Local pesticide use intensity conditions landscape effects on biological pest control

Abstract

Complex landscapes including semi-natural habitats are expected to favour natural enemies thereby enhancing natural pest biocontrol in crops. However, when considering a large number of situations, the response of natural biocontrol to landscape properties is globally inconsistent, a possible explanation being that local agricultural practices counteract landscape effects. In this study, along a crossed gradient of pesticide use intensity and landscape simplification, we analysed the interactive effects of landscape characteristics and local pesticide use intensity on natural biocontrol. During 3 years, using a set of sentinel prey (weed seeds, aphids and Lepidoptera eggs), biocontrol was estimated in 80 commercial fields located in four contrasted regions in France. For all types of prey excepted weed seeds, the predation rate was influenced by interactions between landscape characteristics and local pesticide use intensity. Proportion of meadow and length of interface between woods and crops had a positive effect on biocontrol of aphids where local pesticide use intensity was low but had a negative effect elsewhere. Moreover, the landscape proportion of suitable habitats for crop pests decreased the predation of sentinel prey, irrespectively of the local pesticide use intensity for weed seeds, but only in fields with low pesticide use for Lepidoptera eggs. These results show that high local pesticide use can counteract the positive expected effects of semi-natural habitats, but also that the necessary pesticide use reduction should be associated with semi-natural habitat enhancement to guarantee an effective natural biocontrol.

Crop diversity benefits carabid and pollinator communities in landscapes with semi‐natural habitats

“…A possible explanation is that the value of semi‐natural habitats for beneficial arthropods is dependent upon other local and landscape features. Local crop management such as within field rotation, fertilizer and pesticide applications, or the characteristics of field surroundings such as cropland composition, might strongly drive the level of pest control provided by natural enemies (Muneret et al., 2019; Ricci et al., 2019; Tscharntke et al., 2016), limiting the expected benefits of having abundant semi‐natural habitats in the landscape (Gagic et al., 2019; Rundlöf, Smith, & Birkhofer, 2016). Moreover, semi‐natural habitats may be more important for the temporal stabilization of resource availability in landscapes with simplified crop regimes (Schellhorn et al., 2015).…”

Promoting generalist predators of crop pests in alley cropping agroforestry fields: Farming system matters

“…Other studies also revealed contrasting effects of AEI on weed seed or aphid suppression, depending on the local farming system and pesticide use intensity (i.e. positive effects under organic farming and low pesticide use intensity, negative ones under conventional farming and high pesticide use intensity) (Fischer et al, 2011;Winqvist et al, 2011;Ricci et al, 2019). All these results highlight the key role of organic farming to promote the spillover of predators from AEI towards cropped areas, most likely by increasing resource availabilitya major factor driving the movement of organisms between habitats (Dunning et al, 1992;Corbett and Plant, 1993;Blitzer et al, 2012;Tscharntke et al, 2016).…”

Invertebrate community structure predicts natural pest control resilience to insecticide exposure

“…Current evidence from field studies would suggest that present management strategies (increasing habitat complexity or implementing field margins) may fail to strongly promote resilience of natural pest control, at least in response to commonly used insecticides (Gagic et al, 2019;Ricci et al, 2019). In order for integrated pest management strategies to become a viable option in open arable systems, determining chemicals that maximally impact the pest species while having minimal impact on beneficial invertebrates is an important step.…”

“…beneficial predators). In many instances, broad‐spectrum insecticides not only diminish within‐field natural enemy populations, but nullify attempts to increase their populations (Gagic et al., 2019; Ricci et al., 2019). The obvious mechanism for the negative effects of insecticides on natural enemies is exposure leading to direct mortality (Guedes, Smagghe, Stark, & Desneux, 2016; Stark & Banks, 2003).…”