Biological control of weeds in European crops: recent achievements and future work

Approaches to the biological control of weeds in arable crops and integrati on of biological weed control with other methods of weed management are bro adly discussed, Various types of integrative approaches to biological contr ol of weeds in crops have been studied within the framework of a concerted European Research Programme (COST-816). During the period 1994-99, some 25 institutions from 16 countries have concentrated on five target weed comple xes. Some major scientific achievements of COST-816 are: (i) combination of the pathogen Ascochyta caulina with an isolated phytotoxin produced by thi s fungus to control Chemopodium album in maize and sugar beet; (ii) the ela boration and preliminary field application of a system management approach using the weed:pathogen system Senecio vulgaris:Puccinia lagenophorae to re duce the competitiveness of the weed by inducing and stimulating a disease epidemic; (iii) combination of underseeded green cover with the application of spores of Stagonospora convolvuli to control Convolvulus species in mai ze; (iv) assessment of the response of different provenances of Amaranthus spp, to infection by Alternaria alternata and Trematophoma lignicola, the d evelopment of formulation and delivery techniques and a field survey of nat ive insect species to control Amaranthus spp, in sugar beet and maize; (v) isolation of strains of different Fusarium, spp. that infect all the econom ically important Orobanche spp, and development of novel, storable formulat ions using mycelia from liquid culture. Although no practical control has y et been reached for any of the five target weeds, potential solutions have been clearly identified, Two major routes may be followed in future work, T he first is a technological approach focusing on a single, highly destructi ve disease cycle of the control agent and optimizing the efficacy and speci ficity of the agent. The second is an ecological approach based on a better understanding of the interactions among the crop, the weed, the natural an tagonist and the environment, which must be managed in order to maximize th e spread and impact of an indigenous antagonist on the weed.