Crop consultant Bob Streit describes the 2015 battle with Goss' wilt

In mid-August, consultant Bob Streit sent his clients an analysis of this year's invasion of Goss' wilt and ways to cope with it. 

Today, Bob gave us permission to publish this analysis for everyone. "The word needs to get out, so we can deal with this in coming seasons," he said. Here's the information he gave his clients in early August. His predictions of rapid disease progression in late August and into early September have proven very accurate.

By Bob Streit, as of August 18, 2015

The threat to corn production by Goss' wilt in the Midwest became widely recognized in 2010, as the disease spread over the entire Corn Belt. It morphed from being a minor disease in a small area ranging from Grand Island, NE to Ft Collins, CO to a major disease that moved east into Pennsylvania and north to Manitoba. Dust-trap catches proved it went aerial via storms and harvest dust. It was typically more of a problem in second year corn, but now all corn acres are at risk. Rotation as preached in the past no longer offers protection.    

Growers and crop advisors went through the 2010 thru 2015 seasons knowing the bacteria can survive up to ten months in non-decomposed residue, meaning second-year corn was going to be at risk. Each hybrid’s genetic background would lend tolerance or susceptibility to its level of resistance. Hybrids containing an old ISU inbred developed by Bill Russell are most susceptible.

The seed companies with the best levels of resistance and possessing proprietary germplasm resistant to Goss’ wilt were Syngenta, Pioneer, the Ag-Reliant Group, Mycogen and Dairyland. Check with your seed supplier on the individual ratings. The most susceptible hybrids have been dropped since 2010.

Based on many past years of study, plus very recent research by plant pathologists, including Don Huber, and now veterinarian pathologists, we know that Goss’ wilt is caused by pair of organisms.

The first is a bacteria known as Clavibacter Michigansis subs. Nebraskensis. The second organism is best described as a biomatrix. This entity is so tiny it can only be seen with a scanning electron microscope at magnifications of 12,000 up to 200,000.

The Clavibacter bacteria prefers a moist environment in which to invade. It no longer requires damage to the plant by hail, blowing dirt or other agent as a means of gaining entry. The application of glyphosate and its accompanying surfactants such as POEA are now proven provokers of Goss' infection.

Allowing nutrient deficiencies to occur, such as lack of Cu, Mn, Zn, and Co, allow the plants to remain highly susceptible. Genetic background is also important. Any relationship to B14, an old inbred selection from the Iowa State stiff stalk program, adds a great degree of susceptibility. Included in this category is a University of Minnesota inbred, A632, which was in P3780 and thus many current popular 94 to 102 day relative maturity hybrids.

As of early August in Iowa we had a low level of Goss’ in nearly every field. It has survived in the soil and seemed to be moving into weakened and nutrient starved corn plants.

Recent experiments have demonstrated that the insertion of genetically engineered traits lower the ability of the plants to pull in nutrients. Thus, insertion of stacked traits creates higher levels of nutrient deficiencies.

The visible disease symptoms for the ‘new Goss’ are centered on the V3 or V4 leaf sheaths where the sheath was sloughing off the stalk. Dew and rain funneling down the stalk is captured by the leaf sheaths. Combined with the high temps this summer, it created a perfect incubation chamber for bacterial growth. A few weeks later we will see fields and varieties where the top leaves are wilting and turning brown.

The bacteria produce enzymes that break down stalk tissue, allowing the bacteria to invade the plant's plumbing tissue. As the bacterial populations increase, they plug the plumbing system beginning at the nodal sieve plate. Splitting the stalk can expose blackened tissue.

How quickly the bacteria move up the stalk and begin to create problems is open to debate. With the very wet conditions seen across the Corn Belt clear into Pennsylvania and the high percent of plants that showed definite leaf streaking this could be a year with serious disease problems.

The symptoms typically get bad about three weeks after first detection, or August 10, but this year all bets are off. As to how much damage the disease can do, growers and crop advisors from North Platte, NE have related how yield loss from very susceptible hybrids can be from 50 Bu/A to 100% loss. The greatest loss will be with very susceptible hybrids infected early that begin to wilt during the early stages of kernel development. We think that susceptible genetic hybrids grown on micro-nutrient deficient soils and sprayed with glyphosate will be the most susceptible.

AgDia test strip showing positive for Goss' wilt

One good aid for growers to use is an in-field strip test that allows a crop scout to test plant tissue for the presence of the bacteria. It is called the AgDia CMM kit. It requires the operator to cut out a silver dollar size piece of infected tissue, mash it in the mesh bag, and then insert the detection strip into the wet tissue mix. A positive test causes two pink lines to form. Several soil bacteria can contain sugars that can produce a false positive, so be sure to wash the leaf tissue before macerating it.    

Contrary to published reports, there are products that boost plant health enough to minimize vascular plugging and yield losses. There are products that have done a good job on CMM bacteria in other crops. When those products were tested on corn in the Midwest in 2010, they gave good response — up to +80 Bu/A.

Be aware that the product mix, as well as water pH and surfactants used, are important. Lower the water pH into the 5.5 range. Add 2-3 oz. per acre of WakeUP. Add a micronutrient mix plus 1-2 oz. per acre of Procidic, and possibly ammonia-based foliar nitrogen.

