The document discusses the use of radiation and soil sterilization techniques in plant protection. It describes how radiation is used for food irradiation to kill bacteria, insects and parasites. It also discusses how sterile insect technique works by releasing sterile male insects to reduce wild populations. For soil sterilization, it explains how high temperatures from steam, hot water or dry heat are used to kill pathogens, weeds, insects and other harmful organisms in soil. Chemical sterilization methods using ethylene oxide or other chemicals are also covered. Various techniques for applying steam or heat to soil surfaces and depths are described for effective sterilization.

1. USE OF RADIATION
AND SOIL
STERILIZATION IN
PLANT PROTECTION
BY :
JAYANT YADAV, CCSHAU, HISAR, HARYANA

2. RADIATIONS
O Radiation is the emission of energy as
electromagnetic waves or as moving
subatomic particles, especially high-
energy particles which cause ionization.
O Direct transmission of electromagnetic
energy through space or another
medium.

3. Uses of radiation in agriculture
field
O Food irradiation: kills bacteria insects and parasites that
can cause food borne diseases. It exposes food to
gamma rays.
O Radioisotopes are usually used as tracers.
O Radiation sterilisation as used in biological preparations
like tissue grafts.
O For development of resistant varieties against various
insect-pest.
O Sterile Insect Technique
O Cobalt-60 made radioactive by neutron irradiation, have
been used during recent years for investigating the
radiation susceptibility of insect-pests.

4. Sterile Insect Technique
O Also known as SIT and sterile insect
release method (SIRM).
O It is a biologically- based method for the
management of key insect pests of
agriculture and medical/ veterinary
importance.
O It is defined “ as method of pest control
using area-wide inundative releases of
sterile insects to reduce reproduction in a
field population of same species”.

5. O It is therefore a type of “Birth Control” in which wild
female insect of the pest population do not reproduce
when they are inseminated by released, radiation
sterilised males.
O Sexual sterility is induced with radiation emitted from
radioisotopes such as caesium-137 and cobalt-60.
O The dosage of radiation has no adverse effect on the
males ‘ longevity, searching and mating ability.
O Mating of sterile males with wild females do not yield
offspring and hence reduce population in next
generation when large no of sterile male is released in
population. The proportion of sterile male against wild
male should be 10:1.
O The SIT was first time used to eradicate New World
Screworm.

6. Screworm

7. Soil Sterilization
O Importance of soil sterilization: It provide quick
relief of soils from substances and organisms harmful to plants such
as:
O Bacteria
O Viruses
O Fungi
O Nematodes and other pests
O Further positive effects are:
O All weed and weed seeds are killed
O Significant increase of crop yields
O Relief from soil fatigue through activation of chemical – biological
reactions.
O Blocked nutritive substances in the soil are trapped and made
available for plants.
O Alternative to Methyl Bromide and other critical chemicals in
agriculture.

8. SOIL STERILIZATION
O In simplest terms soil sterilization consist in getting rid of the organisms harmful to plant
growth or atleast, in reducing their numbers to a point where they are no longer of
consequence without permanently eliminating or disturbing the balance of those
organisms essenstial for fertility.
O Basically it is treatment of soil of glasshouses , greenhouse and other horticultural soils
in order to kill weed, seeds, plant disease organisms, and pests.
O Under this soil is sterilized in greenhouses or polyhouses and also in nurseries by
steam or hot water/air.
O Soil treated with hot water or steam at about
50°C – To inactivate or kill majority of nematodes, some oomycetes fungi
60-70°C – most of plant pathogenic fungi and bacteria
82°C – Most of weeds and plant pathogenic bacteria and insects
Some heat tolerant weed seeds and virus like tobacco mosaic virus are killed at
near boiling point depend upon pressure.
O It causes their cell structure to physically degenerate
O Sterilization can be achieved with one or more of the following: heat, chemicals,
irradiation, high pressure, and filtration.
O Sterilisation is distinct from disinfection, sanitization and pasteurization in that
sterilization kills, deactivates, or eliminates all forms of life and other biological agents.
O Example: Molya disease of wheat caused by Heterodera avenae
White tip disease of rice caused by Aphelenchoides besseyi
O Soil borne pathogens like Fusarium, Rhizoctonia, Sclerotia can be controlled by this.

9. Types of sterilization
A.Heat Sterilization
O Heat is used to destroy all forms of life present in
soil. It is thorough, quick- acting and clean. And
heated soil can be used immediately after it has
cooled.
O Heat sterilization is of two types wet/moist and dry
heat sterilization.
O i) MOIST HEAT STERILIZATION: It utilizes hot air
that is heavily laden with water vapour and where
this moisture plays the most imp role in sterilization.
Steam sterilization is non-toxic, inexpensive, rapidly
microbicidal, sporicidal and rapidly heats.
O A widely used method for steam sterilization is the
autoclave, sometimes called a converter or steam
sterilizer.
O Autoclaves use steam heated to 121-134°C under
pressure for a specific period of time.
O A general cycle is 15-20 mins at 121°C at 100 kPa. It
inactivate all resistant bacterial spores in addition to
fungi, bacteria and viruses but not eliminate all
prions.
O For prions, 121-132°C for 60 mins or 134°C for
atleast 18 mins.
O Action on microorganisms: Moist heat causes
destruction of microorganisms by denaturation of
macromolecules, primarily proteins.

