Pest complex in agroforestry systems: the Malawi experience

Mchowa, J.W.; Ngugi, D. N.

doi:10.1016/0378-1127(94)90302-6

Cited by 25 publications

(13 citation statements)

References 9 publications

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“…This polyphagous pest is known to attack groundnut and weeds such as Conyza sumatrensis and Tagetes minuta (Taylor 1981). Sesbania and tephrosia were also found to host H. patruelis (Mchowa and Ngugi 1994;Minja et al 1999) but this insect did not cause death of these species. Therefore, care must be taken not to allow population build up of this insect and also not to plant susceptible crops after crotalaria fallow.…”

Section: Discussionmentioning

confidence: 94%

Abundance of insect pests and their effects on biomass yields of single vs. multi-species planted fallows

Girma

Rao²,

Day

et al. 2006

Agroforest Syst

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Indigenous and exotic leguminous shrubs that are promising for planted fallow for soil fertility replenishment in east and southern Africa have been found to harbour many herbivorous insects, giving suspicion that widespread adoption of fallow systems may aggravate insect pests. Studies were conducted on farms in western Kenya from 1999 to 2001 to monitor the abundance of herbivorous insects and assess their effects on biomass yields of pure and mixed fallows. The treatments tested were single and two-species mixtures of Tephrosia vogelii, Sesbania sesban and Crotalaria grahamiana and a natural fallow in a split plot design, with the fallow systems in the main plots and protection vs. no protection against insects in sub-plots spread over six farms. Eighteen insect species belonging to seven orders and 14 families were identified as pests of the fallows with varied abundance and infestation level across the sites. While Hilda patruelis and Amphicallia pactolicus were most damaging to C. grahamiana, Mesoplatys ochroptera was detrimental to S. sesban. T. vogelii hosted fewer insects than others. Nevertheless the pest infestation did not cause significant biomass yield reduction during the study period. Pest attack was generally greater in villages that had been testing the planted fallows for some years compared with villages that took up the fallows recently. This indicates the potential for increased pest infestation with increased adoption of the system by farmers. Multi-species fallows did not indicate any advantage over single species fallows in terms of either reduced pest incidence or increased biomass production.

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Section: Discussionmentioning

confidence: 94%

Abundance of insect pests and their effects on biomass yields of single vs. multi-species planted fallows

Girma

Rao²,

Day

et al. 2006

Agroforest Syst

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“…Leaf beetles such as M. ochroptera, O. bennigseni and Exosoma sp. can inflict substantial damage to sesbania in Malawi and Zambia (Mchowa and Ngugi 1994;Sileshi et al 2000Sileshi et al , 2002. However, beetles rarely cause tree mortality although beetle damage is aggravated if planting is done late (Sileshi et al 2002).…”

Section: Discussionmentioning

confidence: 98%

Farmers’ perceptions of tree mortality, pests and pest management practices in agroforestry in Malawi, Mozambique and Zambia

Sileshi¹,

Kuntashula

Matakala³

et al. 2007

Agroforest Syst

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Pest management research within the context of agroforestry is in its infancy, and it is often difficult to say when a particular pest justifies investment in research to establish facts. Understanding the potentials and drawbacks of farmers' indigenous ecological knowledge (ethnoecology) may form the basis for constructive collaboration between farmers, agroforestry scientists and extension staff. Therefore, the objectives of the study were to (1) assess farmers' knowledge and perceptions of pests, (2) prioritize pest problems that limit tree planting and maize production based on farmers' own criteria and (3) to identify farmers' indigenous pest management practices for priority pests. Data were collected using community meetings, individual interviews and direct observation by the first author. The farmers involved in this study in eastern Zambia had over ten years of experience, while most of the farmers in Mozambique and parts of southern Malawi were new to agroforestry. Farmers perceived insects as the major causes of tree mortality, followed by drought, bush fires and browsing by livestock. Among the biological constraints to maize production, insects (particularly termites and stalk bores) and weeds (particularly Striga asiatica) were more important in farmers' minds than crop diseases. Fundamentally, the farmers' perception of the causes of tree mortality and crop pests agreed with researchers' perceptions and the literature. Both termite and witch weed problems were associated with low soil quality, and farmers use various indigenous control practices to control these pests. Some farmers did not know the causes of tree mortality, and hence do not take action. Farmer's perception of tree mortality was found to be a function of operator-specific variables such as sex, level of education and years of experience with tree species.

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“…Unfortunately, this situation is likely to provoke problems of root competition between trees and crops when grown together. Root competition occurs when one root system reduces the access of another root system to soil water and nutrients, either by taking them up itself or by impeding the development of the associated root system, for example through allelopathic effects [May and Ash, 1990] or the promotion of root diseases [Mchowa and Ngugi, 1994]. Avoiding the inherent conflict between fertility maintenance through tree roots and competition from tree roots is a key problem in agroforestry.…”

Section: Fixation Of Atmospheric Nmentioning

confidence: 99%

Tree root characteristics as criteria for species selection and systems design in agroforestry

Schroth

1995

Agroforestry: Science, Policy and Practice

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Abstract. This literature review presents information about the role of tree root systems for the functioning of agroforestry associations and rotations and attempts to identify root-related criteria for the selection of agroforestry tree species and the design of agroforestry systems. Tree roots are expected to enrich soil with organic matter. feed soil biomass. reduce nutrient leaching. recycle nutrients from the subsoil below the crop rooting zone and improve soil physical properties. among other functions. On the other hand. they can depress crop yields in tree-crop associations through root competition. After a brief review of favourable tree root effects in agroforestry. four strategies are discussed as potential solutions to the dilemma of the simultaneous occurrence of desirable and undesirable tree root functions: 1) the selection of tree species with low root competitiveness. eventually supplemented by shoot pruning; 2) the identification of trees with a root distribution complementary to that of the crops; 3) the reduction of tree root length density by trenching or tillage; and 4) the use of agroforestry rotations instead of tree-crop associations. The potential and limitations of these strategies are discussed. and deficits in current understanding of tree root ecology in agroforestry are identified. In addition to the selection of tree species and provenances according to root-related criteria, the development of management techniques that allow the manipulation of tree root systems to maximize benefit and minimize competition are proposed as important tasks for future agroforestry research.

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Pest complex in agroforestry systems: the Malawi experience

Cited by 25 publications

References 9 publications

Abundance of insect pests and their effects on biomass yields of single vs. multi-species planted fallows

Abundance of insect pests and their effects on biomass yields of single vs. multi-species planted fallows

Farmers’ perceptions of tree mortality, pests and pest management practices in agroforestry in Malawi, Mozambique and Zambia

Tree root characteristics as criteria for species selection and systems design in agroforestry

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