The rivers of rain which lashed much of the upper Midwest in September and early October spawned an array of stalk rot fungi and bacteria which are now threatening substantial corn yield losses. Here’s a tool you can use this fall — soon as possible — to keep corn alive longer in future years. The final 40 bu. or more is built in during late August until the first frost.
October 12, 2018 — Here’s the management approach we consider very important for preventing stalk rot: Improve your soil health with a wide diversity of beneficial fungi and bacteria.
Healthy soils with a wide array of beneficial organisms speed digestion of heavy stalk residue. That deprives pathogens of overwintering habitat, and stimulates a wider range of crop-friendly, competitive microbes. The term, “disease suppressive soils” is migrating from scientific papers into more common management use. It arose from the work of professionals such as Dr. Bob Kremer, ARS/USDA pathologist at the University of Missouri, and a few crop consultants who emphasize biologically healthy soils. In the war against crop disease, it’s a numbers battle of good guys vs. bad.
That’s the point of this report. Today we can announce a new weapon you can use to help win that struggle. It’s branded Meltdown, from Biodyne USA. It is an enhanced version of Biodyne’s proven Environoc 501 for fall application on stalk residues. Meltdown contains Environoc 501, plus the optimum ratios of nutrients and humic acids to accelerate early proliferation of the sprayed-on organisms. Meltdown also contains a “sticker” to keep it on stalk surfaces longer.
Almost every provider of residue digestion bacteria/fungi advises adding nutrients and carbon sources to the tank mix for the purpose of speeding rapid multiplication of sprayed-on organisms. However — in practice — farmers’ usage of liquid nitrogen, humates, molasses, K-sulfate and other jump-start mixes varies widely. That variation leads to inconsistent results in the field, just as post-harvest rain and temperatures do. Adding a consistent nurturing mix into the standard product reduces one variable. The recommended rate of Meltdown is one quart per acre. The recommended rate of Environoc 401 is a pint per acre. When Meltdown is sprayed at a quart per acre, that delivers 1.5 pints of Environoc 501, plus a pint of “fuel” to help rapidly reproduce the organisms in the first few days while they get established.
Bob Wagner, Midwest agronomist for Biodyne USA, estimates that 85% of Iowa cornfields in a wide strip north of Highway 3, an east-west highway, show signs of serious stalk rot. However, he says: “Less than 10% of cornfields treated with Environoc stalk digesters for the past two to three years show damage from stalk rot.”
In late August — when most Iowa corn was going into what we call premature die-down — Bob Wagner visited several of his clients’ fields and selected sample ears of corn. He weighed them on an accurate gram scale, and calculated averages. Average weight of his first-collected ears in August: 7.76 ounces. Almost a half-pound. Not bad in an average population of 34,000. Two weeks later, Bob visited the same fields — all treated in previous seasons with Environoc 501 — and found the average had risen to 9.52 ounces. And two weeks after that, the third and final sampling showed an average ear weight of 11.28 ounces. The final grain-filling period of fall, through early October, had added about 45% more weight to the average ear. That was only possible because the stalk and most of the leaves remained green and able to pump more nutrients into the finishing ear. The final healthy three weeks can add 40 bu. to your corn crop!
Consulting agronomist Larry Eekhoff of Agronomy Rx (one of our Renewable Farming clients) tested Meltdown earlier this fall, spraying it on part of an early-harvested field. Larry took the photos below only three weeks after spraying the left part of the field, to the left of the yellow marking line we inserted. The application was made Sept. 17 and the pictures were taken Oct. 10.
Below, please see two closeup photos; first the MELTDOWN-sprayed area and second in the unsprayed field. Between spraying and these photos, there was only three weeks of above-freezing, typically rainy weather.
Note the pith of a stalk which has already blackened, and a cob which has already been colonized. The soil and leaves are coated with beneficial fungi.
Below is an unsprayed area of the field. Because weather in the preceding weeks was damp, leaves are showing mold. But tougher parts of the stalk and cobs with more lignin haven’t started breaking down yet.
Even though it can take several seasons and a variety of management tools to build a really effective disease-suppressive soil, a residue breakdown product can help all the way. MELTDOWN — which we have available in totes and jugs for about $10 per acre — greatly helps demolish stalks which enable this year’s pathogens to overwinter and multiply next season. A long-term program of cover crops offers benefits of introducing a wide array of beneficial microbe species which become pathogen fighters.
Here’s yet another field showing the closer part sprayed with Meltdown a week before the photo was taken; the farther part was untreated.
Good bugs in your soil battle nasty pathogens such as these:
Colletotrichum graminicola, a fungus which causes anthracnose stalk rot.
Stenocarpella maydis, the fungus which triggers diploid stalk rot. This is a likely culprit in Iowa fields now, as it’s favored by dry weather before silking and then wet weather into September and October.
Fusarium verticilliodes, which underlies fusarium stalk rot. This is another suspect. Fields with a history of glyphosate are likely to have a microbial balance that’s heavily on the fungal pathogen side. What we call a “healthy” soil has more of a balance between bacteria and fungi.
Purdue extension agronomy offers a comprehensive description in this PDF which explains the fungal and bacterial origins of stalk rots, with photos helping you identify which critter you’re fighting. Note that none of the recommendations in this brochure recommend developing a “disease suppressive soil.”