Nicholas Mills

Professor
PhD  University of East Anglia, UK
  

310 Wellman Hall
Berkeley, California 94720-3114
nmills@nature.berkeley.edu
office: 510-642-1711   lab: 510-642-1711   fax:  510-643-5438

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The focus of my research group is the biological control of insect pests and the ecology of insect parasitism and predation. Classical biological control has an outstanding history of success in the sustained regional control of invading pests and provides exciting opportunities for both lab and field-based ecological research. However, not all biological control introductions result in spectacular reductions of pest damage and so a major emphasis in our work is to address arguably one of the most challenging questions in biological control research: what are the determinants of success in classical biological control? In addition to classical biological control, the augmentation of natural enemy populations is an aspect of biological control that is rapidly gaining attention. The use of natural enemies as biological pesticides raises some very interesting questions about the performance characteristics of natural enemies, strategies for release and optimization of impact.

Natural enemies, and in particular insect parasitoids, are known not only for their importance in biological control but also as model systems for the analysis of many exciting questions in biology. As a result, our research interests include a variety of aspects of natural enemy biology, from behavior and evolutionary biology to population and community ecology through observational, experimental and comparative analysis. One of the most satisfying aspects of our work is the knowledge that the discovery of exciting new elements of natural enemy biology provides a direct linkage to the implementation of improved biological control and a reduced reliance on pesticide intervention in insect pest management.

Biology of Insect Parasitoids and Predators. The lifetime reproductive success of a female natural enemy is dependent on her ability to locate hosts, to assess the quality of each host, and to respond to variation in encounter rates and host quality. Thus parasitoids and predators are ideal model organisms for the study of behavioral ecology – how behavioral decisions influence the fitness or reproductive success of an organism. Current projects focus on dispersal, functional and numerical responses, population structure and hybridization, and a demographic approach to evaluating the compatibility of natural enemies with pesticides. We are currently working with Aphidius transcaspicus, Chrysoperla carnea, Harmonia axyridis, Mastrus ridibundus, Trioxys pallidus, Trichogramma species, and Venturia canescens.

Dynamics of Biological Control Systems. Ecologists have not been slow to address biological control through ecological theory and the development of conceptual models to capture the essence of host-parasitoid interactions. The difference between success and failure in biological control can be due to exogenous limitations or to endogenous processes. We focus on the latter to find more general aspects of the interactions between natural enemies and hosts that can be used to improve success and minimize the risks of biological control. Current projects use simple models to examine the interplay of host population growth rate, host refuges from parasitism, parasitoid fecundity, and generation time ratios in the dynamics of host-parasitoid systems.

Implementation of Biological Control. We currently have three biological control projects in our laboratory, one on the light brown apple moth (Epiphyas postvittana) a recent invader from Australia that is an important pest of garpe vines and pome fruit; a second on the mealy plum aphid (Hyalopterus pruni) a key pest of prunes; and a third on walnut aphid (Chromaphis juglandicola) a well-known pest of walnuts. The first two projects involve foreign exploration, selection of natural enemies for importation, and field release and monitoring. The third project is designed to elucidate reasons for the localized failure of sustained biological control 35 years after the successful introduction of the parasitoid Trioxys pallidus.

DANR Distinguished Service Award, Outstanding Faculty, 1997

CNR Distinguished Teaching Award, 2002

Mills, N. J. 2005. Selecting effective parasitoids for biological control introductions: Codling moth as a case study. Biological Control 34: 274-282.

Bezemer, T. M., Harvey, J. A., and Mills, N. J. 2005. Influence of adult nutrition on the relationship between body size and reproductive parameters in a parasitoid wasp. Ecological Entomology 30: 571-580.

Mills, N. J., Babendreier, D., Loomans, A. J. M. 2006. Methods for monitoring the dispersal of natural enemies from point source releases associated with augmentative biological control. In: Environmental Impact of Invertebrates for Biological Control of Arthropods: Methods and Risk Assessment. Bigler, F., Babendreier, D. and Kuhlmann, U. (Eds.), CABI Publishing, Wallingford, pp. 114-131.

Hougardy, E., and Mills, N. J. 2006. The influence of host deprivation and egg expenditure on the rate of dispersal of a parasitoid following field release. Biological Control 36: 206-213.

Lozier, J. D., Mills, N. J., and Roderick, G. K. 2006. Di- and tri-nucleotide repeat microsatellites for the parasitoid wasp, Aphidius transcaspicus. Molecular Ecology Notes 6: 27-29.

Mills, N. J. 2006. Accounting for differential success in the biological control of homopteran and lepidopteran pests. New Zealand Journal of Ecology 30: 61-72.

Mills, N. J. 2006. Interspecific competition among natural enemies and single versus multiple introductions in biological control. In: Trophic and Guild Interactions in Biological Control. Brodeur, J. and Boivin, G. (Eds.), Springer, pp. 191-220.

Hougardy, E., and Mills, N. J. 2007. Influence of host deprivation and egg expenditure on the patch and host-finding behavior of the parasitoid wasp Mastrus ridibundus. Journal of Insect Behavior 20: 229-246.

McPheron, L. J., and Mills, N. J. 2007. Discrimination learning of color-odor compounds in a paper wasp (Hymenoptera: Vespidae: Mischocyttarus flavitarsis). Entomologia Generalis 29: 125-134.

Lozier, J. D, Roderick, G. K., and Mills, N. J. 2007. Multi-genome evidence for the evolution of host associated species in the aphid genus Hyalopterus. Evolution 61: 1353-1367.

Mills, N. J., and Wajnberg, E. 2008. Optimal foraging behaviour and efficient biological control methods. In: Behavioural Ecology of Insect Parasitoids – From Theoretical Approaches to Field Applications. Wajnberg, E., Bernstein, C., and van Alphen, J. (Eds.), Blackwell, pp. 3-30.

Lozier, J. D., Foottit, R. G., Miller, G. L., Roderick, G. K. and Mills, N. J. 2008. Molecular and morphological evaluation of the aphid genus Hyalopterus Koch (Insecta: Hemiptera: Aphididae), with a description of a new species. Zootaxa 1688: 1-19.

Hougardy, E., and Mills, N. J. 2008. Comparative life history and parasitism of a new color morph of the walnut aphid in California. Agricultural and Forest Entomology 10: 137-146.