Ab uptake through the diet. Our findings suggest that Bt corn and Cry1Ab will not harm A. latestriatus. However, this diplopod excretes considerable amounts of Bt protein with its faeces. The Bt protein is still insecticidally active and, thus, becomes available to other soil organisms. [Copyright &y& Elsevier]

Abstract: We used the cut-sensillum technique to assess the effect of both adult age and egg-to-adult development time on olfactory neuron responses of Z strain moths of the European corn borer, Ostrinia nubilalis. Compounds tested included the pheromone components, (Z)-11-tetradecenyl acetate and (E)-11-tetradecenyl acetate, the behavioral antagonist, (Z)-9-tetradecenyl acetate, and components of the O. furnicalis (Asian corn borer) sex pheromone, (Z)-12-tetradecenyl acetate and (E)-12-tetradecenyl acetate. The proportion of moths having neurons responding to the two O. nubilalis sex pheromone components and antagonist increased with longer development time and age. The spike frequency of neurons responding to (E)-11-tetradecenyl acetate and the antagonist increased with longer development time. Fourteen of 45 moths with neurons sensitive to either of the O. nubilalis pheromone components responded to (Z)-12-tetradecenyl acetate or (E)-12-tetradecenyl acetate. The likelihood of (Z)-12-tetradecenyl acetate stimulating a neuron similar in spike shape and waveform to that responding to (E)-11-tetradecenyl acetate increased with development time. [Copyright &y& Elsevier]

Abstract: Our previous studies suggested that Bacillus thuringiensis (Bt) resistance in a Dipel-resistant strain of Ostrinia nubilalis was primarily due to reduced trypsin-like proteinase activity. In this study, we demonstrated a 254-fold resistance to Cry1Ab protoxin but only 12-fold to trypsin-activated Cry1Ab toxin in the Dipel-resistant strain. Significantly higher resistance to Cry1Ab protoxin than to trypsin-activated Cry1Ab toxin further supports the hypothesis that reduced trypsin-like proteinase activity leading to reduced activation of the Bt protoxin is a major resistance mechanism in the Dipel-resistant strain. To understand the molecular basis of reduced proteinase activity, three cDNAs, OnT2, OnT23, and OnT25, encoding full-length trypsin-like proteinases, were sequenced in Bt-resistant and -susceptible O. nubilalis larvae. Although a number of nucleotide differences were found in sequences from the Bt-resistant and -susceptible strains, the differences were not consistent with reduced trypsin-like activity in the Bt-resistant strain. However, the mRNA levels of OnT23 in the resistant strain were 2.7- and 3.8-fold lower than those of the susceptible strain as determined by northern blotting and real-time quantitative PCR, respectively. Thus, reduced trypsin-like activity may be attributed to reduced expression of OnT23 in Bt-resistant O. nubilalis. Our study provides new insights into Bt resistance management strategies, as resistance mediated by reduced Bt protoxin activation would be ineffective if resistant insects ingest a fully activated form of Cry1Ab toxin, either in spray formulations or transgenic Bt crops. [Copyright &y& Elsevier]

A 42-d feeding experiment with growing Ross × Ross 508 broilers showed that the nutritional value of insect-protected and herbicide-tolerant corn was comparable to that of the genetically similar control and 5 commercial reference corn hybrids. MON 88017 provides protection from feeding damage by coleopteran pest corn rootworm and is tolerant to the action of glyphosate, the active ingredient in the Roundup family of agricultural herbicides. MON 88017 × MON 810 was developed by the traditional breeding of MON 88017 with MON 810, which provides protection from the European corn borer and other lepidopteran pests. A randomized complete block design was used with 8 dietary treatments in each of 5 replicated blocks of pens. No differences among diets were observed (P > 0.05) in performance (final live weights, feed intake, feed conversion, and adjusted feed conversion), carcass yield (chill, fat pad, breast, thigh, wing, and drum weight), or percentage of moisture, protein, and fat in breast meat and moisture and fat in thigh meat. Thigh protein was similar (P> 0.05) in broilers fed diets containing MON 88017 × MON 810 and conventional control or all commercial reference corns; however, differences (P < 0.05) were noted for the percentage of thigh protein among broilers fed the control and 2 of the 5 reference diets, attributable to biological variability among the conventional corn hybrids. Broilers overall performed consistently and had similar carcass yield and meat composition when fed diets containing MON 88017 or MON 88017 × MON 810 as compared with those fed the conventional control and commercial diets, supporting a conclusion of nutritional equivalence. [ABSTRACT FROM AUTHOR]

