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Madhiyazhagan P.,Bharathiar University | Murugan K.,Bharathiar University | Kumar A.N.,Periyar University | Nataraj T.,Bharathiar University | And 12 more authors.
Parasitology Research | Year: 2015

Mosquito-borne diseases represent a deadly threat for millions of people worldwide. Furthermore, pathogens and parasites polluting water also constitute a severe plague for populations of developing countries. In this research, silver nanoparticles (AgNP) were synthesized using the aqueous extract of the seaweed Sargassum muticum. The production of AgNP was confirmed by surface plasmon resonance band illustrated in UV–vis spectrophotometry. AgNP were characterized by FTIR, SEM, EDX, and XRD analyses. AgNP were mostly spherical in shape, crystalline in nature, with face-centered cubic geometry, and mean size was 43–79 nm. Toxicity of AgNP was assessed against Aedes aegypti, Anopheles stephensi, and Culex quinquefasciatus. In laboratory, AgNP were highly toxic against larvae and pupae of the three mosquito species. Maximum efficacy was observed against A. stephensi larvae, with LC50 ranging from 16.156 ppm (larva I) to 28.881 ppm (pupa). In the field, a single treatment with AgNP (10 × LC50) in water storage reservoirs was effective against the three mosquito vectors, allowing complete elimination of larval populations after 72 h. In ovicidal experiments, egg hatchability was reduced by 100 % after treatment with 30 ppm of AgNP. Ovideterrence assays highlighted that 10 ppm of AgNP reduced oviposition rates of more than 70 % in A. aegypti, A. stephensi, and C. quinquefasciatus (OAI = −0.61, −0.63, and −0.58, respectively). Antibacterial properties of AgNP were evaluated against Bacillus subtilis, Klebsiella pneumoniae, and Salmonella typhi using the agar disk diffusion and minimum inhibitory concentration protocol. AgNP tested at 50 ppm evoked growth inhibition zones larger than 5 mm in all tested bacteria. Overall, the chance to use S. muticum-synthesized AgNP for control of mosquito vectors seems promising since they are effective at low doses and may constitute an advantageous alternative to build newer and safer mosquito control tools. This is the first report about ovicidal activity of metal nanoparticles against mosquito vectors. © 2015, Springer-Verlag Berlin Heidelberg.

Boina D.R.,National Institute of Plant Health Management | Bloomquist J.R.,University of Florida
Pest Management Science | Year: 2015

By 2014, huanglongbing (HLB), the most destructive disease of citrus, and its insect vector, the Asian citrus psyllid (ACP), Diaphorina citri (Kuwayama), became established in all major citrus-growing regions of the world, including the United States, with the exception of California. At present, application of insecticides is the most widely followed option for reducing ACP populations, while application of antibiotics for suppressing HLB disease/symptoms is being practiced in some citrus-growing regions. Application of insecticides during the dormant winter season, along with cultivation of HLB-free seedlings and early detection and removal of symptomatic and asymptomatic trees, has been very effective in managing ACP. Area-wide management of ACP by application of insecticides at low volume in large areas of citrus cultivation has been shown to be effective in managing HLB and reducing management costs. As insecticide resistance is a major problem in sustainable management of ACP, rotation/alternation of insecticides with different chemistries and modes of action needs to be followed. Besides control of the insect vector, use of antibiotics has temporarily suppressed the symptoms of HLB in diseased trees. Recent efforts to discover and screen existing as well as new compounds for their antibiotic and antimicrobial activities have identified some promising molecules for HLB control. There is an urgent need to find a sustainable solution to the HLB menace through chemical control of ACP populations and within HLB-infected trees through the judicious use of labeled insecticides (existing and novel chemistries) and antibiotics in area-wide management programs with due consideration to the insecticide resistance problem. © 2014 Society of Chemical Industry.

