Impact of Climate Change on Wheat Pests in KenyaM. Macharia, M. Gethi, C. Ngari& M. NjugunaKARI- Njoro,P.O. Njoro, KENYA
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.
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
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
2: Cereal AphidsImportant aphids include: Russian wheat aphid, Diuraphis noxia, M. dirhodum, Sitobion avenae, Rhopalosiphum padi R. maidis. Schizaphis graminum Cereal aphid species
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
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.
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.
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).
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.
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
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.
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.
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.
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.
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
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.
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.
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.