Pteris : features, anatomy, morphology and lifecycle
2013. Ceballos. Cassava diseases
1. How to get high and stable
yields in cassava?
Dealing with diseases
Hernán Ceballos
2nd
Starch World 2013
Jakarta, Indonesia
(February 2014)
2. How to get high and stable
yields in cassava?
Use improved,
high-yielding
varieties
Quality of planting
material
Adequate weed
control
Timely land preparation
Timely planting
Soil fertility
Pest and diseases
3. How to manage the problem
of diseases in cassava?
Identification of the pathogen
Understanding the pathogen
Avoiding the pathogen
Controlling the pathogen
4. Identifying the pathogen
It is the first step for defining
adequate management practices
In most cases the identification is very
easy and fast, but not always….
5. Viral diseases
Cassava mosaic disease (CMD): a
devastating disease in Africa /India.
Cassava brown streak (CBSD): a
growing.problem in Eastern Africa
8. Unknown pathogen: “frog skin disease”
Suspects: a virus (complex),
phytoplasm or both
Transmitted by the use of
cuttings from diseased plants
There must be an (unknown)
vector transmitting it from infected
to healthy plants
9. Unknown pathogen: “witches´broom”
Most likely induced by a
phytoplasm
Transmitted by the use of
cuttings from diseased plants
There must be an (unknown)
vector transmitting it from infected
to healthy plants
10. Identifying the pathogen
It is the first step for defining
adequate management practices
In most cases the identification is very
easy and fast, but not always….
Once the pathogen is identified proper
control strategies can be implemented
11. How to manage the problem
of diseases in cassava?
Identification of the pathogen
Understanding the pathogen
Avoiding the pathogen
Controlling the pathogen
15. Insects (particularly
white flies) are
important vectors
The cuttings are the
most common way of
transmission
Tools may transmit
diseases
16. Understanding the pathogen
Key elements in the disease cycle are:
The source of inoculum
The ways of transmission
Environmental factors that influence it
17. Water logging conditions promote root rots
In general, adequate
fertilization will allow
the plant to defend
itself
(particularly in
relation to K)
18. How to manage the problem
of diseases in cassava?
Identification of the pathogen
Understanding the pathogen
Avoiding the pathogen
Controlling the pathogen
19. NEVER introduce into a country
vegetative material
For centuries cassava production in Asia has
benefitted from little disease and pest pressures
The best situation is when the cassava plant does
not have to face a source of biotic stress
However, this implies that Asian cultivars are
most likely susceptible to the diseases they have
never faced
Recent events demonstrate the risk of
unsupervised movement of planting material
20. NEVER introduce into a country
vegetative material
The introduction in
Asia of the mealybug (from Africa
or southern Brazil) illustrates the
huge economic damage that introducing new pests
or diseases into Asia can have
22. NEVER introduce into a country
vegetative material
Has frog skin disease been introduced into Asia?
23. NEVER introduce into a country
vegetative material
This restriction is
also applicable to
relatives of
cassava such as
Jathrofa
24. Avoiding the pathogen can also be achieved
through good quality planting material
… so it may be convenient to
clean knives and machetes
Tools may transmit
diseases
25. El “Rincón de la Fortuna”
The “Corner of Prosperity”
A good variety is not enough to have high and
stable yields
The objective of most cassava breeding is to
produce varieties that can efficiently take
advantage of whatever the environment can
offer to them
The best racing car still needs gasoline for
winning a race…
26. Farmers select the best area of the field
(typically10%)
Special care (proper weeding + fertilizers) in
that area
Elimination of diseased plants (e.g. witches
broom)
Inspection of the roots (e.g. good yield or
diseases)
El “Rincón de la Fortuna”
The “Corner of Prosperity”
Harvest the Corner of Prosperity just before
planting material for the new cycle is required
27. At harvest take stems ONLY from
productive plants
Visual
inspection of
root health
(e.g. rots, frog
skin, etc.)
28. Farmers select the best area of the field
(typically10%)
Special care (proper weeding + fertilizers) in
that area
Elimination of diseased plants (e.g. witches
broom)
Inspection of the roots (e.g. good yield or
diseases)
El “Rincón de la Fortuna”
The “Corner of Prosperity”
Take stems only from plants after root
inspection
Harvest the Corner of Prosperity just before
planting material for the new cycle is required
30. How to manage the problem
of diseases in cassava?
Identification of the pathogen
Understanding the pathogen
Avoiding the pathogen
Controlling the pathogen
31. Controlling the pathogen
Several strategies can be used to slow
down or reduce the impact of diseases:
Chemical protection of cuttings
or the plant
32. Chemical control
Chemical protection of cuttings with fungicides and
pesticides is sometimes necessary (+ nutrients…)
But has to be done responsibly…
34. If things are done properly, however, chemical protection
to the plant is seldom necessary in cassava
Chemical control
35. Controlling the pathogen
Several strategies can be used to slow
down or reduce the impact of diseases:
Chemical protection of cuttings
or the plant
The use of resistant varieties
36. Cassava mosaic disease (CMD): a devastating
virus for cassava in Africa and India.
ResistantSusceptible
37. CBSV
(Cassava brown streak virus)
“Clean”
Infected
It should be mentioned that
it is possible to produce
transgenic cassava
… and one of the first
applications of the
technology was to create
resistance to viruses
40. Controlling the pathogen
Several strategies can be used to slow
down or reduce the impact of diseases:
Chemical protection of cuttings
or the plant
The use of resistant varieties
Helping the plant defend itself
41. Helping the plant defend to itself
A cassava plant originated from a healthy and
physiologically sound cutting will not need
much support to defend itself. However, some
practices are recommendable:
Crop rotations are always a smart approach to
prevent building up of the inoculum
Fields with adequate drainage prevent root rots
Adequate fertilization will produce a vigorous
plant that will withstand most biotic problems
Adequate management of weeds also contributes
to a healthy cassava crop
42. We have a great opportunity to make a
difference in cassava’s future. However,
we must act with responsibility and
react fast when a problem arises
You are not alone ! Look for help if
there is a problem.
43. Thank you for your attention
Contacts:
h.ceballos@cgiar.org
c.hershey@cgiar.org
