Grape moth density in Bordeaux vineyards depends on local habitat management despite effects of landscape heterogeneity on their biological control

Abstract

1. Biological control of crop pests is a major ecosystem service affected by several variables acting at multiple spatial scales. Among these variables, heterogeneity at the habitat and landscape scales are known key drivers of trophic interactions and pest density in agroecosystems. However, studies that try to disentangle their relative effects in perennial cropping systems are scarce and nothing is known about their impacts on insect pest density and pesticide applications. 2. We examined the effect of heterogeneity at these two scales on grape moths, one of the most damaging insect pests in European vineyards, and their biological control in 20 vineyards during three consecutive years. We used local vegetation management and the proportion of semi-natural habitats in the surrounding landscape as proxies of heterogeneity at the habitat and landscape scales. Grape moth density was measured over time, as well as biological control services provided by different groups: birds, invertebrate predators, parasitoids and entomopathogenic fungi. 3. Over the 3 years, grape moth density was mainly determined by local heterogeneity, with significantly fewer larvae of the first generation established in vineyards with full compared to partial grass cover. 4. Despite these effects, biological control of grape moths was not primarily affected by local vegetation management but by landscape heterogeneity, and the direction of this effect varied over time. Notably, predation by birds increased with landscape heterogeneity in spring, depending on local vegetation management, while attacks by pathogenic fungi decreased with landscape heterogeneity during winter. 5. Synthesis and applications. Our results suggest that bottom-up processes related to habitat heterogeneity drive grape moth occurrence much more than top-down processes. These results have important implications for the ecological intensification of vineyard landscapes. We found that maintaining full grass cover within vineyards reduced grape moth density to a level below common intervention thresholds. Landscape heterogeneity in the close vicinity of vineyards contributed to improved biological pest control by birds, but depended on local vegetation management. Moreover, opposing effects of landscape management on biological pest control services over time revealed that strategies based only on manipulating landscape heterogeneity might not be the optimal option to limit grape moth density in vineyards.

Organic farming at local and landscape scales fosters biological pest control in vineyards

“…This confirmed that several biological control functions can have opposite responses to management intensity (Rusch et al. ). Direct negative effects of pesticides on natural enemies may limit the biological control potential of grape moths, which explains the negative relationships between crop productivity or pesticide use and biological control services (Geiger et al.…”

“…Our analyses particularly revealed that increasing pesticide use decreased the removal rates of moth eggs and increasing crop productivity decreased the removal rates of moth eggs while increased weed seed removal. This confirmed that several biological control functions can have opposite responses to management intensity (Rusch et al 2017b). Direct negative effects of pesticides on natural enemies may limit the biological control potential of grape moths, which explains the negative relationships between crop productivity or pesticide use and biological control services (Geiger et al 2010, Bommarco et al 2011).…”

“…), which could benefit natural enemies and biological pest control through bottom‐up effects (Langellotto and Denno , Rusch et al. ). Our results corroborate those of several studies that showed positive effects of organic farming at the local scale on some aspects of biological control services (Winqvist et al.…”

Development of the Concept of Agroecology in Europe: A Review

“…This is similar to the case of Spain with the Integrate Pest Management (IPM), or the case of France that has tried to adopt agroecological innovations aimed at reducing the use of pesticides for banana production in the French Antilles [49]. In this regard, Rusch et al [50] reported the positive and practical effects of the ecological intensification through the heterogeneity of the landscape in the biological control of vineyard pests, maintaining that the monitoring of these practices by farmers is an original approach that seeks to identify and analyze alternative systems and supports the development of these techniques. According to Phocas et al [51], agroecology uses ecological processes and local resources instead of chemical inputs to develop productive and resilient systems.…”

Landscape drivers and effectiveness of pest control by insectivorous birds in a landscape-dominant woody crop

“…Other authors have used plasticine models (commonly used to compare attack rates across gradients) to comparatively approach levels of avian insectivory on pests (reviewed in Bateman, Fleming, & Wolfe, 2017). This method have proven useful to explore the effects of agricultural management and landscape heterogeneity on overall pest control (Rusch, Delbac, Thiéry, & Thi Ery, 2017), avian pest control in vineyards (Barbaro et al, 2017) or even to find global latitudinal/altitudinal patterns on predation rates (Roslin et al, 2017). Also, the abundance of insectivorous birds and their predation on plasticine caterpillars has positively been linked to structural heterogeneity (Bereczki, Ódor, Csóka, Mag, & Báldi, 2014).…”