Survival strategies of Dalbulus maidis during maize off‐season in Brazil

Despite the importance of Dalbulus maidis (DeLong & Wolcott) (Hemiptera: Cicadellidae) as a vector of maize‐stunting pathogens, it is not understood how this leafhopper survives the maize off‐season in regions where overwintering hosts do not occur. We investigated migration and the use of alternate hosts as possible survival mechanisms for D. maidis during maize off‐season in Brazil. Dalbulus maidis populations were monitored with yellow sticky cards for 16–29 months in Anastácio (Mato Grosso do Sul State), in two farms with perennial pastures (Pasture1 and Pasture2), where maize had not been planted for >5 years, in a subsistence farm >20 km distant, where maize was annually planted (spring) (Maize1), and in Piracicaba (São Paulo State), where maize was grown year round (Maize2). RAPD‐PCR analysis of leafhoppers sampled on maize in two plots (Maize1 and Pasture1) at 15–20 and 110–120 days after germination was performed. Dalbulus maidis was trapped in the maize plots of all areas, but not in weedy or woody vegetation adjacent to the plots. Higher numbers were trapped throughout the year in Piracicaba, where maize was continuously grown under irrigation, and in the subsistence farm of Anastácio, where volunteer maize plants were available for long periods in the maize off‐season. In Anastácio farms, some population peaks were recorded in the absence of maize from midwinter to early spring, especially after soil plowing. RAPD‐PCR analysis showed that D. maidis populations sampled were genetically similar. Our data suggest that D. maidis uses a mixed strategy to survive the over‐season period in Brazil, in which part of the population overwinters locally on volunteer maize plants or nearby irrigated maize crops, whereas the other individuals migrate to colonize new maize crops in distant areas or regions. We hypothesize that immigrant D. maidis uses the contrast between plowed and vegetated soil as a visual cue for locating new maize crops.     

Population consequences of diapause in a model system: the European corn borer

The diapause biology of the European corn borer (ECB), Ostrinia nubilalis (Hübn.), is described based on natural and controlled environment studies of feral and lab-reared ECB's in North Carolina (NC). The diapause response is described as a function of photophase (h of light/day) as well as a function of larval age (instar) at onset of diapause-inducing conditions. A critical photophase of 14.4 h and a critical mean larval instar of 3.3 is found in the lab studies and supported by three years of insectary studies. Seven years of black light trapping of ECB moths in Goldsboro, NC, revealed the likelihood of up to four moth flights/year.Information about the diapause biology of this insect is used to explain both the number of flights and the relative magnitude of the final moth flights. On average, the majority of ECB lineages pass through three generations/year with early maturing ECB's producing a significant and predictable fourth generation. The timing and magnitude of the fourth flight can be partly explained on the basis of the critical photophase and the timing and age structure of previous ECB generations. In most years, the fourth flight is smaller than the third due to the majority of the fourth generation's predisposition towards diapause. However, in at least one case (1977), the fourth flight was unusually large and could be predicted by slight temporal shifts in the previous three flights resulting in the majority of the fourth generation larvae averting diapause. The value of the ECB-diapause interaction as a model system for the explanation and prediction of dynamic phenological events is discussed.

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Résumé La diapause d'O. nubilalis Hubn. est décrite d'après des études en conditions naturelles et programmées de souches sauvages ou élevées au laboratoire en Caroline du Nord. La diapause est décrite comme une fonction de la photophase (heures de jour/24 heures) et du stade larvaire au début des conditions inductrices de la diapause. Une photophase critique de 14,4 h et un stade critique larvaire de 3,3 ont été établis au laboratoire après 3 ans d'études en insectarium. 7 ans de piégeage à la lumière noire à Goldsboro, ont montré la vraisemblance de l'existence de 4 vols par an. Les données sur la diapause de cet insecte sont utilisées pour expliquer tant le nombre de vols que l'importance relative des derniers vols. En moyenne, la majorité des lignées ont 3 générations par an, O. nubilalis précoces produisant une quatrième génération conséquente et prédictible. La data et l'importance du 4ème vol peuvent être partiellement expliquées d'après la photophase critique, et la data et la structure en âge des générations précédentes. La plupart des années, le 4ème vol est moins important que le 3ème par suite de la prédisposition à la diapause de la majorité de la 4ème génération. Cependant, dans un cas au moins, en 1977, le 4ème était anormalement important et pouvait être prédit par de faibles changements temporels dans les 3 précédents vols, détournant de la diapause la majorité des chenilles de 4ème génération. La discussion porte sur la valeur du modèle fourni par la diapause de O. nubilalis pour expliquer et prédire la dynamique des évéments phénologiques.

