Diversification practices: their effect on pest regulation and production

Abstract

The interest to shift pest management strategies from the intensive use of agrochemicals to more sustainable and ecologically friendly practices has increased in recent years. One alternative to conventional farming systems is the implementation of diversification practices that increase diversity inand aroundthe field to increase the incidence of natural enemies, reduce pest pressure and enhance crop production. In this review we illustrate the theoretical framework on which diversification practices are based and contrast it with the empirical evidence. The detailed review of 62 original studies published in the last ten years, shows that diversification practices (a) enhance natural enemies in 52%, (b) reduce pest pressure in 53% and (c) increase yield in only 32% of the cases where this was examined. We discuss these results on the basis of the reviewed studies providing key elements that should be taken into account to design diversification practices that can be implemented as competitive pest management strategies that cover the farmers’ needs, reducing the intensive use of agrochemicals.

Using biological invasions to improve plant defense theory

“…Plant‐insect interactions, including herbivory, shape the functioning of terrestrial ecosystems worldwide (Yang & Gratton, 2014; Cardoso et al, 2020). From crop yield reduction by agricultural pests (Poveda et al, 2008; Mitchell et al, 2016; Bisht et al, 2019) to boom‐bust cycles of beetles that can restructure entire forests (Brockerhoff & Liebhold, 2017; Goodsman et al, 2017; Fernandez‐Conradi et al, 2021), insects have profound effects on individual plants, plant populations, and communities. How plants defend themselves against attack by a diverse and unrelenting array of herbivores therefore remains an active area of research with far‐reaching ecological and evolutionary consequences.…”

Active management of wildflower strips in commercial sweet cherry orchards enhances natural enemies and pest regulation services

“…Wildflower interventions, employing native species adapted to local environments, can boost the abundance of beneficial arthropods, and the use of perennial species delivers greater consistency in floral resources throughout the year and between years (Isaacs et al, 2009). Deploying native perennial wildflower habitat in sweet cherry orchards has the potential to support natural enemies and reduce the incidence of pests, reduce the need for pesticides, and increase crop yields (Poveda et al, 2008;Redlich et al, 2018;McKerchar et al, 2020). However, there is concern that wildflower areas can harbour disease and be difficult to manage in cropped areas (Kleijn et al, 2019).…”

Extrafloral nectary-bearing leguminous trees enhance pest control and increase fruit weight in associated coffee plants

“…Agroforestry is based on increasing tree diversity in agricultural fields, thus providing important ecosystem services such as carbon sequestration, nutrient cycling, soil fertility, drought resistance, weed and pest control and even mitigate effects of rising temperatures due to climate change (Gomes et al, 2020;Jha et al, 2011;Perfecto et al, 2007Perfecto et al, , 1996Pumariño et al, 2015;Souza et al, 2012;Zhang et al, 2007). The major bottleneck in implementation of agroforestry systems and other plant diversification strategies is that they do not always translate into increased yield (Poveda et al, 2008;Zhang et al, 2007). Indeed, some studies show that increased diversification in crop fields can lead to lower crop production (Letourneau et al, 2011;Poveda et al, 2008), whereas a recent meta-analysis shows that increased plant diversification in agricultural systems does not result in overall significant yield loss (Tamburini et al, 2020).…”

“…The major bottleneck in implementation of agroforestry systems and other plant diversification strategies is that they do not always translate into increased yield (Poveda et al, 2008;Zhang et al, 2007). Indeed, some studies show that increased diversification in crop fields can lead to lower crop production (Letourneau et al, 2011;Poveda et al, 2008), whereas a recent meta-analysis shows that increased plant diversification in agricultural systems does not result in overall significant yield loss (Tamburini et al, 2020). Yet, on-farm diversification has to be designed to support functional biodiversity, provide intended ecosystem services (Landis et al, 2000) and maintain or increase production (Poveda et al, 2008).…”

“…Several hypotheses have been put forward to explain how vegetation diversity can enhance pest control. Increased plant diversity may attract pests away from the crops and increase mortality of the pest due to enhancement of natural enemies (Begg et al, 2017;Gurr et al, 2017;Perović et al, 2018;Poveda et al, 2008;Root, 1973). The underlying ecological mechanisms that explain aggregation and improvement of natural enemies in more diversified habitats are not completely explored (Perović et al, 2018).…”