Comparative susceptibility of two different hosts to genotypic variants of the Anticarsia gemmatalis nuclear polyhedrosis virus

The susceptibility of third instar larvae of Anticarsia gemmatalis (Lepidoptera: Noctuidae) and Diatraea saccharalis (Lepidoptera: Pyralidae) to ten distinct plaque purified genotypic variants of a selected isolate of the Anticarsia gemmatalis multiple-embedded nuclear polyhedrosis virus (AgMNPV), was compared. Despite the fact that this isolate, AgMNPV-Ds20, represents a wild strain of the AgMNPV selected for higher virulence to D. saccharalis, an alternate host, most of the variants are much more virulent to the original host Anticarsia than to Diatraea. Bioassays have shown an over one hundred-fold variation in LD₅₀ values ranging from 1700 polyhedron inclusion bodies (PIBs) to more than 200 000 PIBs/larva. The PIB production in infected larvae increased with the pathogenicity of the variant to the host, showing an average ten-fold reduction in Diatraea when compared to Anticarsia for the same variant. The virus particle yield ranged from 6×10⁷ to more than 10⁹ PIBs/g of infected larvae in Diatraea and from 8×10⁸ to more than 10¹⁰ PIBs/g of infected Anticarsia larvae. The data show a clear difference of the pathogenicity of the genotypic variants of AgMNPV in vivo both between the original and alternate host and between the individual variants for the same host. These differences found in vivo indicate that monitoring of shifts in variant frequency of wild and laboratory-propagated viral isolates in these highly heterogeneous populations would help ensure the efficacy of biological control programs.     

Comparison of some properties of the high-affinity juvenile hormone binding protein from the larval hemolymph of pyralid moths

The properties of the high-affinity low molecular weight juvenile hormone (JH) binding protein present in the hemolymph of larvae of five species of pyralid moths, a noctuid moth, and a sphingid moth were compared. The pyralid moths exhibit a facultative diapause as last-instar larvae. The species employed were the southwestern corn borer, Diatraea grandiosella, the southern cornstalk borer, Diatraea crambidoides, the sugarcane borer, Diatraea saccharalis, the European corn borer, Ostrinia nubilalis, the sunflower moth, Homoeosoma electellum, the cabbage looper, Trichoplusia ni, and the tobacco hornworm, Manduca sexta. The binding characteristics of the proteins were determined using saturation binding assays and competitive binding assays. The dissociation constants of JH I, JH II, and JH III for the binding protein of all the species varied from 0.8 x 10^?7 M to 2.8 x 10^?7 M. Calibrated gel filtration showed that the binding protein of all the species had apparent molecular weights ranging from 29,000 to 31,000. Electrophoresis in 7% acrylamide gels revealed that the relative mobilities of the binding proteins ranged from 0.33 to 0.43. Isoelectric focusing showed that the binding proteins had isoelectric points between 4.4 and 5.0.     

Feasibility of using an alternative larval host and host plants to establish Cotesia flavipes (Hymenoptera: Braconidae) in the temperate Louisiana sugarcane ecosystem

Attempts to establish Cotesia flavipes Cameron (Hymenoptera: Braconidae) in Louisiana sugarcane fields to control the sugarcane borer, Diatraea saccharalis (F.) (Lepidoptera: Crambidae) have been unsuccessful. Experiments were conducted to investigate the feasibility of using an alternative larval host and host plants to overcome barriers preventing establishment. In addition, we evaluated C. flavipes' ability to search for D. saccharalis in sugarcane without above-ground internodes. Diatraea evanescens Dyar (Lepidoptera: Crambidae) was investigated as an alternative host for C. flavipes. Cotesia flavipes was reared for five generations on D. evanescens without any indication of diminishing fitness as measured by days to parasite pupation and average cocoon mass weight. However, there was a significant reduction in percent parasitism, cocoon mass weight, and percent emergence when C. flavipes parasitized D. evanescens as compared with D. saccharalis, resulting in a 75% reduction in the gross reproductive rate (R(0)). Greenhouse studies indicated little difference in parasitism of D. saccharalis on the weed hosts johnsongrass, Sorghum halepense (L.), and vaseygrass, Paspalum urvillei Steud. However, when planted as refuge plots, we found it difficult to establish infestations of D. saccharalis in either of these hosts, or in two energy sugarcanes. After 3 yr of infesting host plants and releasing parasitoids only one parasitized D. saccharalis larvae was recovered within the johnsongrass refuge. Diatraea evanescens readily established in vaseygrass; however, these larvae appear inaccessible to C. flavipes. In contrast, parasitism of D. saccharalis by C. flavipes infesting young sugarcane was 30%.     

