Refuge plants

Refuge plants: allies of biodiversity and agroecology

Cultivating Nature to Grow Better
For many years, agriculture considered spontaneous vegetation and the organisms present in fields as elements to be controlled or eliminated. The goal was to create environments as uniform as possible, in which the main crop could grow without competing with other species. Today, we know that this vision is partial. An agroecosystem rich in biodiversity is often more stable, more resilient, and less dependent on external inputs.
Among the most effective tools for promoting this balance are refuge plants, plant species that provide habitat, nourishment, and breeding sites for beneficial organisms. They represent a fundamental element of modern agroecology, as they enhance the natural processes that regulate the functioning of agricultural ecosystems.

What are refuge plants?
Refugia plants are herbaceous, shrubby, or tree species maintained or deliberately introduced into agroecosystems to promote the stable presence of beneficial insects, pollinators, and other organisms that contribute to biological balance.
The term “refuge” should not be interpreted simply as a place where insects find shelter. These plants are in fact true ecological resources, offering nectar, pollen, microhabitats, wintering sites, and favorable conditions for reproduction.
Refuge plants therefore do not have a direct productive function, but they play an essential role in supporting the ecological processes that make an agricultural system more efficient and stable over time.

A silent army of beneficial organisms
Many beneficial insects play a fundamental role in the natural containment of pests.
Ladybugs and their larvae feed on large quantities of aphids; lacewings prey on numerous small harmful insects; hoverflies, in addition to being excellent pollinators, have larvae that devour aphid colonies; parasitoid wasps, on the other hand, lay their eggs inside other insects, naturally limiting their development.
Spiders, ground beetles, staphylinids, and numerous other predators also contribute daily to the biological control of pest populations.
To survive, however, these organisms require diverse habitats and year-round food sources. Agricultural crops alone, often characterized by short flowering periods, are not sufficient to guarantee these resources.
It is precisely in this context that refuge plants take on strategic importance.

Much more than just flowers
When we talk about refuge plants, we often think of a band of flowers along the edge of a field. In reality, the concept is much broader.
A refuge plant can be a spontaneous species preserved at the edge of a plot, an aromatic plant nestled between crops, a field hedge, a grassy strip, a permanent meadow, or a small company grove.
What these elements have in common is the ability to maintain functional biodiversity, that is, the component of biodiversity that directly contributes to the ecosystem services of agriculture.

Most commonly used species
Among the most commonly used species are phacelia, yarrow, wild fennel, dill, coriander, borage, marigold, and alyssum, all characterized by blooms that are highly prized by beneficial insects.
Numerous aromatic plants, such as lavender, thyme, oregano, santolina, sage, and rosemary, are also widely used in Mediterranean environments, as well as shrubs such as mastic, myrtle, and hawthorn, which contribute to creating permanent habitats.
The choice of species always depends on the climate, the type of crop, and the business objectives. In general, it is preferable to use native species or species well adapted to the area, capable of ensuring staggered blooms throughout most of the year.

Refuge Plants and Biological Control
One of the most interesting aspects concerns so-called conservation biological control.
Rather than artificially introducing beneficial insects, this strategy aims to create favorable conditions for them to establish spontaneously and maintain stable populations over time.
Refuge plants therefore represent a prevention tool. The richer the agroecosystem, the greater the likelihood that natural predators will already be present when the first pest outbreaks appear.
This often allows for reduced pest management and improved biological stability of the entire production system.

Applications in Different Cropping Systems
Refuge plants are used in virtually every agricultural context.
In vineyards, they are sown along the rows or at headlands to favor parasitic hymenopteran insects, hoverflies, and pollinators, also helping to reduce soil erosion.
In Mediterranean olive groves, they are planted along the borders or integrated into grassy areas with aromatic and shrubby species that host numerous beneficial insects.
In organic gardens, they are placed between flowerbeds to maintain populations of pollinators and natural predators throughout the entire crop cycle.
Ecological strips are also an increasingly important element in the design of agroecosystems in cereal systems and agroforestry farms.

A fundamental element of agroecology
Agroecology considers the farm as a complex ecosystem, in which each component performs a function.
From this perspective, refuge plants are not simply ornamental elements, but true ecological infrastructures.
They contribute simultaneously to biological control, pollination, soil protection, biodiversity conservation, and the resilience of the entire agricultural system.
For this reason, they are increasingly being integrated with hedges, buffer strips, permanent grassland, cover crops, and other nature-based solutions.

Design, not simply plant
The effectiveness of refuge plants depends above all on design.
It’s not enough to plant a few flowering species: it’s necessary to create a succession of blooms throughout the year, ensure permanent habitats, avoid mowing all vegetation simultaneously, and limit the use of insecticides in areas designated for beneficial organisms.
Good design also considers the ecological continuity between the different elements of the agricultural landscape, promoting connections between hedges, ditches, borders, meadows, and surrounding natural areas.

