In the world of bugs there are the bugs that eat your crops and—usually in much smaller numbers—there are the bugs that eat, parasitize or otherwise neutralise the bugs that eat your crops.
In England, the Centre for Ecology and Hydrology is looking at a way to even up those numbers. It’s looking at providing habitat for beneficial insects, in the form of strips of brightly coloured flowers, planted throughout farm fields.
Last fall (2017) the CEH planted strips of annual wildflowers in fields on 15 farms in central and eastern England. The carefully chosen plants included oxeye daisy, red clover, common knapweed and wild carrot.
The flower strips are six metres wide, 100 metres apart and take up just two per cent of the total field area. They will be monitored over five years, through a crop rotation from winter wheat to oil seed rape to spring barley.
The plan is to support diverse communities of insects that prey on pest insects. In other words, there has to be something in those strips for all the good guys, from ground crawling bugs to those that prey on the pests living in stems or seed pods. For example, many parasitic wasps need access to open flowers. The number of eggs they can lay is directly related to their consumption of pollen and nectar.
And, those showy and fragrant blooms will attract more pollinators too, drawing them into the centres of fields. So, along with pest control, the flower strips are enhancing crop pollination and good bug propagation.
Although this is the first experiment with in-field flower strips, using wildflower margins to support hoverflies, parasitic wasps and ground beetles has been proven effective in other studies.
In one study, flower strips were sown alongside 10 winter wheat fields and compared with 15 fields with adjacent wheat strips.
Cereal leaf beetle density of larvae was reduced by 40 per cent and adults of the second generation by 53 percent. Plant damage caused by CLB was reduced by 61 per cent in fields with flower strips compared with the control fields. Natural enemies of CLB were strongly increased in flower strips and in part also in adjacent wheat fields
This practice reduced CLB pest levels below the economic threshold, offering a viable alternative to insecticides.
For more information: http://rspb.royalsocietypublishing.org/content/282/1814/20151369
- Shirley Byers