Agricultural lands are often characterized as poor lands regarding flora and fauna biodiversity. Indeed, cropping systems often reduce the plant richness to one species (for example, monocultures of wheat, maize or cabbage) in a wide area. Therefore, the consequence on fauna is often the decrease in species number, notably species of insects. As a consequence, fields are mostly invaded by one specific species (called key pest) causing a lot of yield losses if not treated with pesticides.

One of the solution proposed by the EUCLID project is to increase plant richness in the agricultural landscapes in order to bring back arthropods richness in the fields, notably natural enemies richness. A lot of studies already show the importance of natural areas (forest, grass strips, riparian forest) in the increase of biocontrol in surrounding fields, which lead us to wonder if crop plant richness could also increase the presence of natural enemies in our cropped fields.

In order to answer that question, a field trial was developed by the National Institute of Research in Agronomy (INRA, France) and Chinese Academy of Agricultural Sciences (CAAS, China) at the Langfang experimental station in China. First results were very promising: two main tendencies were the increase in tomato yield into polycultural systems and the increase in parasitism rates. Specialists pests were more attracted by monocultural system on the contrary of generalist pests that were found in higher quantities in polycultural systems.

 

landscape diversification
Polyculture (left and middle) and monoculture system (right) tested in the field trial at Langfang experimental station, China.