Olive-derived additive may help farmers fight resistant oilseed rape pest

A natural compound derived from olives could help restore the performance of widely used insecticides against cabbage stem flea beetle (CSFB), a pest that has become a major threat to oilseed rape production in the UK and parts of Europe, according to research from Rothamsted Research and ApresLabs.

In simulated field experiments, combining the compound, known as SYN-A, with the pyrethroid insecticide lambda-cyhalothrin increased beetle mortality to 75%, compared with about 20% when the insecticide was used alone. Plant damage was reduced by at least half relative to standalone treatments, the researchers said.

The findings, published in Pest Management Science, indicate that SYN-A acts as a synergist — enhancing the effectiveness of an existing insecticide rather than serving as a pesticide by itself. Researchers reported that using the additive alongside just 20% of the standard lambda-cyhalothrin rate delivered more than twice the level of control achieved with a full-rate spray on its own.

CSFB has emerged as one of the most difficult pests for oilseed rape growers to manage. Populations in several regions have developed resistance to pyrethroid sprays, while regulatory restrictions, including the European Union’s ban on neonicotinoid seed treatments, have narrowed available control options. The result has been rising crop losses and increased production risk for growers.

According to the research team, SYN-A works by blocking enzymes that resistant insects use to break down insecticides, allowing existing chemistry to remain effective at lower doses. ApresLabs, which developed and patented the compound, said wider use of such synergists could help extend the useful life of established insecticides at a time when few new active ingredients are reaching the market.

The potential to reduce insecticide volumes may also support policy goals aimed at cutting overall pesticide use while maintaining crop protection. Researchers suggested the approach could allow growers to achieve effective control with substantially less chemical input.

However, the study also identified possible environmental trade-offs. Laboratory tests showed that the SYN-A and lambda-cyhalothrin mixture had similar harmful effects on Microctonus brassicae, a parasitoid wasp that naturally suppresses adult CSFB populations. Such non-target impacts could complicate how and when the product might be used in practice.

The authors said careful application strategies, including timing treatments to avoid peak activity of beneficial insects, would be essential. They also emphasized that larger-scale field trials are still needed to confirm both performance and environmental effects under commercial farming conditions.

While still at an early stage, the work points to a potential new tool for managing resistant pests using existing chemistry — an approach that could draw attention as growers, regulators and manufacturers seek more sustainable crop protection strategies.