Plant species diversity for sustainable management of crop pests and diseases in agroecosystems: a review

Abstract

Farmers are facing serious plant protection issues and phytosanitary risks, in particular in the tropics. Such issues are food insecurity, lower income in traditional lowinput agroecosystems, adverse effects of pesticide use on human health and on the environment in intensive systems and export restrictions due to strict regulations on quarantine pests and limits on pesticide residues. To provide more and better food to populations in both the southern and northern hemispheres in a sustainable manner, there is a need for a drastic reduction in pesticide use while keeping crop pest and disease damage under control. This can be achieved by breaking with industrial agriculture and using an agroecological approach, whose main pillar is the conservation or introduction of plant diversity in agroecosystems. Earlier literature suggest that increasing vegetational biodiversity in agroecosystems can reduce the impact of pests and diseases by the following mechanisms: (1) resource dilution and stimulo-deterrent diversion, (2) disruption of the spatial cycle, (3) disruption of the temporal cycle, (4) allelopathy effects, (5) general and specific soil suppressiveness, (6) crop physiological resistance, (7) conservation of natural enemies and facilitation of their action against aerial pests and (8) direct and indirect architectural/ physical effects. Here we review the reported examples of such effects on a broad range of pathogens and pests, e.g. insects, mites, myriapods, nematodes, parasitic weeds, fungi, bacteria and viruses across different cropping systems. Our review confirms that it is not necessarily true that vegetational diversification reduces the incidence of pests and diseases. The ability of some pests and pathogens to use a wide range of plants as alternative hosts/reservoirs is the main limitation to the suppressive role of this strategy, but all other pathways identified for the control of pests and disease based on plant species diversity (PSD) also have certain limitations. Improving our understanding of the mechanisms involved should enable us to explain how, where and when exceptions to the above principle are likely to occur, with a view to developing sustainable agroecosystems based on enhanced ecological processes of pest and disease control by optimized vegetational diversification.

Farming system design for innovative crop-livestock integration in Europe

“…This reinforces the idea that implementing innovations in complex and dynamic systems raises many social and economic questions in biological and technical domains (Folke et al, 2010). However, innovations relying on biologically diversified farming systems such as introducing grasslands in crop rotations for soil fertility effects (Franzluebbers and Stuedemann, 2009) or biological regulation (Ratnadass et al, 2012), need to be better documented to move from general principles to locally adapted practices.…”

Ecological principles underlying the increase of productivity achieved by cereal-grain legume intercrops in organic farming. A review

“…Cereal/legume intercropping is regarded as highly relevant in low-N-input systems and organic farming where nitrogen is often a limiting resource for crop growth (Willey 1979a;Ofori and Stern 1987;Vandermeer 1989;Willey 1990;Fukai and Trenbath 1993;HauggaardNielsen et al 2003;David et al 2005;Desclaux et al 2008;Bedoussac andJustes 2010a, 2010b;Naudin et al 2010). Intercropping has also been shown to: (i) improve soil conservation (Anil et al 1998), (ii) favour weed control (Banik et al 2006;Corre-Hellou et al 2011), (iii) reduce pests and diseases (Trenbath 1993;Altieri 1999;Hauggaard-Nielsen et al 2007;Corre-Hellou and Crozat 2005;Ratnadass et al 2012) and (iv) provide better lodging resistance (Anil et al 1998). Hauggaard-Nielsen et al (2007);(2001a, 2001b; Knudsen et al (2004) and Naudin et al (2009) HW durum wheat, SW soft wheat, B barley, F faba bean, P pea, NO no N-fertilization N organic N-fertilization Willey and Osiru (1972):…”

Multiple cropping systems as drivers for providing multiple ecosystem services: from concepts to design

“…habitat fragmentation. Resource dilution of a host plant in the plant mixture potentially makes the pest less efficient in locating and colonizing its host (Trenbath 1993;Ratnadass et al 2012). Resource dilution has been shown to be an appropriate means of managing many pests, such as aphids (A'Brook 1968;Smith 1976) and other phytophageous insects (Altieri 1999).…”

“…For example, fusarium head blight is very severe for wheat sown after maize (Pirgozliev et al 2003). Moreover, multiple cropping systems may contain species that produce biochemical cues that disrupt the development of diseases, pests, root parasitic nematodes, and weeds (Ratnadass et al 2012). These allelopathic effects are created mainly by the introduction of particular species into the intercrop (group A) or the crop sequence (group B).…”