Tool For Biological Control Research Articles

Efecto de Steinernema sp. sobre larvas de Ancognatha scarabaeoides (Coleoptera: Scarabaeidae) en condiciones de laboratorio e invernadero

En la última década, por su amplia distribución mundial, selectividad y efectividad en el control de insectos plaga, organismos como los nematodos que parasitan insectos (entomonemátodos) han jugado un papel fundamental como herramientas del control biológico en programas de manejo integrado de plagas (MIP). El objetivo del presente trabajo fue evaluar el efecto de Steinernema sp. sobre larvas de Ancognatha scarabaeoides en laboratorio e invernadero. El nematodo se obtuvo de larvas infectadas por A. scarabaeoides encontradas en campo en los municipios de Yacuanquer y Ospina (Nariño, Colombia) una importante zona productora de papa. Para la evaluación de eficacia in vitro, se colocó una larva de A. scarabaeoides en una suspensión de 3 ml de nematodos a diversas concentraciones (1, 5, 15, 30, 50, 100 y 150 nemátodos/ml). El porcentaje acumulado de mortalidad de las larvas de A. scarabaeoides 18 días después de la inoculación fue de 100% y 90% con las concentraciones de 150 y 100 nematodos/ ml respectivamente y a una concentración letal 90 (CL90) de 87 nematodos/ml. En invernadero Steinernema sp. se evaluó a las concentraciones letales 50 (CL50) y 90 (CL90), presentando a los 15 días de aplicados los tratamientos porcentajes de mortalidad de larvas de 33,3% y 79,3%, respectivamente. Este resultado abre la posibilidad de incluir este biocontrolador nativo en el manejo integrado de chisas en el departamento de Nariño.

Plant volatiles: new perspectives for research in Brazil

Agroecosystems consist on complex trophic relationships among host plants, herbivores and their natural enemies. This article reviews the research of plant volatiles in Brazil, in order to determine multiple resistance mechanisms of economically important crops and to contribute to the understanding of insect-plant interactions. Most pest management programs, including chemical and biological control, do not consider the impact of these chemicals on herbivores and their natural enemies. Alternative control methods are being developed in order to improve our understanding on the endogenous mechanisms of plant induced defenses against phytophagous arthropods. The use of plant volatiles technology as an additional tool in integrated pest management programs would offer a new and environmentally sound approach to crop protection. This technique involves the development of baits that attract beneficial organisms and the manipulation of biochemical processes that induce and regulate plant defenses, key factors in the improvement of control programs against economically important pests. The elucidation of the mechanisms involved in the indirect defenses of plants will result in useful tools for biological control of crop pests.

Biological control of Canada thistle in temperate pastures using high density rotational cattle grazing

Extensive research exists on the eVects of Canada thistle [Cirsium arvense (L.) Scop.] (CT) in annual cropland, but few studies have examined CT impacts on pasture and rangeland. While it is known that grazing impacts weed presence and abundance, little is understood about how speciWc grazing systems can be used as a prescriptive tool to alter weed populations, including CT. The purpose of this study was to experimentally test three cattle grazing systems, including (1) continuous or season-long grazing (SL), (2) short duration (SD) (or low intensity-high frequency) rotational grazing, and (3) high intensity-low frequency (HILF) rotational grazing, for their ability to reduce CT and release non-CT herbage within permanent pastures of central Alberta, Canada. A secondary objective was to evaluate season-long changes in the quality of CT shoots as potential forage throughout the growing season. Results showed that SL grazing maintained or increased severe CT infestations and reduced forage yield. In contrast, the HILF rotational system reduced CT shoot density and biomass, as well as Xowering, and resulted in greater weed suppression than the SD system. Two intense defoliations annually over 2–3 years nearly eliminated CT stems. Remaining CT shoots were also primarily vegetative and greater in forage quality under HILF grazing. As a weed biological control tool for CT, prescribed grazing with an HILF system may be particularly important in areas where other control options, including the use of herbicides, are not possible due to environmental restrictions or inaccessibility to equipment.

Effect of Conservation Strips on the Abundance and Distribution of Natural Enemies and Predation of <I>Agrotis ipsilon</I> (Lepidoptera: Noctuidae) on Golf Course Fairways

Habitat manipulation in the form of beetle banks and flowering insectary strips has been a successful method to increase natural enemy and alternative prey abundance. In this study, beetle banks and flowering insectary strips were combined to create conservation strips as refuge for a variety of natural enemies in golf course ecosystems. Conservation strips were installed in the roughs next to golf course fairways. Pitfall traps were used to monitor the abundance of predatory, parasitoid, alternative prey, and pest insects in the roughs and fairways near conservation strips and in roughs and fairways without conservation strips (controls). In addition, Agrotis ipsilon (Hufnagel) larvae were placed in the roughs and fairways to evaluate the effect of conservation strips on the predation of pests. Conservation strips were successful at increasing predator, parasitoid, and alternative prey abundance in golf course fairways and roughs overall. Increases were most evident within 4 m of conservation strips. Moreover, predation of A. ipsilon larvae was greater in fairways adjacent to conservation strips than fairways adjacent to roughs only. Differences in predation did not correspond to differences in predator abundance in the fairways, suggesting “predator abundance” may not be the most reliable estimate of the effect of habitat manipulations. These results suggest conservation strips could be an important new tool in conservation biological control on golf courses and may be applicable in other agro-ecosystems. Other methods of estimating and enhancing the effects of conservation strips are discussed.

