Insect Pests Of Maize Research Articles

Phytochemistry and insecticidal activity of Annona mucosa leaf extracts against Sitophilus zeamais and Prostephanus truncatus

A new oleanane type triterpene characterized as 3α, 24-diacetoxy-12-oleanene (1) together with known compounds 2-10, were isolated from Annona mucosa leaf extracts. Their structural elucidation was accomplished using physical and spectroscopic methods. The compounds showed weak to moderate insecticidal activities against stored maize insect pests Sitophilus zeamais and Prostephanus truncatus.

Azotobacter chroococcum inoculation can improve plant growth and resistance of maize to armyworm, Mythimna separata even under reduced nitrogen fertilizer application.

Nitrogen (N) is essential to crop yield improvement and it can change crops' ability to defend against herbivores. To maximize economic yield, a higher amount of N-fertilizer is often applied than the minimum required. Azotobacter is a good alternative to reduce N fertilizer application. In this study, we studied the yield and secondary defensive chemicals of maize, as well as the response of the key maize insect pest, Mythimna separata, as fed on maize plants inoculated with Azotobacter chroococcum and cultivated at different N fertilizer rates (i.e. the control rate of nitrogen fertilizer (CR), 80%CR and 60%CR) from 2018 to 2019. A. chroococcum inoculation just positively increased yield production of maize at 80%CR. Moreover, reduced N-fertilizer application and A. chroococcum inoculation had opposite impacts on the foliar contents of jasmonic acid (JA), isoleucine conjugate of JA (JA-Ile) and DIMBOA in maize, and they both negatively decreased the pupation rate and fecundity, and positively increased the eclosion rate and approximate digestibility (AD) of M. separata (P < 0.05). Furthermore, reduced N-fertilizer application negatively prolonged larval life-span, and decreased pupal weight, relative growth rate (RGR), efficiency of conversion of ingested food (ECI) and efficiency of conversion of digested food (ECD) of M. separata even A. chroococcum inoculation had positive effects on these indexes of M. separata (P < 0.05). These results help in understanding of the effects of low-level N-fertilizer and A. chroococcum inoculation on maize production and maize resistance to insects. This will be conducive to the integrated control of agricultural pests. © 2020 Society of Chemical Industry.

Effects of a Reserve Protein on Spodoptera frugiperda Development: A Biochemical and Molecular Approach to the Entomotoxic Mechanism.

Talisin is a storage protein from Talisia esculenta seeds that presents lectin-like and peptidase inhibitor properties. These characteristics suggest that talisin plays a role in the plant defense process, making it a multifunctional protein. This work aimed to investigate the effects of chronic intake of talisin on fifth instar larvae of Spodoptera frugiperda, considered the main insect pest of maize and the cause of substantial economic losses in several other crops. The chronic intake of talisin presented antinutritional effects on the larvae, reducing their weight and prolonging the total development time of the insects. In addition, talisin-fed larvae also showed a significant reduction in the activity of trypsin-like enzymes. Midgut histology analysis of talisin-fed larvae showed alterations in the intestinal epithelium and rupture of the peritrophic membrane, possibly causing an increase of aminopeptidase activity in the midgut lumen. Talisin also proved to be resistant to degradation by the digestive enzymes of S. frugiperda. The transcription profile of trypsin, chymotrypsin and aminopeptidase genes was also analyzed through qPCR technique. Talisin intake resulted in differential expression of at least two genes from each of these classes of enzymes. Molecular docking studies indicated a higher affinity of talisin for the less expressed enzymes.

Evaluation of the Field Efficacy of Heterorhabditis Bacteriophora Poinar (Rhabditida: Heterorhabditidae) and Synthetic Insecticides for the Control of Western Corn Rootworm Larvae.

