Project Number: 1907-22620-002-00
Project Type: Appropriated

Start Date: Feb 25, 2003
End Date: Aug 31, 2005

Objective:
Assess the ecological risk of the biological control of purple loosestrife by elucidating the interactions between the introduced natural enemies and Lythrum species and determine the relationships between physiological and ecological host ranges. Sub-objective 1: Determine the physiological interaction between the introduced biological control agents of purple loosestrife and their host. Sub-objective 2: Identify the ecological host range of the introduced insect enemies of purple loosestrife.

Approach:
Olfactometry experiments will be conducted to determine if the 2 Galerucella species, Hylobius transversovittatus & Nanophyes marmoratus, are attracted to purple loosestrife by plant volatiles & whether olfactory cues mediate host-finding in biological control herbivores of Lythrum salicaria. We will test the attractiveness of the beetles, with & without purple loosestrife foliage. We will collect and concentrate volatiles from these tests & will compare insect responses to artificial blends of components constructed from the GC/MS profiles to responses to crude plant volatile mixtures. We will examine whether Galerucella spp. overcome plant defenses by relating insect-host utilization patterns to patterns in leaf secondary chemistry. We will assess the physiological relationship of the biological control agents with L. salicaria, L. alatum, L. virgatum & Decodon verticillatus, using survival & developmental rates from egg to adult in the laboratory. The ecological host range will be developed by comparing the ecological requirements of purple loosestrife, potential alternate hosts & the biological control agents themselves under natural field conditions. Data will be collected from both purple loosestrife sites & the non-targeted Lythraceae sites. A web-based inquiry using standardized protocols & having a national focus will be used to analyze habitats, climate, release history, agent combination, extent of infestation & other factors that may influence whether biological control of Lythrum salicaria is successful or not & the impact the introduced insects have had on non-target species. To provide a greater understanding of the ecology of purple loosestrife & an assessment of the plant-insect interaction, we will characterize seasonal changes in carbon source/sink relationships in purple loosestrife before, during & after insect defoliation. Seasonal changes in absolute concentrations of starch, sugars & total nonstructural carbohydrates (TNC), & in starch partitioning (e.g. starch/sucrose ratios), will be assessed to determine how defoliation alters storage carbohydrate partitioning & may assist in plant recovery. Risk assessment will be developed by combining the data from the above research on the physiological & ecological bases for host specificity. We will provide a measure of fitness of each of the 4 introduced insect species as biological control agents for purple loosestrife in North America. We will use these data to assess the risk of these biological control agents to native plants. Finally, we will develop a projection for the impact of the biological control program for purple loosestrife in North America.

Project Team

Gibson, Donna

Project Annual Reports

FY 2003

Related National Programs

Crop Protection & Quarantine (304)

Related Projects

Evaluating Successful Biological Control of Purpleloosestrife (Lythrum Salicaria)    Assessing the Effect of Galerucella Spp. on Carbon Acquisition and Partitioning in Purple Loosestrife