     

Biosorption of oxybenzene using biosorbent prepared by raw wastes of Zea mays and comparative study by using commercially available activated carbon

Organic pollutants present in waste water have undesirable effect on the environment. Industry activities are the key sources of organic pollutants. Prime pollutants released from various sources react instantly with the environment and become derived (secondary) pollutants, which stay for an elongated time. The present research work has been carried out using biosorbent prepared from various Zea mays wastes for elimination of oxybenzene. Different parameters viz contact time, initial concentration; adsorbent dose, temperature and pH were optimized for the biosorption of oxybenzene on to the biosorbent samples. BCS (Baby corn silk) showed higher percentage of biosorption at optimum contact time of 3 h, pH between 5 and 6 and temperature at 25 °C. Analysis of equilibrium biosorption data in terms of several isotherm models revealed that Langmuir isotherm and Freundlich isotherm indicates better agreement with the experimental data. The kinetics of oxybenzene biosorption on to the biosorbents was described with the pseudo-first-order model. Thermodynamic parameters indicated that biosorption onto biosorbent was feasible in nature, spontaneous, and endothermic for some biosorbents, but on contrary not feasible, exothermic and non spontaneous for other biosorbents. The result of this study showed that the biosorbent derived from Zea mays can be used as a prospective biosorbent for oxybenzene in wastewater and also can be an alternative for the commercially activated carbon.     

Landscape genetic analyses reveal host association of mitochondrial haplotypes in the Asian corn borer,Ostrinia furnacalis

Crop expansion often leads to high pest pressure. These pests may have fitness trade-offs related to host use, and some host-associated genotypes may benefit and increase in frequency. However, evidence concerning the effect of host availability on spatial distribution and frequency of mitochondrial haplotypes is scarce. We studied genetic variation of the Asian corn borer, Ostrinia furnacalis (Guenée), across a large area during 2 years (2016 and 2017). Mitochondrial sequence data were obtained from 530 individuals collected from 79 locations in Shandong Province, China. In total, 155 haplotypes were found based on the combined cytochrome oxidase subunit 1 (COI) and COII genes. Three haplotypes (H2, H12, and H23) were dominant, whereas most of the other haplotypes occurred in low frequency. A haplotype network showed that the 155 haplotypes can be grouped into three clusters. Haplotype clusters seemed to be randomly distributed. The frequency of H12 (in Cluster 1) was positively correlated with maize crop proportion, but negatively correlated with other crops (primarily vegetables, oilseed crops, and cotton) at all spatial scales (1-, 3-, and 5-km radius). Cluster 2 had haplotype H23, and this cluster was negatively correlated with semi-natural habitats. Cluster 3 had no dominant haplotype and was not affected by landscape factors. We conclude that H12 may be a maize-associated haplotype. Further study is needed to verify the possibility that the carriers of this haplotype may possess some fitness trade-offs. Our study highlights the importance of host availability in O. furnacalis haplotype distribution and frequency.     

玉米田三种螟虫转移为害规律及防治对策

通过连续７年的定点、定时系统观察，对春、夏玉米田桃蛀螟、玉米螟和高粱条螟幼虫的不同虫龄、不同世代，以及随玉米生育期变化的转移为害规律作了详细的调查研究，并提出了科学的防治对策。     

Immunoelectron microscopic localization of calmodulin in corn root cells

Methods for the localization of plant calmodulin by immuno-gold and immuno-peroxidase electron microscopy have been developed. In both corn root-cap cells and meristematic cells, calmodulin was found to be localized in the nucleus, cytoplasm, mitochondria as well as in the cell wall, In the meristematic cells, calmodulin was distinctly localized on the plasma membrane, cytoplasmic face of rough endoplasmic rcticulum and polyribosomes. Characteristically, calmodulin was present in the amyloplasts of root-cap cells. The widespread distribution of calmodulin may reflect its plciotropic functions in plant cellular activities.     

Isolation of 4-acetyl-benzoxazolin-2-one (4-ABOA) and diferuloylputrescine from an extract of gibberella ear rot-resistant corn that blocks mycotoxin biosynthesis, and the insect toxicity of 4-ABOA and related compounds

Bioassay-directed fractionation of an extract of a gibberella ear rot-resistant corn hybrid resulted in the isolation of a fraction that inhibited mycotoxin production, but not growth, of Fusarium culmorum. The fraction contained diferuloylputrescine and a new allelochemical 4-acetyl-benzoxazolin-2-one (4-ABOA). This report describes the isolation of the bioactive fraction and tests of the effect of 4-ABOA on 3-acetyl deoxynivalenol (3ADON) and aflatoxin production. In addition, data are reported on the effects of 4-ABOA and related compounds on a number of insect species and some preliminary studies on the mechanism of insect toxicity. The effect of 4-ABOA on F. culmorum and Apergillus flavus was similar. Production of toxin was reduced without a concomitant reduction of growth. A 50% inhibition of 3ADON production occurred at ca. 4 μM and 0.12 mM for alfatoxin. 4-ABOA was slightly toxic to Spodoptera frugiperda.     

Immunofluorescent localization of a substance immunologically related to insulin in the protocerebral neurosecretory cells of the European corn borer

Summary A substance immunologically related to mammalian insulin was demonstrated by immunofluorescence in one of five types of neurosecretory cells in the protocerebrum of the European corn borer, Ostrinia nubilalis. This A₂ cell type contains a secretory material stainable with paraldehyde fuchsin.E.R.A. CNRS n° 850