A genetically modified Bt176 corn hybrid, which contains an insecticidal protein against the European corn borer, and its conventional, nonmodified counterpart were evaluated in 4 separate trials to verify substantial equivalence in feeding value and animal performance. Thirty-six individually kept laying hens and 3 replicates of 94 broiler chickens each, assigned to 12 cages, were fed 2 different hen and broiler diets containing either 60% conventional or 60% Bt176 corn. The nutrient compositions of the 2 corn hybrids and the 2 corn diets revealed no major differences. Furthermore, metabolism and performance data revealed no significant differences between the birds that received the conventional, nonmodified corn, and those that received the modified corn diets, The detection of the genetic modification, by PCR, in feed obtained from insect-resistant Bt corn, in tissues and products from animals fed Bt corn is described. In all evaluated chicken tissues of muscle, liver, and spleen, the corn-chloroplast ivr gene fragment was amplified. It can be deduced from these findings and from other studies that the transfer of DNA fragments into the body is a normal process that takes place constantly. Nevertheless, no recombinant plant DNA fragments such as recombinant bla or crylA(b) fragments could be found. Bt-gene specific constructs from the Bt corn were not detected in any of the poultry samples, neither in organs, meat, nor eggs. [ABSTRACT FROM AUTHOR]

Abstract: Transgenic corn expressing the Cry1Ab toxin from Bacillus thuringiensis is highly toxic to European corn borer, Ostrinia nubilalis, larvae. A putative Cry1Ab receptor (OnBt-R1) molecule was cloned and sequenced from a cDNA library prepared from midgut tissue of O. nubilalis larvae. The 5.6Kb gene is homologous with a number of cadherin genes identified as Cry1 binding proteins in other lepidopterans. Brush border membrane vesicles were prepared using dissected midguts from late instars. A 220-kDa protein was identified as a cadherin-like molecule, which bound to Cry1Ab toxin and cross-reacted with an anti-cadherin serum developed from recombinant expression of a partial O. nubilalis cadherin peptide. Two additional proteins of smaller size cross-reacted with the anti-cadherin serum indicating that Cry1Ab binds to multiple receptors or to different forms of the same protein. Spodoptera frugiperda (SF9) cells transfected with the OnBt-R1 gene were shown to express the receptor molecule which caused functional susceptibility to Cry1Ab at concentrations as low as 0.1μg/ml. These results in combination suggest strongly that a cadherin-like protein acts as receptor and is involved with Cry1Ab toxicity in O. nubilalis. [Copyright &y& Elsevier]

Abstract: The effectiveness and cost of managing the suite of insect pests that attack sweet corn in Virginia were evaluated using multiple foliar applications of pyrethroid insecticides and Bt transgenic sweet corn in 2000 and 2002. Several Bt cultivars and their non-transgenic isolines were tested in different locations in Virginia to examine efficacy over a range of growing conditions and pest pressure. Overall, insect damage was far less in the Bt cultivars than in the non-Bt isolines that were not sprayed or sprayed with lambda-cyhalothrin up to six times. When insect pressure was low to moderate, Bt sweet corn did not require supplementary insecticide applications for a high percentage (88%) of ears to be considered fresh-market quality. In contrast, when insect pressure was extremely high, Bt sweet corn required two insecticide applications for a high percentage (88%) of ears to be considered fresh-market quality. Based on an economic comparison between insecticide-treated conventional sweet corn and Bt sweet corn, growers should expect a $547/ha gain by growing Bt sweet corn. If Bt sweet corn was sprayed twice with an insecticide, this gain should be approximately $1777/ha. We conclude that Bt sweet corn is an effective and economically sound pest management strategy for growers in Virginia. [Copyright &y& Elsevier]

Proteinase activities were compared in soluble and membrane fractions of guts obtained from larvae of Bacillus thuringiensis-resistant and -susceptible Ostrinia nubilalis. Overall, serine proteinases from soluble fractions of the susceptible strain were more active than those of the resistant strain. The soluble trypsin-like proteinase activity of the resistant strain was approximately half that of the susceptible strain. The number and relative molecular masses of soluble and membrane serine proteinases were different. However, there were no significant differences in the activities of serine proteinases and aminopeptidases extracted from midgut membranes of the two strains. Cry1Ab protoxin hydrolysis by soluble proteinase extracts of the resistant strain was reduced approximately 20–30% relative to that of the susceptible strain. Reduced protoxin processing due to decreased activities of Bt protoxin activation proteinases may be associated with resistance to Bt toxin in this resistant strain of O. nubilalis. [Copyright &y& Elsevier]