The western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte (Coleoptera, Chrysomelidae), is an important insect pest of maize in North America and Central and Eastern Europe. In Central Europe, the larvae emerge in May and its three instars feed intensively on maize roots in June, causing plant lodging that leads to a loss of economic yield. A three-year field experiment (2016–2018) was conducted to compare the effectiveness i) of soil-applied granular insecticide based on the active ingredient tefluthrin, ii) of maize seeds dressed with thiacloprid, and iii) entomopathogenic nematodes Heterorhabditis bacteriophora Poinar (Rhabditida: Heterorhabditidae, product Dianem) against WCR larvae. An additional treatment with alcohol ethoxylate (i.e., soil conditioner) mixed with entomopathogenic nematodes was performed in 2017 and 2018 to check for any increase of entomopathogenic nematodes’ effectiveness. Field tests were carried out in two fields infested naturally with a WCR pest population, one in Bučečovci (Eastern Slovenia) and the other in Šmartno pri Cerkljah (northern Slovenia), exhibiting dissimilar pedo-climatic conditions and soil pest densities. The treatments were performed in five replicates per experiment in each year. The efficacy of the treatments was very similar at both locations, despite the approximately five-fold lower WCR soil pest densities in northern than in eastern Slovenia, as well as being constant over time. The largest number of WCR beetles was observed in the negative control, followed by that of beetles subjected to thiacloprid treatment (insignificant decrease taking into account the entire three-year dataset). Treatments with tefluthrin (44.1 ± 11.7%), H. bacteriophora (46.2 ± 7.4%), and H. bacteriophora + alcohol ethoxylate (49.2 ± 1.8%) significantly decreased the numbers of emerging beetles. Treatments of thiacloprid, H. bacteriophora, and H. bacteriophora + alcohol ethoxylate additionally led to significantly increased maize plant weights. Furthermore, entomopathogenic nematodes were able to persist in maize fields for almost five months at both experimental locations in silty and sandy loam soils. It was concluded that the control of WCR larvae in maize using the entomopathogenic nematode H. bacteriophora is as effective as a tefluthrin treatment, and could thus offer a sustainable Diabrotica v. virgifera biological control management option in Europe.

Reproductive performance of the larger grain borer Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) on three different food hosts

The reproductive performance, damage and weight loss of the Larger Grain Borer (LGB), Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) on three food hosts namely cassava (TMS 30572, TME 419 and TMS98/0505), maize (SUWAN-1-SR-Y, BR 9943-DMR-SR and 2009 TZEWDT STR) and wood (Albizia glaberrima, Gmelina arborea and Tectona grandis) were investigated. Samples of 100g of the food host were weighed in four replicates into 250ml Kilner® jar and infested with 10 pairs of 1-5 day old LGB. The developmental period of LGB on each of the food host was noted and recorded. Similarly, weight loss and weight of damaged grains was determined as basis for determining the susceptibility of the food hosts to LGB infestation. Proximate composition of infested and un- infested food hosts of LGB were determined following the analytical procedures. Maize was the most preferred host, followed by cassava as indicated by the high number of adult LGB and grain damage recorded on them. The development of LGB was completed on all maize and cassava varieties but not on any of the wood species examined. Percent damage, weight loss, and percent dust were significantly (P&lt;0.05) different among the food hosts. The mean percent damage (79.0), percent weight loss (57.0) and percent dust (25.0) recorded in cassava variety-TMS30572 was significantly (p&lt;0.05) higher than on other food hosts. No weight loss was recorded on T. grandis. This study revealed the ability of P. truncatus to breed and feed on the maize and cassava varieties with no evidence of breeding on the three wood species. Carbohydrate contents were higher in the most preferred food host, maize (70.91) and less preferred food, cassava (82.02) than non-preferred wood species (13.56), indicating that carbohydrate was an essential component in most preferred food. Infestation of LGB caused significant reduction (P&lt;0.05) in the nutritional component of the food hosts. This study showed that LGB still remains an economically important insect pest of maize and cassava. Considering the importance of these two crops to the livelihood of smallholder farmers, appropriate monitoring and control measures should therefore be put in place to safe guard maize and cassava from the ravages of this pest for the attendant enhancement of food security in Nigeria.

