EPIDEMIOLOGY

EPIDEMIOLOGY

What is Plant Disease Epidemiology?

        Plant disease epidemiology is the study of disease in plant populations. It is often looked at from a multi-disciplinary approach, requiring biological, statistical, agronomic and ecological perspectives.

Epidemic and Epidemiology?

            Epidemic means pathogen spreads over a wide area within a relatively short time while epidemiology is the study of epidemics and the factors that influence them.

The elements of epidemic 

Therefore, the importance of epidemiology is to determine the selection of efficient disease controlling strategies by changing the conditions of the components in disease epidemic or disease triangle.

What are the factors affect the disease development or epidemics development?

Host factors

            Levels of genetic resistance or susceptibility of host. Vertical Resistance is when some host plant do not allow a pathogen to become established in them. A plant may be completely resistant to a pathogen. Horizontal Resistance is when some of them might be infected, but the level of epidemic is depends on the level of resistance and environmental conditions. A plant never completely resistant or completely susceptible.

            Degree in genetic uniformity of host plant.When genetically uniform host plants were grown over a large area, the chances for new pathogens to develop epidemic are high. High level of epidemic development was observed in vegetatively propagated crop. Low rates of epidemic development was observed in natural populations.Then, types of crop. Last, age of plant.

Pathogen factors

          Levels of virulence.High virulence pathogen could rapidly infected the plant host. Second, quantity of inoculum near host.The greater the number of inoculum near the plant, the greater development of epidemic. Third, type of reproduction of pathogen.Polycyclic pathogens. Example: Fungi, Bacteria, Viruses. Monocyclic pathogens. Example: Smuts and several short cycle rusts. Next, ecology of pathogen. Most fungi, the inoculum is produced on the surfaces of plant. They can be easily dispersed and can cause widespread epidemics. Besides, some pathogen reproduce inside the plants. These pathogens require a lot of vectors (insect) to develop epidemic. Last, mode of spread of pathogen.The spores of some inoculum can be dispersed by air. Meanwhile, some pathogens are dispersed by rain.

Environment factors

          First, moisture. Most pathogens require high level of moisture to develop epidemic. Second, temperature. Low temperature reduces the amount of inoculum of fungi, bacteria and nematodes and reduces the number of vectors.

References

• Phil A. Arneson Plant Disease Epidemiology: Temporal Aspects,2001- https://www.apsnet.org/edcenter/advanced/topics/EpidemiologyTemporal/Pages/default.aspx

•  https://en.wikipedia.org/wiki/Plant_disease_epidemiology

Prepared by: Nor Azmina Binti Abdul Razak (2018400394)