Presentation by Dr. Munene Macharia (KARI, Kenya) at Wheat for Food Security in Africa conference, Oct 9, 2012, Addis Ababa, Ethiopia.

1. Impact of Climate
Change on Wheat
Pests in Kenya
M. Macharia, M. Gethi, C. Ngari
& M. Njuguna
KARI- Njoro,
P.O. Njoro, KENYA

2. Wheat production in Kenya
 Area under wheat- 150,000 ha
 Average yields - 2.5 t/ha.
 Strategic plan : To ensure self sufficiency by
(i) Increasing yields per unit area.
(ii) Expanding area under production.
 Possible by closing the gap between:
 Potential yield of wheat varieties (6- 7 t/ha).
 Actual realized by farmers (1.5- 2.5 t/ha).
 Gap is largely due to damage by diseases &
pests.

3. 1. African termites (Microtermes
spp)
 Occur in marginal areas
& cause 10-20%
damage.
 Their presence &
abundance depends
on temperature,
humidity, soil moisture
and soil type.
Termites

4. African termites….
 Attack wheat plants through the roots and stem &
reduce crop stand.
 Have changed food preference to wheat instead
of grasses.
 Decreasing rainfall &increasing temperatures has
resulted in increased termites incidences &
damage.
 Many growers are now reporting termite damage
unlike in the past.
 Expansion of wheat in marginal areas will result
in increased damage

5. 2: Cereal Aphids
Important aphids
include: Russian
wheat aphid,
 Diuraphis noxia,
 M. dirhodum,
 Sitobion avenae,
 Rhopalosiphum padi
 R. maidis.
 Schizaphis graminum
Cereal aphid species

6. Cereal Aphids….
 Responsible for most of the control interventions
on wheat.
 Crop losses vary from 10 - 100 %.
 Vectors of Barley yellow dwarf & cause 10- 60
% crop loss.
 Aphids prefer warm humid growing conditions
which promote outbreaks,
 Climate change may increase or decrease their
densities

7. Cereal Aphids….
 Sensitive to precipitation & are killed by heavy rains.
 A decrease in rainfall could result in reduced aphid
developmental rates.
 Drought stressed wheat crops reduce the
reproductive capacity of aphids.
 Responsive to climate change due to
(i) short generation time,
(ii) high reproductive rates, &
(iii) efficient dispersal mechanisms.
 Efficient cereal aphids control is important for both
adaptation to, and mitigation of climate change.

8. 3: African bollworm (Helicoverpa
armigera)
 One of the worst
agricultural pests in
Africa.
 Attacks a wide range of
cash and subsistence
crops.
 Highly polyphagous with
damage localized on
ears of wheat and thus
Boll worm attacking the ear of wheat influencing yield directly.

9. African bollworm….
 Ability to adapt to diverse cropping
systems have contributed to this pest
status (Konus, 2004).
 Diapauses can be induced by drought
(Jallow and Zaluchi, 1998).
 Highly migratory and can fly long
distances (Fitt, 1989).

10. African bollworm….
 Adopts two strategies to cope with seasonality
of their habitat; (i) spatial redistribution by
migration and (ii) diapause through periods of
drought.
 Diapausing pupae are more tolerant of drought.
 Fecundity is also influenced by temperature,
humidity and nutrition of adult and larvae
 Effectiveness of fungal bio-pesticides is also
affected by temperature and relative humidity.

11. 4: African armyworm (Spodoptera
exempta)
 An important major pest
of cereal crops (maize,
sorghum, millet, wheat ).
 Devastates both small
scale subsistence and
commercial wheat
production.
 30% of crop is lost in
outbreak years Armyworm caterpillar

12. African armyworm….
 In areas of erratic rainfall, pest cause
90% losses of crops.
 Pest is sporadic, with 3- 5 year cycles.
 Applications of bio-pesticides to control
army worm require tactical response to
seasonal climatic conditions.
 High temperatures do not favour
applications of pesticides or bio-pesticides.

13. African armyworm….
 Increased temperatures cause foliar
sprays to have increased viscosity,
resulting to spraying inefficiencies.
 Control of armyworm is a large scale
venture and requires national
collaboration.
 Armyworm attacks are reported and
fighting of the armyworm is reported to
Crop Protection Branch, MoA in Kenya.

14. 5: Red billed Quelea birds (Quelea
quelea)
 A major pest of small
grains throughout sub-
Saharan Africa.
 Africa’s main pest bird
problem and continue to
threaten small grain
cereal production.
Male Female  Worst major threat to
both small scale & large
scale wheat farming
causing 100% loss.

15. Red billed Quelea birds……
 Migratory movements vary with rainfall patterns
and grass seed availability .
 The management of this pest is complicated by
their extensive migrations within Africa.
 Rainfall pattern and resultant availability of fresh
grass seed influence the timing of the migratory
movements.
 Increased rainfall causes them migrate further,
increases their no.s & thus increasing damage
levels.
 Rainfall failure due to climate change, causes
them to remain sedentary.

16. 6: Rodents (Mastomys spp &
Arvicanthis spp)
 Are major known
rodents in Africa.
 Are a nuisance in
agriculture causing
severe economic
losses.
 Population explosions
of these rodents occur
at irregular intervals. Rats

17. Rodents …..
 Crop losses of over 50% have been recorded
during outbreaks in Kenya.
 Most damage in cereal crops occurs during
seedling stage and just before harvest.
 30% in pre-harvest and over 50% post harvest
losses are common.
 Weather (high rainfall and humidity) has a
distinct influence on occurrence of mass
appearance of rodents.

18. Rodents …..
 Temperature and humidity are also significant
factors in determining rodent activity.
 Farming in marginal areas has reduced native
vegetation cover & consequently the diversity of
the rodents.
 Both species are the most locally threatened due
to increasing habitat change.

19. Conclusion
 At present, the impacts of climate change on
wheat pests are not clear and unpredictable.
 Most pests can adapt to a wide range of
environment through selection and evolution.
 Climatic factors will play an important role in
limiting distribution and determining the life cycle.
 Higher temperatures may cause some pests to
disappear or become minor insect pests.
 In the face of climate change, there will be need to
develop and deploy new coping IPM strategies
and reduce overuse of pesticides.

20. THANK YOU