Egg-Laying Pattern of Helicoverpa zea1 in Sweet Corn: A New Pest Management Prospect

The corn earworm, Helicoverpa zea (Boddie), is a major insect pest of maize (Zea mays L.), cotton (Gossypium hirsutum L.), and vegetable crops. Maize silk is a favorite egg-laying site of H. zea. However, other parts of the maize plant might be even more attractive for oviposition by H. zea. Under field conditions and in insect-proof cages in a greenhouse, egg-laying distribution patterns were assessed on a late and an early sweet corn cultivar, i.e., Java (Technisem) and Garrison (Syngenta), respectively. Maize tassels on both cultivars were the main egg-laying sites of the pest. In insect-proof cages, at the maize silking stage, more than 60% of the total number of eggs collected were on tassels. In the field, oviposition by H. zea began at tassel emergence, and more than 80% of the total number of eggs were collected from tassels. Egg distribution on leaves and silk varied according to the sweet corn cultivar. The findings offer new prospects to control H. zea. The tassel emergence stage is the best period for controlling H. zea in maize fields and the best phenological stage to use maize as a trap crop for the pest.

Attraction of Chelonus insularis to host and host habitat volatiles during the search of Spodoptera frugiperda eggs

Egg parasitoids use different strategies than do larval parasitoids to locate hosts. The wasp Chelonus insularis Cresson is a key egg parasitoid of the fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith), one of the main insect pests of maize (Zea mays L.). Using a Y-glass tube olfactometer, in this study we determined the roles of chemical cues from host and host habitats used by C. insularis when they search for FAW eggs. We found that C. insularis females were attracted to volatiles emitted by host egg masses, host females (i.e., sex pheromone), and maize seedlings with and without FAW eggs. The responses of the parasitoids to host and maize seedling volatiles increased after their first oviposition experience, making it possible for females to discriminate between maize seedlings with and without FAW eggs. The information generated in this study may be useful in the development of future biological control programs of S. frugiperda using C. insularis in either augmentation or conservation approaches.

Transcriptome and differentially expressed genes of Busseola fusca (Lepidoptera: Noctuidae) larvae challenged with Cry1Ab toxin

Busseola fusca (Fuller) (Lepidoptera: Noctuidae), a major insect pest of maize in sub-Saharan Africa, has developed high levels of non-recessive resistance to Cry1Ab toxin expressed in genetically modified Bt maize. Multiple resistance mechanisms to various Cry toxins have been identified in Lepidoptera, but no study has yet been done to determine the mechanism of Cry1Ab resistance in B. fusca. Therefore, the larval transcriptome of B. fusca was sequenced, de novo assembled and characterized. Differential expression analysis was performed to compare gene expression profiles of Cry toxin challenged and unchallenged neonate larvae to assess the molecular basis of the defence mechanism employed by this insect. Several genes associated with Cry toxin resistance in other lepidopteran pests were detected in B. fusca. Results suggest that differential expression of metabolic and immune-related genes might explain Cry1Ab toxin defence in this pest (supplemental file). Transcript expression profiles of neonates demonstrated that 33.59% and 60.31% of the 131 differentially expressed genes were upregulated and downregulated in the toxin-challenged neonate larvae, respectively. Transcripts were grouped into two subclusters according to the similarity of their expression patterns. Transcripts in subcluster 1 were moderately upregulated in the toxin-challenged neonate larvae, and, conversely, downregulated in the unchallenged neonate larvae. The solute carrier organic anion transporter, which is involved in insecticide detoxification, was upregulated in the toxin-challenged neonate larvae. Conversely, most of the transcripts in subcluster 2 were moderately downregulated in the toxin-challenged neonate larvae, and upregulated for neonates feeding on non-challenged maize. Four unidentified transcripts were extremely down-regulated in the toxin-challenged neonate larvae, and upregulated in the unchallenged neonate larvae. Further studies are recommended to establish if there is a direct correlation between these differentially expressed genes and the observed resistance. Elucidation of such defence mechanisms is crucial for developing insect resistance management strategies to ensure sustainable use of genetically modified maize in Africa. Nevertheless, this is the first study on gene expression profiles of B. fusca strains challenged with Cry toxin. The transcriptome characterized in this study provides a significant resource base for future studies on B. fusca and contributes to understanding some of the gene regulation and signalling networks involved in the defence of B. fusca against Cry1Ab toxin.

