scholarly journals EFFECT OF CERTAIN ECOLOGICAL FACTORS ON POPULATION DENSITY OF Thrips tabaci LIND. ATTACKING ONION CROP

2011 ◽  
Vol 2 (11) ◽  
pp. 925-930
Author(s):  
Neama Abd El-Hameed ◽  
M. Haydar ◽  
Marwa Mousa
Keyword(s):  
Population Density ◽  
Ecological Factors ◽  
Thrips Tabaci

scholarly journals Allium cepa L. responses when Gaeolaelaps aculeifer Canestrini and Parasitus bituberosus Karg are used to control Thrips tabaci Lindeman

2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Mayerly Alejandra Castro-López ◽  
John Wilson Martínez-Osorio
Keyword(s):  
Population Density ◽  
Allium Cepa ◽  
Plant Development ◽  
Insect Pest ◽  
Predatory Mites ◽  
Thrips Tabaci ◽  
Physiological Variables ◽  
Allium Cepa L ◽  
Mite Density ◽  
Chlorophyll Index

Thrips tabaci Lindemann is the main insect pest of Allium cepa L., causing both direct and indirect damage to crops. T. tabaci is controlled by applying chemically synthesized products; however, this insect has already developed resistance to organophosphates, carbamates, and pyrethroids. This study evaluated the effect of soil predatory mites (Gaeolaelaps aculeifer Canestrini and Parasitus bituberosus Karg) on the population density of T. tabaci in potted bulb onion (Allium cepa L.) plants and on the response of physiological variables related to photosynthesis and plant development. Seven treatments were evaluated that released 50, 75 or 100 G. aculeifer or P. bituberosus adults, along with a control without predatory mites. Significant differences (P≤0.05) in the population density of T. tabaci were observed for 13 weeks, with a 78% reduction of individuals in the presence of G. aculeifer and a 72% reduction with P. bituberosus, regardless of mite density, as compared to the control. In addition, the relative chlorophyll index, foliar area, dry leaf weight and fresh bulb weight increased, as compared to the control. The application of 100 individuals of the two species recorded the highest values in the evaluated variables. These results indicate that G. aculeifer and P. bituberosus controls should be explored as an option for integrated T. tabaci management.

Texcoco Region Archaeology

1975 ◽  
Vol 40 (2Part1) ◽  
pp. 227-230 ◽  
Author(s):  
Richard E. Blanton
Keyword(s):  
Population Density ◽  
Agricultural Land ◽  
General Pattern ◽  
Ecological Factors ◽  
The Political ◽  
Regional Centers

Charlton (1973) argues that Parsons' (1969, 1970) explanation for the abandonment of the central Texcoco region, Mexico, during the Early Toltec period, is misleading because Parsons considered only “non-ecological” factors. Specifically, Parsons suggested that this zone was not occupied because it was the boundary between the political spheres of two competing regional centers, Tula and Cholula. Charlton argues instead, that the region was abandoned due to “ecological” factors. Namely, he argues, the Early Toltec period was a period of low population density, when only the most suitable agricultural land was occupied; thus the central Texcoco region was not utilized because it is agriculturally marginal. Charlton’s emphasis on the use of “ecological” factors to explain the distribution of Early Toltec settlements is misleading because it does not allow prediction of the locations of other known Early Toltec settlements in the Valley of Mexico. Abandonment of large portions of the Valley of Mexico was a general pattern during this period, due to “Balkanization” and competition between local centers.

scholarly journals Impact of Some Ecological Factors on Fecal Contamination of Drinking Water by Diarrheagenic Antibiotic-ResistantEscherichia coliin Zagazig City, Egypt

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Ahmed Elsadek Fakhr ◽  
Maha Kamal Gohar ◽  
Amal Hassan Atta
Keyword(s):  
Drinking Water ◽  
Population Density ◽  
Distribution Systems ◽  
Virulence Genes ◽  
Fecal Contamination ◽  
Antibiotic Sensitivity ◽  
Ecological Factors ◽  
Antibiotic Resistant ◽  
Major Health Problem ◽  
E Coli

Fecal contamination of drinking water is a major health problem which accounts for many cases of diarrhea mainly in infants and foreigners. This contamination is a complex interaction of many parameters. Antibiotic resistance among bacterial isolates complicates the problem. The study was done to identify fecal contamination of drinking water by Diarrheagenic Antibiotic-ResistantEscherichia coliin Zagazig city and to trace reasons for such contamination, three hundred potable water samples were investigated forE. coliexistence. Locations ofE. colipositive samples were investigated in relation to population density, water source, and type of water pipe. SixteenE. colistrains were isolated. Antibiotic sensitivity was done and enterotoxigenic, enteropathogenic, and enterohaemorrhagic virulence genes were investigated by PCR. Probability of fecal contamination correlated with higher population density, with increased distance from Zagazig water plant, and with asbestos cement water pipes. Resistance to at least one antimicrobial drug was found in all isolates. Virulence genes were detected in a rate of 26.27%, 13.13%, 20%, 6.67%, and 33.33% for LT, ST, stx1, stx2, and eae genes, respectively. This relatively high frequency of fecal contamination points towards the high risk of developing diarrhea by antibiotic resistant DEC in low socioeconomic communities particularly with old fashion distribution systems.

MODELLING AND ANALYSIS OF THE SPREAD OF MALARIA: ENVIRONMENTAL AND ECOLOGICAL EFFECTS

2005 ◽  
Vol 13 (01) ◽  
pp. 1-11 ◽  
Author(s):  
SHIKHA SINGH ◽  
J. B. SHUKLA ◽  
PEEYUSH CHANDRA
Keyword(s):  
Infectious Disease ◽  
Population Density ◽  
Human Population ◽  
Ecological Factors ◽  
Ecological Effects ◽  
Mosquito Population ◽  
Human Population Density ◽  
Survival And Growth

In this paper, general SIS and SIRS models with immigration of human population for the spread of malaria are proposed and analyzed. Effects of natural as well as human population density related environmental and ecological factors, which are conductive to the survival and growth of mosquito population, are considered. It is shown in both the cases that as the parameters governing environmental and ecological factors increase, the spread of malaria increases. It is also found that due to immigration, this infectious disease becomes more endemic.

scholarly journals Opposing effects of population density and stress on Escherichia coli mutation rate

2018 ◽  
Author(s):  
Rok Krašovec ◽  
Huw Richards ◽  
Danna R. Gifford ◽  
Roman V. Belavkin ◽  
Alastair Channon ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Population Density ◽  
Mutation Rate ◽  
Ecological Factors ◽  
Rich Media ◽  
Rate Minimum ◽  
Induced Mutagenesis ◽  
Opposing Effects ◽  
Relationship Of ◽  
Opposing Effect

AbstractEvolution depends on mutations. For an individual genotype, the rate at which mutations arise is known to increase with various stressors (stress-induced mutagenesis – SIM) and decrease at high population density (density-associated mutation-rate plasticity – DAMP). We hypothesised that these two forms of mutation rate plasticity would have opposing effects across a nutrient gradient. Here we test this hypothesis, culturing Escherichia coli bacteria in increasingly rich media. We distinguish an increase in mutation rate with added nutrients through SIM (dependent on error-prone polymerases Pol IV and Pol V) and an opposing effect of DAMP (dependent on MutT, which removes oxidised G nucleotides). The combination of DAMP and SIM result in a mutation rate minimum at intermediate nutrient levels (which can support 7×108 cells ml−1). These findings demonstrate a strikingly close and nuanced relationship of ecological factors – stress and population density – with mutation, the fuel of all evolution.

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