- Fruits: grapes
- Additional Plants: ornamentals
- Crop Production: strip tillage
- Education and Training: demonstration, networking, on-farm/ranch research, participatory research
- Farm Business Management: whole farm planning
- Natural Resources/Environment: indicators, hedges - woody
- Pest Management: biological control, compost extracts, cultural control
- Production Systems: agroecosystems, holistic management
- Soil Management: organic matter, soil quality/health
- Sustainable Communities: social networks
In collaboration with wine grape growers in Napa and Sonoma County, the project evaluated the strategy of floral resource provisioning (FRP) to enhance biological control of two key vineyard pests: grape leafhopper and vine mealybug. FRP species included annual buckwheat, lacy phacelia, sweet alyssum, bishops weed and wild carrot. While overall findings support the hypothesis that FRP can enhance populations of natural enemies and contribute to pest regulation and the maintenance of soil quality, additional research will be necessary to better understand the specific ecological mechanisms that lead to reduced pest densities in the presence of flowering ground covers.
Pest management in wine grape production frequently depends upon the use of synthetic chemical control strategies (UC IPM 2009). Many of the commonly used insecticides are known to have significant and negative environmental quality and human health risks. In addition, the long-term viability of pesticide use is uncertain due to decreasing pesticide effectiveness resulting from the development of genetic resistance to pesticides by arthropod pests, increasing pesticide costs for growers and an increasingly restrictive regulatory environment (Van Driesche et al. 2008). To systemically address these pressing social and environmental issues, new approaches to pest management must be continuously tested and developed.
This project was developed in response to the expressed interest of California wine grape growers for new ecologically-based pest management strategies for wine grapes, many of whom are responding to increased consumer demand for wines made from organically and/or “sustainably” grown grapes (Wine Institute 2007). Building upon prior research in conservation biological control, this project has been the first comprehensive study of the effects of annual flowering intercrops in multiple sites in Napa and Sonoma county wine grape vineyards.
Local habitat manipulation in crop fields, such as cover crops that provide floral resources, can enhance arthropod pest management (Landis et al. 2000, Altieri and Nicholls 2004, Andow 1991). A review of prior research showed that in over 50% of cases studied, localized (field-scale) habitat diversification led to reduced pest populations, reduced crop damage and/or increased yields. In contrast, results from the other habitat diversity studies showed pest populations remained unaffected (15%) or increased (35%) (Andow 1991). While habitat diversity per se can potentially enhance biological control, inconsistent results have led researchers to conduct studies on more specific types of on-farm habitat provisioning in order to isolate which plant species may convey the greatest functional benefit (Wäckers et al. 2005). Multiple mechanisms can determine the success of habitat manipulation for biological control, including overwintering habitat requirements, dispersal patterns and the availability and influence of floral nectar and pollen (Thomas et al. 1991, Landis et al. 2000, New 2005)
Although use of ground covers and floral resource provisioning in vineyards has shown some reduction in pest densities (Nicholls et al. 2001, Costello and Daane 2003, English-Loeb et al. 2003, Berndt et al. 2006), no single habitat management program has been developed that consistently reduces pests below thresholds growers consider economically significant. Such inconsistencies in research findings have limited adoption of conservation biological control and resulted in continued reliance on conventional pest management practices. This is partially due to previous studies not clearly identifying causation for the observed reductions in pest densities (Cullen et al. 2008).
Widespread adoption of novel pest management practices occurs best when the information is conveyed to growers in a practical format. Towards this goal, we plan a series of field days to extend information on the research progress and receive feedback from participating growers. From past experience, we anticipate 30 – 50 participants at each field day, and some of these growers will be interested in adopting all or some of the management practices highlighted. Through our research, at grower-participatory discussions at field days and with the grower-collaborators, we can better develop sustainable pest management tools that are practical and economical – resulting in greater adoption.
The research and extension components of this project were integrated to derive cost-effective applications of floral resource provisioning for vineyards. To date, no other published study analyzes large-scale alley cropping of floral resources for pest management in Napa and Sonoma County wine grape agroecosystems, although there has been considerable interest in this management tool.
California, Oregon and Washington wine grapes represent one of the larger and more valuable specialty crops in the western U.S. – with an estimate annual crop value over $4 billion and even more value to the region’s economy through associated employment and tourism. Many of these wine grape regions are recognized internationally for fine wines and a burgeoning agricultural tourism industry. Major wine grape grower organizations are already seeking to demonstrate the wine-grape industry’s commitment to more sustainable farming (CAWG 2008). Their stated objectives are to improve the environmental quality of grape growing practices and develop management strategies that are more sensitive to the environment, responsive to the interests of society-at-large and economically feasible to implement and maintain (WGA 2008; CSWA 2008). This project intended to provide a scientific basis for new environmental stewardship and pest management initiatives for wine grapes.
As stated in the original proposal, the project was to be developed and implemented via a participatory process involving wine grape growers to test plant diversification strategies that may enhance the soil food web and native biological control services by creating a functional ecological infrastructure in and around vineyards. Since the 2008 season, we have been assessing the effectiveness of specific agroecological management strategies (e.g., flowering summer cover crops) on the improvement of soil quality and the enhancement of functional biodiversity for pest regulation in California vineyard agroecosystems. The ultimate goal of the research is to contribute to the scientific understanding of the requisite ecological design components (e.g., landscape structure, cover crop species composition and the management of such plants) needed to stimulate soil biological activity, enhance and sustain soil quality and sponsor cost-effective ecological management of key wine grape pests.
A key objective of the project has been to construct a study that is participatory in nature, so that farmers are engaged in the management and evaluation of the agroecological treatments. Another objective is to incorporate an extensive outreach and education component of the project to assure ample sharing, distribution and accessibility of the research findings among farmers, thus facilitating the widespread adoption of agroecological management practices.
Changes in objectives as the project unfolded:
With additional funding from The California Department of Food and Agriculture (CDFA) in 2009, we added a fully replicated research site at the UC Kearney Agriculture Research Center (KAC) in Fresno County. The addition of this research site allowed researchers to study the impact of floral resource provisioning on biological control of vine mealy bug (VMB) and to conduct a series of related laboratory studies to measure the ecological processes theorized to be enhanced through FRP. In 2010, the research project expanded further to include a fully replicated research design in Lodi, California.