Grover M.,Indian Central Research Institute for Dryland Agriculture | Madhubala R.,National Institute of Plant Health Management | Ali S.Z.,Agri Biotech Foundation | Yadav S.K.,Indian Central Research Institute for Dryland Agriculture | Venkateswarlu B.,Indian Central Research Institute for Dryland Agriculture
Journal of Basic Microbiology | Year: 2014

Microorganisms isolated from stressed ecosystem may prove as ideal candidates for development of bio-inoculants for stressed agricultural production systems. In the present study, moisture stress tolerant rhizobacteria were isolated from the rhizosphere of sorghum, pigeonpea, and cowpea grown under semiarid conditions in India. Four isolates KB122, KB129, KB133, and KB142 from sorghum rhizosphere exhibited plant growth promoting traits and tolerance to salinity, high temperature, and moisture stress. These isolates were identified as Bacillus spp. by 16S rDNA sequence analysis. The strains were evaluated for growth promotion of sorghum seedlings under two different moisture stress conditions (set-I, continuous 50% soil water holding capacity (WHC) throughout the experiment and set-II, 75% soil WHC for 27 days followed by no irrigation for 5 days) under greenhouse conditions. Plate count and scanning electron microscope studies indicated successful root surface colonization by inoculated bacteria. Plants inoculated with Bacillus spp. strains showed better growth in terms of shoot length and root biomass with dark greenish leaves due to high chlorophyll content while un-inoculated plants showed rolling of the leaves, stunted appearance, and wilting under both stress conditions. Inoculation also improved leaf relative water content and soil moisture content. However, variation in proline and sugar content in the different treatments under two stress conditions indicated differential effect of microbial treatments on plant physiological parameters under stress conditions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mutunga J.M.,Virginia Polytechnic Institute and State University | Mutunga J.M.,International Center for Insect Physiology and Ecology | Boina D.R.,Virginia Polytechnic Institute and State University | Boina D.R.,National Institute of Plant Health Management | And 7 more authors.
Archives of Insect Biochemistry and Physiology | Year: 2013

A series of bis(n)-tacrines were used as pharmacological probes of the acetylcholinesterase (AChE) catalytic and peripheral sites of Blattella germanica and Drosophila melanogaster, which express AChE-1 and AChE-2 isoforms, respectively. In general, the potency of bis(n)-tacrines was greater in D. melanogaster AChE (DmAChE) than in B. germanica AChE (BgAChE). The change in potency with tether length was high in DmAChE and low in BgAChE, associated with 90-fold and 5.2-fold maximal potency gain, respectively, compared to the tacrine monomer. The optimal tether length for Blattella was 8 carbons and for Drosophila was 10 carbons. The two species differed by only about twofold in their sensitivity to tacrine monomer, indicating that differential potency occurred among dimeric bis(n)-tacrines due to structural differences in the peripheral site. Multiple sequence alignment and in silico homology modeling suggest that aromatic residues of DmAChE confer higher affinity binding, and the lack of same at the BgAChE peripheral site may account, at least in part, to the greater overall sensitivity of DmAChE to bis(n)-tacrines, as reflected by in vitro assay data. Topical and injection assays in cockroaches found minimal toxicity of bis(n)-tacrines. Electrophysiological studies on D. melanogaster central nervous system showed that dimeric tacrines do not readily cross the blood brain barrier, explaining the observed nonlethality to insects. Although the bis(n)-tacrines were not good insecticide candidates, the information obtained in this study should aid in the design of selective bivalent ligands targeting insect, pests, and disease vectors. © 2013 Wiley Periodicals, Inc.

Sakthivel P.,Nehru Memorial College Autonomous | Sakthivel P.,National Institute of Plant Health Management | Neelanarayanan P.,National Institute of Plant Health Management | Mohan Rao A.M.K.,National Institute of Plant Health Management
Pestology | Year: 2011

Experiments were conducted on the lesser bandicoot rat, Bandicota bengalensis (Gray), softfurred field rat, Millardia meltada (Gray) and Indian field mouse, Mus booduga (Gray) to establish their preference for either germinated or non-germinated grains - cereals (Paddy - Oryza sativa, Pearl millet - Pennisetum typhoides and Ragi - Eleusine coracana) and pulses (Green gram Phaseohis aureus, Black gram - Phaseolus mungo and Bengal gram - Cicer arietinum). The grains were tested separately as two-choice (germinated and non- germinated) tests and multiplechoice tests. In multiple-choice tests, the six grain types were provided together in different containers in the germinated form. The results of two-choice tests revealed that germinated grains were preferred to non-germinated grains by both sexes of three species of test animals. The differences between the quantities of consumed germinated and non-germinated grains were statistically significant (p<0.01). The results of Duncan's Post Hoc Multiple Comparison Tests based on germinated grains' consumption by all the three species of rodents were categorized into 4 subsets. The first subset consisted of green gram, pearl millet and ragi and the second subset had paddy. Considering the cost of all these grains, it is suggested that any one among them which is cheapest could be used as a rodenticide bait-base for the control of any of the three rodent pest species. However, this requires field based trials for making a final recommendation.

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