Be sure to check your fields now. [Note: This advice was first sent in mid-August] What we identify as this ‘new’ Goss' disease is not recognized by most agronomists and agents. It is different, and high magnification of the prion-like matrix entity proves this. If you see a caramel colored stalk lesion, run the AgDia strip test. The crop report released on June 30 verified that the Midwest corn crop has excess moisture problems and the diseases that result. Stay on top of each.

The top products in use as of 2015 to cope with Goss' wilt are: 42PHI from a company near Winnipeg, Manitoba which was formulated by Jarrett Chambers. The formula was copper based. Procidic was EPA registered by Steve Knauss and Bill Darrington and can be effective. It is OMRI approved and is widely used in the horticulture and ornamental fields.

The first testing in the field of a product called Bio-Impruv was performed in late August of 2014 in central Iowa. It is being field tested again in 2015 in replicated trials and thus far looks tremendous with a 2.5 to 3 month residual.

An improved version of Bio-Impruv was developed to offer better control of many fungal diseases. Its mode of action was to supply nutrition to help the plant's immune system to fight several diseases. It was developed by a noted biochemist with a strong background, in this instance focusing on immunological response to CMM, CMN and CMS using bacterial extracts.

Any Goss’ management program needs to include soil and tissue tests to track soil and plant nutritional status. The mineral profile must include sufficient levels of Zn, Mn, Cu and Bo to mount an adequate immune response to ward off fungal and bacterial infection. Traited hybrids are more susceptible.

The cause of this as researched by Zobiole and Johnson is that insertion of certain traits lowers the levels of key micronutrients needed to fuel the disease resistance of the variety. Work by Clapperton and Taheri also suggests that frequent manipulation using Agrobacterium tumifaceans of the corn genome reduces or eliminates the ability of the plants to communicate with the comensual microbes in the rhizosphere.

This interruption of the ‘cross talk’ between plant cells and microbes causes a cessation in the uptake of those vital immune-response dependent nutrients. Foliar application of chelating pesticides can also lead to shortages of those same elements in the plants. Soil residues of the same chelating and microbiocidal pesticides can kill off microbial populations that make those same minerals plant-available.  

 

Keep in mind that the analysis above was shared with Streit's consulting clients around August 18.  In the month following, symptoms of Goss' — and several other diseases including Northern Corn Leaf Blight erupted the first two weeks of September. Agronomists are still scrambling to explain the abrupt die-down of corn across wide regions of the Corn Belt. 

On Sept. 22, AgWeb posted a feature, "What's Knocking Down Your Yields" by Sonja Begemann, which confirms Bob Streit's expectations he expressed a month earlier.  Ironically, the AgWeb sources do not list Goss' wilt among the stalk rot diseases blamed for collapsing stalks. If you visit AgWeb and read that article, also look at the first comment below it, from Mark Daggy of Humboldt, Iowa. Mark points out that he has worked with consultant Michael McNeill for several years, healing the nutritional deficiencies which Bob Streit has described above. Now, his stalk strength is not a problem — and that's because he healed the nutrition, not because he sprayed for diseases. We'll lift a relevant section from Mark's comment:  "Testing the soils for availability for micro-nutrients was also done with the guidance of Michael McNeill, who is experienced in this area. Adding 1 or 2 micro-nutrients per year, first dosing the depleted areas and now spreading a uniform amount on all acres for maintenance, our lodging disappeared. Too many tenant farmers have been mining the soils and are now suffering the consequence of spending their profits on machinery and toys when they should have invested in the soils."

By mid-September, some corn fields in southeast Iowa were so fragile, and the pith so blackened from Goss' wilt, that Keith Schlapkohl of Stockton, IA told us: "Any serious wind would flatten the entire field." 

Here in northeast Iowa, along both sides of Highway 20 from Fort Dodge to Dubuque, corn is standing well and transitioned somewhat more gradually into die-down, compared with fields south of Interstate 80.

Even though it's almost certainly too late to take remedial action in the field now, ordering an AgDia test kit and making a definite diagnosis would offer useful data for future seasons.

In August 2014, our test farm did several 310-foot long test strips with an early formulation of the Bio-Impruv "remedy." This refers to the 2014 trials which Streit mentioned above. It was applied very late, August 26, 2014, and we had only 14 test strips available. Goss' symptoms were already evident, although stalk pith was still intact.

In three paired trials (6 strips), use of the Bio-Impruv resulted in a 10-bu. yield benefit. In another four paired trials (eight strips), WakeUP Summer was included with the foliar application of Bio-Impruv, and the yield benefit climbed to 17 bushels. This type of enhancement is often seen with foliar products — simply because WakeUP carries more of the effective ingredients into the crop, and through the crop's phloem circulation system.  

This season, we have 20 test plots of corn using the upgraded version of Bio-Impruv coming up for harvest soon. This time, the product was sprayed July 18 — somewhat earlier than last year. It very likely needs to be applied much earlier in the season for best results. Streit has lined up several on-farm trials this summer, plus work at ACRES research farm here near Cedar Falls, IA, to check out this means of dealing with this "binary" bacterial disease.

Published Sept. 20, 2015

Updated Sept. 22, 2015