Stephen C. Welter

Professor Emeritus


Research Interests

Plant-insect interactions and agricultural entomology

Research Description

Research projects in my laboratory have generally fallen within two major categories: plant-insect interactions or understanding and managing insect populations in agricultural settings. One recent emphasis of the plant-insect work has been to understand the consequences of changes in either system traits or plant characteristics on the interactions of plant, herbivores, and their natural enemies. Contrasts of wild and domesticated plants have provided insights into the consequences of plant life history shifts, changes in plant architecture, and allocation strategies on the plant tolerance to herbivory. In addition, changes in plant phenotype or system traits from domestication has negatively impacted the efficacy of their natural enemies as well as increased plant susceptibility to herbivory for some model systems. A second recent emphasis has been on examining multi-trophic factors that may constrain herbivore host choices or shifts to novel hosts.

The management component of my research has focused on developing environmentally rational integrated pest management programs for tree fruit or vegetable crops with a strong emphasis on the behavioral ecology of moths in pheromone permeated environments. Recent projects include area wide use of pheromone mating disruption to management key pests of apples, pears, and nut crops; use of molecular approaches to evaluate generalist predators as potential biological control agents; and determination of plant constraints on the biological control of pest populations.

Current Projects

In collaboration with graduate students and post-doctoral researchers in my laboratory, projects on plant-insect interactions include examination of the role that crop domestication has played in shaping the relative importance of natural enemies in wild and agricultural sunflowers. Changes in both plant and habitat characteristics are being examined for lepidopterous herbivores and their associated natural enemies. Another project includes partitioning the relative roles that plant characteristics and natural enemies play in shaping the evolution of plant architecture in native sunflower habitats.PCR-based probes are being developed and used to determine the relative impacts of generalist predators in agricultural systems. Long-term goals are to evaluate their potential for understanding food web linkages under shifting environmental conditions.A third set of projects include pheromone mating disruption of codling moth and navel orangeworm in 3 cropping systems as alternatives to pesticides looking at multiple levels of study including: 3D mapping of antennal responses within orchards using field portable electroantennagrams, understanding individual and population level movement in response to pheromone or plant volatiles, evaluation of the behavioral responses of the herbivore and the efficacy of alternative pheromone dispensing devices in orchard ecosystems. Currently, I am involved with a large 3-state effort to implement pheromone mating disruption of codling moth in the western United States.

Selected Publications

Weddle, P.W., S.C. Welter and D Thomson. 2009. History of IPM in California pears-50 years of pesticide use and the transition to biologically intensive IPM. Pest Management Sci. 65: 12: 1287-1292.Welter, S. C. and F Cave. Development of an alternative pheromone mating disruption system for codling moth management in California Pears. 2008. IX Inter. Pear Symposium. Peniche, Portugal. ISHS Acta Horticulturae. 800. 857-866.Goodman, KR, V. R. F. Morris, S. C. Welter, and G.K. Roderick. 2008. Isolation and characterization of microsatellite markers in an endemic Hawaiian planthopper (Nesosdyne chambersi: Delphacidae). Mol. Ecol. Resources. 8: 1436. 1438.Daugherty M. P., Briggs, C.J. and S.C. Welter. 2007. Bottom-up and top-down control of pear psylla (Cacopsylla pyricola): Fertilization, plant quality, and the efficacy of the predator Anthocoris nemoralis. Biol. Control. 43: 257–264.

Chen, Y. H. and S. C. Welter. 2007. Crop domestication creates a refuge from parasitism for a native moth. Journal of Applied Ecology. 44 (1): 238-245.

Douhovnikoff, V. C. Nerney, G. Roderick, C. Newton and S. C. Welter. 2006. Isolation of nine microsatellite loci in Dolichogenidea homoeosomae (Hymenoptera) a parasitoid of the sunflower moth Homoeosoma electellum (Lepidoptera). Mol. Ecol. Notes. 6 (1): 96-97.

Chen, Y. H. and S. C. Welter. 2005. Crop domestication disrupts a native tritrophic interaction. Ecological Entomology 30 (6): 673-684.

Welter, S.C, C. Pickel, J. Millar, F. Cave, R. A. Van Steenwyk, and J. Dunley. 2005. Pheromone mating disruption offers selective management options for key pests. Calif. Agric. 59 (1): 16-22.

Walker, K. R .and S. C. Welter. 2004. Biological control potential of Apanteles aristoteliae (Hymenoptera: Braconidae) on populations of Argyrotaenia citrana (Lepidoptera: Tortricidae) in California apple orchardsEnvironmental Entomology 33 (5) : 1327-1334.