Influence of weather conditions and density of Doru luteipes (Dermaptera: Forficulidae) on Diatraea saccharalis (Lepidoptera: Crambidae) egg mortality

The influence of weather factors and the predator Doru luteipes Scudder density on Diatraea saccharalis (F.) egg predation was studied. Mortality of D. saccharalis eggs was determined by artificially infesting maize plots with egg masses at various times within each of two maize-growing seasons. Each egg cohort was monitored every 24-48 h to determine the fate of eggs, and predation rates were calculated. Doru luteipes were sampled every 7-10 d, and the mean air temperature, the minimum percentage of relative humidity, and rainfall accumulations were recorded during the egg exposure period. To test the effects of abiotic and biotic variables on egg predation, we used a generalized linear model (GLM). Diatraea saccharalis egg predation was negatively associated with rainfall, whereas D. luteipes density and mean temperature were positively correlated with mortality. The implications of these findings for the management of D. saccharalis are discussed.     

An immunochemical study of the diapause-associated protein of the southwestern corn borer,Diatraea grandiosella

The distribution and titre of the diapause-associated protein (DAP), which accumulates in the fat body of diapausing larvae of the southwestern corn borer, Diatraea grandiosella, were determined using an antibody raised to the purified protein. Immunoblotting and immunodiffusion showed that the highest concentration of DAP was present in the fat body. Small amounts of the protein were present in the haemolymph and even lower levels were detected in other tissues. Rocket immunoelectrophoresis showed that DAP accumulated in the fat body at the beginning of diapause, reached a plateau, and gradually declined towards the end of diapause. Similarly, the titre of DAP in last instar non-diapausing larvae treated with a JH analogue increased, reached a plateau and then declined. Double immunodiffusion and immunoblotting using the DAP-antibody and extracts of the fat body of D. grandiosella and the southern cornstalk borer, Diatraea crambidoides, and the sugarcane borer, Diatraea saccharalis, revealed the partial immunochemical identity of the DAP of D. grandiosella and a protein present in these two species. Denaturing electrophoresis with immunoblotting showed that the DAP-related proteins of D. crambidoides and D. saccharalis have apparent molecular weights of 33,000 and 36,000, respectively, as compared to a molecular weight of 35,000 for DAP of D. grandiosella. A dot blot analysis showed that no cross reaction occurred between the “diapause proteins” present in the haemolymph of adults of the Colorado potato beetle, Leptinotarsa decemlineata, and the DAP of D. grandiosella.     

Organization of the retrocerebral gland system in lepidopterous larvae of the family pyralidae

The organization of the retrocerebral gland system in larvae of six species of Lepidoptera belonging to the family Pyralidae was compared using light and electron microscopy. We have demonstrated for the first time the presence of separate corpora cardiaca and corpora allata in the following economically important borers: the southwestern corn borer, Diatraea grandiosella, the sugar cane borer, Diatraea saccharalis, the European corn borer, Ostrinia nubilalis, and the rice stalk borer, Chilo plejadellus. In these species a long nervus corporis allati (ca. 300 μm) runs from the corpus cardiacum to the corpus allatum which is attached to the duct of the mandibular gland.The identity of the corpora allata of D. grandiosella was confirmed by transplantation. Corpora allata removed from pre-diapausing larvae and implanted into the haemocoele of early last stage non-diapausing larvae led to a high incidence of supernumerary larval rather than pupal ecdyses.     

Mise en évidence d'une densonucléose chezDiatraea saccharalis [Lep.: Pyralidae]

Résumé Ravageur important de la canne à sucre, le LépidoptèreDiatraea saccharalis F. est sensible à une virose de type densonucléose. Le virus se multiplie intensément dans les noyaux des cellules de différents tissues, comportant de l'ADN et mesurant 22 mμ, il peut être rangé parmi lesParvovirus et attribué au genreDensovirus.

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Summary Diatraea saccharalis is a pest of sugar cane crop and is susceptible to a virus disease of the densonucleosis type. The virus multiplies in the cell nuclei of different tissues, it contains DNA and measures 22 mμ. It may be included in theDensovirus genus of Parvoviruses.

