According to a study published in the journal Proceedings of the Royal Society BWhen fields of oilseed rape are exposed to exhaust gases and ozone found in vehicle and industrial emissions, the number of predatory insects - natural enemies of aphids is significantly reduced, reports Phys.org portal.
A team led by scientists from the University of Reading used special equipment to deliver controlled amounts of diesel exhaust gases and ozone to oilseed rape plants. They also added aphids to plants and measured the reproductive vigor of a population of parasitic wasps, which usually lay their eggs inside freshly stung aphids.
The total number of parasitic insects is decreasing. This is a worrying result, as many sustainable farming practices rely on natural pest control to keep aphids and other unwanted insects away from valuable crops.
Diesel fuel and ozone appear to make it harder for wasps to find aphids to prey on, and so the wasp population will decline over time.
In the presence of both contaminants, oilseed rape plants produced more of the compounds that give crops of the brassica family, including mustard and cabbage, their characteristic bitter, tangy, and peppery notes. Usually they repel insects, but in the case of Diaretiella rapae wasps, large numbers and reproductive success associated with diesel exhaust and ozone together.
Diaretiella rapae especially likes to prey on cabbage aphids. Some flavor and odor compounds found in rapeseed, turn into substances that really attract D. rapae.
Perhaps D. rapae is a good choice to deal with pests in areas polluted with diesel fuel and ozone. It does show that the only way to predict and mitigate the impact of air pollutants is to study entire biological systems.
As vehicles move from diesel fuel to electric motors, the degree of air pollution will vary. Knowing how parasitic wasps responding to these progressive changes will be important for planning mitigation strategies to ensure sustainable food security now and in the future. This study shows that we must also consider the impact of different types of pollution on plants, wasps and insect prey, as well as the interaction between them.