Transcript
How to get high and stable yields in cassava?
Dealing with diseasesHernán Ceballos
2nd Starch World 2013Jakarta, Indonesia
(February 2014)
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
How to manage the problem of diseases in cassava?
Identification of the pathogen
Understanding the pathogen
Avoiding the pathogen
Controlling the pathogen
Identifying the pathogen
It is the first step for defining adequate management practices
In most cases the identification is veryeasy and fast, but not always….
Viral diseases
Cassava mosaic disease (CMD): a devastating disease in Africa /India.
Cassava brown streak (CBSD): a growing.problem in Eastern Africa
Super elongation disease.
Cercospora leaf spot
Fungal diseases
Root rots
Bacterial diseases
Cassava bacterial blight
Unknown pathogen: “frog skin disease”
Suspects: a virus (complex), phytoplasm or bothTransmitted by the use of cuttings from diseased plants There must be an (unknown) vector transmitting it from infected to healthy plants
Unknown pathogen: “witches´broom”
Most likely induced by a phytoplasmTransmitted by the use of cuttings from diseased plants There must be an (unknown) vector transmitting it from infected to healthy plants
Identifying the pathogen
It is the first step for defining adequate management practices
In most cases the identification is veryeasy and fast, but not always….Once the pathogen is identified proper control strategies can be implemented
How to manage the problem of diseases in cassava?
Identification of the pathogen
Understanding the pathogen
Avoiding the pathogen
Controlling the pathogen
Understanding the pathogen
Key elements in the disease cycle are:
The source of inoculum
Mealy bug in planting material Stems with witches´ broom
Understanding the pathogen
Key elements in the disease cycle are:
The source of inoculumThe ways of transmission
Insects (particularlywhite flies) are important vectors
The cuttings are the most common
way of transmission
Tools may transmitdiseases
Understanding the pathogen
Key elements in the disease cycle are:
The source of inoculumThe ways of transmission
Environmental factors that influence it
Water logging conditions promote root rots
In general, adequate
fertilization will allow the plant to
defend itself(particularly in
relation to K)
How to manage the problem of diseases in cassava?
Identification of the pathogen
Understanding the pathogen
Avoiding the pathogen
Controlling the pathogen
NEVER introduce into a country vegetative material
For centuries cassava production in Asia has benefitted from little disease and pest pressuresThe best situation is when the cassava plant does not have to face a source of biotic stressHowever, this implies that Asian cultivars are most likely susceptible to the diseases they have never facedRecent events demonstrate the risk of unsupervised movement of planting material
NEVER introduce into a country vegetative material
The introduction inAsia of the mealybug (from Africaor southern Brazil) illustrates the huge economic damage that introducing new pests or diseases into Asia can have
NEVER introduce into a country vegetative material
NEVER introduce into a country vegetative material
Has frog skin disease been introduced into Asia?
NEVER introduce into a country vegetative material
This restriction isalso applicable to relatives of cassava such as Jathrofa
Avoiding the pathogen can also be achieved through good quality
planting material
… so it may be convenient to clean knives and machetes
Tools may transmitdiseases
El “Rincón de la Fortuna”The “Corner of Prosperity”
A good variety is not enough to have high andstable yields
The objective of most cassava breeding is toproduce varieties that can efficiently take advantage of whatever the environment canoffer to them
The best racing car still needs gasoline for winning a race…
Farmers select the best area of the field (typically10%)Special care (proper weeding + fertilizers) in that areaElimination 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
At harvest take stems ONLY from productive plants
Visual inspection of
root health (e.g. rots, frog
skin, etc.)
Farmers select the best area of the field (typically10%)Special care (proper weeding + fertilizers) in that areaElimination 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
High-yielding variety +
Good quality planting material
El “Rincón de la Fortuna”The “Corner of Prosperity”
How to manage the problem of diseases in cassava?
Identification of the pathogen
Understanding the pathogen
Avoiding the pathogen
Controlling the pathogen
Controlling the pathogen
Several strategies can be used to slow down or reduce the impact of diseases:
Chemical protection of cuttings or the plant
Chemical control
Chemical protection of cuttings with fungicides and pesticides is sometimes necessary (+
nutrients…)
But has to be done responsibly…
Controlling the pathogen
Thermotherapy of the cuttings can be useful for some diseases , buttemperature needs to be checked very carefully….
If things are done properly, however, chemical protection to the plant is seldom necessary in cassava
Chemical control
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
Cassava mosaic disease (CMD): a devastating virus for cassava in Africa and India.
ResistantSusceptible
CBSV(Cassava brown streak virus)
“Clean”Infected
It should be mentioned that it is possible to producetransgenic cassava… and one of the first applications of the technology was to create resistance to viruses
Resistant
Susceptible
Bacterial blight (Xanthomonas sp.)
Super elongation disease (fungal)Resistant Susceptible
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
Helping the plant defend to itselfA 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 inoculumFields with adequate drainage prevent root rotsAdequate fertilization will produce a vigorous plant that will withstand most biotic problemsAdequate management of weeds also contributes to a healthy cassava crop
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.
Thank you for your attention
Contacts:h.ceballos@cgiar.orgc.hershey@cgiar.org
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