How Sustainable Farmers are Using All-Natural Rock Dust for Slug Management

Slug Management

Slugs have always thrived in the cool, damp weather of Oregon’s Willamette Valley. Yet in recent years, slugs have been eating their way through wider swaths of valuable crops. It’s a problem that continues to get worse—and one that can’t be solved with chemicals. (Even chemicals seem to lose their effectiveness rather quickly, as slugs develop an aversion to the toxins while surrounding species suffer.)

The situation has become so dire that in March 2015 Oregon State University (OSU) hosted a “Slug Summit” in the state’s capital to try to figure out what to do. Unfortunately, the “Slug Summit” didn’t reveal any concrete answers. Growers and researchers still don’t know exactly why the slippery mollusks are becoming harder to control. One theory is that sustainable, no-till and reduced tillage farming practices, while good for the earth, leave more vegetation for slugs to find shelter.

Whatever the reasons, the bottom line is that slugs are costing farmers some very big bucks. According to some estimates, grass seed growers alone lose about $15 million per year to slug damage. One study showed that soon after grass seed farmers adopted no-till practices in the early 2000s, there were nearly 30 times as many slugs in no-till ryegrass fields than in conventionally tilled fields.

(Sources: “Slugs Are Destroying the Businesses of Oregon’s Sustainable Farmers” by Leah Sottile takes a close look at the problem and how some growers are trying to cope. More information on slugs and slug management is available via OSU’s College of Agricultural Sciences website.)

An Integrated Approach to Slug Management

You would be hard pressed to find a grower in the Willamette Valley who doesn’t support greener farming practices—in theory. Still, despite the proven benefits of no-till farming (e.g., healthier soil with more beneficial microbes), many are hesitant to give up plowing the soil because they fear being invaded by slugs.

So what can a sustainable farmer do? There doesn’t appear to a single best answer—what works for one grower doesn’t necessarily work for another. That’s why OSU’s College of Agricultural Sciences is seeking an increase in funding from the state legislature to hire extension agents to study and control slugs.

In the meantime, farmers are finding innovative ways to deal with slugs and integrating management practices to minimize the financial damage to their crops. Some of the variety of tools for managing slugs are chemical baits like Sluggo and Deadline, natural enemies like ground beetles and birds, and barriers like copper foil and abrasives like ashes and rock dust. According to the University of California’s Integrated Pest Management Program, “barriers of dry ashes or other abrasives heaped in a band 1 inch high and 3 inches wide around the garden also can be effective.” (Source:

Some farmers are using all-natural Cascade Minerals Remineralizing Soil Booster as part of an integrated approach to land management. The variable grit size of our volcanic rock dust acts as a physical barrier that slugs are loathe to cross. At the same time, essential rock minerals are released back to the soil which further enhances microbial activity. So far, the results have been positive and we look forward to participating in more research because we believe that all-natural volcanic rock dust can be part of an effective, integrative and non-chemical approach to managing these pests and preventing further damage to Oregon’s precious crops.