Abstract
This study evaluated how the proportional area of natural habitat surrounding a vineyard (i.e. landscape diversity) worked in conjunction with crop vigor, cultivar and rootstock selection to influence biological control of the western grape leafhopper (Erythroneura elegantula Osborn). The key natural enemies of E. elegantula are Anagrus erythroneurae S. Trjapitzin & Chiappini and A. daanei Triapitsyn, both of which are likely impacted by changes in landscape diversity due to their reliance on non-crop habitat to successfully overwinter. Additionally, E. elegantula is sensitive to changes in host plant quality which may influence densities on specific cultivars, rootstocks and/or vines with increased vigor. From 2010–2013, data were collected on natural enemy and leafhopper densities, pest parasitism rates and vine vigor from multiple vineyards that represented a continuum of landscape diversity. Early in the season, vineyards in more diverse landscapes had higher Anagrus spp. densities and lower E. elegantula densities, which led to increased parasitism of E. elegantula. Although late season densities of E. elegantula tended to be lower in vineyards with higher early season parasitism rates and lower total petiole nitrogen content, they were also affected by rootstock and cultivar. While diverse landscapes can support higher natural enemy populations, which can lead to increased biological control, leafhopper densities also appear to be mediated by cultivar, rootstock and vine vigor.
Highlights
Natural habitats are an important source of ecosystem services to agriculture, including biological control of crop pests [1,2,3]
The aim of this study was to evaluate whether or not natural enemy populations and biological control of E. elegantula are influenced by changes in the proportion of natural habitat surrounding the vineyard; the analyses considered the effects of grape cultivar, rootstock and vine vigor on E. elegantula densities
Abundance of spiders in the family Anyphaenidae were increased in vineyards with more natural habitat and Miturgidae density was elevated at sites with high E. elegantula density
Summary
Natural habitats are an important source of ecosystem services to agriculture, including biological control of crop pests [1,2,3]. Trichomes and leaf hairs are a structural defense that interfere with insect movement [11] while the production of certain secondary metabolites in plant tissue that are toxic to herbivores act as a chemical defense [12, 13]. These traits are not exclusive, for instance glandular trichomes combine both structural and chemical defenses [14]. The presence or absence of such traits associated with a specific crop cultivar or rootstock can be a strong determinant of pest densities regardless of natural enemy impact [15]
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