Farmers use more chemical pesticides when nearby plots are under organic cultivation. However, when there is a substantial increase in the total area of organic farming or when organic fields are clustered, pesticide usage decreases. This finding of an American study is reported in the scientific journal Science. The empirical study builds on a theoretical study from 2013, in which ecologist Felix Bianchi from Wageningen University & Research drew similar conclusions.
"Natural enemies of pest insects are more abundant on organically managed fields than on traditionally managed fields," explains Bianchi. "This leads to a natural balance, where populations of pest insects are kept in check by their natural enemies." When pest insects migrate to fields where pesticides are used, problems arise because natural enemies, such as spiders, parasitic wasps, and predatory beetles, are much less abundant. This prompts farmers to resort to more intensive use of pesticides, as revealed by the study.
According to Bianchi, the findings from the two studies highlight the need for a further transition towards sustainable agriculture. "In the Netherlands, we should transition more rapidly to cultivation methods that use little or no chemical pesticides. Currently, less than 5 percent of the agricultural land is managed organically; if that were to increase to 20 or 30 percent, farmers would need to spray much less because there would be more natural enemies present in our landscapes."