10. ii) Dry heat sterilization:
O It is one of the earliest form of sterilization used.
O Dry heat utilizes hot air that is either free from water
vapour or has very little of it, and where this moisture
plays a minimal or no role in the process of
sterilization.
O In this process heat is absorbed by the exterior
surface of an item and then passed inward to next
layer. Eventually, the entire item reaches the proper
temperature needed to achieve sterilization.
O The proper time and temperature for dry heat
sterilization is 160°C (320°F) for 2 hours or 170°C
(340°F) for 1 hour. Instrument should be well dried
before used since water will interfere the process.

11. Generally there are 2 type of hot-air convection
sterilizers:
O A) Gravity Convection
O B) Mechanical Convection
A) Gravity Convection Process:
O As air is heated, it expands and possesses
less density (weight per volume) than cooler
air. Therefore the heated air rises and
displaces the cooler air (the cooler air
descends). It produces inconsistent
temperatures within the chamber and has a
very low turnover.

12. B) Mechanical Convection Process:
O It contains a blower that actively forces
heated air throughout all areas of
chamber.
O The flow created by the blower ensures
uniform temperatures and the equal
transfer of heat throughout the load.
O It is more efficient.

13. Instruments used for dry
heat sterilization
O Hot Air Oven
O Incineration or Burning
O Flamming
O Radiation
O Microwave
O Bunsen burner
O Glass Bead Sterilizer

14. Application of hot steam
O In horticulture as well as nurseries for
sterilization of substrates and top soil.
O In agriculture for sterilization and heating
of molasses.
O In Mushroom cultivation for pasteurization
of growing grooms and sterilization of top
soil and combined application as heating.

15. Hot Air Oven
O These are electrical devices
which use dry heat to sterilize.
O Originally developed by Pasteur.
O Generally, they can be operated
from 50-300°C, using a
thermostat to control the
temperature.
O Process involves heating the
oven to the required temperature,
maintaining that temperature for
the proper time interval for that
temperature, turning the machine
off and cooling the articles in the
closed oven till they reach room
temperature.
O The standard settings for a hot air
oven are:
O 1.5 to 2 hours at 160°C (320°F)
O 6 to 12 mins at 190°C (374°F)

16. B.Chemical Sterilization
O In these chemicals either as gases or in liquid form,
can be used as sterilants.
O Ethylene oxide:
O This gas is used to sterilize objects that are sensitive
to temperatures greater then 60°C and radiation.
O Ethylene oxide treatment is generally carried out
between 30°C and 60°C with relative humidity above
30% and a gas concentration between 200 and 800
mg/l.
O It penetrates well through paper, cloth and some
plastic films.
O Ethylene oxide can kill all known viruses, bacteria
and fungi.
O However it is highly flammable, toxic, and
carcinogenic with a potential to cause adverse
reproductive effects.
O Two most important ethylene oxide sterilization
methods are: the gas chamber method and the micro
dose method.
O It is delivered by flooding a large area with a
combination of ethylene oxide and other gases
(CFCs or carbon dioxide )as diluents.
O Other chemicals used are nitrogen oxide,
formaldehyde and hydrogen peroxide.

17. Methods of sterilization
Steaming with superheated steam
O Superheated steam at 180-200°C an
optimal soil disinfection can be achieved.
O Soil only absorbs a small amount of
humidity.
O Micro organisms become active once the
soil has cooled down.
O Different types of such steam application
are also available in practice, including
substrate steaming and surface steaming.

18. Surface Steaming
O Sheet steaming
O The steaming hood
O Depth steaming with vaccum
O Combined surface and depth injection of
steam (Sandwitch steaming)

19. Sheet Steaming
O Surface steaming with
special sheets in order to
steam large areas
reaching from 15 to 400 m
sq. in one step using a
steam injector.
O Use of two polythene
sheets are highly effective
one is used for steaming
and other one for steam
injection.

20. Steaming with hoods
O It is a mobile device consisting of
corrosion-resistant materials such as
aluminium, which is put down onto the
area to be steamed.

21. Depth steaming with vacuum
O Steaming with vacuum which is induced
through a mobile or fixed installed pipe
system in depth of area to be steamed, is
the method that reaches best penetration.

22. Combined Surface and Depth
Injection of Steam
O It represents combination
of both surface and depth
steaming.
O For this area to be
steamed must be
equipped with deep
steaming injection
system, is covered with a
steaming hood. The
steam enters the soil from
the top and the bottom at
the same time.

23. THANKS