3. SURVEY AND SURVEILLANCE
INTRODUCTION:
Survey means to view the situation comprehensively and extensively at
different periodicity.
Surveillance is vigilant supervision of a situation ( to keep close and
constant watch).
survey methodology studies the sampling of individual units from
a population
Disease surveillance is an information-based activity involving the
collection, analysis and interpretation of large volumes of data originating
from a variety of sources.
4. IMPORTANCE:
Plant disease surveys are basic guide to disease progress that
helps in fixing the priorities
It may serve as forewarning for certain actions to be taken
It also tells about the impact of the changing agricultural
technology, especially plant disease management tools
SURVEY PROCEDURE:
The procedure adopted for disease survey will depend
on the objectives and type of information (primary or secondary)
required. Following are some common ways used for disease
surveys:
5. 1. Random sampling: Area sampling stratified or purposive (only specific
area or growers to be covered).
Random sampling Fixed plot sampling
6. 2. Trap nurseries: Generally used for detecting new virulence in an area and
screening of germplasm.
To evaluate the genotypes against local race of
yellow rust, Seed multiplication of the three
International Trap Nurseries are established:
a. International Yellow Rust Trap Nursery
b. International Stem Rust Trap Nursery
c. International Leaf Rust Trap Nursery
7. 3. Mobile units: The mobile plant clinic vans go in different
directions, on pre-planned routes and collect samples at
predefined distances to cover large geographic area.
8. 4. Spore trapping: Spore trapping devices or spore trap nurseries give
information about arrival (time and quantity) of air borne inoculums.
9. It is an indirect indicator of pathogen activity and
threat potential to the crop in the season.
Aphid populations are monitored by the use of
suction traps
This helps in developing distribution and
movement maps of vector species
For accurate risk assessment, additional
information of virus carrying status is required.
This can be obtained either by feeding the
trapped vectors on susceptible plants
Use of molecular methods
Sensitive ELISA tests can detect the presence
of virus even in single aphid (sugar beet yellows
and potato leaf roll virus).
5. Vector
population:
