Farmscaping for conservation: Factors that influence growers' conservation behavior and the potential of hedgerows for enhancing biological control services

On California's Central Coast, growers have been incorporating non-crop vegetation (e.g. hedgerows, insectary plants, and cover crops) on their ranches in order to conserve natural resources. This research explores the extent of and motivation behind these conservation practices in the region and the potential benefits of one particular practice, the planting of hedgerows, to enhance biological control services. Using a social psychological framework, in 2007 a mail survey was sent to 600 growers in the Central Coast of California and had a 30% response rate. Survey results indicate that conservation practices have increased slightly over the previous five years and are mostly geared toward soil and water conservation. Growers report several benefits gained from conservation practices such as better soil and water quality, however they also cite many concerns, such as loss of profit, attraction of pest species and food safety conflicts, that may limit their use in ranches. Moreover, growers' conservation behavior on the ranch is likely influenced by social identities and attitudes toward the environment.Hedgerows may improve conservation biological control in highly disturbed, annual crop systems by providing insect predators and parasitoids with stable refugia and food resources. To test the habitat quality of hedgerow plants for insect natural enemies and pests, in 2005 and 2006, vacuum samples were taken on six common plant species at four hedgerows adjacent to organic vegetable fields. To track dispersal patterns of pests and natural enemies from hedgerows into adjacent vegetable fields, in 2006, insects were marked with a fluorescent pigment and captured on sticky traps at 25 and 100 m from the hedgerows. Finally, the effect of hedgerows on biological control services in adjacent vegetable fields was tested using a sentinel pest the cabbage looper, Trichoplusia ni (Lepidoptera: Noctuidae). Results indicate that (1) insect natural enemy and pest species were present in hedgerows and were distributed differently across plant species, (2) natural enemies were generally more abundant than pests on hedgerows and on certain plants, like Baccharis pilularis , (3) insect predators had higher rates of movement from hedgerows at least 100 m into adjacent crop fields. While these results indicate that hedgerows have the potential to increase biological control services, the variability in parasitism rates of cabbage looper and the sensitivity of this parameter to the presence/absence of cole crops made it impossible to make any generalizations. Conservation-based farming will most likely increase in the Central Coast of California, although the rate of increase will depend upon addressing the concerns and constraints that growers have reported and being able to better quantify agro-ecological services gained from conservation areas, such as hedgerows.