Effect of botanicals on the population dynamics ofNephotettix virescens, rice tungro disease incidence and yield of rice

2000 ◽  
Vol 28 (2) ◽  
pp. 109-113 ◽  
Author(s):  
K. Rajappan ◽  
C. Ushamalini ◽  
N. Subramanian ◽  
V. Narasimhan ◽  
A. Abdul Kareem
Keyword(s):  
Population Dynamics ◽  
Disease Incidence ◽  
Rice Tungro Disease

Eco-friendly management of wilt caused by fusarium oxysporum f.sp. Ciceri in chickpea

2015 ◽  
Author(s):  
Chandar Kala ◽  
S. Gangopadhyay ◽  
S. L. Godara
Keyword(s):  
Population Dynamics ◽  
Disease Control ◽  
Fusarium Oxysporum ◽  
Seed Treatment ◽  
Disease Incidence ◽  
Trichoderma Viride ◽  
Organic Amendments ◽  
Chickpea Wilt ◽  
Maximum Inhibition

Antagonistic potentiality of Trichoderma viride, T. harzianum and Pseudomonas fluorescens were evaluated against Fusarium oxysporum f. sp. ciceri under in vivo conditions. The effect of organic amendments viz; farm yard manure, vermicompost and mustard cake on disease control potentiality of test antagonists against chickpea wilt and on population dynamics of the antagonists and pathogen in soil was also studied. Maximum inhibition of mycelial growth of F. o. f. sp. ciceri was recorded in presence of P. fluorescens (%) followed by T. harzianum (%) and T. viride (%). Seed treatment with P. fluorescens was more effective in suppressing the disease incidence as compared to T. harzianum and T. viride. The disease control efficacy and population dynamics of all the three test antagonists was enhanced in response to application of organic amendments. Among the three organic amendments tested, mustard cake was most effective in enhancing the disease control potentiality of these antagonists.

scholarly journals Inoculum Density-Disease Development Relationship in Verticillium Wilt of Artichoke Caused by Verticillium dahliae

Plant Disease ◽  
2007 ◽  
Vol 91 (9) ◽  
pp. 1131-1136 ◽  
Author(s):  
M. Berbegal ◽  
A. Ortega ◽  
J. García-Jiménez ◽  
J. Armengol
Keyword(s):  
Population Dynamics ◽  
Verticillium Dahliae ◽  
Symptom Severity ◽  
Disease Incidence ◽  
Growing Season ◽  
Inoculum Density ◽  
Disease Development ◽  
Growing Seasons ◽  
Negative Exponential ◽  
The Relationship

The relationship between inoculum density of Verticillium dahliae in soil and disease development was studied in 10 commercial artichoke fields. Inoculum density of V. dahliae varied between 2.2 and 34.2 microsclerotia (ms) g–1 of soil near planting. Artichoke plants were monitored for disease at the beginning and the end of each growing season. There was a significant correlation, which was best described by negative exponential models, between inoculum density and disease incidence, symptom severity, and recovery of the pathogen from the plants. Inoculum densities ranging from 5 to 9 ms g–1 of soil were associated with a mean percentage of infected plants of about 50%. Additionally, three fields were monitored in two consecutive growing seasons to evaluate the population dynamics of V. dahliae microsclerotia in soil and disease development. Numbers of microsclerotia per gram of soil decreased significantly by the end of the first growing season but slightly increased at the end of the second growing season. In these fields, symptom severity was greatest during the second growing season when high percentages of infected plants also were recorded.

scholarly journals Population dynamics of Myrothecium roridum Tode ex. Fr. and Rhizoctonia solani Kühn in commercial coffee nurseries

1969 ◽  
Vol 80 (3) ◽  
pp. 145-156
Author(s):  
Fabio Bautista-Pérez ◽  
Rocío del P. Rodríguez
Keyword(s):  
Population Dynamics ◽  
Rhizoctonia Solani ◽  
Disease Incidence ◽  
Primary Source ◽  
Primary Role ◽  
Canker Disease ◽  
Coffee Pulp ◽  
Myrothecium Roridum ◽  
Highly Correlated ◽  
Stem Cankers

