Renewable Farming

You can help this team protect your health against toxins in harvest dust

Wet spring. Dry summer and fall. Western wildfire smoke. Thousands of acres of wind-flattened, stalk-rotted corn. Now, swarms of big chopper-equipped combines are spewing fine particles into a dry atmosphere. It’s the perfect recipe for respiratory stress. On top of the Covid-19 menace.

Oct. 11, 2020 By Jerry Carlson  — Last Friday Dr. Lyn Patrick, co-chair of the Environmental Health Symposium, e-mailed a colleague, Iowa crop consultant Bob Streit, about the threat of atmospheric contaminants drifting eastward from West Coast wildfires. Lyn asked Bob for knowledgeable sources who might help people deal with this.

Bob’s response was to add another air contamination concern: toxic fungus and bacteria carried high into the atmosphere by the cumulative “dust storm” of Midwest corn and soybean harvest. In a reply to Lyn Patrick, Bob noted: “A few years ago, 80% of the farmers around Greensburg, KS visited their physician with severe lung infections. A few died. The same types of symptoms showed up in Iowa and Illinois.”

Bob added in his message to Lyn:

“Besides the wildfire smoke, there’s harvest dust in Corn Belt air. In the evening when the sun is down, just point a strong flashlight upward. A friend had samples of harvest-time air analyzed by a lab for bacterial counts. Lots of Bacillus showed up. Let me check with several very observant medical and ag people, and propose a Zoom meeting with you. We already know the health problem has intensified with GMO crops and their contents. There is also an issue with engineered mycoplasms, which affect a high percentage of people.”

More than a decade ago, the USDA/Ag Research Service found that continued use of glyphosate weedkiller shifts the microbial balance in soils and crop residue toward domination by fungal species, many of them pathogenic. In recent years, a shift to no-till corn has multiplied the load of undigested stalk residue, which is a harbor for fungus and bacteria.

Last week, I visited by phone with Iowa farmer/consultant Terry Kucera, who emphasized that a major reason for accelerating stalk residue digestion biologically is to reduce the carryover potential for stalk rot and bacterial diseases. Cover crops help buffer this problem: Each added cover crop species stimulates about 10 beneficial species of soil organisms, which compete against dominance of mycotoxin-producing fungus. 

Conventional advice on cornstalk stubble is to leave stalks standing to collect snow. However, much of the moisture in snow cover is lost to runoff while soil is frozen. Also, delaying stalk breakdown into the early growing season devours nitrogen needed for corn, as microbes eat first. If stalks are at least partially digested by bean planting time, no-till planters can clip through the easily shattered stalks for uniform seed depth. Wallace’s Farmer’s October 2020 issue recommends against shredding stalks and makes no mention of accelerating residue recapture. Renewable Farming can provide you effective inoculants for stalk digestion, including Biodyne’s Meltdown.  Call or email us for more information; contacts are at this link.

Our website posted reports on the health impact of harvest dust in 2015 and 2018. Although air-conditioned combine and tractor cabs make harvest dust more survivable, fine particles remain suspended in the air for several days unless rain washes the atmosphere.

We’ll follow up with any helpful ideas which Bob, Lyn and their colleagues come up with.  

If you’re interested in sharing ideas or evidence on this health issue, e-mail Bob Streit at or Dr. Lyn Patrick at 

Harvest haze in Grundy County, Iowa from combines in soybean and corn Oct. 10, 2020