Lindsey du Toit

Salad lovers may not realize that much of the spinach we eat is grown here, and farmers face big challenges keeping those crops disease-free. Lindsey du Toit, a Washington State University plant pathologist from Mount Vernon, is playing a big role in that fight.

The spinach seed crop is fickle. It requires long stretches of daylight to induce bolting, the phase that produces seeds. It’s heat intolerant, so mild summers are a must. As a result, Western Washington and Western Oregon have prime spinach seed crop real estate. In fact, the Pacific Northwest grows about 20 percent of the world’s supply of spinach seed, according to du Toit. She knows a thing or two about spinach. Based at WSU’s Mount Vernon Northwestern Research & Extension Center, she and her team have doubled the capacity for spinach seed production in Skagit County and surrounding counties can produce–thanks to their research into a fungus named Fusarium.

There are numerous strains of this fungus that can attack many different plants and have varying degrees of destruction. For spinach, the problem extends beyond a single crop, du Toit explains. “Once the disease shows up in a field, it can persist in the soil for a very long time.” Fifteen years long. However, waiting even 15 years for a Fusarium-tainted field to clear may not be enough, she says, recounting a story of a farmer who thought he was in the clear only to have a ruined crop.

That encounter prompted du Toit to develop a soil test. Every December for the past nine years, local growers bring buckets of soil to the research facility. Researchers then plant three types of spinach seeds they know range from “Fusarium resistant” to “very susceptible” in each soil sampling. By February, growers and seed companies can better gauge the risks of planting each seed variety in each field.

Going a step further, du Toit noticed that in Denmark, the world’s fourth-biggest producer of spinach seed, growers rotate their fields every five years. They have high pH levels, meaning less acid in their soil, which suppresses Fusarium. She began amending our soil with Limestone (Calcium Carbonate) to reduce the acidity.

This tactic, she says, doesn’t “get rid of the disease, but significantly reduces how badly the disease develops.” Test runs have proven growers can successfully grow spinach seed crops on a 50 percent shorter rotation schedule while maintaining very good yields. For spinach lovers and local growers, that’s a game changer.


WSU NW Research & Extension Center
Mount Vernon
360.848.6120 |
"'Once the disease shows up in a field, it can persist in the soil for a very long time.'"