Farmers’ indigenous knowledge and management of insect pests in Maize and Tomato crops at West Hararghe Zone, Oromia Region, Ethiopia

The survey involved 207 purposely selected farmers (Key Informants (KI) and Focus Group Discussion (FGD) who were interviewed using structured questionnaires. Majority of the farmers estimated that the insects, the most serious pest infesting maize and tomato crops, mainly were army worm, maize stalk borer, and African ball worm on maize and spider mite, white fly, and African ball worm on tomato crop. Averagely from all the study areas, more than 25.9% of the farmers make use of cultural control method when comparing with chemical insecticides. Only 12.0% had access to chemical insecticides in controlling of insect pests of both the crops. Most of discussants traditionally used by adding various particles like ash, urea, soils and botanical extracts such as tobacco, garlic, Datura (banji), green pepper and also soap particles (66.6 and 18.5% from Darolebu and 29.7 and 4.7% from Chiro districts), respectively. From all the study areas, 26.40% respondents were used mechanically by the removal of infested plants in the fields. But 14.3% of respondents were not used any traditional methods.

Damage Assessment and Management of Armyworm [Mythimna separata, Walker] in Winter Maize at Rampur, Chitwan

Mythimna separata Walker commonly known as armyworm (Rice Ear-Cutting Caterpillar), belonging to Lepidoptora: Noctuidae is one of the major insect pests of maize in Nepal. Application of selective pesticide is mostly used approach to control the pest population to minimize its possible damage. A field experiment was carried out to find out the loss by armyworm in maize field (variety RML32/17) during winter season of 2016/17. The experiment was laid under Randomized Complete Block Design with eight treatments and three replications in the research field of National Maize Research Program (NMRP), Rampur. The treatments consisted of: i) Metarrhizium anisopliae ii) Nuclear Polyhedrosis Virus iii)Spinosad iv)Furadon v) Magik vi)Lara-909 vii) Multineem viii) Control. The treatments were applied three times at 30DAS, 45DAS and 60DAS for each replication and armyworm damaged plants were counted after a week of application among the 30 sample plants tagged in each plot. Number of damaged plants by armyworm after each spraying and maize yield in each plot were recorded and analyzed by GenStat. It was found that least number of plants were damaged in plots applied with treatments Lara-909, subsequently followed by Spinosad while more plants were damaged successively in control and M. anisopliae. The highest average yield (6.73 ton/ha) was found in Lara-909 treated plot followed by Spinosad (6.67 ton/ha) which were significant with the lowest average yield found in control (5.76 ton/ha) but only statistical at par with rest of the treatments. Spinosad (Natural product of Saccharopolyspora spinosa) was found to be the best alternative of chemical pesticides for the eco-friendly management of armyworm.

Bio-Rational Management of Armyworm (Mythimna separata) (Lepidoptera: Noctuidae) in Chitwan Condition of Nepal

