- Vegetables: broccoli, cabbages, cauliflower, brussel sprouts
- Education and Training: demonstration, extension, networking, on-farm/ranch research
- Farm Business Management: whole farm planning
- Pest Management: biological control, field monitoring/scouting, integrated pest management
- Production Systems: agroecosystems, holistic management
- Sustainable Communities: sustainability measures
Pest control by resident populations of natural enemies is influenced by the landscape context of the farm. Natural enemies, measured by weekly insect surveys, increased with the proportion of natural habitat in the surrounding landscape in all years of the study. Pest control function, assessed by a cage experiment, was also higher in more diverse landscapes. The effect of natural habitat on aphid distributions was not consistent across growing season or years, however. Identifying source habitat for aphids may be an equally important consideration in predicting aphid distributions as understanding the role played by their natural enemies.
The intensification and expansion of agriculture in the latter part of the 20th century has amplified the age-old competition between humans and arthropod herbivores for food produced from crops. The recognition of the risks of pesticides has led the study of arthropod relationships at the interface of agricultural and natural systems in hopes of regaining aspects of natural pest control in our industrialized agriculture. Natural habitat near agricultural areas could provide resources for the natural enemies of agricultural pests, supplying these beneficial insects to farms to aid in pest control. Research in pest management has begun to focus on how landscape structure around farms affects natural enemy communities and the pest control services they provide on farm sites.
Across a range of cropping systems and natural enemy species, farms embedded in more complex landscapes (those with greater proportions of natural habitat) are associated with more abundant natural enemy populations(1), as well as more diverse natural enemy communities(2). Natural enemy function, measured in rates of parasitism and predation, also increases with landscape complexity(3). Through enhancements to natural enemy abundance, diversity, and function, complex landscapes may provide farms with improved pest control, depending on whether they also serve as a source of pests. Landscape studies have typically ignored the possibility that natural habitat may enhance pest populations as well as natural enemies, and what farmers are really concerned about is not natural enemies per se, but the net effect on their pests. My research, however, examines the commingling variables of natural habitat affecting natural enemies affecting pests, and natural habitat affecting pests directly.
Many experiments manipulating natural enemies densities under constant pest densities have demonstrated that greater abundance of natural enemies can help contain pest populations(4). Removal of these key natural enemies results in dramatic explosions of pest populations(5). Until recently, pest control studies did not include their experimental variables in a landscape context(6). However, even the few landscape pest-control studies that exist have been correlative in nature, relating crop damage and natural enemy abundance to the landscape gradient, but stopping short of proving that natural enemies were the cause of the increased yield. My study bridges this gap, investigating both enemies and pests in order to determine the mechanisms governing pest abundance.
(1) Colunga-Garcia et al. 1997. Environmental Entomology 26:797-804: Elliot et al. 2002. Biological Control 24:214-220; Elliot et al. 2002. Environmental Entomology 31:253-260; Frank and Riechart 2004. Bulletin of Entomological Research 94:209-217; French et al. 2001. Environmental Entomology 30:225-234; Letourneau and Goldstein 2001. Journal of Applied Ecology 38:557-570; Menalled et al. 2003. Agriculture Ecosystems & Environment 96:29-35; Schmidt and Tscharntke 2005. Journal of Biogeography 32:467-473.
(2) Buddle et al. 2004. American Midland Naturalist 151:15-26; French and Elliot 2001. Southwestern Entomologist 26:315-324; Kruess and Tscharntke 1994. Science 264:1581-1584; Marino and Landis 1996. Ecological Applications 6:276-284; Menalled et al.1999, Tscharntke et al. 1998, Tscharntke et al. 2002.
(3) Kruess 2003, Ostman et al. 2001, Menalled et al. 1999. Ecological Applications 9:634-641; Thies et al. 2003. Oikos 101:18-25; Thies et al. 2005. Proceedings of the Royal Society B-Biological Sciences 272:203-210; Tscharntke et al. 1998. Journal of Applied Ecology 35:708-719; Tscharntke et al. 2002. Ecological Applications 12:354-363.
(4) Chang and Snyder 2004. Biological Control 31: 453-461; Ostman 2004. Biological Control 30:281-287; Sunderland and Samu 2000. Experimentalis Et Applicata 95:1-13.
(5) Cardinale et al. 2003. Ecology Letters 6:857-865; Ostman et al. 2003. Ecological Economics 45:149-158; Riechert and Bishop 1990. Ecology 71:1441-1450; Schmidt et al. 2003. Ecology 77:1975-1988.
(6) Thies and Tscharntke 1999. Science 285:893-895; Thies et al. 2003. Oikos 101:18-25.
- To determine whether and to what degree natural habitat provides pest control services to nearby farmland. This addresses SARE Western Region’s goal of protecting the health and safety of those involved in food and farm systems by reducing the use of toxic materials in agricultural production (understanding how to achieve a sustainable and natural means of pest control will help to reduce our dependency on pesticides).
To quantify the amount and/or type of natural habitat necessary for a given level of pest control service, in order to enable economic valuations of this service. This addresses SARE’s national and regional goal of enhancing and promoting good stewardship of the natural resource base upon which the agricultural economy depends (by enabling cost-benefit analyses of land-use in agricultural areas, helping to better quantify the value of natural habitat).