     

Conventional resistance of experimental maize lines to corn earworm (Lepidoptera: Noctuidae), fall armyworm (Lepidoptera: Noctuidae), southwestern corn borer (Lepidoptera: Crambidae), and sugarcane borer (Lepidoptera: Crambidae)

Plant resistance is a useful component of integrated pest management for several insects that are economically damaging to maize, Zea mays L. In this study, 15 experimental lines of maize derived from a backcross breeding program were evaluated for resistance to corn earworm, Helicoverpa zea (Boddie); fall armyworm, Spodoptera frugiperda (J. E. Smith); southwestern corn borer, Diatraea grandiosella Dyar; and sugarcane borer, Diatraea saccharalis (F.). Experimental line 100-R-3 was resistant in the field to leaf feeding by fall armyworm and line 116-B-10 was resistant in the field to leaf feeding by fall armyworm and leaf and stalk feeding by southwestern corn borer. When corn earworm larvae were fed field harvested silks from experimental line 81-9-B in the laboratory, their pupal weights were significantly lower than the pupal weights of larvae that were fed silks from the resistant control, Zapalote Chico. Maysin levels lower than those commonly associated with corn earworm resistance were present in the resistant experimental line, 107-8-7, indicating a new basis confers resistance to corn earworm in this line. These resistant experimental lines will provide plant breeders with new sources of resistance to lepidopterous insects for the development of improved maize breeding populations.     

Polyunsaturated fatty acid and sterol requirements of the southwestern corn borer, Diatraea grandiosella

The southwestern corn borer, Diatraea grandiosella, was reared on a meridic diet and its lipid requirements were determined. A dietary supplement of wheat germ oil was found to contain factors which were essential for larval growth and normal wing development. An investigation into the nature of these factors showed that linoleate or linolenate promoted normal wing development whereas β-sitosterol enhanced the larval growth rate.     

Organ culture of the terminal abdominal segment of an adult female lepidopteron

Summary Organ cultures containing the sex pheromone gland ofDiatraea saccharalis (F.) (sugarcane borer) were maintained for over 2 months. Juvenile hormone but not ecdysterone appeared to be essential for the maintenance of integrity of the sex pheromone gland in the organ culture system. Muscles associated with these cultures pulsated during hte entire culture period with or without juvenile hormone, suggesting that the hormone requirement was specific for the sex pheromone gland and not a general requirement of the cells of the organ-cultured segment.     

Morphometry of the midgut epithelium of Diatraea saccharalis Fabricius, 1794 (Lepidoptera) parasitized by Cotesia flavipes Cameron, 1891 (Hymenoptera)

The morphometric study of the midgut in Diatraea saccharalis (Lepidoptera) larvae parasitized by the Cotesia flavipes (Hymenoptera) showed that there was significant increase in the columnar, goblet and regenerative cells and their nuclei; the midgut lumen diameter and the epithelial height were also increased in the parasitized larvae. The multivariate analysis showed that parasitism affected the columnar cell only in the posterior region, and the goblet cells along the midgut length (anterior and posterior regions).     

Natural presence of Beauveria bassiana (Balsamo) Vuillemin in the sugar cane (Saccharum sp. hybrid) in Cuba

The natural presence of Beauveria bassiana was determined (Balsamo) Vuillemin from insects with mycotic symptoms collected in leaves and in the stalks of sugar cane (Saccharum sp. hybrid) in Pinar del Río, Ciudad de la Habana, Habana, Matanzas, Villa Clara, Cienfuegos and Camagüey. The results obtained demonstrate the natural presence of the entomopathogen fungus in larvae and chrysalises of Diatraea saccharalis (Fabricius) and they suggest the basis for the strategy of biological control against this borer.     

Wolbachia infection dynamics in experimental laboratory populations of Metaseiulus occidentalis

The present study examined the acceptability and suitability of Old World stemborers (Chilo partellus and C. orichalcociliellus) for the development of New World parasitoids (Apanteles deplanatus and A. minator) and New World stemborers (Diatraea saccharalis and D. grandiosella) for the development of Old World parasitoids (Cotesia sesamiae, C. flavipes and C. chilonis). Results revealed that acceptance and suitability were high in old associations. In new associations, parasitoids accepted about 60% of the new association hosts. In addition, 10 out of 17 new associations were successful. Apanteles species appeared to be more physiologically host specific than Cotesia species. For example, two of four new association hosts were accepted by A. deplanatus and only one (D. saccharalis) was partially suitable for progeny development. Among the Cotesia species, Cotesia flavipes appeared to have a wider host range than the two other species. It attacked all hosts offered and successfully parasitized all but one (D. grandiosella). Diatraea saccharalis was accepted and was a suitable host for the development of all parasitoid species tested, whereas D. grandiosella was unsuitable for the development of four out of five parasitoid species tested. No clear pattern was observed as behavioral acceptance did not always agree with the pattern of physiological suitability. Implications of these findings for importation biological control of stemborers are discussed.     