The armyworm, Mythimna separata Walker is the potential insect pest of maize, causes a severe damage on the vegetative and reproductive stages of that plant. Insecticides are the common practices to manage the broad categories of the pest in a maize field. Further, these practices have been linked to farmers health, biodiversity loss and declining of predatory arthropods. However, pest management by adopting a tool of integrated pest management is one potential option to reduce the pesticide in maize fields. Field experiments were conducted in winter maize with the aim of evaluating the potential bio-rational pesticides to manage the armyworm. The studies were conducted for two consecutive years in 2015/16 and 2016/17 at Rampur, Chitwan. Treatments were: Metarrhizium anisopliae (0.2ml/lit water), Nuclear Polyhedrosis Virus (NPV) ( 2.5gm/lit water), Spinosad 45% SC (0.25ml/liter of water), Multineem (Azadriachta indica) (2 .0 ml/ liter water), Furadan 3G (3-4g/ Whorl application), Lara (Chloropyriphos 50 EC + Cypermethrin 5 EC) (1.0 ml/liter of water), Magik (Imidacloprid 17.8% (0.5ml/liter of water) and Control. The experiments were completely randomized block design with three replicates. Spinosad treated plots demonstrated the lowest damage (0.884%) followed by Magik (1.27%) which was significantly lower (P&lt; 0.05) than other treatments in 2015/2016. However, in 2016/2017, Spinosad treated plot also showed the significantly lowest damage (1.67%) followed by Lara plots (2.67%), both of these were significantly different (P&lt; 0.05) to Metarhizium and control plots, but similar to the other treatments, but not significantly so. Maximum yield was recorded in spinosad treated plots (9.8 t/ha and 9.12 t/ha) followed by Lara treated plots (9.17t/ha and 8.69t/ha) and were lowest in control plots (4.55 t/ha and 7.18 t/ha) for both years. Hence, Spinosad (soil actinomycete bacterium, Saccharopolyspora spinose ) has the potentiality to maximize the maize yield and also potentially to the reduce the pesticide consumption and incurred cost caused by the pesticide use. Such a safe and eco-friendly insecticide has the potential to replace the synthetic pesticide and provide the benign environment to the natural predators and service providing units of multiple ecosystem services in maize agro-ecosystem.

On-farm maize insect pest and mycotoxin levels in Ghana: Presentation

Maize post-harvest losses are perennial in Ghana but reliable comparative information on on-farm losses of maize produced in the Middle and Northern Belts of Ghana is lacking. Two studies were conducted from September 2015 to February 2016 to identify factors contributing to on-farm losses of maize in these two Belts. In the Northern Belt, the study was conducted in six communities including Adubiyili, Diari, Pong-Tamale, Savelugu, Toroyili and Zamnayili; and in the Middle Belt, in Ejura, Sekyedumase and Amantin communities. Moisture content, percent weight loss, percent insect damaged kernels (IDK) on numerical basis (%IDKnb) and percent IDK by weight basis (%IDKwb), insect pest abundance, and mycotoxin levels were estimated. Moisture content values of maize at pre-harvest and heaping stages in all nine communities were below 15%. Sitophilus zeamais, Sitotroga cerealella, Cathartus quadricollis, and Carpophilus dimidiatus were found to attack maize onfarm in communities in the Middle Belt, but no adult insect pests were collected on pre-harvested maize in the Northern Belt. The %IDKnb values on-farm in all nine communities were < 2% per 250 g. Mean aflatoxin levels below 15 ppb were obtained from pre-harvested maize in both regions but levels above 15 ppb were obtained from heaped maize on-farm. Fumonisin levels of maize were below 4 ppm on pre-harvested and in heaped maize in both regions. Results show that heaping maize on-farm increases aflatoxin levels beyond the acceptable threshold level and should not be practiced.

Diversity and distribution of lepidopteran stemborer species and their host plants in Botswana

Lepidopteran stemborers are amongst the most important insect pests of maize, sorghum and sugarcane in sub-Saharan Africa. With the exception of Chilo partellus (Swinhoe), which was accidentally introduced into Africa, the other stemborer pests are indigenous to the continent and have co-evolved with native grasses and sedges. In addition to pest species, wild habitats harbour diverse non-economic stemborer species, some of which are new to science. However, the diversity and distribution of both non-economic and pest species of stemborer are currently mostly unknown in Botswana. Accordingly, country-wide surveys were conducted during 2014/15 and 2015/16 austral summer to determine species diversity and distribution in cultivated and wild host plants of stemborers in Botswana. A total of 1597 stemborer larvae and 228 pupae were collected, constituting 63.1 and 36.9 larvae and 84.8 and 15.2% pupae from cultivated versus wild habitats, respectively. In addition to C. partellus, Sesamia calamistis Hampson and Eldana saccharina Walker which were previously reported, 12 more stemborer species were recorded for the first time in Botswana, including nine undescribed species. These species were from the Sciomesa, Sesamia and Conicofrontia genera and Tortricidae and Pyralidae families. Fourteen wild host and two cultivated host plant species of stemborers were recorded. Chilo partellus was most abundant (89.5%) in cultivated habitats whilst E. saccharina (33.6%) was most abundant in wild habitats. Stemborer species diversity was higher in wild habitats than cultivated. Current results highlight the significance of wild, especially wetland habitats for ecological functions and conservation of lepidopteran stemborer biodiversity.