Transgenic ice nucleation-active Enterobacter cloacae reduces cold hardiness of corn borer and cotton bollworm larvae

The ice nucleation (IN) gene iceA of Erwinia ananas 110 was integrated into the chromosomes of two Enterobacter cloacae strains (Enc1.2022 and Enc1.181). These two newly derived transgenic strains, designated Enc2022-I and Enc181-I, respectively, possessed ice nucleation activity at −2.5 °C, significantly higher than their parent strains (active at approx −10 °C or lower). After ingesting these transgenic bacteria, the mean supercooling points (SCPs) of corn borer and cotton bollworm larvae were −3 to −4 °C, significantly higher than those of untreated controls. The SCPs remained significantly elevated over the 9-day period after ingestion, which matched well with the efficient gut colonization of the bacteria during this period. All treated larvae froze and eventually died after exposure for 6 h to a temperature of −7 °C, and more than 95% died after 12 h at −5 °C. In contrast, few or none of the untreated control larvae froze and died under the same conditions. Furthermore, the growth ability of these transgenic ice nucleation-active (INA) En. cloacae strains on corn leaves was reduced, compared to that of wild-type epiphytic E. ananas, as revealed by pot tests conducted in both greenhouse and outdoor conditions. The stable colonization in insect guts and their lower affinity to plants would make these transgenic INA bacteria useful as a novel tool for biological control of insect pests in agricultural fields.

Lack of infection of vertebrate cells by the densovirus from the maize worm Mythimna loreyi ( MlDNV)

Several densoviruses have been used successfully in biological control of pests in the tropics. The densovirus from Mythimna loreyi ( MlDNV) could also be an important tool in biological control of important pests. However, safety concerns remain as previous reports suggested that densoviruses may infect and transform L cells (from mouse). In this study, we show using molecular-biology tools that neither L nor other vertebrate cells support replication or transcription of densovirus, either after infection or after transfection. Quantitative PCR indicated no increase of viral DNA due to replication in vertebrate cells, in contrast to that in insect LD652 cells. After transfection, both the NS and VP mRNAs could be detected in LD652 cells but not in L cells. Moreover, the viral genome was excised from the plasmid after transfection of the infectious clone in LD652 cells, indicative of viral NS protein production, in contrast to L cells. The viral genome was able to integrate in the host chromosome of L cells after transfection, but not after infection. However, no viral transcription could be detected after integration.

Enhancing parasitism of wheat aphids through apparent competition: a tool for biological control

As cereal aphids are only present during 2–3 months per year in cereal crops, their parasitoids rely on alternative hosts to complete their life cycle. These parasitoids often have the same aphid hosts, which leads to apparent competition. Development on alternative host may increase parasitoid abundance and consequently increase their pressure on cereal aphids. Intensive agriculture frequently reduces the availability of non-crop habitats where alternative aphids may be present. The apparent competition hypothesis was examined in two traditional wheat plots compared to two other plots, with strips of alternative host aphids on leguminosae (red clover and alfalfa) and graminae (ryegrass and meadow fescue). In June/July, parasitism on wheat aphids ( Metopolophium dirhodum, Sitobion avenae, and Rhopalosiphum padi) was higher in 1998 than in 1997, in all the plots studied. During summer 1998, significantly more parasitised wheat aphids were found in strip-designed plots than in the controls, and this higher parasitism rate was positively correlated to a higher parasitoid activity during May, due to the presence of alternative hosts. The interaction between wheat aphids in summer and aphids in the strips in spring is an example of apparent competition, mediated by shared parasitoids. Alternative hosts allow parasitoids to increase their numbers and consequently to apply a higher pressure on aphids in wheat crops.

Biological control tools for wastewater reclamation and reuse. A critical review

The health related risk of wastewater reclamation and reuse is usually defined by laws, rules or regulations by using only biological tools; i.e. bacteria, viruses, or other pathogens or indicators determination. Those determinations exert some influence in the costs of the mentioned practices, and it seems probable that in the near future more determinations will be required. Nevertheless, a total indication of wastewater biological quality is not given by such organisms; in fact, long-term toxicity is not detected by such means. The future of biological control of reclamation and reuse systems and the price associated to such determinations is examined through a practical application case.

