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Biological Control of Gramineous Stemborers in Kenya, Africa
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| Overview | Biological control of stemborers in Africa provides a sustainable solution for crop damaged crops. |
| Scale | organization, enterprise, collective, commercial farm, local region, bioregion, landscape, nation |
| Location | Nairobi, Kenya, Africa (1.2°S, 36.5°E), Coastal areas of East Africa in Kenya |
| Elevation | 0 to 300 meters |
| Climate | Tropical and subtropical steppe climate (BSh) |
| Agricultural Region | Shifting Cultivation - C |
| Population Density | 10-25 persons / square kilometer |
| Principle Crops | Maize (Zea mays), Sorghum (Sorghum bicolor), Pearl Millet (Pennesitum glaucum) |
| Domestic Animals | none |
| Soils | Alfisols, Ustalfs (A3), warm subhumid to semi-arid; dry >90 days (some Reddish Chestnut and Red & Yellow Podzolic soils) |
| Natural Vegetation | Grass and other herbaceous plants, broadleaf deciduous, shrubform, minimum height 3 feet, growth singly or in groups or patches (GDsp) |
| Ecoregion | Savanna Province, seasonally dry forest, open woodland , tall grass (TR1) |
| Basic Principles addressed | Use Renewable Resources, Minimize Toxics, Manage Ecological Relationships, Manage Whole Systems, Maximize Long-Term Benefits, Value Health |
| Page Author and Date | Chris Bley |
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Beneficial insects can be introduced to destroy other insects that are considered harmful to crop plants. Three gramineous stemborers (Chilo partellus, Chilo orichalcociliellus and Sesamia calamistis) are considered to be the most damaging in Africa, destroying maize, millet and sorghum crops. All stemborers found in Africa are thought to be native with the exception of Chilo partellus which has spread to all countries in East and southern Africa from Asia. Studies conducted in Kenya introduced a parasitic insect, Cotesia flavipes (native to Indo-Australia) to test its effectiveness in controlling the three most damaging gramineous stemborers. During a 6-8 week period in 1993 (March-July), C. flavipes were released in three sites along the coast of Kenya to determine the predation on the stemborer insects. Results demonstrate that all three stemborers were parasitized by C. flavipes, and annual recovery of the stemborers three years after the release supports the theory that C. flavipes has been established as a permanent predator of stemborers along coastal areas in Kenya. |
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Biological control of insect pests prevents crop destruction that would otherwise be solved with continued pesticide applications. The stemborer C. partellus, responsible for the greatest damage to maize and sorghum crops, was most effected by the introduction of C. flavipes. Being an exotic in Africa, C. partellus does not have natural enemies controlling its population size and crop destruction goes unchecked. Introduction and colonization of predators can control and manage the adverse effects of stemborers in Africa. However, this successful introduction of a predatory species was the third attempt in the region, illustrating the difficulties in biological control by this approach. |
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Use Renewable Resources Biological control keeps insect pest populations in balance, eliminating the use of non-renewable off-farm inputs.
Minimize Toxics Biological control of insect pest populations eliminates the use of toxic materials that harm the environment. Manage Ecological Relationships Introduction of natural predators manages pests instead of "controlling" them. Manage Whole Systems Colonization of predatory insects has lasting effects across farms, landscapes and bioregions. Maximize Long-Term Benefits Introduction of predatory insects is a long-term strategy for controlling proliferation of harmful insects. |
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