By Bob Streit CPCS, CCA Boone, IA Published April 25, 2016
As the 2016 corn planting and growing season arrive, more growers are remembering the early death of their corn crop last fall and in previous seasons. They recognize they have seen it, they know their yields did not meet expectations, and they often saw some of the worst stalk lodging ever last fall.
None of their typical sources of information — local fertilizer and Ag input suppliers, the seed company agronomists or Extension service reps — have provided any definitive answers on why it has occurred earlier each season, or offered curative steps to minimize its impact.
Farmers recognize it is having an important effect on their crops and on their income and they need to know what it is and what should be done about it.
The old ‘Goss’s Wilt’ first appeared in the late 1960s in western Nebraska. It was confined to eight counties in Nebraska, plus two in eastern Colorado until 2009. Then it moved east to Pennsylvania and north to Manitoba. It previously was a slow-moving bacterial disease that typically appeared after a windstorm or hailstorm that caused damaging entry points into corn leaves and stalks. Since 2009 it has greatly increased the percentage of fields it affects across the Midwest, and intensified its negative yield impact.
Something changed its biology. That is part of the story. The typical symptomology was an orange or red flashing of the upper leaves followed by the appearance of watery, freckled lesions on the leaves followed by the leaves drying down prematurely. It used to be problematic in second year corn where the inoculums could overwinter easily on corn residue. What an investigative team found over 16 years was that a metallic crystal or biomatix was present. Their theory was that this biomatrix could form because the corn had a low mineral and nutrient environment caused partly by reliance on an N-P-K only fertility programs and too much emphasis on chelating, biocidal herbicides.
The ‘New Goss’s Wilt’ — complexed with this biomatrix — has been a rising problem since 2009. It can show the same foliar symptoms, but more often appears as caramel colored lesions that appear at ground level at V8 to V10 when the lower V3 – V4 leaf sheaths begin to slough off the stalk. Those leaves or stalks will show a brown mottling ranging from faint to very pronounced in color and appearance. Later in the summer large brown or blackish fingerprint-like lesions will appear on the stalks.
Rookies scouting for the lesions should buy $5 strip test kits from Ag Diagnostics of Elkhart, IND to help them make the diagnoses at first. In time they will not need the strip kits. Regardless of whether the season is wet or dry, there is enough overnight dew to help the bacteria multiply and begin to cause problems.
As the plants grow and bacteria inside the stalk multiply, stalks will become progressively plugged at the nodes. Splitting the stalk lets you detect a brown or black layer at the lower nodes and browning in the crown region of the roots. This plugging by the bacteria and the biomatrix continues during summer. Then, when a hot, dry and windy three to seven day period in mid to late August creates a large water and mineral demand in the upper plant, the xylem tubes from roots up into the stalk can’t meet moisture demand by the leaves, and entire fields die in two to three days. The plants turn almost white. Sometimes this starts at the top leaves, sometimes at the lower leaves. Late-season nitrogen shortages accentuate this as there can be cannibalization of the upper leaves. The second ears turn mushy and very stinky.
A group of growers and plant researchers have been finding that if appearance and tissue samples early in the season verify mineral deficiencies, then applying the correct foliar micronutrients helps corn survival. Other growers find benefits in building a healthy root with combinations of in-furrow nutrients and biologicals at planting. The biologicals applied in-furrow increase mineral uptake are very important.
Early curative and preventative products like Procidic and 42PHI have worked, but with limitations. Foliar-applied ammonia based N fertilizers also help stall or kill the bacteria.
The best product we have found to constrain Goss’s wilt is a nutritional based product called BioEmpruv. It is made in a Utah fermentation lab. We are recommending it be applied in stages: first at planting or thru V4-6, then again at V14 to VT. It lasts nearly three months within corn metabolism. Consider canopy coverage and how growth dilutes it.
In 2015 field tests, treated corn stayed green and continued to fill for another 3 to 4 weeks with greatly improved standability compared with neighboring untreated fields. Those three weeks represent 35% to 46% of the normal 55 to 60 days of grain fill. It is a safe product and can be tank mixed with other products. Too often corn growers have battled Goss’s solely with fungicides, which has not worked because Goss’s is a bacteria.