Recombination in Wolbachia.

Wolbachia are widely distributed intracellular bacteria that cause a number of reproductive alterations in their eukaryotic hosts. Such alterations include the induction of parthenogenesis, feminization, cytoplasmic incompatibility, and male killing [1-11]. These important bacteria may play a role in rapid speciation in insects [12-14], and there is growing interest in their potential uses as tools for biological control and genetic manipulation of pests and disease vectors [15-16]. Here, we show recombination in the Wolbachia outer surface protein gene (wsp) between strains of Wolbachia. In addition, we find a possible ecological context for this recombination. Evidence indicates either genetic exchange between Wolbachia in a parasitoid wasp and in the fly that it parasitizes or horizontal transfer of Wolbachia between the parasitoid and the fly, followed by a recombination event. Results have important implications for the evolution of these bacteria and the potential use of Wolbachia in biological control.

Characterization of a Viral EPS-Depolymerase, a Potential Tool for Control of Fire Blight

ABSTRACT A 3.3-kb fragment of genomic DNA from bacteriophage Phi-Ea1h encoding an amylovoran-directed depolymerase lyase was sequenced, and three open reading frames (ORFs) were detected. The first ORF could encode a lysozyme and the second a holin that may form a pore supporting cell lysis by the lysozyme. The third ORF encodes a protein of 657 amino acids and deletion mutation in this DNA fragment abolished extracellular polysaccharide (EPS)-degrading activity. A putative promoter and a ribosome binding sequence were located in front of the gene. A polymerase chain reaction product spanning the gene was inserted into multi copy plasmids including fusions with a Histidine-tagged sequence to facilitate its purification on a nickel nitrilotriacetic acid column. Maximal activity of the purified protein was observed between pH 4 and 5 at 52 degrees C. Visualized by staining with fluorescein isothiocyanate-labeled lectin from Abrus precatorious, the enzyme degraded the EPS-capsules of Erwina amylovora. In virulence assays, no symptoms were detected for a low inoculum of an E. amylovora strain when pear slices were soaked in a solution of depolymerase in contrast to control slices without addition of the enzyme. Furthermore, gfp- or lux-labeled E. amylovora cells were not propagated, when their amylovoran capsules were removed by the depolymerase. The enzyme could be a tool for biological control of fire blight.

Site-selective cyclic AMP analogs provide a new approach in the control of cancer cell growth

Site-selective cyclic AMP analogs bind to site 1 or site 2 of the known cAMP-binding sites depending on the position of substituents on the purine ring, either at C-2 and C-8 (site 1) or at C-6 (site 2). The growth inhibitory effect of such site-selective cAMP analogs used in this investigation with 15 human cancer cell lines surpassed that of analogs previously tested. The most potent analogs were 8-chloro, N 6-benzyl and N 6-phenyl-8- p-chlorophenylthio-cAMP. The combination of a C-8 with an N 6 analog had synergistic effects. The 24 site-selective analogs tested produced growth inhibition ranging from 30 to 80% at micromolar concentrations with no sign of toxic effects. Growth inhibition was not due to a block in a specific phase of the cell cycle but paralleled a change in cell morphology, an increase of the R II cAMP receptor protein and a decrease of p21 ras protein. Since the adenosine counterpart of the 8-chloro analog produced G 1 synchronization without affecting the R II and p21 ras protein levels, it is unlikely that an adenosine metabolite is involved in the analog effect. Site-selective cAMP analogs thus provide a new biological tool for control of cancer growth.

INTENTIONAL CONTROL OF GENE EXPRESSION BY TEMPERATURE USING THE REPRESSOR-PROMOTER SYSTEM OF BACTERIOPHAGE LAMBDA

We investigated a gene expression system which could be regulated by temperature manipulation to develop a biological tool for intentional control of microbial processes. For this purpose we used a...

Sea urchin pathogen: a possible tool for biological control

A sea urchin pathogen recently exerted great impact on the Nova Scotia near-shore community by releasing large areas of habitat to seaweed colonization and growth. The pathogen has promise for use as a tool for biological control because it is virulent, apparently species specific, can be maintained and transferred in the laboratory, and is waterborne. The purpose of this study was to demonstrate that it could be transferred from the laboratory to the field. This was accomplished in a reciprocal transplant experiment. Sea urchins from 2 sites 3.5 km apart were brought to the laboratory; one group was exposed to the disease-causing agent and the other served as control. Both groups were returned to the field but released at opposite sites. Sea urchins naturally occurring near the release of the exposed sea urchins developed disease symptoms within 4 wk; and by 8 wk when the temperature became too low for transfer of disease, diseased sea urchins were found as far as 120 m from the release site. No disease occurred at the control site by 8 wk or in S additional areas within a few kilometers of the 2 release sites