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Armyworm Management in Africa:
What do we know and what can we learn?
1 Professor Ken Wilson [email protected]
FAO Expert Meeting on Fall Armyworm Accra, Ghana (18th – 20th July 2017)
Fall armyworm
(Spodoptera frugiperda)
African armyworm
(Spodoptera exempta)
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Prof Ken Wilson Professor of Evolutionary Ecology
Insects & Parasites Ecology Group
Lancaster Environment Centre
Lancaster University
[email protected]
Host-pathogen
interactions
Ecology of insect
crop pests
Biocontrol of crop
pests using
baculoviruses
Nutritional ecology
of insects
1990
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Unanswered questions about Fall armyworms:
FAO Harare meeting February 2017
• Where did the Fall armyworm come from?
• How does its life-cycle differ from that of the African
armyworm?
• Will it spread and will it persist long-term?
• How do we control it?
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Unanswered questions about Fall armyworms
• Where did the Fall armyworm come from?
• How does its life-cycle differ from that of the African
armyworm?
• Will it spread and will it persist long-term?
• How do we control it?
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Unanswered questions about Fall armyworms
• Where did the Fall armyworm come from?
• How does its life-cycle differ from that of the African
armyworm?
• Will it spread and will it persist long-term?
• How do we control it?
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FAW: 2 strains, 4 haplotypes (Nagoshi et al.)
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Genetic analysis of Fall armyworm from Africa
Maximum likelihood
condensed bootstrap
barcode of Zambian
larval samples using
135 bp mitochondrial
cytochrome oxidase I
(COI) sequence.
Results from Tanzania
and Rwanda being
processed.
Fall armyworm
rice strain (RS)
Fall armyworm
corn strain (CS)
Samples courtesy of ZARI
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Genetic analysis of Fall armyworm from Africa:
strain ID using CO1 markers
68
32
Overall Tanzanian FAW Strains (n = 28 moths from trap in
maize field, 1 region)
% Rice % Corn
82
18
Overall Zambian FAW Strains (n = 44 larvae on maize, all
regions)
% Rice % Corn
Overall Rwandan FAW Strains (>300 larvae on
maize, all regions)
% Rice % Corn
36
64
Overall Togo FAW Strains (n = 62 larvae on maize, all regions, Nagoshi et al 2017)
% Rice % Corn
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Genetic analysis of Fall armyworm from Africa:
haplotype ID using CO1 polymorphic sites
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67
Overall Tanzanian Corn Strain Haplotypes
(n = 9 moths)
% h1 % h2 % h3 % h4
100
Overall Zambian Corn Strain Haplotypes
(n = 8 larvae)
% h1 % h2 % h3 % h4
Note relatively small
sample sizes
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Unanswered questions about Fall armyworms
• Where did the Fall armyworm come from?
• How does its life-cycle differ from that of the African
armyworm?
• Will it spread and will it persist long-term?
• How do we control it?
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How will Fall and African armyworms interact?
African armyworm
(Spodoptera exempta)
Fall armyworm
(Spodoptera frugiperda)
Photo: G. Goergen
Photo: Kansas State University
Photo: K. Wilson
Photo: K. Wilson
• Movement and outbreaks of both species
determined by similar environmental
factors
• Both eat maize (vegetative vs
reproductive parts)
• FAW is cannibalistic (more competitive?)
• Both susceptible to disease – do they
share pathogens (enemy release vs
spillover)?
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Unanswered questions about Fall armyworms
• Where did the Fall armyworm come from?
• How does its life-cycle differ from that of the African
armyworm?
• Will it spread and will it persist long-term?
• How do we control it?