Cultivating biodiversity for better production
Experience gained in recent decades demonstrates that investing in biodiversity means investing in the stability of agroecosystems.
Refuge plants do not completely eliminate the presence of pests, but they help maintain them within levels compatible with the biological balance of the system, reducing dependence on chemical inputs and increasing crop resilience.
Ultimately, they represent one of the simplest, most economical, and effective tools through which agriculture can collaborate with natural processes rather than oppose them.
The true innovation of agroecology lies precisely in this shift in perspective: not considering nature as an obstacle to production, but as the main ally in building productive, sustainable agricultural systems capable of addressing the environmental challenges of the future.

Guido Bissanti

Useful Bibliography
Fundamental Texts on Agroecology
Altieri, M. A. (1995). Agroecology: The Science of Sustainable Agriculture (2nd ed.). Boulder, CO: Westview Press.

Altieri, M. A. (2002). Agroecology: The science of natural resource management for poor farmers in marginal environments. Agriculture, Ecosystems & Environment, 93(1–3), 1–24.

Altieri, M. A., & Nicholls, C. I. (2004). Biodiversity and Pest Management in Agroecosystems (2nd ed.). New York: Food Products Press / Haworth Press.

Bissanti, G., Guccione, G. D., Manachini, B., Quatrini, P., & Sturla, A. (2025). Principi e fondamenti di Agroecologia. Associazione Medinova. ISBN 979-1280140401.

Caporali, F. (2011). Agricoltura e biodiversità. La scienza agroecologica per la sostenibilità. Bologna: Edagricole.

Gliessman, S. R. (2015). Agroecology: The Ecology of Sustainable Food Systems (3rd ed.). Boca Raton, FL: CRC Press.

Functional biodiversity, refuge plants and conservation biological control
Landis, D. A., Wratten, S. D., & Gurr, G. M. (2000). Habitat management to conserve natural enemies of arthropod pests in agriculture. Annual Review of Entomology, 45, 175–201. https://doi.org/10.1146/annurev.ento.45.1.175

Gurr, G. M., Wratten, S. D., & Snyder, W. E. (Eds.). (2012). Biodiversity and Insect Pests: Key Issues for Sustainable Management. Oxford: Wiley-Blackwell.

Gurr, G. M., Wratten, S. D., Landis, D. A., & You, M. (2017). Habitat management to suppress pest populations: Progress and prospects. Annual Review of Entomology, 62, 91–109. https://doi.org/10.1146/annurev-ento-031616-035050

Bianchi, F. J. J. A., Booij, C. J. H., & Tscharntke, T. (2006). Sustainable pest regulation in agricultural landscapes: A review on landscape composition, biodiversity and natural pest control. Proceedings of the Royal Society B: Biological Sciences, 273, 1715–1727.

Tscharntke, T., Klein, A. M., Kruess, A., Steffan-Dewenter, I., & Thies, C. (2005). Landscape perspectives on agricultural intensification and biodiversity–ecosystem service management. Ecology Letters, 8, 857–874.

Ecological infrastructure and agricultural landscape management
Boller, E. F., Häni, F., & Poehling, H. M. (Eds.). (2004). Ecological Infrastructures: Ideabook on Functional Biodiversity at the Farm Level. Lindau, Switzerland: IOBC/WPRS.

Kremen, C., & Miles, A. (2012). Ecosystem services in biologically diversified versus conventional farming systems: Benefits, externalities, and trade-offs. Ecology and Society, 17(4), 40.

Power, A. G. (2010). Ecosystem services and agriculture: Tradeoffs and synergies. Philosophical Transactions of the Royal Society B, 365, 2959–2971.

Agroecology and sustainability of agricultural systems
FAO – Food and Agriculture Organization of the United Nations. (2018). The 10 Elements of Agroecology: Guiding the Transition to Sustainable Food and Agricultural Systems. Rome: FAO.

HLPE – High Level Panel of Experts on Food Security and Nutrition. (2019). Agroecological and Other Innovative Approaches for Sustainable Agriculture and Food Systems that Enhance Food Security and Nutrition. Rome: FAO.

Push-pull systems and integrated management of agroecosystems
Khan, Z. R., Midega, C. A. O., Bruce, T. J. A., Hooper, A. M., & Pickett, J. A. (2010). Exploiting phytochemicals for developing a push–pull crop protection strategy for cereal farmers in Africa. Journal of Experimental Botany, 61(15), 4185–4196.

Khan, Z. R., Pickett, J. A., van den Berg, J., Wadhams, L. J., & Woodcock, C. M. (2000). Exploiting chemical ecology and species diversity: Stem borer and Striga control for maize and sorghum in Africa. Pest Management Science, 56, 957–962.