- Vegetables: broccoli, cauliflower, cucurbits, greens (leafy)
- Education and Training: networking, on-farm/ranch research
- Natural Resources/Environment: habitat enhancement, hedgerows
- Pest Management: biological control, prevention
- Sustainable Communities: sustainability measures
Vegetable producers in the Central Coast of California are establishing hedgerows in the borders of their fields. Theoretically, adding perennial vegetation in annual crop systems can increase arthropod diversity. The goal of this project was to determine if hedgerows enhance biological control potential in annual vegetable systems by providing habitat to key natural enemies of crop pests. I monitored indicator natural enemies and pests of vegetable systems on six plant species at four farm sites with hedgerows, tracked dispersal rates of pests and natural enemies from hedgerows into adjacent vegetable fields and tested parasitism rates in those fields and fields without hedgerows.
In the Central Coast of California, growers are establishing hedgerows in the borders of their fields. Hedgerows are linear assemblages of perennial shrubs, trees, grasses and forbs. The value of hedgerows for biodiversity conservation, including beneficial insects, is well documented in Europe (van Emden 1965b, Pollard 1971, Dover 1994, Paoletti 1999), where hedgerows have a long history for their use as fences, windbreaks, erosion control and sources of firewood and timber (Baudry et al. 2000). California hedgerows are more recent additions to the landscape, being promoted for beneficial insect habitat, soil and water conservation, weed suppression, wildlife habitat and windbreaks. Hedgerows in the Central Coast of California can be quite diverse, ranging from 10 to 40 managed species (mostly native). However, farm advisers tend to recommend a core group of hedgerow species (Achillea millefolium, Baccharis pilularis, Ceanothus spp., Eriogonum spp., Heteromeles arbutifolia, and Rhamnus californica) with overlapping bloom periods with the aim of providing insect natural enemies with pollen and nectar resources throughout the year.
Widespread adoption of hedgerows for enhancing biological control services depends in large part on understanding the conditions that maximize arthropod predator and parasitoid colonization and residence within farms and being able to quantify biological control services gained from the practice. Since the quality and accessibility of food resources and shelter varies from one plant to another, and among different natural enemies, the mix of perennial vegetation used in hedgerows will determine, to some extent, the abundance and diversity of natural enemies present.
The objectives of this research were 1) to investigate the effectiveness of hedgerows in the Central Coast of California for biological control in mixed-vegetable systems and 2) to make practical recommendations to producers on semi-natural habitat management for pest management in mixed-vegetable systems. To meet these objectives, three main areas were addressed in this research project: 1) monitoring key arthropod natural enemies and pests attracted to hedgerow vegetation, 2) tracing the movement of these indicator arthropods into adjacent vegetable fields, and 3) measuring the rate of biological control (parasitism) in the vegetable fields. Research findings have been widely disseminated through regional on-farm workshops and national and international conferences. Additionally, future publications in agriculture periodicals and academic journals will help inform both growers and researchers about the habitat quality of hedgerows for the conservation of insect natural enemies.