Attractiveness of California Native Perennial Plants to Natural Enemy and Pest Insects
Physical and Biological Sciences
ENVS 195
In light of the negative effects that pesticides and fertilizers are having on human health and the environment, many people are turning towards organic agriculture as a source of healthy produce with lower environmental impacts. Rather than using chemical additives, organic agriculture focuses on amplifying natural processes to support the growth and development of food plants. One important feature of organic agriculture, termed biological control, is promoting the use of natural enemy insects to manage pest populations rather than spraying toxic chemicals on crops. Biological control of pest populations, through the conservation and augmentation of beneficial predators and parasitoids, has the potential to minimize pest damage to economically unimportant levels.
Both predators and parasitoids eat pollen and nectar as a supplement to their diets. In order to attract these natural enemy insects, many organic farmers have added non-crop flowering plants to their fields as part of their farm management plans. Currently, the most common insectary plants used in bolstering predator and parasitoid populations are a few well-studied annuals. However, recent research suggests that perennial plants may be comparable to annuals in their ability to attract natural enemy insects to farms.
In the spring and fall of 2011, I surveyed the insect communities of 11 California native perennials. I used a net to collect insects so that I could observe the behavior of each insect prior to catching it. The highest abundances of natural enemies were found on coyote brush (Baccharis pilularis), Santa Cruz Island buckwheat (Eriogonum arborescens), St. Catherine’s lace (Eriogonum giganteum), coffeeberry (Rhamnus californica), and black sage (Salvia mellifera). I observed many natural enemies visiting non-flowering plants and plant parts, suggesting that these insects may visit plants for reasons not exclusive to nectar and pollen resources. I suggest that the quality of shelter that is provided by perennial plants in agroecosystems is an important, but underappreciated factor attracting insects to plants.