The development of genetically modified Bt-corn, incorporating various toxin genes from Bacillus thuringiensis that act as a chemical defense against insect pests, such as the European Corn Borer, provides farmers with a new pest management option. However, the emergence of insect resistance is a threat to the continued use of Bt-corn. The United States Environment Protection Agency (US EPA) has developed planting strategies, for preventing insect resistance by planting a mixture of Bt- and non-Bt-corn. Decisions about the exact proportion of Bt- and non-Bt-corn are based on complex spatially explicit mathematical models using detailed biological assumptions about the population genetics and life history of the European Corn Borer. We develop an alternative simpler model for the spread of resistance based on the logistic growth model, which we believe has utility in situations where it is impossible or impractical to estimate the different life history and genetics parameters required by more detailed models. We use our model to investigate the US EPA’s planting rules for Bt-corn and find that short-term economic behavior is likely to lead to these rules not being followed. Our results add weight to existing work on this problem. We also investigate the economics of planting Bt-corn in markets where consumers do and do not differentiate between the modes of production for the corn. We find that Bt-corn appears to be economic in markets that do not differentiate and uneconomic in markets where consumers do differentiate. [Copyright &y& Elsevier]

We developed a flexible fixed-precision sequential sampling plan for estimating the density of European corn borer, Ostrinia nubilalis Hu¨bner and corn earworm, Helicoverpa zea (Boddie), larvae, using infestation data collected from 1994 to 2000. The purpose of each sampling plan was to provide statistically sound estimates of larval densities for each pest in sweet corn ears, near harvest, with minimal cost. Sweet corn variety plots and commercial production fields were sampled to obtain a wide range of O. nubilalis and H. zea densities typically found in sweet corn, in the Midwestern USA. Sampling parameters were estimated from 84 and 68 data sets for O. nubilalis and H. zea, respectively. An additional 15 independent data sets, for each species, were used to validate the fixed-precision sequential sampling plans with resampling software. Dispersion patterns for O. nubilalis and H. zea were determined to be random and uniform, respectively, from Taylor's power law. For O. nubilalis, at densities of 0.24–4.08 larvae/ear, an average sample number (ASN) of only 38 ears was necessary to achieve a desired precision level (SE/mean) of 0.25. As the precision level was increased to 0.10, average sample size increased to 227 ears. For H. zea, at densities of 0.20–2.05 larvae/ear, an ASN of 27 ears was required to achieve a desired precision level of 0.25. As the precision level was increased to 0.10, sample size increased to 160 ears. The sequential sampling plans will be useful to researchers for quantitative assessment of integrated pest management (IPM) strategies, via rapid estimation of larval density per ear, the primary determinant of IPM efficacy and product quality near harvest. Additionally, these plans can be used to determine the background density necessary for estimating the frequency of O. nubilalis or H. zea larvae found in transgenic Bt sweet corn ears expressing Bacillus thuringiensis proteins. [Copyright &y& Elsevier]

European corn borer Ostrinia nubilalis Hu¨bner (Lepidoptera: Crambidae) larvae that have completed development on Event 176 Bt corn hybids have either survived exposure to sublethal doses of Cry1Ab Bt toxin or exploited plant tissues that do not express the toxin. To evaluate the impact of such exposure on larval establishment and survival, Event 176 plants with and without tassels and a non-Bt isoline were infested with O. nubilalis egg masses during anthesis. On the non-Bt plants, larval establishment occurred primarily on pollen collecting in the leaf axils, silks and ears. In contrast, almost no larvae were recovered from leaf axils of the Bt treatments and at least 50% fewer larvae were recovered from the silks and ears during the first 2 weeks after infestation relative to the non-Bt plants. The larvae recovered from Bt treatments weighed significantly less than those observed in the non-Bt isoline at 4 weeks after infestation. By the eighth week, the larval weights of all three treatments were similar in three of four different field tests, suggesting that second generation larvae have the ability to compensate for initial exposure to sublethal doses of Bt toxin. In laboratory assays involving exposure of neonate larvae to silks of Event 176 and non-Bt corn, survival of neonate O. nubilalis was not different although larval weights were significantly reduced (2- to 6-fold). These results suggest that second generation larvae completing development on Event 176 corn do not completely avoid exposure to the Bt toxin, although those that do survive are able to compensate for these sublethal effects. The implication of these results is that Event 176 hybrids do not appear to satisfy requirements for high dose that are recommended for resistance management purposes. [Copyright &y& Elsevier]

