Journal of Shellfish Research, Vol. 17, No.1, 177-183, 1998.
THE POTENTIAL FOR USING BIOLOGICAL
CONTROL TECHNOLOGIES IN THE MANAGEMENT OF DREISSENA SPP.
DANIEL P. MOLLOY
Biological Survey
New York State Museum
The State Education Department
Cultural Education Center Albany, NY 12230
ABSTRACT Broadly defined, biological control is the use of one species for the
suppression of another. Two groups of organisms have potential as Dreissena
control agents: selectively toxic microbes and natural enemies. Selectively
toxic microbes are naturally occurring soil and water microorganisms that
simply by chance happen to be toxic to Dreissena. Applied at
artificially high densities to water, the microbial cells per se or
their released metabolites are selectively lethal to Dreissena. In
contrast, natural enemies are organisms that, by their evolutionary nature,
will debilitate or kill Dreissena, including predators, parasites (both
multicellular and microbial), and benthic competitors (organisms capable of
competitively displacing Dreissena from substrates).
Selectively Toxic Microbes: In the short run, these microorganisms represent the
most promising candidates as biological control agents, The use of
highly-specific, toxic microbes has a clear record of commercial success and
environmental safety in the control of invertebrate pests in North America. and
strains lethal to Dreissena have been already isolated. Considering how
quickly a selectively toxic microbe could move from the laboratory to
commercialization, continued research to develop this microbial control
strategy is a high priority.
Natural Enemies; In North America, as in Eurasia, there will likely be isolated field
reports of major impacts by natural enemies, and, on the whole, we will likely
see a cumulative effect of a complex of enemies having a constant, but limited,
role in naturally suppressing Dreissena populations. In the majority of
cases, Dreissena populations will cause economic and ecological effects
at densities well below those that their enemies could naturally maintain.
This does not mean, however. that certain natural enemies could not be artificially
manipulated (e.g., mass produced and released in an inundative fashion) to
cause major Dreissena reductions.
1.
Parasites:
These natural enemies would
likely be the most environmentally-safe biocontrol agents, due primarily to
their high host specificity. Comprehensive investigations to identify parasites
that are strictly specific to Dreissena and that can be economically
mass produced are a key research priority. Parasites from Dreissena's native
Eurasian range should be studied to identify species that would be "nearly
risk free" candidates for importation into North America. Research to uncover
parasites of Dreissena that are already present in North America should
be intensified.
2.
Predators:
Although organisms, such as
fish and birds, have sometimes been documented to consume Dreissena at
high rates, this does not necessarily mean that they would be effective
candidates for use in control programs. Predators are typically not specific
enough in their prey choices. A predator introduced to a waterbody from outside
its natural range may highly prefer Dreissena as a prey item, but will
also consume other aquatic organisms. The consumption of such nontarget prey
could potentially have serious, adverse, ecological impacts.
3.
Benthic
Competitors; In addition to
being micro/macrofouling organisms themselves, the lack of specificity of
species that can competitively displace Dreissena from substrates (e.g.,
sponges) significantly reduces their potential as biocontrol agents.
KEY WORDS: Zebra
mussels, quagga mussels, selectively toxic microorganisms, natural enemies,
predators, parasites, benthic competitors