Role of vectors and their host plants in the epidemiology of MLN, presented at the International Conference on “MLN Diagnostics and Management in Africa,” organized by AGRA (Alliance for Green Revolution in Africa) and CIMMYT, 12-14 May, 2015

1. Role of vectors and their host plants in
the epidemiology of maize lethal
necrosis disease
Nyasani, J
Elizabeth, K
Subramanian, S

2. Complexities of MLN Epidemiology
Maize chlorotic
mottle virus
(MCMV)
Sugarcane
mosaic virus
(SCMV) or
other cereal
potyvirus
Maize
Vectors of
MCMV –
Thrips,
beetles and
others?
Vectors of
potyviruses
– Aphids and
others ?
Maize
- MLN
Alternate hosts – Weeds or cultivated crops
Natural enemies of vectors

3. Information so far on insect vectors
• Maize chlorotic mottle virus
• Corn thrips, Frankliniella williamsi
• Cereal leaf beetle, Oulema melanopa
• Corn flea beetle, Chaetocnema
pulicaria
• Rootworms, Diabrotica spp
• Sugarcane mosaic virus
• Aphids, Rhopalosiphum maidis
Source: Pest net and
Fotoopa
What else??

4. Distribution of potential vectors:
Kenyan situationKenyan situation

5. Distribution of thrips on maize in Kenya (Jun-Sep 14)

6. Distribution of aphids on maize in Kenya (Jun-Sep 14)

7. Distribution of beetles on maize in Kenya (Jun-Sep 14)

8. Distribution of stemborers on maize (Jun-Sep 14)

9. Distribution of leafhoppers on maize (Jun-Sep 14)

10. Distribution of whiteflies on maize (Jun-Sep 14)

11. Confirmed vectors of MCMV

12. Corn thrips
Onion thrips
Thrips
Common blossom thrips

13. Distribution of vector thrips in east Africa
Frankliniella williamsi Frankliniella schultzei
Thrips tabaci

14. Other vectors - Beetles
Curculionid weevil Sap beetle
Cereal leaf beetle

15. Vectors of SCMV
Cereal leaf aphid

16. Host range of MCMV and
SCMV and their vectorsSCMV and their vectors

17. Role of host plants spread of MCMV and SCMV
A: Role of wild grasses
in spread of SCMV
B: Role of finger millet in
spread of MCMV
A B

18. Presence of MCMV and SCMV in non-maize plants
Finger millet showing mottle
symptom
Tested positive for MCMV by ELISA and
RT-PCR
A wild grass showing chlorotic
and streak symptoms
Tested positive for SCMV by ELISA and
RT-PCR

19. Presence of MCMV and SCMV in wild and
domesticated grasses, and cereal crops
Plant species MCMV SCMV
Wild grasses
Digitaria abyssinica + +
Cynodon dactylon + +
Pennisetum cladestinum + +
Digitaria velutina + +
Cyperus rotundus + -
Bracharia brizantha + +Bracharia brizantha + +
Domesticated grasses
Saccharum officinarum + +
Pennisetum purpureum + -
Cereals
Eleusine coracana + +
Sorghum bicolor - +

20. Vector management: Thrips
16
18
Numberofthripspermaizeplant
Control (seed treatment alone)
Ctrl +soil applic of Trichoderma+Nurelle-D spray at 2 weeks interval
Ctrl+soil applic of Trichoderma+Maetarhizium spray at 2 weeks interval
Ctrl+soil applic of Trichoderma+Metarhizium spray-Nurelle-D-Metarhizium spray
Ctrl+Nurelle-D spray at 2 weeks interval
Ctrl+Metarhizium spray at 2 weeks interval
Ctrl+soil applic of Trichoderma alone
0
2
4
6
8
10
12
14
Week 1 Week 2 Week 3 Week 4 Week 5 Week 6
Numberofthripspermaizeplant

21. Vector management: Beetles
1.6
1.8
Numberofbeetlespermaizeplant
Control (seed treatment alone)
Ctrl +soil applic of Trichoderma+Nurelle-D spray at 2 weeks interval
Ctrl+soil applic of Trichoderma+Maetarhizium spray at 2 weeks interval
Ctrl+soil applic of Trichoderma+Metarhizium spray-Nurelle-D-Metarhizium spray
Ctrl+Nurelle-D spray at 2 weeks interval
Ctrl+Metarhizium spray at 2 weeks interval
Ctrl+soil applic of Trichoderma alone
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
Week 1 Week 2 Week 3 Week 4 Week 5 Week 6
Numberofbeetlespermaizeplant

22. Vector management: Aphids
10
Numberofaphidspermaizeplant
Control (seed treatment alone)
Ctrl +soil applic of Trichoderma+Nurelle-D spray at 2 weeks interval
Ctrl+soil applic of Trichoderma+Maetarhizium spray at 2 weeks interval
Ctrl+soil applic of Trichoderma+Metarhizium spray-Nurelle-D-Metarhizium spray
Ctrl+Nurelle-D spray at 2 weeks interval
Ctrl+Metarhizium spray at 2 weeks interval
Ctrl+soil applic of Trichoderma alone
0
2
4
6
8
Week 1 Week 2 Week 3 Week 4 Week 5 Week 6
Numberofaphidspermaizeplant

23. Concluding remarks
Corn thrips, common blossom thrips, sap beetles,
and onion thrips are vectors of MCMV
Corn leaf aphid is a vector of SCMV
There could be other vectors for the two viruses
The distribution of the vectors differs with season
and plant stageand plant stage
Wild and domesticated grasses serve as alternative
host of MCMV and SCMV
The suitable areas for the grasses are mainly
located in the key maize growing counties
Biopesticides are effective in the management of
vectors of viruses causing MLN

24. Way Forward: Capacity building for detection, monitoring
and management of MLN and its vectors

25. Acknowledgements
Kenya Agricultural Productivity and Agribusiness Project