小蔗螟Cytb基因序列的分析研究(鳞翅目:螟蛾总科:草螟亚科)

扩增并测定了小蔗螟线粒体细胞色素b(Cyt b)基因,其序列全长1146 bp,利用分子生物学软件分析了包括小蔗螟在内的4目(鳞翅目、双翅目、鞘翅目、缨尾目)共19条Cyt b基因序列.分析结果显示:鳞翅目昆虫AT含量明显低于其它昆虫,其中小蔗螟AT含量为75.1%;AT含量与A或T碱基使用的偏倚没有明显的相关性;碱基替换主要发生在密码子第三位,并且颠换率远大于转换率;密码子使用频率与基因碱基组成AT偏倚有相关性;相比于核苷酸数据,氨基酸所显示的遗传距离更为准确;使用Cyt b基因构建的系统进化树支持昆虫的单源进化学说.     

Selection and characterization of mexican strains ofBacillus thuringiensis active against four major lepidopteran maize pests

In order to isolate novel delta-endotoxins fromBacillus thuringiensis Berliner, a total of 426 native isolates (in varying numbers for each pest) were screened against four major maize pests: corn earworm,Helicoverpa zea; fall armyworm,Spodoptera frugiperda; southwestern corn borer,Diatraea graridiosella, and sugarcane borer,Diatraea saccharalis. Spore-crystal complexes from the isolates were integrated into semi-artificial diets of each pest and mortality was assessed 7 days after treatment. A total of 25 isolates were selected on the basis of highest larval mortality against at least one insect species. There was no correspondence of the most toxic isolates when tested against the four different insect species. Most of the 25 selected isolates caused higher toxicities against all four pests than the standard strain HD-1, regardless of not achieving 100% mortality in any bioassay.H. zea demonstrated the highest level of mortality (96%) and was susceptible to the largest number of isolates (98). None of the other insect species were found susceptible at levels greater than 60%. All the selected active strains were isolated from stored grain dusts (except for LBIT-167), and had bipyramidal crystals with Cry I-like proteins. Most isolates also formed an associated square (cubic) inclusion, with Cry Il-like proteins according to SDS-PAGE analysis of their parasporal bodies. The most active isolates will be subjected to further studies, in order to identify putative novel genes to be expressed in transgenic maize     

Competition of <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> Cry1 Toxins for Midgut Binding Sites: A Basis for the Development and Management of Transgenic Tropical Maize Resistant to Several Stemborers

Binding and competition of five Bacillus thuringiensis toxins—Cry1Ab, Cry1Ac, Cry1Ba, Cry1Ca, and Cry1Ea—for midgut binding sites from three pests, Spodoptera frugiperda, Diatraea saccharalis, and Diatraea grandiosella, were investigated as part of a strategy to develop tropical transgenic maize resistant to several stemborers. On S. frugiperda, Cry1Ab and Cry1Ac compete for the same binding site; Cry1Ba and Cry1Ca compete for a second binding site. Cry1Ea recognizes a third specific binding site in S. frugiperda and does not compete with any of the other toxins. On D. grandiosella and D. saccharalis, Cry1Ac competes with Cry1Ab and not with Cry1Ba and Cry1Ca. Cry1Ba and Cry1Ca recognize each a specific binding site and do not compete with any of the other four toxins. Cry1Ea does not recognize any binding site on Diatraea species. Combinations of toxins are proposed to develop transgenic maize resistant to the three stemborers while allowing resistance management.     

Population dynamics of caterpillars on three cover crops before sowing cotton in Mato Grosso (Brazil)

