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close this bookAbstracts on Sustainable Agriculture (GTZ; 1992; 423 pages)
Open this folder and view contentsAbstracts On Traditional Land-Use Systems
Open this folder and view contentsAbstracts on farming systems research and development
Open this folder and view contentsAbstracts on integrated systems
Open this folder and view contentsAbstracts on cropping system
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View the documentAcknowledgements
View the document1. Designing integrated pest management for sustainable and productive futures.
View the document2. Biotechnology's bitter harvest: herbicide-tolerant crops and the threat to sustainable agriculture.
View the document3. Chemistry, agriculture and the environment.
View the document4. Mise au point de techniques appropriées de lir qui seront utilisés par les petits agriculteurs traditionnels d'Afrique tropicale.(developing appropriate ipm technology for the traditional small-scale farmer in tropical Africa).
View the document5. Biological control in developing countries: towards its wider application in sustainable pest management.
View the document6. Transforming plants as a means of crop protection against insects.
View the document7. Utilization of va-mycorrhiza as a factor in integrated plant protection.
View the document8. Activity of four plant leaf extracts against three fungal pathogens of rice.
View the document9. A useful approach to the biocontrol of cassava pathogens.
View the document10. Evaluation of the biological activity of flax as a trap crop against orobanche parasitism of vicia faba.
View the document11. Insect pest management.
View the document12. Economic contributions of pest management to agricultural development.
View the document13. The effects of intercropping and mixed varieties of predators and parasitoids of cassava whiteflies (hemiptera: aleyrodidae) in Colombia.
View the document14. Prospects for traditional and cultural practices in integrated pest management of some root crop diseases in rivers state, Nigeria.
View the document15. Studies on cowpea farming practices in nigeria, with emphasis on insect pest control.
View the document16. Effect of various fertilizers and rates on insect pest/pearl millet relationship in Senegal.
View the document17. Insect pests of intercrops and their potential to infest oil palm in an oil-palm-based agroforestry system in India.
View the document18. Using weather data to forecast insect pest outbreaks.
View the document19. Insect pest management and socio-economic circumstances of small-scale farmers for food crop production in western Kenya: a case study.
View the document20. Rodent communities associated with three traditional agroecosystems in the San Luis potosi plateau, Mexico.
View the document21. Grain storage losses in Zimbabwe.
View the document22. Controlling weeds without chemicals.
View the document23. Weed management in agroecosystems: ecological approaches.
View the document24. Manual on the prevention of post-harvest grain losses.
View the document25. Evaluation of efficient weed management systems in pigeonpea (cajanus cajan l.)
View the document26. Weed management in a low-input cropping system in the Peruvian Amazon region.
View the document27. Poblaciones, biomasa y banco de semillas de arvenses en cultivos de maiz zea mays l. Y frijol phaseolus vulgaris l. Efecto de m+todos de control y rotaciones. (Weed population, biomass, and seed bank in maize and bean crops. Effects of control methods and crop rotations).
View the document28. Effects of groundnut, cowpea and melon on weed control and yields of intercropped cassava and maize.
View the document29. Intercropping and weeding: effects on some natural enemies of African bollworm, heliothis armigera (hbn.) (lep., Noctuidae), in bean fields.
Open this folder and view contentsAbstracts on water management
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13. The effects of intercropping and mixed varieties of predators and parasitoids of cassava whiteflies (hemiptera: aleyrodidae) in Colombia.

Bull. ent. Res., 79, 1989, pp. 115-121

In this paper, the responses of natural enemies of cassava whiteflies to different cropping systems and their role in bringing about reduced whitefly load in cassava intercropped with cowpea are reported.

In this regard, the effects of different cropping systems on the whitefly predator Delphastus pusillus (Le Conte) and on the combined action of the parasitoides Amitus aleurodinus Haldeman and Eretmocerus aleyrodiphaga (Risbec) are discussed.

The predator D. pusillus was low in numbers during the intercrop period and was significantly lower in cassava-cowpea plots than in other treatments for much of the trial. Correlation analysis of predators and prey indicated that the beetles displayed a functional response. D. pusillus was abundant for many months but was unable to control whitefly populations. Ratios of whiteflies to predators coupled with information on prey consumption suggest that predators played only a minor role in whitefly population dynamics. Bettle arrival in the field lagged behind that of the whiteflies, and the highest populations of D. pusillus were in the final month of the trial, reflecting a lack of synchronicity between predator and prey.

D. pusillus attacks a range of whitefly species, but within the systems employed in this study it can be considered a relative specialist because neither cowpea nor maize provided alternative hosts. D. pusillus was never observed on the associated crops, suggesting that they did not provide nectar or pollen to this bettle. However, the presence of cowpea and maize intercrops may have enhanced the activity of this predator. A functional response strongly suggested by beetle distribution in the postintercrop period was not in evidence when intercrops were in the field, and predator: prey ratios were highest in cassava-cowpea systems at this time.

Parasitism of A. socialis was a far more important mortality factor than predation. The role of parasitism in this species was even more important on CMC 40, where predator populations were very low, than on MCOL 2257. Rates of combined parasitism of A. socialis by Amitus aleurodinus and E. aleyrodiphaga were equal between treatments. Overall mortality of the pupal stage was also similar across cropping systems.

Parasitism of T. variabilis was negligible, and for this whitefly D. pusillus was the most important natural enemy.

Intercropping cassava with cowpea reduced populations of the cassava whiteflies Aleurotrachelus socialis and T. variabilis. The effect of the intercrop was residual, with lower populations persisting for six months after cowpea harvest. However, predators were opportunistic, with higher populations correlated with greater numbers of prey in monocultures.

Parasitism levels were independent of cropping system. Therefore, the natural enemies hypothesis can be rejected in explaining the lower populations of whiteflies found on intercropped cassava. Furthermore, the residual effect of the cowpea intercrop on whitefly populations cannot be explained by a build-up of natural enemies in this system during the intercrop period.

A. socialis and T. variabilis larvae suffered substantial mortality in addition to the effects of predators.

Differences in whitefly populations in various cropping systems, including residual effects, cannot be attributed to mortality factors.

In this regard, the effects of different cropping systems on the whitefly predator Delphastus pusillus (Le Conte) and on the combined action of the parasitoids Amitus aleurodinus Haldeman and Eretmocerus aleyrodiphaga (Risbec) are discussed.

1207 92 - 10/134

Plant protection

Africa, Nigeria, study, rain forest belt, lowlands, root crops, diseases, integrated pest management, traditional methods, agronomic practices, IITA

ODURO, K.A. et al.

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