Published November 29, 2006 | By Michael Petersen, Precision Tillage Agronomist, Orthman Mfg., Inc.
We hear from Texas to South Dakota and California to Ohio that more residues on the surface are the main causal agent to disease pressures. And to remedy that growers bring out the disk or even (gasp!) the moldboard plow to bury that stuff and that will fix the problem. Please be cautious and become more informed everyone!
Causes known to the spread of these diseases:
Stalk rot, Fusarium moniliforme a very common pathogen in corn has plagued many, many fields this year. Along with this disease are some of the leaf diseases that weaken the plant, corn borer wounds, hail damage – all contributing to impairment of the leaf tissues to manufacture photosynthates to finish the grain.
Stalk-rot is a stress related problem. Pathologists have determined when drought stress, leaf losses from insect pressures, hail, low sunlight days all contribute to lowered carbohydrate output the plant will rob from cells in the stalk. This weakens the stalk and the plant fighting-off abilities of fungi or bacteria infections.
Environmental conditions have an important impact in how diseases affect plants. Diplodia and Fusarium stalk rots are favored by dry conditions early in the season. Then along comes warm more moist to hot conditions at pollination and right afterwards, a double whammy! If nitrogen has been leached or in low quantities the plant can really feel the infection. Nearby grass hosts carry the pathogens; johnsongrass, crabgrasses, and escaped cereal rye. The spores do survive on residues and spread from wind onto the growing leaves or splash from debris to leaves.
Nearly all of the Universities crop and pathological departments are releasing sound information (see a short listing at end of this release to read more about the diseases) to help you growers manage and defend against heavy crop losses due to disease issues. They are offering great suggestions to incorporate into your farm management program.
How may you mitigate the risks in higher residue farming?
Knowledge that ethanol production asks for more corn on corn production and the leaving of more residues for growers to consider seems to some fraught with concern. Corn prices are better than we have seen in many years and that drives the corn to be planted in 2007. Wise conservation rotations can and should be part of the solution to disease control.
Here at Orthman Manufacturing, Inc we believe several options are available to the grower for dealing with disease pressures, including Gray Leaf Spot, numerous species of stalk rots, Anthracnose leaf blight, and Goss s Wilt. Some of those options include: 1) purchasing disease resistant varieties (your seed company representatives are helpful in those choices), 2) wise nitrogen use to help stimulate residue breakdown early in the crops lifecycle, 3) wise use of fungicides can have some positive results, consult your agronomists to their effectiveness, 4) rotation from corn to a broadleaf crop to help break the cycle, 5) be cautious how much residue is brought up close to the tilled area where you intend to plant corn (wise use of residue managers with strip-till tools) can be a help too, and 6) sound pre-plant starter fertilization programs will offer gains in getting ahead of stress. Farming with row direction that can facilitate longer duration of sunlight harvest and steady growth potential, has demonstrated some help in reducing diseases gaining the upper hand.
Farming with more previous years crop residues give us all challenges and many benefits. As soils become healthier, releasing more organic sources of N-P-K, hosting more friendly microbes in the surface soil layers, more earthworms, cooler soil and micro-climate conditions between rows, and slowing desiccating winds from crop damage – farmers can deal with these pressures. Choosing to hitch up the moldboard plow and bury that confounded trash is not the answer folks. The plow creates so many more problems with diminished soil condition, overall soil health, loss of carbon sources, wind and water erosion issues, loss of phosphates, breakdown of soil pores, smothering of microbes, and so on. Just to bury residue and hopefully rid oneself of the diseases?
To gain more insight we urge you to be well informed. Any of the following resources may be of great value as you consider your options in 2007.
From Purdue University:
http://www.entm.purdue.edu/entomology/ext/targets/p&c/P&C2004/P&C26_2004.pdf
http://www.kingcorn.org/news/articles.03/Notill-SeedSoil-0429.html
From University of Kentucky:
http://www.uky.edu/Ag/kpn/kpn_05/pn051121.htm#corsel
http://www.uky.edu/Agriculture/kpn/kpn_04/pn041025.htm#cornor
http:// www.uky.edu/Agriculture/kpn/kpn_04/pn041011.htmcornor
From University of Nebraska:
http://nu_distance.unl.edu/homer/disease/agron/corn/CoAnthrac.html
http://nu_distance.unl.edu/homer/disease/agron/corn/CoGlsp.html
http://pdc.unl.edu/corn/fusariumStalkRot/index.html
http://nu-distance.unl.edu/homer/disease/agron/corn/CoFusRot.html
From Ohio State University:
http://ohioline.osu.edu/ac-fact/0022.html
From Kansas State University:
http://www.oznet.ksu.edu/library/plant2/L741.pdf
http://www.oznet.ksu.edu/library/crpsl2/s125.pdf