Field trials to evaluate efficacy of two sprayable formulations of a binary pheromone blend of the maize pest Sesamia nonagrioides, were carried out from 1997 to 1999 in Spain, Greece and France. Efficacy was measured through inhibition of trap catches in treated fields and reduction of pest population growth between the first and second generations. Most treated fields showed over a 60% of trap catch inhibition within the 15 days following pheromone application. Reduction of pest population increase was variable in Spain and Greece according to the year, but mostly higher than 60%, and consistently high in France where values were above 65% during the 3 years in all replicates. Pheromone release rate was high during the first 2–3 days following application: less than 20% of the pheromone components sprayed remained on or were adsorbed into leaves 4–5 days after application. The effectiveness of mating disruption to control the S. nonagrioides population was at least as good as chemical application and additionally it is compatible with biological control applied in some areas of southern Europe. [Copyright &y& Elsevier]

The strategy of targeting expression of a constitutively regulated gene to generate H2O2 in the extracellular matrix, to reduce herbivory of the European corn borer (ECB) [Ostrinia nubilalis (Hu¨bner)] was tested by transforming corn with germin, a wheat oxalate oxidase (OXO) gene, regulated by the rice actin promoter elements (pAct-OXO). With two independent transformation events, enzyme activity was stable over seven generations of backcrossing into three maize inbred lines. Enzyme activity remained associated with the cell wall debris fraction of water extracted tissues. Leaf tissue of the germin transgenics had elevated levels of H2O2. In vitro leaf feeding bioassays demonstrated that ECB larvae feeding was significantly reduced and larval growth and development were delayed on all ECB infested germin transgenic lines. This reduced ECB feeding was confirmed under field conditions. Most significantly, stalk tunneling damage, measured at plant harvest, was substantially reduced in all germin transgenic lines. The reduction of tunneling by 50% in the transgenic lines is indicative of lower levels of ECB survival which should be significant in ECB epidemiology. Possible mechanisms of resistance include modifications in plant cell wall chemistry, activation of pathogen resistance genes and effects of H2O2 and germin on insect physiology are discussed. [Copyright &y& Elsevier]

• Pest damage in maize plants can cause electromagnetic material changes in stalks. • Electrical measurement instrument was developed to quantify pest damage in maize. • Link between pest damage and electromagnetic changes statistically shown in maize. The European Corn Borer (ECB), Ostrinia nubilalis, is an agricultural pest which bores small holes in the rind of maize stalks and then proceeds to consume the pith. Because most of the damage to the stalk is internal, it is difficult to quantify the damage to an individual stalk without time-consuming, manual examination. This work focused on determining the feasibility of detecting internal damage using non-destructive, electrical measurements. Laboratory experiments and numerical simulation studies predicted changes in capacitance of stalks due to hollow core ECB damage. A guarded probe device to measure electrical impedance from 500 Hz to 100 kHz was designed and constructed for data collection. A field test with the measurement device was conducted and frequency-swept impedance measurements were taken on field-grown plants with and without ECB damage. Field measurements demonstrated that statistically significant capacitance changes associated with ECB damage could be detected in agreement with numerical simulations of stalk damage. Numerical, laboratory, and field test results all supported the hypothesis that electrical impedance measurements, in particular, capacitance, provide a promising new avenue for ECB damage evaluation. While further research will be needed to further refine this concept, this measurement approach is non-destructive, thus allowing measurements to be performed without sacrificing the infested plants. [ABSTRACT FROM AUTHOR]