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Presumed distribution of FAW: Feb 2017
Data from Rose et al. (2000)
https://youtu.be/A8VTL1sP0KE
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Presumed distribution of FAW: Jun 2017
Data from Rose et al. (2000)
https://youtu.be/CWhk1u2DBjU
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Historical analysis of armyworm
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Patterns of African armyworm outbreaks
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Providing free accessible information on
Fall and African armyworm The Armyworm Network http://www.lancaster.ac.uk/armyworm @spodoptera007
Fall armyworm spread movie: https://youtu.be/CWhk1u2DBjU (updates available on the Armyworm Network)
50 years of African armyworm outbreaks: https://youtu.be/A8VTL1sP0KE
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Early-warning system needed – the power of pheromones!
Courtesy of Prof Nkunika, UNZA
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Early-warning system needed – the power of pheromones!
Rain gauge
Community forecaster with
pheromone traps
Community-based armyworm forecasting:
- Pheromone trap
- Rain gauge
- Local operators chosen by the village
- Simple rules for assessing risk of attack
Mushobozi, Grzywacz, Musebe, Kimani & Wilson (2005) Aspects of Applied Biology 75: 37-45.
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How do we control it?
• Chemicals?
- Which chemicals are effective and safe? Resistance?
• GM crops?
- Is Africa ready? Costs? Resistance?
• Biological pesticides?
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Biological control
• Bt pesticide spray can be effective (resistance?)
• Botanicals (e.g. neem) can also be effective, especially
for smallholder farmers who lack access to chemicals
• Biopesticides – natural diseases of insects (viruses,
fungi, bacteria, etc.) …
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Botanicals
• Botanicals (e.g. neem, Tephrosia vogelii, pawpaw, etc.)
can also be effective, especially for resource-poor
smallholder farmers who lack access to chemicals.
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Biopesticides
Ken Wilson (Lancaster University,
U.K.)
David Grzywacz (Natural Resources
Institute, U.K.)
Wilfred Mushobozi (EcoAgriConsult Ltd,
Tanzania)
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A virus-processing plant built in Tanzania
ready to produce tonnes of SpexNPV biopesticide locally
Funding for registration and commercialisation to end product is still needed
There is a similar biopesticide (SfMNPV) that is being produced commercially against Fall armyworm in the Americas!
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Does SpexNPV also kill African FAW?
Probably not … but
Very preliminary results at this stage (just one replicate of each, single isolates)
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Resistance management
• Baculoviruses compatible with other IPM approaches due to
low impact on non-target organisms
• Baculoviruses tend to be genetically diverse (more targets
for selection) - >100 genotypes of SpexNPV in Tanzania alone
• Resistance very unlikely (only one known case, swiftly
resolved)
• Governments panic buy pesticides, so let’s make sure there
are safe pesticides for purchase (registration).
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What about microbes in the wild - NPV?
Preliminary analyses of Tanzanian moths suggest the presence of
SfMNPV virus – possibly 2 strains (but needs sequencing); lower
prevalence in Zambian larvae – plus other viruses may be present.
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What about microbes in the wild - fungus?
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What about other natural enemies?
Earwig (Dermaptera)
Parasitoids (incl. Campoletis sp.)
Other natural enemies of AAW well described
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Summary • Fall armyworm has spread across Africa at an alarming rate,
though the true impact on maize production has yet to be
established
• We know lots more than we did even just a few months ago –
but there still remain many unanswered questions
• We can learn a lot from African armyworm experiences, as
well as experiences in the native range of the FAW
• We now need a regional strategy for the monitoring and
management of this new invasive pest.
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The End
LANCASTER UNIVERSITY
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S. frugiperda host strain: Corn Strain (CS) EcoRV negative (GATACC), Rice Strain (RS) = EcoRV positive (GATATC)
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S. frugiperda host strain: Nucleotides 1178-1183: Corn Strain (CS) EcoRV negative (GATACC), Rice Strain (RS) = EcoRV
positive (GATATC)
Nucleotides 1164/1287 Corn Strain Haplotype 1 = A/A Corn Strain Haplotype 2 = A/G Corn Strain Haplotype 3 = G/A Corn
Strain Haplotype 4 = G/G