ACCUMULATION DYNAMICS OF TRICLOPYR ESTER IN LEAF PACKS AND
EFFECTS ON DETRITIVOROUS INSECTS


Janelle Shepherd

Department of Biology and Chemistry
Lake Superior State University
Sault Ste. Marie, MI 49783



Abstract. Previous field studies by the Canadian Forest Service have demonstrated that
residues of the herbicide, triclopyr butoxy ethyl ester (TBEE), can accumulate in
submered leaf material of aquatic systems at concentrations up to 20 times the maximum
aqueous concentration. Accumulated TBEE residues may pose a risk of adverse effects to
detritivorous invertebrates inhabiting and utilizing natural leaf packs. The dynamics of
TBEE accumulation and persistence in leaf material of laboratory microcosms and flow-
through test units were examined and the ecological significance of this in terms of effects
on detritivorous invertebrates and oQ~aric matter processing were determined.
Accumulations of TBEE in leaf packs of laboratory lentic microcosms were up to 80 X
aqueous concentrations, and residues persisted for up to five days. Leaf material of flow-
through units accumulated TBEE at a much higher rate of up to 1000 X aqueous
concentrations, but residues cleared at a faster rate.  Accumulation and persistence in
flow-through units were dependent on depth and velocity of water and exposure duration.
Despite accumulations ofTBEE in leafpacks at up to 90ug/g in systems treated at or near
expected environmental concentrations (EEC), there was no significant mortality of
detritivorous insects and no significant reductions in leaf consumption.  Significant
mortality and reduced feeding occurred only in systems treated at concentrations well
above (up to 10 X) EEC. To put things in perspective, an airplane would have to spray a
body of water, six inches deep, three times with TBEE to give the EEC, showing there is
really no environmental risk posed to macroinvertebrates.


Selected References
Anderson, N. H., & Sedell, J. R. (1979). Detritus processing by macroinvertebrates in
stream ecosystems. Annual Review of Entomology, 24, 351-377.

Kreutzweiser, D. P., & Capell 5.5. (1992). A simple stream-side test system for
determining acute lethal and behavioral effects of pesticides on aquatic insects.
Environmental Toxicology and Chemistry, 11, 993-999.

Kreutzweiser, D.P., Holmes S.B., & Behmer, D.J. (1994). Effects ofthe herbicides
hexazinone and triclopyr ester on aquatic insects. Ecotoxicology and Environmental
Safety 23, 364-374.