mln workshop: role of vectors and their host plants in maize lethal necrosis epidemiology -- j...
TRANSCRIPT
Role of vectors and their host plants in the epidemiology of maize lethal
necrosis disease
Nyasani, JElizabeth, KSubramanian, S
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
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??
Distribution of potential vectors: Kenyan situationKenyan situation
Distribution of thrips on maize in Kenya (Jun-Sep 1 4)
Distribution of aphids on maize in Kenya (Jun-Sep 1 4)
Distribution of beetles on maize in Kenya (Jun-Sep 14)
Distribution of stemborers on maize (Jun-Sep 14)
Distribution of leafhoppers on maize (Jun-Sep 14)
Distribution of whiteflies on maize (Jun-Sep 14)
Confirmed vectors of MCMV
Corn thrips
Onion thrips
Thrips
Common blossom thrips
Distribution of vector thrips in east Africa
Frankliniella williamsi Frankliniella schultzei
Thrips tabaci
Other vectors - Beetles
Curculionid weevil Sap beetle
Cereal leaf beetle
Vectors of SCMV
Cereal leaf aphid
Host range of MCMV and SCMV and their vectorsSCMV and their vectors
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
Presence of MCMV and SCMV in non-maize plants
Finger millet showing mottle symptomTested positive for MCMV by ELISA and RT-PCR
A wild grass showing chlorotic and streak symptomsTested positive for SCMV by ELISA and RT-PCR
Presence of MCMV and SCMV in wild and domesticated grasses, and cereal crops
Plant species MCMV SCMV Wild grassesDigitaria abyssinica + +Cynodon dactylon + + Pennisetum cladestinum + + Digitaria velutina + + Cyperus rotundus + -Bracharia brizantha + + Bracharia brizantha + +
Domesticated grassesSaccharum officinarum + +Pennisetum purpureum + -
CerealsEleusine coracana + + Sorghum bicolor - +
Vector management: Thrips
16
18
Nu
mbe
r of t
hrip
s pe
r mai
ze p
lan
t
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
Nu
mbe
r of t
hrip
s pe
r mai
ze p
lan
t
Vector management: Beetles
1.6
1.8
Nu
mb
er o
f be
etle
s p
er
ma
ize
pla
nt
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
Nu
mb
er o
f be
etle
s p
er
ma
ize
pla
nt
Vector management: Aphids
10
Nu
mbe
r of a
phid
s pe
r mai
ze p
lan
t
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
Nu
mbe
r of a
phid
s pe
r mai
ze p
lan
t
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
Way Forward: Capacity building for detection, monitoring and management of MLN and its vectors
Acknowledgements
Kenya Agricultural Productivity and Agribusiness Project