Good Bug, Bad Weed

Hillary Thomas' biological control research on a leaf-eating beetle that targets saltcedar has scored a bullseye.

Thomas, a doctoral candidate in entomology at UC Davis, has received a $15,000 Robert and Peggy van den Bosch Memorial Scholarship to support her research.

Saltcedar or tamarix (Tamarix spp.) is a major pest that threatens waterways. In the western United States alone, the plant impacts several million acres of prime riparian land. 

Thomas researches Diorhabda elongata, a saltcedar leaf beetle native to Central Asia and  a natural enemy of the pest.

She won the award for her project, “Impact of Host-Plant Preferences on Establishment and Efficacy of Diorhabda elongata (Coleoptera: Chrysomelidae), a Biological Control Agent of Saltcedars.” She studies with major professor Frank Zalom, an integrated pest management specialist.

“Hillary is an outstanding young scientist who is committed to the implementation of biological control,” said Zalom. “Her dissertation research on host plant acceptance by the beetles introduced for control of invasive saltcedar is not only useful for that system but will lead to better understanding of the importance of post-release evolution in biological control agent establishment.  She is highly motivated."

 "The beetle has shown great potential to control the weed in some release areas," said Thomas, who collaborates with the Exotic and Invasive Weeds Unit of the U.S. Department of Agriculture/Agricultural Research  Service.  "It causes defoliation to the extent that it appears there will be a population-level effect on tamarix stands.”

Thomas' work initially focused on improving insect establishment success in the Cache Creek watershed, near Rumsey, Yolo County, where Tamarix parviflora grows.  Today she compares the host plant preferences of two populations: the field population beetles and a  source lab colony.

“It seems there might be an increase in host plant acceptability of Tamarix parviflora by the field population,” Thomas said. “I am repeating both field and laboratory experiments at the moment to determine whether there is substantial evidence to support this.”

Saltcedar, first imported to the United States from the Middle East in the 1880s for erosion control and as an ornamental, is extremely aggressive and invasive. As a shrub or small tree, it forms dense thickets, displacing native plants and animals. Its long tap roots suck in massive amounts of water.  It also drops its salt-infused foliage on the surface, inhibiting other plant growth.

A single saltcedar can produce as many as 600,000 seeds annually, according to weed specialist Joseph DiTomaso of the UC Davis Department of Plant Sciences. Chemical, mechanical and cultural control techniques are effective, but expensive and temporary.  

Three other UC Davis doctoral candidates shared in the Robert and Peggy van den Bosch scholarships.

Amanda Hodson, who studies with major professor Edwin Lewis (he holds a joint appointment in  nematology and entomology) received $10,000 to continue her research on “Ecological Influence of Entomopathogenic Nematodes in Pistachio Orchards.”

Yao Hua Law, of entomologist Jay Rosenheim's lab, received $5000 to support his work on "Multiple Predators Improve Biocontrol: Niche Complementarity and Cannibalism.” He also received a $1115 van den Bosch travel award to attend the Ecological Society of America annual meeting in Milwaukee, Wisc., to present his work on predation.

 Andrew Sutherland, of entomologist Michael Parrella's lab, received a $1500 van den Bosch travel award for his “Manual Transmission of Powdery Mildew Fungi Mediated by Activity of an Obligate Mycophagous Beetle (Coleoptera: Coccinellidae).” He will attend the Brazilian Society of Entomology conference, set Aug. 24-29. .

The van den Bosch scholarship program provides a total of $60,000 to $80,000 annually  for work related to biological control,  said coordinators Kent Daane and Nicholas Mills,  co-directors of the Center for Biological Control, UC Berkeley. Eligible to apply are doctoral candidates from UC Davis, UC Berkeley and UC Riverside. Typically, the winners receive $15,000, $10,000 or $5,000. Selection is by a panel of biocontrol faculty representing the three schools. 

In addition, Daane and Mills annually present  travel awards totalling $15,000 to $20,000. The maximum amount is $1500 per student.

Others receiving scholarships were UC Berkeley students Rebecca Chaplin-Kramer (major professor: Claire Kremen, also a UC Davis Department of Entomology affiliate), Mel Stravrinides (major professor:  Nicholas Mills); and Eleanor Blitzer (major professor:  Stephen Welter). Receiving travel funds: Mel Stravrinides and Eleanor Blitzer, UC Berkeley; and Jason Mottern and Jennifer Henke, UC Riverside. 

Robert van den Bosch (1922-1978) served as a researcher, teacher, and an administrator in the Division of Biological Control and the Department of Entomological Sciences, UC Berkeley, from 1963 until his death. A native of Martinez, Calif., he was a lifelong advocate of  biological control.  His colleagues said he searched tirelessly for natural enemies of agricultural pests, an effort that resulted in the importation and establishment of 17 natural enemy species.

With the recent death of his wife, Peggy, more funds (at her request) were added to the van den Bosch awards program.