Sources of inoculum and population dynamics of Myrothecium roridum and Rhizoctonia solani, causal organisms of cankers and root rot in nursery coffee plants, were studied. Six commercial nurseries were selected on the basis of presence of disease, and samples were taken every eight weeks. Correlated with disease incidence were variables such as density of propagules for both pathogens ¡n soil of diseased plants, apparently healthy plants, and chlorotic plants; in fumigated and non fumigated soil; in organic matter used for the mixture; and in sand from the seedbed. Density of propagules of M. roridum was estimated on the basis of the colony-forming units (CFU); that of R. solani, on the basis of percentage of colonized sugarbeet seeds. Neither of the pathogens was detected in the coffee pulp. Higher density of propagules was obtained in the soil at 5-cm depth.The highly correlated density of M. roridum with disease incidence per season and nursery indicated its primary role in coffee stem cankers in the nurseries. The presence of M. roridum in the sand of asymptomatic seedlings and the high correlation with its density in soil of plants in the nursery suggests that seedlings are the primary source of inoculum for canker disease of plants in the nursery.

Effect of kasugamycin, oxytetracycline, and streptomycin on in-orchard population dynamics of Erwinia amylovora on apple flower stigmas

Plant Disease ◽  
2020 ◽  
Author(s):  
Suzanne Slack ◽  
Kellie J Walters ◽  
Cory Outwater ◽  
George W. Sundin
Keyword(s):  
Population Dynamics ◽  
Fire Blight ◽  
Erwinia Amylovora ◽  
Disease Incidence ◽  
Population Data ◽  
Antibiotic Activity ◽  
The Other ◽  
Control Efficacy ◽  
Weather Parameters

We assessed the effect of three antibiotics (streptomycin, oxytetracycline, and kasugamycin) on populations of the fire blight pathogen Erwinia amylovora on apple flower stigmas during three field seasons. Timing of application relative to E. amylovora presence on flower stigmas had little impact on both population dynamics and subsequent disease incidence. While E. amylovora populations on water-treated flowers increased to 106-7 cfu flower-1 after 4-5 days in each experiment, the antibiotics streptomycin and kasugamycin caused statistically-significant reductions of stigma populations by as many as 4-5 logs over a 4-5 day period in two of the three experiments. In contrast, the effect of oxytetracycline on E. amylovora populations on stigmas was more variable, with reductions in E. amylovora populations only observed in one of the three experiments. In agreement with the population data, disease incidence was significantly higher on oxytetracycline-treated flowers compared to the other antibiotic treatments in two of three years. Statistical analyses of effects of weather parameters on antibiotic activity revealed that solar radiation and temperature negatively impacted the activity of both kasugamycin and oxytetracycline. We further assessed the potential for photodegradation of formulated kasugamycin (Kasumin 2L, Arysta LifeSciences), and found that Kasumin 2L was susceptible to degradation in vitro after exposure to a 16-hr photoperiod of daily light integrals (DLIs) varying from 6 to 35 mol·m–2·d–1. We further determined that exposure to three consecutive 16-hr photoperiods of DLIs of 23 or 35 mol·m–2·d–1 reduced the available concentration of Kasumin 2L (assessed using a bioassay) from 100 g ml-1 to 10-20 g ml-1. Our results correlate the superior blossom blight control efficacy of kasugamycin and streptomycin to significant population reductions of E. amylovora on apple flower stigmas but indicate that, similar to oxytetracycline, kasugamycin is vulnerable to photodegradation which would suggest that further considerations should be made when applying this antibiotic.

scholarly journals Genetic Structure and Population Dynamics of Xanthomonas axonopodis pv. manihotis in Colombia from 1995 to 1999

2004 ◽  
Vol 70 (1) ◽  
pp. 255-261 ◽  
Author(s):  
Silvia Restrepo ◽  
Claudia M. Velez ◽  
Myriam C. Duque ◽  
Valérie Verdier
Keyword(s):  
Population Dynamics ◽  
Temporal Dynamics ◽  
Disease Incidence ◽  
Bacterial Pathogen ◽  
Rate Of Change ◽  
High Genetic Diversity ◽  
Cassava Bacterial Blight ◽  
Xanthomonas Axonopodis ◽  
Haplotype Frequencies ◽  
Site Diversity

