Impact of Climate Change on Wheat Pests in Kenya


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

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Impact of Climate Change on Wheat Pests in Kenya

  1. 1. Impact of Climate Change on Wheat Pests in KenyaM. Macharia, M. Gethi, C. Ngari& M. NjugunaKARI- Njoro,P.O. Njoro, KENYA
  2. 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. 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. 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. 5. 2: Cereal AphidsImportant aphids include: Russian wheat aphid, Diuraphis noxia, M. dirhodum, Sitobion avenae, Rhopalosiphum padi R. maidis. Schizaphis graminum Cereal aphid species
  6. 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. 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. 8. 3: African bollworm (Helicoverpaarmigera)  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 thusBoll worm attacking the ear of wheat influencing yield directly.
  9. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 20. THANK YOU