Revisiting the Success of Natural Enemies To Provide Sustainable Ecosystem Services and Reduce Pollution

EPA Grant Number: FP917248
Title: Revisiting the Success of Natural Enemies To Provide Sustainable Ecosystem Services and Reduce Pollution
Investigators: Andersen, Jeremy Catalin
Institution: University of California - Berkeley
EPA Project Officer: Lee, Sonja
Project Period: August 18, 2010 through August 17, 2013
Project Amount: $111,000
RFA: STAR Graduate Fellowships (2010) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Fellowship - Ecosystem Services: Terrestrial Systems Animal Ecology


The United States has more than 300 million acres of agro-ecosystems, which are highly dependent upon regulating ecosystem services such as pollination and biological control. These agro-ecosystems are also major contributors to nonpoint source pollution from pesticides. Biological control can be a sustainable approach to pest management through the reduction of pesticide use. For this approach to be truly sustainable, it is necessary to study what factors may influence the evolution of biological control agents after their introduction. In this project, I propose to investigate how intraspecific hybridization among different strains of imported insect parasitoids and variation in the susceptibility of aphid clones to parasitism can influence the sustainability of biological control services in the management of invasive crop pests. My research will lead to improved understanding of the management of ecosystem services, and to a reduction in pesticide usage and consequently to a reduction in nonpoint source pollution from agricultural ecosystems.


To protect U.S. agriculture from arthropod pests, pesticides continue to be used extensively. Pesticides, however, have been linked to pest resistance, pollution, loss of biodiversity, and are becoming politically unpopular. Biological control can be a sustainable approach for reducing damage by crop pests, but to ensure their safety and viability we need to re-examine previous successes to determine how evolution can influence the sustainability of biological control services.


The first stage of research will include sampling of the biological control agent Trioxys pallidus, a parasitoid wasp introduced to control aphids in walnut and hazelnut orchards. Separate strains of T. pallidus were introduced for each crop, and both systems have been textbook examples of successful biological control. Now, 40 years after the initial introductions, both systems are starting to fail. Using molecular DNA techniques, individuals will be genotyped to examine whether or not hybridization has occurred between the two strains of T. pallidus introduced into the western United States. After the rates of hybridization are determined in the orchards, samples will be brought back to the lab where crossing experiments and behavioral assays will be performed to determine the specific effects of hybridization on the efficiency of biological control in this system and the potential for the pest species to develop resistance either through novel secondary symbionts or behaviors.

Expected Results:

This data will then be used to identify the population structure of T. pallidus in California and Oregon, and the incidence of hybridization in orchards. We expect that hybridization has occurred between the two strains, and that gene flow is occurring between the two parasitoid strains. This result could have widespread implications for existing biological control programs, due to the fact that multiple introductions/strains have often been introduced into other systems as well. It is likely that the co-adapted gene complexes between the parasitoids and their aphid hosts will be disrupted due to the introgression of novel genetic material, reducing the success of larval development, and thus limiting the effectiveness of T. pallidus as a control agent. It is likely as well that the pests have been able to adapt to the natural enemies introduced to control them. The potential for horizontal transfer also makes the acquisition of novel defensive symbionts an attractive explanation for the rise in walnut and filbert aphid populations.

Potential to Further Environmental/Human Health Protection:

Biological control has the potential to be a sustainable pest control option. Immediately following the release of T. pallidus in walnut and hazelnut orchards, the use of pesticides to control aphids was completely eliminated, protecting the environment from nonpoint source pollution pesticide runoff into waterways, and reducing costs to farmers. This work will directly be involved in the re-establishment of that control. In addition, to establish the long-term effectiveness of biological control programs in general, we need to examine the evolutionary potential of control agents in their new habitats. By studying the effects of hybridization in biological settings we can make informed management decisions about the release of natural enemies and reduce the pollution and negative health effects associated with the use of pesticides.

Supplemental Keywords:

biological control, hybridization, evolution, pesticides, pollution, insect pests, agriculture, IPM, sustainable, agro-ecosystems, parasitoid, natural enemies,

Progress and Final Reports:

  • 2011
  • 2012
  • Final