ABSTRACT Restriction fragment length polymorphisms (RFLPs) were used to study the population genetics and temporal dynamics of the cassava bacterial pathogen Xanthomonas axonopodis pv. manihotis. The population dynamics were addressed by comparing samples collected from 1995 to 1999 from six locations, spanning four different edaphoclimatic zones (ECZs). Forty-five different X. axonopodis pv. manihotis RFLP types or haplotypes were identified between 1995 and 1999. High genetic diversity of the X. axonopodis pv. manihotis strains was evident within most of the fields sampled. In all but one site, diversity decreased over time within fields. Haplotype frequencies significantly differed over the years in all but one location. Studies of the rate of change of X. axonopodis pv. manihotis populations during the cropping cycle in two sites showed significant changes in the haplotype frequencies but not composition. However, variations in pathotype composition were observed from one year to the next at a single site in ECZs 1 and 2 and new pathotypes were described after 1997 in these ECZs, thus revealing the dramatic change in the pathogen population structure of X. axonopodis pv. manihotis. Disease incidence was used to show the progress of cassava bacterial blight in Colombia during the 5-year period in different ecosystems. Low disease incidence values were correlated with low rainfall in 1997 in ECZ 1.

Dynamics of infectious disease

2007 ◽  
Author(s):  
Bryan Grenfell ◽  
Matthew Keeling
Keyword(s):  
Infectious Disease ◽  
Population Dynamics ◽  
Natural Enemy ◽  
Population Biology ◽  
Plant Pathogens ◽  
Disease Incidence ◽  
Host Pathogen Interactions ◽  
Incidence Data ◽  
Pathogen Dynamics ◽  
Host Pathogen

Host–pathogen associations continue to generate some of the most important applied problems in population biology. In addition, as foreshadowed in Chapter 5 of this volume, these systems give important insights into the dynamics of host– natural enemy interactions in general. The special place of pathogens in the study of host–natural enemy dynamics arises partly from excellent longterm disease-incidence data, reflecting the public health importance of many infections. However, we argue that host–pathogen dynamics are also distinctive because the intimate association between individual hosts and their pathogens is often reflected with particular clarity in the associated population dynamics. Throughout this chapter we focus in parallel on the population dynamics of host–pathogen interactions and the insights that host–pathogen dynamics can provide for population biology in general. Population-dynamic studies of infectious disease have a long history, which predates the modern foundations of ecology (Bernoulli, 1760). During the twentieth century, the preoccupation of population ecologists with the balance between extrinsic and intrinsic influences on population fluctuations and the role of nonlinearity and heterogeneity (Bjørnstad and Grenfell, 2001) find strong parallels in epidemiological studies of human diseases (Bartlett, 1956; Anderson and May, 1991). In terms of the ecological effects of parasitism, the traditional view held that ‘welladapted’ parasites would not have a consistent impact on the ecology of their hosts (Grenfell and Dobson, 1995). The 1970s saw a new departure, when Anderson and May pointed out the potential of infectious agents to exert nonlinear—regulatory or destabilizing—influences on the population dynamics of their hosts (Anderson and May, 1978, 1979; May and Anderson, 1978, 1979). There has since been an explosion of work on the population biology of human, animal, and plant pathogens. This work spans a huge range: from highly applied to basic theoretical work; from within-host to the metapopulation scale; from short-term population dynamics to long-term evolutionary processes. In this chapter we first outline the simple theory of epidemiological models; we then refine this picture to illustrate the potential impact of pathogens on the population dynamics of their hosts, as well as aspects of host–pathogen interactions which provide important insights into more general ecological dynamics.

scholarly journals PENYEMPURNAAN PENGENDALIAN TERPADU PENYAKIT TUNGRO DENGAN STRATEGI MENGHIDARI INFEKSI DAN PERGILIRAN VARIETAS TAHAN