Direct seeding mulch-based cropping systems under a preliminary cover crop such as millet are common in some areas of Brazil. Lepidopteran pests that damage cotton, soybean and maize crops can proliferate on cover crops, so preventive chemical treatments are necessary. Very little data is available on these pests on cover crops. This paper presents the dynamics of Spodoptera frugiperda, S. eridania, Mocis latipes and Diatraea saccharalis caterpillars monitored at Primavera do Leste, Mato Grosso state (Brazil) during the of 2005/2006 and 2006/2007 cropping seasons on four cover crops, i.e. finger millet (Eleusine coracana), pearl millet (Pennisetum glaucum), sorghum (Sorghum bicolor) and ruzigrass (Brachiaria ruziziensis). The pests were visually counted on plants within a 1 m2 transect (wooden frame). Caterpillars were reared to facilitate identification of collected species and parasitoids. Many S. frugiperda caterpillars were observed on millet in 2005, with a maximum of 37 caterpillars/m2. On sorghum, we found 30 caterpillars/m2, or 0.83 caterpillars/plant. The Diatraea borer attacked sorghum later than the other pests. M. latipes was also observed on millet. The millet cover crop had to be dried for at least 1 month before direct drilling the main cotton crop in order to impede S. frugiperda infestations on cotton plantlets, thus avoiding the need for substantial resowing. The comparative methodological aspects are discussed.     

Ant predation of larval Diatraea saccharalis Fab. (Lep., Crambidae) in new sugarcane in Brazil

Abstract: Ant predation of natural field populations of larval sugarcane borers, Diatraea saccharalis , was evaluated by using insecticidal check techniques, and through survivorship studies of artificial high-density infestations, in plantations in Brazil. Areas of ant suppression had higher levels of D. saccharalis than unsuppressed areas, although both types of areas normally had extremely low D. saccharalis populations. Artifical infestations of D. saccharalis yielded significantly lower larval survivorship in unsuppressed areas than in suppressed areas. Fire ants ( Solenopsis spp.) were always the most abundant ant. This study has demonstrated that ants are important pest predators in Brazilian sugarcane fields.     

Pathogens associated with southwestern corn borers and southern corn stalk borers (Lepidoptera: Crambidae)

A study was undertaken to isolate entomopathogens of southwestern corn borer, Diatraea grandiosella Dyer, and southern corn stalk borer, Diatraea crambidoides (Grote). Field-collected diapausing larvae of southwestern corn borer (three sites in Mississippi) and southern corn stalk borer (one site in North Carolina), and a laboratory strain of D. grandiosella in the diapause state were maintained in a simulated winter followed by a simulated spring environnent. Few larvae (< or = 6%) collected from any of the field sites died in the winter environment, and most insect mortality (11-25%) occurred after transfer of the larvae to the simulated spring environment. Mortality during the simulated spring period differed among the collection sites, and the highest mortality was recorded for southwestern corn borers from Washington County (25%), followed by Marshall (16%) and Oktibbeha (11%) Counties. A high level of mortality was also observed in southern corn stalk borers during the simulated spring period (27%). No viruses were observed, but a number of bacteria, microsporidia, and fungi were isolated from both southwestern corn borer and southern corn stalk borer larvae and pupae. In most instances, numerous bacterial taxa were isolated from cadavers, but on some occasions a single taxon predominated. The most prevalent bacterial taxon from larval and pupal cadavers was Enterococcus faecalis (Andrewes & Horder) Schleifer & Kilppel-Balz, but Bacillus spp., Pseudomonas aeruginosa (Schroeter) Migula, and Serratia marcescens Bizio were frequently isolated as well. Few fungi (1-7%) were recovered from southwestern corn borer and southern corn stalk borer larvae and pupae. The most common entomopathogenic taxon isolated was Beauveria bassiana (Balsamo) Vuillemin from southern corn stalk borer larvae. Microsporidia were not isolated from southern corn stalk borers. However, Nosema spp. were isolated from southwestern corn borer cadavers from Washington (15%), Marshall (1%), and Oktibbeha (3%) Counties in Mississippi. In addition, we observed parasitism of southern corn stalk borer larvae by Macrocentrus cingulum Reinhard (Hymenoptera: Braconidae). No parasitism of southwestern corn borers was observed. Isolates of Bacillus, Beauveria, Entercoccus, Nosema, Pseudomonas and Serratia were all pathogenic to southwestern corn borer larvae under controlled environmental conditions, and with the exception of B. bassiana, these are novel pathogens of Diatraea corn borers.     

DNA barcode information for the sugar cane moth borer Diatraea saccharalis

We reviewed the use and relevance of barcodes for insect studies and investigated the barcode sequence of Diatraea saccharalis. This sequence has a high level of homology (99%) with the barcode sequence of the Crambidae (Lepidoptera). The sequence data can be used to construct relationships between species, allowing a multidisciplinary approach for taxonomy, which includes morphological, molecular and distribution data, all of which are essential for the understanding of biodiversity. The D. saccharalis barcode is a previously undescribed sequence that could be used to analyze Lepidoptera biology.