Kora Mousseaux dips a glass jar into Larson Creek in search of the residue of spring gardening and roadside weed-removal efforts.

She's collecting water from Bear Creek Basin tributaries that flow by orchards, vineyards, forests and Interstate 5, looking for an assortment of chemical killers local residents apply on everything from dandelions to blackberries. 

"We're trying to get more of the urban influence at this site," said Mousseaux, an urban planner for the Jackson Soil and Water Conservation District.

Early into a 10-year study of Bear Creek tributaries, the results consistently, and some say surprisingly, show that pesticides are present in levels well below minimum benchmarks for protecting aquatic communities and the ecosystems around them.

Three years of data collected by the JSWCD has detected 17 active pesticide agents or their breakdown products, but all at relatively low levels and some in minuscule fractions of what is considered unhealthy for aquatic insects and fish.

The pesticide tracking targets so-called "non-point sources," or those not directly pinpointed, such as water-treatment plants, where a single source like a discharge pipe carries pollutants to waterways.

"It's nice to know there's not a large problem out there," said JSWCD Manager Randy White. "But that doesn't mean we can't do better."

Trying to do better is the task of the Pesticide Stewardship Partnership, a group of government representatives, pesticide-using landowners and other stakeholders looking to educate land-users how best to apply herbicides to reduce their influences on watersheds.

Such activities include reducing the amount of pesticide mist that can be carried away in even light winds, creating buffers around streams or simply turning off the sprayer as an orchardist turns his tractor in the field, White said.

For urban sprayers, it can be as simple as reading the labels and following application directions, White said.

The results are surprising to people used to seeing Bear Creek Basin streams routinely violating state and federal standards for pH, phosphorus and dissolved oxygen.

"I would think that if anywhere in the Rogue Basin you'd be likely to find high levels of herbicides and insecticides, it would be in the Bear Creek Basin," said Brian Barr, executive director of the Rogue River Watershed Council.

"I am very surprised, and I don't know how to explain it away," Barr said. "It's possible the people using herbicides and insecticides are following the guidelines."

Now in its fourth year of testing through a state Department of Environmental Quality grant, JSWCD collects water and air samples twice a month at key locations along Jackson Creek, which drains large swaths of western Jackson County, Larson Creek, which powers through east Medford, Payne Creek at Fern Valley Road near Phoenix, and two locations on Wagner Creek in Talent.

The samples are bottled, labeled, packed on ice and shipped overnight to the DEQ's lab in Portland for analysis and compared to separate water flow levels either recorded at stream gauges or measured by Jackson County Assistant Watermaster Ben Thorpe.

The results are reported in nanograms of pesticide per liter, as well as overall loads in the water that day.

Results from 2016 testing, for instance, showed mid-April levels of six different herbicides were present in lower Jackson Creek outside of Central Point, according to JSWCD data.

An acid commonly known as AMPA, a breakdown product of chemicals in Roundup, Rodeo and other common herbicides, tested at less than one-millionth of a percent of the aquatic benchmark standard, results show.

Sulfometuron-methyl, which is found in herbicides such as Patriot and Oust Weed Killer, tested out at .03 percent of the benchmark, results show.

This year's sampling, however, comes after a very wet winter and continued wet spring, which will increase runoff from urban and agricultural lands.

"This year will be interesting," White said. "With the amount of rain we had this year, there will be more overland flow during times when more herbicides are being used."

That includes the east Medford backyards wedged within the Larson Creek drainage.

 "You can go anywhere now and see people using Roundup around fences and ditches," White said.

— Reach Mail Tribune reporter Mark Freeman at 541-776-4470 or mfreeman@mailtfribune.com. Follow him on Twitter at www.twitter.com/MTwriterFreeman.