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Biocontrol
of Purple Loosestrife on the Columbia River
Background Information:
 Wetland
and riparian areas along the lower Columbia River are an important component
salmonid habitat. The Lower Columbia River Estuary Partnership (LCREP)
is currently developing high-resolution
spatial data sets of important estuarine and riparian habitats. The
goal of the LCREP study is to produce an estuary-wide map of vegetation
and substrate habitats at multiple
spatial scales; however, exotic invasive species, such as purple loosestrife,
will not be mapped as part of the LCREP project. Unfortunately, Purple
Loosestrife is well established among the Columbia River Channel Islands.
The effect of Purple Loosestrife on salmonid habitat is not well known.
Recent observations at other wetlands in Oregon suggest that increasing
densities of Purple Loosestrife result in a decrease in species richness
of other wetland plants. As the number of plant species decrease, so does
insect species richness (S. Schooler, unpublished data). Insects are an
important food web link between the primary production of the wetland
and salmon.
 Insects
are also important in current efforts to control Purple Loosestrife. During
the past two years, several species of insects have been released at selected
sites on the Columbia River. Their effectiveness as biocontrol agents
is being evaluated by soon-to-be Dr. Shon Schooler. Shon is evaluating
the biocontrol agent's effectiveness at several spatial scales: at the
individual plant scale, he is assessing damage to leaves; at the population
scale, he is quantifying the reduction of Purple Loosestrife plant densities.
Collecting this type of information is very labor intensive.  Consequently,
Shon and Dr. Garono are working to use recently collected hyperspectral
imagery to evaluate Purple Loosestrife infestation on entire sections
of the Columbia River. If successful, remotely sensed imagery can be used
to develop a better understanding of the factors that control and regulate
the abundance of Purple Loosestrife on the Columbia River and can potentially
lead to a powerful tool for natural resource managers.
 For
our study, we used a combination of fieldwork and image analysis to evaluate
past biocontrol agent release sites to determine if control agent augmentation
was necessary. We also selected new release sites and six sites at which
to evaluate the relationship between Purple Loosestrife and insect communities.
In July 2002, a group of Earthwatch students joined us for 10 days on
the Columbia River. We used a variety of approaches to characterize our
study sites. We measured (1) Purple Loosestrife stem densities, (2) damage
from biocontrol agents, and (3) insect diversity in and around the release
sites.
Earthwatch
Students sampled insect and plant communities at six Wallace Island
sites. We set up our Bug Lab at Sea
Resources in Chinook, WA and processed samples (click here for photos
of the trip).
This Research is Sponsored by the
Oregon State Weed Board & The
Earthwatch Institute
Contact Information
Wetland & Watershed Assessment Group
Earth Design Consultants, Inc.
230 SW Third St., Suite 212
Corvallis, OR 97330
(541) 757-7896
(541 757-7991 FAX
http://www.earthdesign.com
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