In this blog post José M. Herrera discusses their latest research, conducted alongside co-authors, which looks at the temporal relationship between the nightly activity patterns of the common pipistrelle bat (Pipistrellus kuhlii) and the olive fruit moth (Prays oleae). To enhance biocontrol services, they propose increasing the availability of suitable roosting and foraging sites as well as conserving areas of remnant native woodland and scattered hollow-bearing trees.

Biocontrol agents and crop pests

Biocontrol services provide undeniable incentives to effectively motivate farmers to integrate biodiversity into daily farm management. Crop production intensification often leads to the structural simplification of production systems, severely impacting biodiversity and the provisioning of biocontrol services. To date, population declines of biocontrol agents in response to crop production intensification, including structural simplification, have been considered as the main cause of disruption of biocontrol services in production systems worldwide.

However, whether and how this disruption is driven by temporal mismatches between the activity patterns of biocontrol agents and crop pests still remains understood. Far from being trivial, overcoming this gap in our knowledge is pivotal, especially if we aim to provide robust estimations of the ecological significance of biocontrol services in agriculture and the economic impact of their lost.

The role of bats

Bats are widely reported to play a key role as biocontrol agents in production systems around the world. In all these production systems, disruptions in bat-mediated biocontrol services have mostly been attributed to bat population declines as a result of crop production intensification and have therefore estimated biocontrol services based exclusively on the spatial match between bats and crop pests.

Using olive (Olea europaea subsp. europaea) production systems as a study case, we demonstrate that the spatial match between bats and pests does not necessarily guarantee the provision of biocontrol services and that the temporal match between the flight activity patterns of species pairs should be also considered.

In our study, we specifically investigated the temporal match between the flight activity patterns of the Kuhl pipistrelle (Pipistrellus kuhlii) and the olive fruit moth (Prays oleae), a major olive pest worldwide. Interspecies flight activity was investigated in 60 olive groves from Alentejo (Portugal), representing an increasing gradient of structural simplification (as a surrogate of agricultural intensification), ranging from structurally complex olive groves to structurally simple olive groves.

Our findings

We found that, while bat population abundance significantly decreased along the structural simplification gradient, potential biocontrol services provided by P. kuhlii against P. oleae were significantly compromised even in structurally complex olive groves due to strong temporal mismatches between the flight activity patterns of species pairs.

Moreover, because we found no effects of the surrounding landscape on the flight activity patterns neither of P. kuhlii nor P. oleae, we suggest these temporal mismatches were mostly driven by environmental correlates at grove-level, particularly the lack of suitable roosting and foraging sites. To a large extent, this is because the lack of roosting and foraging sites undoubtedly force bats to fly over long distances to reach olive groves, leading to short and late peaks of activity for foraging purposes.

Recommendations

The availability of suitable roosting sites within olive groves can be increased both artificially (by placing man-made bat refugees) or naturally (by conserving native hollow-bearing trees). Suitable foraging sites can be ensured by conserving (and increasing) native scattered trees, which are typically removed or ignored until they eventually die.

Scattered trees will not only facilitate the movement of bats throughout the landscape, but will also will increase the availability of natural refuges for native prey insects, thereby increasing the likelihood of bats entering olive farms and the time spent for foraging purposes. Ultimately, these trees will increase the encounter probabilities between bats and pests and, in turn, the provision of biocontrol services.

Read the full article “Temporal mismatches in flight activity patterns between Pipistrellus kuhlii and Prays oleae in olive farms: Implications for biocontrol services potential” in Journal of Applied Ecology