What does climate change mean for UK arable pests?

With a focus on aphids, Dr Laura Underdown explains the complex relationship between changing weather patterns and crop pest populations.

In my first blog in this climate change series, I discussed changing weather patterns and the general impacts on crop production.

In this blog, I consider the specific impacts on a major pest of cereals and oilseeds: aphids.

As insects are ectothermic, which means cold-blooded, external temperatures largely determine their growth, development and survival.

According to the State of the UK Climate Report 2025, last year was the warmest in the UK, with the last four years in the top five warmest, based on a weather series that started in 1884.

This year, we’ve already seen many temperature records broken.

A warmer climate means many pest species will:

• Develop faster
• Produce more generations and larger populations each year
• Survive winters in greater numbers
• Expand into new geographical areas

We may also see new insect-spread disease threats.

Ultimately, rising temperatures will increase insect feeding activity and some predict they may hit temperate regions, which include the UK, the hardest.

The above points apply to aphid pests, which include bird cherry-oat aphid, grain aphid, rose-grain aphid, peach-potato aphid and the potato aphid.

Some aphid species may produce as many as five more generations each year, based on less than a 2°C temperature rise, according to modelling studies.

A lack of cold is not helping, either.

The State of the UK Climate Report cited a steady decline in the number of air and ground frosts since the 1980s, meaning more aphids now survive through the winter.

Evidence shows that winters were already increasing aphid survival 20 years ago. Since then, the number and severity of UK frosts have continued to decrease.

Increases in aphid activity can be seen in the annual Rothamsted Insect Survey (RIS) data, which are based on aphid flight data gathered from a GB network of suction traps over the last 60 years.

In addition to greater autumn aphid activity, the survey is also detecting changes at the start of the year.

RIS issues spring aphid forecasts for the major cereal, brassica and potato aphid species. These clearly show that warmer winters encourage earlier spring migrations.

Several research papers also cite evidence of earlier spring migration in many aphid species.

One found that adult potato aphids emerge around two weeks earlier for every 1°C increase in mean January and February temperature, which is the best indicator of the timing and size of spring migrations.

Barley yellow dwarf virus (BYDV) is mainly spread in winter cereals by bird cherry-oat aphid and grain aphid, with the former species often dominating suction-trap catches in the autumn.

Aphid activity is reduced by:

• Temperatures under about 11ºC, which tend to stop aphid flights
• Temperatures below 3ºC, which greatly reduces aphid activity
• Hard frosts, which kill aphids

It is why we are seeing longer autumn migrations, increased overwinter activity and survival, and earlier spring migrations.

Put simply, it means aphids can spread BYDV for longer.

Typically, autumn infections result in the biggest yield impacts, after which the impact gradually decreases.

After growth stage 32, new BYDV infection has a negligible impact on yield.

There's still a lot to learn about weather and pest and predator life cycles, as well as their interactions.

For instance, prolonged hot and dry periods can reduce aphid survival and virus spread.

Warmer conditions may also reduce aphid responses to alarm signals, which could increase predation by natural enemies.

In contrast, warmer temperatures could shorten the juvenile aphid stages often preferred by natural enemies.

However, such interactions are complex and difficult to predict.

Rainfall also influences aphid populations.

For example, increased autumn rainfall may disperse aphids and spread BYDV infection, depending on the species.

Heavy rain has been shown to increase grain aphid movement across plants.

This hasn’t been seen in bird cherry-oat aphid, but this species is impacted in other ways.

Compared to other aphid species, the population growth of bird cherry-oat aphid is relatively rapid in waterlogged situations, and they demonstrate improved survival when floating or submerged.

Uncertainty means that traditional calendar-based aphid management is often unreliable and integrated pest management (IPM) is increasingly important:

• Prevent: suppress pest populations and the risk of economic damage. For example, sow resistant or tolerant varieties, manage rotations and drill later
• Detect: use crop inspections, insect trapping and aphid monitoring services
• Control: as there is no treatment threshold, use the new BYDV tool to target sprays in response to risk

Do not rely on historic spray timings.