Biological control by conservation

• Definition and role in the reduction of phytosanitary products : long-term development of an environment favorable to the natural enemies of crop pests. This involves providing them with places to lay eggs and refuge, but also food resources (pollen, floral and extra-floral nectars) essential for the adults of certain species (lacewings, hoverflies, parasitoids) as well as secondary prey. Beneficiaries thus attracted can contribute to controlling pest populations present on crops. Insecticide treatments can then be avoided as a consequence and must also be avoided in order to preserve the auxiliaries.
• Against which pests? Various aerial pests (mealybugs, aphids, whiteflies, mites, etc.).
• On which crops? Market gardening, roots and tubers.
• When ? Some facilities are permanent (hedges) but others must be put in place each year (grass and flower strips).
• Where ? It is advisable to introduce plant diversity (relay plants) at several levels:
  • inside the plots (association of crops, intercropping plants, isolated plants).
  • around plots or at the entrance to greenhouses (grass and flower strips, plant beds, rational management of weeds, isolated plants).
  • at the landscape scale (orchards, hedges, groves).

Collective management of the landscape on a scale greater than that of exploitation is desirable because the diversity of habitats and refuge species influences that of auxiliaries.

• In what conditions ? The selection of relay plants is made according to the pests to be regulated in the plot: choose plants that host phytophagous of the same genus as the pests to feed the auxiliaries when the pests are not present. These phytophagous must not attack the farm's cash crops. Choose plant species with good nectariferous and polliniferous capacities. Be vigilant by avoiding species that can favor bio-aggressors and which can become reservoirs of pests or diseases for neighboring crops (plants of the same family). Choose plant species already present locally, to avoid introducing new, potentially invasive plants. In addition, auxiliaries more easily colonize a plant that they are already used to occupying rather than a new plant. It is preferable to introduce several species in the same arrangement and to mix perennial and non-perennial species to provide resources to auxiliaries throughout the year. If the plots are large, the plants must be distributed within them. It is advisable to mow as late as possible when flowering is over or, failing that, to alternate mown and unmown strips. In the case of hedges, these must occupy at least 5% of the surface of the plot to offer shelter to auxiliaries and be irrigated for the first 3 years. A mixture of species is preferable, the hedge must be sufficiently dense, connected to other sources of biodiversity (ecological corridor). Nevertheless, it would seem that in arid zones hedgerows are rather a refuge for pests.
• Regulations : the rules of good agricultural and environmental conditions (GAEC) encourage the establishment of grass buffer strips along watercourses with a width of at least 5 m. Only native species are allowed, except for invasive species.
• Working time : increase for sowing or planting, observation and management of developments: between 15 and 20 hours for the establishment of a 100 m hedge and 1 hour/year for its maintenance (the 1st year and to a lesser extent subsequently, one or more weeding operations are necessary between planting and the annual trimming or pruning of the hedge).
• Compatibility of alternative techniques with each other :  
  • +: inundative biological control , push-pull , chemical substitution .