The European corn borer (ECB), Ostrinia nubilalis Hübner (Lepidoptera: Crambidae), is a key pest of maize (Zea mays L.). In Northern Italy, larvae of the 2nd generation may damage cobs and kernels and the feeding activity can promote the proliferation of aflatoxigenic fungi, such as Aspergillus flavus , the major producer of aflatoxin B 1 (AFB 1). During 2017–2018, the efficacy of two strategies to control ECB in maize was assessed. Biological control strategy (Trichogramma brassicae Bezdenko and Bacillus thuringiensis Berliner) , conventional chemical strategy (chlorantraniliprole) and an untreated control were compared to assess: i) the effect of the strategies on ECB infestation; ii) the association of ECB and AFB 1 kernels contamination; iii) the impact of the strategies on beneficial arthropods. The conventional chemical strategy demonstrated the best control of ECB infestation, followed by biological control strategy and the untreated control. No significant differences in maize yield were found among strategies. The role of ECB on AFB 1 concentration was demonstrated only in 2017, when higher level of infestations occurred simultaneously with an extended period of drought and high temperatures, sanctioning the important role of meteorological conditions on AFB 1 contamination. The activity density of ground beetles, rove beetles and spiders and the mean number per leaf of the most abundant beneficial insects dwelling on plants (coccinellids, predatory thrips and lacewings) did not show significant changes between pre-and post-treatment with chlorantraniliprole, highlighting the selectivity of this pesticide in the short time. This study provides some contribution for the reduction of non-renewable input in Italian maize fields, demonstrating that biological control strategy, although less effective than conventional chemical control, can be a feasible approach to control ECB second larval generation, without any increment of AFB 1 level in grains and yield loss. In this study, we compared two strategies for controlling the European corn borer (conventional chemical vs biological control) with the purpose to provide the best practice guideline to reduce chemical inputs in maize agroecosystems of Northern Italy. Our results represent a practical contribution for sustainable maize production in Italy, demonstrating that biological control strategy can be feasible in biological system to partially reduce the second larval generation, without any yield loss and increment of AFB 1 in grains. Image 1 • Lower infestation of ECB in conventional chemical strategy. • Biological strategy reduced ECB larval infestation in comparison with control. • Maize yield wasn't significantly affected by ECB control strategies. • Beneficials didn't change between pre and post treatments for ECB control. • Large yearly variation in aflatoxin contamination mostly due to climatic conditions. [ABSTRACT FROM AUTHOR]

• The O. nubilalis orthologs of Ago2, Dcr2, and R2D2 were sequenced and characterized. • Transcripts of all three genes were detected in all stages and tissues. • Comparison of evolutionary distances for domains revealed significant variations. • Injection of ds GFP had no effect on Ago2, Dcr2, or R2D2 expression. • Ingestion of ds GFP could induce up/down-regulation of some transcripts. RNA interference (RNAi) is commonly used in the laboratory to analyze gene function, and RNAi-based pest management strategies are now being employed. Unfortunately, RNAi is hindered by inefficient and highly-variable results when different insects are targeted, especially lepidopterans, such as the European corn borer (ECB), Ostrinia nubilalis (Lepidoptera: Crambidae). Previous efforts to achieve RNAi-mediated gene suppression in ECB revealed low RNAi efficiency with both double-stranded RNA (dsRNA) injection and ingestion. One mechanism that can affect RNAi efficiency in insects is the expression and function of core RNAi pathway genes, such as those encoding Argonaut 2 (Ago2), Dicer 2 (Dcr2), and a dsRNA binding protein (R2D2). To determine if deficiencies in these core RNAi pathway genes contribute to low RNAi efficiency in ECB, full-length complementary DNAs encoding OnAgo2, OnDcr2, and OnR2D2 were cloned, sequenced, and characterized. A comparison of domain architecture suggested that all three predicted proteins contained the necessary domains to function. However, a comparison of evolutionary distances revealed potentially important variations in the first RNase III domain of OnDcr2, the double-stranded RNA binding domains of OnR2D2, and both the PAZ and PIWI domains of OnAgo2, which may indicate functional differences in enzymatic activity between species. Expression analysis indicated that transcripts for all three genes were expressed in all developmental stages and tissues investigated. Interestingly, the introduction of non-target dsRNA into ECB second-instar larvae via microinjection did not affect OnAgo2 , OnDcr2 , or OnR2D2 expression. In contrast, ingestion of the same dsRNAs resulted in upregulation of OnDcr2 but downregulation of OnR2D2. The unexpected transcriptional responses of the core machinery and the divergence in amino-acid sequence between specific domains in each core RNAi protein may possibly contribute to low RNAi efficiency in ECB. Understanding the contributions of different RNAi pathway components is critical to adapting this technology for use in controlling lepidopteran pests that exhibit low RNAi efficiency. [ABSTRACT FROM AUTHOR]