Agusti, N.,Unruh, T. R.; and S. C. Welter. 2003. Detecting Cacopsylla pyricola (Hemiptera: Psyllidae) in predator guts using COI mitochondrial markers. Bulletin of Entomological Research 93 (3) : 179-185.

Chen, Y. H., and S. C. Welter. 2003. Confused by domestication: incongruent behavioral responses of the sunflower moth, Homoeosoma electellum (Lepidoptera: Pyralidae) and its parasitoid, Dolichogenidea homoeosomae (Hymenoptera: Braconidae), towards wild and domesticated sunflowers. Biological Control 28:180-190.

Chen, Y. H. and S. C. Welter. 2002. Abundance of a native moth (Homoeosoma electellum, Lepidoptera: Pyralidae) in relation to activity of its indigenous parasitoids in wild and agricultural sunflower fields. Environmental Entomology 31(4): 626-636.

Welter, S. C. 2001. Contrasting plant responses to herbivory in wild and domesticated habitats. pp. 161-184. In Biotic stress and yield loss. R. K. D. Peterson and L. G. Higley (eds) CRC Press. Boca Raton.

Gratton, C.; S. C. Welter. 2001. In press. Parasitism of natural populations of Liriomyza helianthi Spencer and Calycomyza platyptera (Thomson) (Diptera: Agromyzidae). Biological Control.

Brunner, J.F., S. Welter, C. Calkins, R. Hilton, E. Beers, J. Dunley, T. Unruh, A. Knight, R. Van Steenwyk; P. Van Buskirk. 2001. Mating disruption of codling moth: a perspective from the Western United States. IOBC wprs Bulletin Vol. 25(1): 207-215

Udayagiri, Sujaya and Welter, Stephen C. 2000. Escape of Lygus hesperus (Heteroptera: Miridae) eggs from parasitism by Anaphes iole (Hymenoptera: Mymaridae) in strawberries: Plant structure effects. Biological Control. 17 (3): 234-242.

Udayagiri, S.; Welter, S. C.; Norton, A. P. 2000 Biological control of Lygus hesperus with inundative releases of Anaphes iole in a high cash value crop. In: Southwestern Entomol. (23): 27-38.

Dunley, J. E.; S. C. Welter. 2000. Correlated Insecticide Cross-Resistance in Azinphosmethyl Resistant Codling Moth (Lepidoptera: Tortricidae). J. Econ. Entomol. 93: 955-962.

Gratton, C and Welter, SC. 1999 Does "enemy-free space" exist? Experimental host shifts of an herbivorous fly. Ecology. 80:773-785.

Walker, K.R.; Welter, SC. 1999. Effects of lure dose on efficacy of pheromone traps for monitoring Argyrotaenia citrana (Lepidoptera: Tortricidae) in California apple orchards. J. Econ. Entomol. 92: 574-582.

Gratton, C; Welter, SC. 1998. Oviposition preference and larval performance of Liriomyza helianthi (Diptera: Agromyzidae) on normal and novel host plants. Environ. Entomol. 27:926-935.

Welter, S. C. 1996. Interseasonal Thresholds. pp. 227-248. In L. Higley and L. P. Pedigo (eds). Economic thresholds for pest management. Univ. of Neb. Press.327 pp 327.

Rosenthal, J. P.; S. C. Welter. 1995. Tolerance to herbivory by a stemboring caterpillar in architecturally distinct maizes and wild relatives. Oecologia. 102: 146-155.

Welter, S. C.; J. W. Steggall. 1993. Contrasting the tolerance of wild and domesticated tomatoes to herbivory: Agro-ecological implications. Ecological Applications. 3: 271 - 278.

Honors and Awards

  • Distinguished Teaching Award, 2002, University of California, Berkeley
  • Federal Laboratory Consortium for Technology Transfer - 1999. National USDA Award for technology transfer. Given to a consortium of researchers from 3 Universities and USDA-ARS.
  • Agricultural Research Service Technology Transfer Award - 1998. Western Regional award given to a consortium of researchers in 3 Universities and USDA-ARS.
  • Visiting Professorship, IRTA, Barcelona, Spain – 1994-1995.
  • Innovator in Integrated Pest Management Award - 1994. Granted by California Environmental Protection Agency and California Department of Pesticide Regulation

Recent Teaching


Contact Information


Office: 5063 VLSB

Office Phone: 510-642-2355

Fax: 510-643-7430


Office Hours

By Appointment

Research Group(s)

Mailing Address

Dept of Environmental Science, Policy, & Management
UC Berkeley
130 Mulford Hall #3114
Berkeley, CA 94720