Development and characterization of the first dsRNA-resistant insect population from western corn rootworm, Diabrotica virgifera virgifera LeConte.

The use of dsRNA to control insect pests via the RNA interference (RNAi) pathway is being explored by researchers globally. However, with every new class of insect control compounds, the evolution of insect resistance needs to be considered, and understanding resistance mechanisms is essential in designing durable technologies and effective resistance management strategies. To gain insight into insect resistance to dsRNA, a field screen with subsequent laboratory selection was used to establish a population of DvSnf7 dsRNA-resistant western corn rootworm, Diabrotica virgifera virgifera, a major maize insect pest. WCR resistant to ingested DvSnf7 dsRNA had impaired luminal uptake and resistance was not DvSnf7 dsRNA-specific, as indicated by cross resistance to all other dsRNAs tested. No resistance to the Bacillus thuringiensis Cry3Bb1 protein was observed. DvSnf7 dsRNA resistance was inherited recessively, located on a single locus, and autosomal. Together these findings will provide insights for dsRNA deployment for insect pest control.

Mapping of Quantitative Trait Loci for Resistance to Fall Armyworm and Southwestern Corn Borer Leaf‐Feeding Damage in Maize

Fall armyworm [FAW, Spodoptera frugiperda (J. E. Smith)] and southwestern corn borer (SWCB, Diatraea grandiosella Dyar) are damaging insect pests of maize (Zea mays L.) that result in significant yield and economic losses. A previous study identified quantitative trait loci (QTL) that contribute to reduced leaf‐feeding damage by these insects in the maize mapping population created by crossing Mp704 (resistant) × Mo17 (susceptible). The current study reports a more complete map by adding 151 simple sequence repeat (SSR) and single‐nucleotide polymorphism markers to the original map of 73 SSRs for QTL analysis. Composite interval mapping (CIM) identified 24 QTL explaining up to 26.5% of the total phenotypic variation (chromosome bin 9.03), and multiple interval mapping (MIM) identified 36 QTL (including five new QTL found compared with the previous study) and 10 interactions for FAW leaf‐feeding damage. Twenty‐nine QTL explaining up to 29% of the total phenotypic variation (chromosome bin 7.02) were identified using CIM for SWCB leaf‐feeding damage, and 21 QTL (including five new QTL) and 11 interactions were identified using MIM for this trait. The addition of significantly more markers to the previously reported map allowed for the identification of new QTL and a better assessment of QTL positions and effects, which can improve breeding applications and the detection of candidate genes controlling FAW and SWCB resistance.

Population dynamics of stored maize insect pests in warehouses in two districts of Ghana

Understanding what insect species are present and their temporal and spatial patterns of distribution is important for developing a successful integrated pest management strategy for food storage in warehouses. Maize is stored in bags in warehouses in many countries in sub-Saharan Africa, but little monitoring information is available on insect activity in those warehouses. We monitored the populations of major post-harvest insect pests of maize at three different warehouses (MiDA, Gundaa and Wienco) in two regions in Ghana (Middle Belt and Northern Belt). The study was conducted from September 2015–July 2016, which represents a common maize harvest and storage period in the two regions. The most abundant insect pest found in the warehouses was Plodia interpunctella (Hübner), but other major pest species were recovered during the study. Sitotroga cerealella (Oliver) and Prostephanus truncatus (Horn) which are major pests on farms, were more likely to be captured in traps outside or at nearby farms than inside the warehouses. When recovered inside they tended to be found in the receiving and cleaning areas. Sitophilus spp. were commonly captured in the warehouses, but were more abundant in the Middle Belt warehouse. Our results identified the major species found during warehouse storage of maize in Ghana and suggest that the specific pest species may be different in warehouses compared to on-farm storage.

