Stephen C. Welter
Associate Professor and Associate Entomologist
5063 VLSB
Phone #: (510) 642-2355
FAX #: (510) 642-7428
welters@nature.berkeley.edu
Research Interests
Research project in my laboratory have generally fallen within two major
groupings: plant-insect interactions or understanding and managing insect
populations in agricultural settings. The emphasis of the plant-insect work
has been on understanding the responses of plants to insect damage from
the physiological to the organismal level. The long-term objectives are
to understand the costs of crop domestication on plant tolerance to herbivory
and to predict the effects of insect damage on crop productivity. Measures
of plant responses to herbivory have ranged from short-term changes in leaf
gas exchange rates to assessing long damage and recovery in the productivity
of perennial plants. 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 plant tolerance to herbivory.
The management component of my interests has focused on developing environmentally
and economically rationale integrated pest management programs of tree fruit
or vegetable crops. Research has included enhancing biological control using
augmentative or conservation techniques, developing more stable IPM programs
by managing insecticide resistant genotypes, establishing criteria for decision
making in IPM, or developing non-chemical alternatives to broad spectrum
insecticides, e.g. pheromone mating disruption. Elements of insect behavior,
genetics, and ecology are woven into almost all projects.
Current Projects
Our laboratory projects in plant-insect interactions include understanding
the consequences of crop domestication on the tolerance of maize, tomato,
and strawberry to herbivory. Contrasts of wild progenitors with multiple
lines of domesticated taxa with dramatically different architectures include
physiological, growth, or reproductive responses to insect damage. These
data have implications for understanding the evolution of plant phenotypes
and for developing criteria for breeding crops to enhance tolerance to insect
damage. Another project includes partitioning the relative roles that plant
characteristics, natural enemies, and competition play in shaping the evolution
of host range for a series of native leafmining insects on native sunflowers.
The second foci within our laboratory includes developing criteria for approaching
pest management on the appropriate ecological and genetic scale. Efforts
to manage simultaneously pest population numbers and insecticide resistant
genotypes have required the development of large-scale regional efforts
using pheromone mating disruption to control codling moth in California
pears. Elements of the larger effort include: characterizing the levels
and distribution of insecticide resistance; quantitative genetics of organophosphate
resistance; determining fitness costs associated with insecticide resistance;
and developing non-selecting alternatives. Newer projects include determination
of rates gene flow among codling moth populations that are coupled with
insect dispersal studies so as to understand codling moth movement on a
regional and local scale.
Implementation of large scale substitution of pheromone mating disruption
for broad spectrum insecticide use for control of codling moth has required
developing an enhanced understanding of mate location in pheromone permeated
environments by codling moth, development of novel monitoring approaches,
and addressing the cascading effects of system changes on non-target species.
Other laboratory efforts include a project on the behavior and ecology of
an egg parasitoid of a pest in strawberries. Using multiple massive releases
of the egg parasitoid, commercially acceptable control has been achieved
within coastal strawberry fields. Understanding individual behavior (e.g.
intra-specific interactions and dispersal) are key to predicting program
efficacy and release strategies.
Selected Publications
Varela, L.G. and S.C. Welter. 1992. Parasitoids of the leafminer, Phyllonorycter
nr. elmaella (Lepidoptera: Gracillariidae), on apple in California: Abundance,
impact on leafminer, and insecticide-induced mortality. Biological Control.
2: 124-130.
Norton, A.P., S.C. Welter, L. Flexner, C.G. Jackson, J. Debolt and C. Pickel.
1992. Parasitism of Lygus hersperus by Anaphes iole (Mymaridae) and Leiophron
uniformis (Braconidae) parasitism in California strawberry. Biological Control.
2: 131 - 137.
Varela, LG., S.C. Welter, V.P. Jones, J.F. Brunner, and H. Riedl. 1993.
Monitoring and characterization of insecticide resistance in codling moth
(Lepidoptera: Tortricidae) in four western states. J. Econ. Entomol. 86:
1- 10.
Welter, S.C. and J. W. Steggall. 1993. Contrasting the tolerance of wild
and domesticated tomatoes to herbivory: Agro-ecological implications. Ecological
Applications. 3: 271 - 278.
Rosenthal, J.P. and S.C. Welter. 1995. Tolerance to herbivory by a stemboring
caterpillar in architecturally distinct maizes and wild relatives. Oecologia.
102: 146-155.
Courses Taught:
- Insect Ecology, ESPM 113
- Environmental Issues, ESPM 10
Current Graduate Students:
- Yolanda Chen
- Claudio Gratton
- John Steggall
- Kathleen Walker
Current Postdoctoral Researchers:
- Andrew Shedlock
- Sujaya Udayagiri
Staff Research Associate: