Modelling the interactions between landscape structure and spatio-temporal dynamics of pest natural enemies: Implications for conservation biological control

Abstract

Pest control is still a major issue for the agricultural sector. Conservation biological control, which controls pests using their natural enemies (NE), appears to be a promising strategy considering the negative impacts of pesticides on the environment and human health. Conservation biological control relies on two main processes: the conservation of a large abundance of NE and their biological control function per se. To implement conservation biological control, it was suggested to increase the proportion of semi-natural habitats (SNH) at the landscape scale, because they contain important resources for NE, especially for survival during overwintering. However, empirical studies show mixed results, and the mechanisms involved are not well understood. Here, we focus on the temporality of the biological control process as a key driver of the efficiency of pest regulation and the resulting limitation of crop yield losses. Using a modelling approach, we analyse the interplay between the landscape structure and the spatio-temporal dynamics of the interactions between crops, pests, and NE in a virtual agricultural landscape comprising crops and SNH. To characterise the pest control service, we use several indicators, including crop yield response defined as a function of the temporal outcomes of the species interactions. We also test two ecological traits that are assumed to be important: pest colonisation rate and NE dispersal behaviour. We observe a positive response of the NE visitation rate of colonised crops when increasing the SNH proportion. However, optimising the pest control service at the crop cell scale requires much more SNH than maximising the visitation rate due to the influence of temporal trophic interactions. Indeed, increasing the SNH proportion makes it possible for NE to arrive at the crop cells faster after the pest colonisation, which reduces the average crop losses. However, there is a trade-off in optimising the crop yield at the cell or landscape scale, because of the conversion of the productive crop area into SNH. Overall, our results suggest that modifying the SNH proportion in agricultural landscapes can enhance the delivery of the pest control service, provided that the landscape design allows NE to arrive at the right place at the right time in the event of pest colonisation.