Biodiversity strips around glasshouses attract more beneficial insects

At the end of 2024, twenty glasshouse horticulture businesses across the Netherlands established a 250-square-metre biodiversity strip next to their greenhouse. In 2025, researchers tracked how these strips developed over six monitoring rounds. The findings were compared with equally sized areas of short-mown grass. The project’s central question is whether flowers and other plants around the greenhouse attract more beneficial insects, without causing extra influxes of pests.

“The first results show that biodiversity strips contain more bees, bumblebees, hoverflies and butterflies than grass,” says WUR researcher Kyra Vervoorn. “On average, we recorded more than twenty times as many bees and bumblebees there. Natural enemies of glasshouse pests were also present in higher numbers, including Orius (a small predatory bug) and lacewings. Ladybirds were observed three to four times more often.”

That does not automatically mean that more natural enemies are also present inside the greenhouse itself. That link has not yet been studied at this stage. The results do show that the strips function as habitat for beneficial insects in the immediate surroundings of the greenhouse.

In total, the researchers identified 23 aphid species. Many of these appear to be associated with specific plants in the strips or in the surrounding vegetation. Most species are specialist or depend on plants outside the greenhouse. “Most of the aphids we find therefore do not pose a risk to the crop,” says Vervoorn. "They may actually serve as a food source for natural enemies."

In addition to insect numbers, the researchers are also examining possible virus transmission. During the summer months, thrips numbers increased, a pattern consistent with earlier observations. Thrips from flower samples were tested for Tomato spotted wilt virus (TSWV) using PCR, a method that can detect viral genetic material.

TSWV fragments were found in thrips at thirteen of the twenty businesses, spread across all regions. “This means that viral genetic material is present, but it does not confirm that thrips are actually able to transmit the virus,” says Vervoorn. “What is more, TSWV was also found in plants in the control areas. On the basis of these results, the virus therefore cannot be directly linked to the biodiversity strips.”

The results are based on one monitoring year. In 2026, the researchers will continue the study. They will again analyse plants from biodiversity strips and control areas, and will look more closely at the relationships between plant species, pests and natural enemies. The aim is ultimately to provide growers with well-substantiated guidelines for biodiversity around glasshouses.

The project is a collaboration between Glastuinbouw Nederland, Wageningen University & Research and Universiteit Leiden, with funding from the Ministerie van Landbouw, Visserij, Voedselzekerheid en Natuur (LVVN), Stichting KijK, Innovatiefonds Hagelunie, provincie Zuid-Holland (via Greenport West-Holland), gemeente Westland, Glastuinbouwpact Bommelerwaard & Tielerwaard and het Hoogheemraadschap Delfland. The project is also supported by Biobest, ECW Energy and the Federatie Vruchtgroente Organisaties.