2006 ◽  
Vol 6 (2) ◽  
pp. 92-99
Author(s):  
Burhanuddin Burhanuddin ◽  
I Nyoman Widiarta
Keyword(s):  
Virus Resistance ◽  
Disease Incidence ◽  
Planting Date ◽  
Climate Anomaly ◽  
Green Leafhopper ◽  
South Sulawesi ◽  
Resistant Varieties ◽  
Rice Tungro Disease ◽  
Fluctuation Pattern ◽  
Almost All

Refining integrated rice tungro disease management based on escaped strategy and varieties rotation. Rice tungro virus transmitted mainly by green leafhopper, N. virescens, infected rice in central rice  production in Indonesia. Tungro epidemic in South Sulawesi were succesfully controlled by integrating appropriate planting time and rotation of green leafhopper resistant varieties since 1973. Tungro was reported in 1998 after climate anomaly, caused by El-Nino and La-Nina. Pattern of green leafhopper population fluctuation and tungro disease incidence and green leafhopper adaptation to green leafhopper resistance variety were evaluated. The results showed that the fluctuation pattern of green leafhopper population in Lanrang which represents of areas  in Eastern Coarse of South Sulawesi  has changed. Green leafhopper colonies from endemic area in South Sulawesi were almost all well adapted to 4 groups of green leafhopper resistance varieties. Therefore it was suggested to adjust planting date and recommended to plant tungro virus resistance variety instead of green leafhopper resistance varieties.

scholarly journals A Theoretical Assessment of the Effects of Vector-Virus Transmission Mechanism on Plant Virus Disease Epidemics

2000 ◽  
Vol 90 (6) ◽  
pp. 576-594 ◽  
Author(s):  
L. V. Madden ◽  
M. J. Jeger ◽  
F. van den Bosch
Keyword(s):  
Population Dynamics ◽  
Plant Virus ◽  
Virus Disease ◽  
Disease Incidence ◽  
Virus Transmission ◽  
Rate Of Change ◽  
Transmission Mechanism ◽  
Model Parameters ◽  
Disease Epidemics ◽  
Plant Virus Disease

A continuous-time and deterministic model was used to characterize plant virus disease epidemics in relation to virus transmission mechanism and population dynamics of the insect vectors. The model can be written as a set of linked differential equations for healthy (virus-free), latently infected, infectious, and removed (postinfectious) plant categories, and virus-free, latent, and infective insects, with parameters based on the transmission classes, vector population dynamics, immigration/emigration rates, and virus-plant interactions. The rate of change in diseased plants is a function of the density of infective insects, the number of plants visited per time, and the probability of transmitting the virus per plant visit. The rate of change in infective insects is a function of the density of infectious plants, the number of plants visited per time by an insect, and the probability of acquiring the virus per plant visit. Numerical solutions of the differential equations were used to determine transitional and steady-state levels of disease incidence (d*); d* was also determined directly from the model parameters. Clear differences were found in disease development among the four transmission classes: nonpersistently transmitted (stylet-borne [NP]); semipersistently transmitted (foregut-borne [SP]); circulative, persistently transmitted (CP); and propagative, persistently transmitted (PP), with the highest disease incidence (d) for the SP and CP classes relative to the others, especially at low insect density when there was no insect migration or when the vector status of emigrating insects was the same as that of immigrating ones. The PP and CP viruses were most affected by changes in vector longevity, rates of acquisition, and inoculation of the virus by vectors, whereas the PP viruses were least affected by changes in insect mobility. When vector migration was explicitly considered, results depended on the fraction of infective insects in the immigration pool and the fraction of dying and emigrating vectors replaced by immigrants. The PP and CP viruses were most sensitive to changes in these factors. Based on model parameters, the basic reproductive number (R0)—number of new infected plants resulting, from an infected plant introduced into a susceptible plant population—was derived for some circumstances and used to determine the steady-state level of disease incidence and an approximate exponential rate of disease increase early in the epidemic. Results can be used to evaluate disease management strategies.

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