This presentation was given during East Africa community workshop on MLN in Nairobi

1. Dr. Suresh, L.M
Maize Pathology – Sub Saharan Africa
CIMMYT- Kenya
Management practices to MLN
Global Maize Program
EAC-CIMMYT
Regional Stakeholders Forum on Maize Lethal Necrosis (MLN) Disease
22nd
to 24th
May, 2018, Nairobi, Kenya

2. MLN is a viral disease caused by
combined infection of maize with
Maize Chlorotic Mottle Virus
(MCMV) and any of the
Potyviruses infecting cereals,
especially Sugarcane Mosaic
Virus (SCMV)
The disease was first reported
in Africa, particularly in Kenya
in Sept 2011, and since then
reported in Uganda, Tanzania,
Rwanda, D.R. Congo, and
Ethiopia.

3. MLN Disease Development
Vectors:
Presence of
aphids and
thrips
Environment:
Conditions
favoring
vectors and
disease
Susceptible
Germplasm
Virus: Either
individual or
compound

4. MCMVMCMV
Potyvirus
SCMV
MDMV
WSMV
MLNMLN
• Individual infection with mixture of viruses can also cause disease
• Typically, infection with one virus results in milder symptoms than MLN but
reaction depends on germplasm and viral strain.
Maize Lethal NecrosisMaize Lethal Necrosis

5. Why is the MLN devastating in EA?
• MCMV is new to the region
• Potentially new strains of SCMV/MDMV
• Conducive environment – continuous maize cropping
in certain areas leading to continuous build-up of virus
inoculum
• Seed contamination by MLN-causing viruses,
especially MCMV, besides local spread through insect
vectors
• Widespread cultivation of susceptible germplasm that
has never been screened for MCMV
• A very large proportion of commercial maize
varieties in eastern Africa as well as other regions in
sub-Saharan Africa are highly vulnerable to MLN.

6. Tackling the MLN challenge

7. Disease Symptoms
• Dying leaves, leading to premature plant death
• Failure to tassel and sterility in male plants
• Malformed or no ears
• Rotting cob

8. Symptoms of the disease
• Symptoms observed vary widely depending on;
-Germplasm
-Time of infection
-Prevailing environmental conditions
-Ratios of the viruses infecting the plant
• The symptoms can easily be confused with drought ,
micro- nutrient deficiency or stalk borer infestation

9. Symptoms in artificially inoculated maize plants in
screen house
MCMV SCMV

10. Chlorosis and Mottling Diffuse mottling and chlorosis
Early MLN Symptoms

11. Severe chlorosis and leaf necrosis

12. Shortened internodes and severe chlorotic mottle

13. ‘Dead Heart’ symptoms

14. Premature drying of the husks

15. Poor or no grain filling

16. 16
VIRULANT PATHOGEN
SUSCEPTIBLE
HOST
CONGENIAL
ENVIRONMENT
TIME
DISEASE

17. Management Strategies of Viral Diseases
Avoidance:
•Avoid continuous planting.
•Timely planting so that plants are at a less susceptible in early growth stages when the virus and the vectors is
present.
Avoidance:
•Avoid continuous planting.
•Timely planting so that plants are at a less susceptible in early growth stages when the virus and the vectors is
present.
Exclusion
•Impose quarantine (local and international)
•Use virus free seeds.
Exclusion
•Impose quarantine (local and international)
•Use virus free seeds.
Eradication:
Use herbicides to kill the weed hosts.
Rogue infected plants.
Use insecticides to kill vectors
Eradication:
Use herbicides to kill the weed hosts.
Rogue infected plants.
Use insecticides to kill vectors
Protection
Plant barrier crops.
Plant MLN resistant or tolerant maize cultivars.
Protection
Plant barrier crops.
Plant MLN resistant or tolerant maize cultivars.

18. Avoidance :
 Avoid visiting your maize field once in contact with any MLN affected maize field.

19. Avoidance
 Don’t feed infected MLN plants to livestock (cattle, sheep, goat., etc.,)

20. Avoidance :
Use clean tools and equipment’s during cultivation
 Keep your farm equipment clean and disinfect after and before use.

21. Avoidance
Community of Practice (CoP)
 Discuss within community and get common solution in consultation
with the ministry of agriculture

22. Avoidance:
Disease free certified seeds
 Use certified seeds from a reputed seed agency or a seed company
 Use disease resistant hybrids

23. Avoidance
 Do not use seeds from MLN / MCMV infected maize plants

24. Exclusion
 Remove the weed host and alternate host before and during the crop
cultivation

25. Exclusion
Maize free period
 Avoid growing maize up to 2 months

26. Exclusion:
Crop Rotation
• Grow non-maize crop like legumes after the maize
crop to avoid regular MLN host.

27. 27
SUCKING PESTS ROLE
Aphids
SuckingPests
Whitefly
Thrips
Transmits
Viruses

28. Eradication
Insect vector management
• It is very important to spray suspected or infected field with
systemic insecticide in consultation with your local ministry of
agriculture.

29. Eradication:
Rogue the suspected MLN plants
• Rogue the infected plants and burn them
– Rogue the plant during evening hours after pesticide spray.

30. Other approaches on seed transmission and contamination
• Study is going on about knowledge and relationship between
seed infestation and seed transmission of MCMV.
• Seed disinfection study on maize chlorotic mosaic virus seed
transmission is on progress.
• Initial encouraging result showed significant effect on
elimination of virus on maize seeds.
• Large scale protocol harmonization is in progress
Maize seed anatomy
Seedling grow out – After seed treatment
with chemical at MLN Screening facility
Naivasha
Treated Seeds

31. MLN Screening Facility established by CIMMYT-KALRO at Naivasha, Kenya

32. MLN - infected MLN - free

33. Thank you
for your
interest!