Persistence of triclopyr, dicamba, and picloram in the environment following aerial spraying for control of dense pine invasion
Date: 8th December 2023
Congratulations to Carol Rolando from SCION who won the front-page competition for the above article (also see link to article below) in the Weed Society of America journal.
Management implications from the study are as follows: While the treatment is effective, given the large amounts of active ingredient used (∼20 kg ha−1), practitioners have concerns about the persistence of the herbicides in the environment and the potential impact on future restoration efforts. The objective of this study was to determine the persistence of triclopyr, dicamba, and picloram in cast needles, forest floor, mineral soil, and stream water following aerial spraying of P. contorta with the operationally used herbicide mix at three geographically distinct locations in New Zealand. A lack of laboratory capacity for testing aminopyralid in New Zealand precluded its inclusion in this study.
Key results of this study were:
- All three herbicides (triclopyr, picloram, and dicamba) were still present in the forest floor layer 2 yr after spraying; that is, herbicides were retained in a heavy lignin-rich layer of dead/cast needles overlaying the soil.
- Only triclopyr was detected in the soil for the first year after spraying.
- Where a no-spray buffer zone (30 m) was used on the edge of streams intersecting the aerially sprayed area, herbicides in water did not exceed environmental exposure limits when rainfall occurred shortly after spraying.
The persistence of the active ingredients in the forest floor litter layer is unlikely to pose a risk to terrestrial organisms but could persist at levels that affect revegetation efforts that commence within 18 months after aerial spraying.
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