Trials at the Game and Wildlife Conservation Trust’s Allerton Project have found low disturbance tillage systems could give beneficial insect populations a boost, reducing pressure from pests including aphids and cabbage stem flea beetle.
Trials comparing min-till, ploughed and no-till plots of wheat showed noticeable yellowing in ploughed plots due to infection from barley yellow dwarf virus-carrying aphids. In contrast, direct drilled plots adjacent showed no effect from virus.
Dr Alistair Leake, who heads the Allerton Project, said: “It has taken us a long time to work it out. At first we thought because you have a lot of trash, the aphids cannot see the emerging wheat so they do not colonise it, but the project’s entomology department begged to differ.
"It found when you have got stubble, you have a structure for spiders to form a web on. This means aphids, cabbage stem flea beetle and other pests get caught up in those webs.”
The wheat trials were then replicated and researchers used vacuums to suck insects out of crops for identification.
Dr Leake said: “We found in the ploughed system there were not many spiders, min-till was doing better, but there was a big chunk of spiders in the no-till plot.
“The pest species were quite numerous in the ploughed system, still fairly numerous in the min-till, but we could not find any in the no-till crop at all.
“Unfortunately, in 2019 the spiders did not turn up for work, which highlights the problems of biological control in the field. We have a lot of work to do, but if we can find ways to manipulate the ecological infrastructure to improve habitat, survival and the reliability of those spiders, then this would be helpful.”