Wildflower Strips Attract Beneficial Insects That Naturally Control Crop Pests

Julian Gold grows flowers he will never harvest, and every hectare of them costs him money. Gold manages about 750 hectares at Hendred Farm Partnership in Oxfordshire, on the edge of the Berkshire Downs. The in-field wildflower strips running through his crops cost £776.02 per hectare once you count the grain he gives up to grow them, and government payments do not close the gap. Roughly £100 a hectare comes out of the business.

He is out of pocket on purpose, on ground that could be growing wheat. What he is buying instead is insects. Ladybirds. Hoverflies. Lacewings. Parasitic wasps so small you would look twice to see one. The bet is that they will do work he would otherwise pay a machine and a tank of chemicals to do. For years, that bet rested on faith and the odd thing a farmer noticed in passing. Then researchers started measuring.

The Middle of a Big Field Is a Lonely Place to Be a Predator

Beneficial insects mostly live in hedges and field margins. They hunt inward from the edges, and they run out of range fast.

“Our research has shown that levels of natural pest control fall off rapidly from the edges of large arable fields,” Professor Richard Pywell of the UK Centre for Ecology and Hydrology explained. On a small field, that barely matters. On a modern one, the middle goes unpoliced.

So the idea was to stop asking insects to commute. Run the flowers straight through the crop, and give the predators a road in. UKCEH researchers called them predator highways. Gold’s strips sit roughly 90 metres apart.

Britain tested it properly through ASSIST, a programme funded by NERC and BBSRC, which put in-field strips on 15 large arable farms across central and eastern England and monitored them for five years. The seed mixes were unglamorous: oxeye daisy, red clover, common knapweed, wild carrot. Ordinary flowers, asked to do a serious job.

What Happened When Scientists Planted Flowers Between the Beets

In April 2026, a paper landed in the Journal of Applied Ecology with a title that does not hedge: Insecticide-level pest control provided by in-field flower strips.

Ingo Glock and colleagues tested flower mixtures across 10 sites in Germany, tracking aphids, natural enemies and yield in sugar beet. Every mixture reduced aphid numbers more than the bare controls did. Some reduced them about as much as insecticides did.

Read that again, because it is the sentence a farmer waits a career to hear. Flowers, holding the line where a spray tank usually does.

Mixtures containing legumes performed best, which the authors think comes down to the particular predators legumes attract. That is a proposed explanation, not a settled one.

And the line that matters to anyone running a business: sugar yields came out similar across all the plots, flowers or spray or neither. Nobody paid for the wonder in tonnage.

Ten sites in one country is not the whole of agriculture. But this was a real crop in real fields, and the flowers held their own.

Switzerland Got There First

A decade earlier, Swiss researchers at Agroscope had already glimpsed it.

Matthias Tschumi and colleagues sowed tailored flower strips along 10 winter wheat fields and compared them against 15 fields with ordinary wheat strips. Cereal leaf beetle larvae dropped 40 percent. Second-generation adults dropped 53 percent. Damage to the wheat fell 61 percent.

Pest numbers fell below the economic threshold, the point at which spraying starts to pay for itself. That let the team conclude that the strips offer “a viable alternative to insecticides.”

In potato fields, the same approach was linked with aphid density running about 75 percent lower.

Two Flower Species Beat One by a Long Way

Here is where it gets practical, because not every flower strip works. Nika Jachowicz and Lene Sigsgaard at the University of Copenhagen pooled 24 studies covering 382 trials. Across the whole dataset, flower strips lifted natural enemy numbers by 48 percent. Sow a single species and the effect was not statistically significant. Sow two or more and there were 70 percent more natural enemies than in fields with no flowers at all. Each species after that added roughly 4.1 percent more.

“Our study confirms that diversity pays off. The more species in the flower strip, the more natural enemies in the field,” Sigsgaard said.

“You can be lucky that one flower species performs well, but if you have only one species, it all depends on how it grows,” Jachowicz added.

Shape matters as much as variety. Open flowers let small insects get inside. As UKCEH puts it, “many parasitic wasps need access to open flowers so that they can feed on pollen and nectar.” A tiny wasp cannot fuel up on a bloom it cannot reach. Whole harvests can turn on a detail that fine.

The Study That Says Slow Down

Not every trial lands in the same place, and honesty about that is part of the story. In Skåne, Sweden, Neus Rodríguez-Gasol and colleagues studied 10 pairs of perennial flower strips and control margins alongside cereal fields. The strips did pull in pollinators and beneficial insects. What they did not clearly do was protect the crop next door.

“We observed that some insects spread about ten meters into the field. However, this did not translate into any clear changes in pest abundance in the crop itself,” said co-author Mattias Jonsson.

Their colleague Maria Viketoft put it plainly: “There is no universal solution. To maximize benefits, flower strips need to be designed with local conditions and specific goals in mind.”

Pywell has always framed it the same careful way. “Our goal is not to replace pesticides, but provide other management options that allow farmers to be less reliant on them.”

Ten metres of spillover or a whole field protected depends on the mix, the crop, the pest and the land around it. This is a tool, not a switch.

The Work You Never See Getting Done

The upside keeps surfacing in places nobody designed for. Gold noticed his oilseed rape needed fewer slug pellets. “It’s possibly due to the predation of slugs by beneficial insects using these habitats,” he said, and he is careful to call that anecdotal.

At Rothamsted Research, PhD student Hannah McGrath has been testing strips in carrots, where aphid-borne viruses cost the UK industry around £20 million in 2015. Her reason for looking is blunt: “resistance has developed to many commercial insecticides.”

That is the quiet argument underneath all of this. Chemistry keeps losing ground to evolution. A hoverfly does not.

A Field That Does Two Jobs at Once

Wildflowers keep turning out to be one of the cheapest levers we have. An English town swapped eight miles of mowed grass for wildflower meadows and saved money while the bees and butterflies came back. The same blooms that feed a parasitic wasp feed the pollinators our food supply leans on and the wild bees most of us never notice.

What the evidence supports right now is measured but real, and it is quietly remarkable: well-designed, species-rich flower strips raise the number of pest-eating insects, and in the best trials they cut pest damage enough to stand in for a spray. Where, and how well, still depends on the details.

Gold is still paying for his. He no longer counts the strips as land he lost. “Using a factory analogy, we run a food production line alongside ecosystem services,” he said.