Diversity and abundance of lepidopteran stem borers and their host plants in Ethiopia

AbstractLepidopteran stem borers are among the most important insect pests of maize, sorghum and sugarcane in sub‐Saharan Africa. Except for Chilo partellus, the other stem borer pests in Ethiopia are indigenous to Africa and are assumed to have coevolved with some native grasses and sedges in the natural habitat. In addition to pest species, natural habitats harbour diverse non‐economic stem borer species, some of which are new to science. However, with the growing threats to natural habitats, some non‐economic stem borer species may switch or expand their host ranges to include cultivated crops and evolve as “new” pests. Besides host switch, some of the unknown species currently limited to natural habitats may disappear. We examined the diversity, abundance and interactions of lepidopteran stem borers and their wild host plants in five different vegetation mosaics in Ethiopia. The stem borer species diversity varied among vegetation mosaics and host plants. Forty‐four stem borer species belonging to 14 different genera in the families of Noctuidae, Crambidae, Pyralidae and Tortricidae were recorded from 34 wild host plants and through light trap. Among these families, Noctuidae was the highest in species richness in which 31 species were identified, out of which 15 species and two genera were new to science. This paper discusses the ecological interpretation of host plant–stem borer species interactions, particularly in relation to habitat disturbances.

The effect of knockdown of insulin receptor substrates 1 and 2 on glucose and lipid metabolism in human hepatoblastoma cells

The European corn borer (Ostrinia nubilalis) is one of the most important insect pests of maize, and has a significant impact on the production of this crop. In this work, we examined the effects of different insecticides on the antioxidative defense system of O. nubilalis larvae. The experimental setup consisted of a completely randomized block design with 4 replicates. Four experimental groups were formed as follows: control (C), indoxacarb (250 mL ha-1), chlorantraniliprole (100 mL ha-1) and the chlorantraniliprole+lambda cyhalothrin (200 mL ha-1) group. Larvae from maize stems were collected 20 days after insecticide application and the whole larvae were homogenized. The activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione S-transferase (GST), and the total amount of free SH groups were assessed. Comparison of the experimental groups showed that indoxacarb significantly affected the activities of GST, GPx and the total amount of free SH groups, while chlorantraniliprole significantly affected the activities of SOD, CAT, GST and the total amount of free SH groups, while chlorantraniliprole+lambda cyhalothrin significantly affected the activities of CAT, GST and the total amount of free SH groups. The results show that exposure to insecticides considerably affects the antioxidative defense components of the European corn borer larvae, especially chlorantraniliprole (T2).

Lespesia postica: A New Report as a Parasitoid ofSpodoptera frugiperdaat Chiapas, México

Fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), is the most important insect pest of maize, Zea mays L., because it causes great economic loss and insecticide to be overused for its control, which increase costs of production and contaminate the environment. However, the pest is naturally controlled by various parasitoids of the Tachinidae family. Here, we report molecular identification of a new species of the genus Lespesia parasitizing larvae of S. frugiperda in the central region of Chiapas, Mexico.

Do Refuge Plants Favour Natural Pest Control in Maize Crops?

The use of non-crop plants to provide the resources that herbivorous crop pests’ natural enemies need is being increasingly incorporated into integrated pest management programs. We evaluated insect functional groups found on three refuges consisting of five different plant species each, planted next to a maize crop in Lima, Peru, to investigate which refuge favoured natural control of herbivores considered as pests of maize in Peru, and which refuge plant traits were more attractive to those desirable enemies. Insects occurring in all the plants, including the maize crop itself, were sampled weekly during the crop growing cycle, from February to June 2011. All individuals collected were identified and classified into three functional groups: herbivores, parasitoids, and predators. Refuges were compared based on their effectiveness in enhancing the populations of predator and parasitoid insects of the crop enemies. Refuges A and B were the most effective, showing the highest richness and abundance of both predators and parasitoids, including several insect species that are reported to attack the main insect pests of maize (Spodoptera frugiperda and Rhopalosiphum maidis), as well as other species that serve as alternative hosts of these natural enemies.