The Effects of Triclopyr

The following report and photos were submitted by a friend of the lake who is a lifelong naturalist and a trained observer.  To better understand his comments, we first offer this simplified explanation of how triclopyr actually works.

Triclpoyr is a synthetic chemical called an auxin. Auxins are a class of chemicals found in plants that help regulate their growth. For example, phototropism is caused by inhibition of auxins by sunlight, so that the shaded underside of the plant grows more than the sunny part, causing the plant to ‘grow toward the sun.’  Abnormal amounts of these auxins can disrupt the normal growth of a plant, even kill it, so auxins are also used as herbicides.  Also, different species of plants respond differently to auxins, making them useful for weed control. Finally, triclopyr is an effective herbicide for dicots (flowering plants and trees) but not for monocots (grasses and conifers).  More information HERE.

June 9th, one week after treatment

I rowed out yesterday to review post therapy effects.   In the Middle brook cove the Eurasian watermilfoil is already dark grey and on the bottom.   I did not look for Eurasian watermilfoil in deeper areas.  As would be predicted there was a “side effect” of the treatment.   The triclopyr mimicked the growth hormone and accelerated the growth in other dicots.

Water Lily Stems Elongated Three Times their Normal Length



The white water lily (Nymphaea) showed the most effect with lengthening of the stem to three times normal.   Thus the leaves are overturned and the stems lie in a tangle of the surface.  There were areas near the water inlet of Middle brook that were not affected.  All plants at our end (southwest) of the lake showed these changes.




The Cow Lily (yellow water lily) (Nuphar)  was less affected in the large beds at Middle brook with the leaf stems only being twice lengthened.  The leaves looked healthy.    In other areas the whole cow lily plant looked fine with well formed flowers.


White Water Lily Root


Here is a photo of the white water lily root.    As you can see, the leaves and flower buds come right out of the root (which is under the mud on the floor of the lake).   So my conclusion is that even if the water lily looses some leaves from the triclopyr the whole plant will recover and continue to thrive.


These monocots were not affected in the Middle brook cove nor at our end of the lake: Elodea, Potamogeton, Typha, Vallisneria, or Najas.

Potamogeton (Pondweed) is a monocot which seems to be doing fine