Influence of ground cover on spider populations in a table grape vineyard

Abstract

Abstract. 1. Cover crops and/or resident ground vegetation have been used in California vineyards to increase the number of predators and decrease the number of pestiferous herbivores. The most common resident predators in vineyards are spiders (Araneae). Several observational studies suggest that the addition of cover crops results in an increase in spider density and a decrease in insect pest densities.2. To test experimentally the effects of cover crops and/or resident ground vegetation (hereafter collectively referred to as ground cover) on spider populations, a 3-year study was undertaken in a commercial vineyard. Large, replicated plots were established with and without ground cover during the growing season. Spider species diversity was analysed on the vines and on the ground cover.3. On the vines, there was no significant difference in spider species richness or the total number of spiders in plots with and without ground cover. There were differences in the relative abundance of two spiders between treatments, with one species (Trachelas pacificus [Chamberlin & Ivie]) more abundant in plots with ground cover and another (Hololena nedra Chamberlin & Ivie) more common on vines in plots with no ground cover. Annual variation in spider abundance was greater than variation due to ground cover treatment.4. On the ground cover, the spider species diversity was considerably different from that found on the vines above, suggesting that there is little movement of spiders between the ground cover and the vines. Enhancement of T. pacificus populations on vines with ground covers may be a result of prey species movement between the ground cover and the vines. Spider abundance was sparse on the bare ground.5. The maintenance of ground cover increased spider species diversity in the vineyard as a whole (vine and ground cover). However, the relatively small changes in spider abundance on the vines indicate there are limitations in the use of ground covers for pest management with respect to generalist predators.

Spider and Leafhopper (<I>Erythroneura</I> spp.) Response to Vineyard Ground Cover

“…The lack of consistency between years may simply be that over all spider density was too low in the Þrst year of study (1993) to be able to statistically separate differences among treatments. In a separate study, T. pacificus density was consistently higher on grapevines with ground covers (Costello and Daane 1998a), but in that study it comprised �40% of the spider community, compared with �7% in the current study. And because T. pacificus density was not signiÞcantly different be tween Cover and Exclusion treatments, it is unlikely that the importance of the ground cover for T. pacificus was in providing additional habitat.…”

“…One of our stud ies showed no consistent differences in total spider density on grapevines (where leafhopper nymphs are found) grown with ground cover or not (Costello and Daane 1998a). An alternative hypothesis is the possi ble inßuence of ground covers on grapevine vigor.…”

Impact of Weed Management Practices on Grapevine Growth, Yield Components, Plant and Arthropod Abundance, and Carabid Seed Predation in Paso Robles Vineyard

“…Overall, the results of this study were consistent with previous findings in perennial systems, which indicated that weed management practices affect groundcover vegetation (Monteiro and Lopes, 2007) and can influence the composition of terrestrial arthropod communities (Altieri and Schmidt, 1985;Costello and Daane, 1998;O'Neal et al, 2005). Thus, incorporating vegetation strips as a part of weed management practices in vineyards, whether using resident vegetation or low-growing cover crop species, can help neutralized the impacts of herbicides on biodiversity of the system.…”

“…There are very few studies involving arthropod communities in vineyard, especially those that are classified as ground dwellers, and their roles as natural enemies of vineyard pests (Costello and Daane, 1998;Costello and Daane, 2003). Landis et al (2000) stated that conservation biological control (of crop pests) involves manipulation of the environment to enhance the survival, fecundity, longevity, and behavior of natural enemies to increase their effectiveness.…”

Vineyard floor management affects soil, plant nutrition, and grape yield and quality

“…Many California growers are also willing to plant cover crops because they protect soil from nutrient and sedi-ment loss in winter storms (Bettiga et al 2006), suppress weeds (Lanini and Bendixen 1992), harbor beneficial arthropods (Costello and Daane 1998), enhance vine mineral nutrition (Patrick et al 2004) and increase soil organic matter (Ingels et al 2005).…”