Oregon State University researchers race the clock to study alternatives to banned pesticide

Soon after the 2020 announcement of a ban on an effective and relatively inexpensive pesticide, Oregon State University Extension Service researchers were at work on finding alternatives for affected growers in Oregon.

Chlorpyrifos, which is being phased out, targets persistent insects affecting more than 40 specialty crops that help drive Oregon’s economy.

Evidence that chlorpyrifos, an organophosphate, is associated with neurological damage in humans prompted the U.S. Environmental Protection Agency and the Oregon Department of Agriculture to ban the pesticide on food crops in 2021 with final phase-out on all crops by Dec. 31, 2023, according to Kaci Buhl, director of the OSU Extension Pesticide Safety Education Program and associate professor of practice in the College of Agricultural Sciences.

The prohibition hits hard at growers of crops like strawberries, vegetables, grass seed, mint and orchard fruits and nuts who have used chlorpyrifos since the 1960s.

When the ban was announced, ODA awarded OSU Extension a three-year, $162,794 Specialty Crop Grant to undertake research to find chlorpyrifos alternatives. A statewide research team led by Silvia Rondon, director of OSU’s Oregon Integrated Pest Management Center, began by surveying farmers who require new products and methods for controlling pests that damage their crops.

″Chlorpyrifos is one of the tools our growers have been using for ages,″ said team member Navneet Kaur, OSU Extension entomologist and assistant professor in the College of Agricultural Sciences. ″It’s a product used for many, many years that’s been effective. When the ODA announced the ban, growers were not happy because they had no other alternatives.″

Navneet Kaur (left), assistant professor and Extension entomologist, and Silvia Rondon, director of the Oregon IPM Center, are conducting research to identify chlorpyrifos alternatives for controlling pests in Oregon crops. The Environmental Protection Agency and Oregon Department of Agriculture banned the pesticide due to concern over its neurological impacts on humans.

Credit Lynn G. Ketchum

The OSU research team conducted a critical-use survey of farmers in 2020-2021 to identify the reasons they use chlorpyrifos. They cited symphylan, a fast-moving, soil-dwelling arthropod, in addition to aphid, scale insect, root maggot, sod webworm, root borer, cutworm and weevil, among other agricultural and horticultural pests. To fight them, farmers most commonly chose chlorpyrifos for its effectiveness and for lack of alternatives, but its lower cost was a reason, too.

Symphylan attacks almost all of the specialty crops grown in Oregon except tree fruits and nuts and are extremely difficult to control. Growers of all affected crops reported symphylan as the targeted pest for 12% to 25% of their chlorpyrifos applications.

Kaur is concentrating on pest control for grass seed, a major crop in Oregon’s Willamette Valley. More grass seed is produced in the valley than anywhere else in the United States. Kaur studied the efficacy of alternative pesticides for sod webworm and symphylan.

Kaur’s research looked at multiple insecticide chemistries for their efficacy to determine their ability to control symphylan and insect pests. For the study different chemistries were applied to plots planted with the same crop in various locations.

Regional faculty study regional crops

In regions across the state, Extension faculty concentrated on crops important to their area. In western Oregon, Kaur concentrated on grass seed. Clover was the focus of Dani Lightle, specialty crops pesticide registration research leader based at the North Willamette Research and Experiment Station (NWREC) and assistant professor of practice in the College of Agricultural Sciences.

Eastern Oregon onions were the focus of Rondon and Stuart Reitz, director of the Malheur Experiment Station in Ontario and professor in the College of Agricultural Sciences. In the Columbia River Gorge, cherries were the subject of research for Chris Adams, Extension fruit tree specialist and assistant professor in the College of Agricultural Sciences based at the Mid-Columbia Agricultural Research and Extension Station in Hood River.

Lightle partnered with Kristi Buckland, vegetable and specialty seed crop specialist at NWREC and associate professor in the College of Agricultural Sciences. They studied radish and turnips in particular, which have been plagued by cabbage maggot.

Research was conducted on numerous chemistries in the field using replicated plots, including a control plot where no pesticide was sprayed. Some trials were completed at NWREC, and others were planted on private farms. The targeted insects were collected and counted in the different areas to determine if any of the trial products were effective. Results varied.

Some of these new chemistries like anthranilic diamides (Vantacor and Besiege), which represent a new mode of action, were promising for sod webworm control. A liquid-ready formulation of bifenthrin (Capture LFR) was consistently found to be effective for symphylan management in grass seed crops, but no clear alternatives were identified as highly effective in vegetable crops yet.

″Chlorpyrifos is cheap and when working on a low-profit margin, an application could cost $15 an acre while newer material can run $100 an acre,″ Lightle said. ″If you’re looking at the bottom line, older pesticides are often much less expensive. In terms of effectiveness the clear advantage is a broad-spectrum insecticide that is used against a large number of insects.″

Alternatives ‘benefit everybody’

However, destroying all the insects in the field is not environmentally sustainable, Lightle said. The beneficial insects that often feed on the destructive insects would also be killed. The OSU Extension faculty working on the chlorpyrifos project are looking for lower risk but effective products in an integrated pest management (IPM) management strategy, which focuses on sustainable methods for insect, disease and weed management.

No matter what products have promise, it takes years for a new product to go through the EPA approval process, Buckland said. And because Oregon has so many specialty crops, more than one pesticide is necessary to battle all the different insect pests. In addition, pesticides can lose efficacy over time, so it takes more than one for a successful control strategy.

Research continues, said Kaur, who runs seven to eight efficacy studies every year in an attempt to find chlorpyrifos alternatives.

″Alternatives are important for a lot of reasons,″ Lightle said. ″For growers, the bottom line for pest management is effective tools. Continuing to develop alternatives goes above and beyond pest management, though. It has value for the environment and human health. In general, new materials tend to be lower risk to field workers and have lower environmental risk. Therefore, if we can get a good alternative, it will benefit everybody.″