C.O.R.N. Newsletter 2004-38

Yield Loss Questions On Corn Crazy Top

Authors: Patrick Lipps, Dennis Mills

Growers frequently discover interesting things by observing corn plants while operating the combine at harvest. We have had several questions about odd looking corn plants in several fields. The very wet conditions this past spring caused saturated and flooded soils in many locations in Ohio after much of the corn had been planted and emerged. These wet conditions predisposed corn plants to seedling bights and root rots causing loss of stands. Additionally, these flooded conditions promoted the development of a disease known as crazy top. This disease is caused by a water-mold that is in the soil. Infection occurs when soils have been flooded shortly after planting and before plants are in the four- to five-leaf stage. Infection results in strange looking plants. Frequently affected plants have excessive tillering, rolling and twisting of the upper leaves. Other symptoms include proliferation of the tassel or ears where these resemble a mass of leafy structures. Because of the replacement of the ear and tassel with leaves, these plants generally do not produce grain.

In general, plants affected by crazy top are found around low areas in fields where plants had died from seedling blights due to flooded conditions. Therefore, more plants are usually lost to seedling blights associated with flooded conditions than are affected by crazy top. However, when scouting fields this past summer crazy top was evident in many locations where seedling mortality did not occur. For a picture of a plant with crazy top symptoms and a fact sheet describing the disease in more detail visit the Ohio Field Crop Disease web site at http://www.oardc.ohio-state.edu/ohiofieldcropdisease/corn/crazytop.htm

Corn Stalks Continue To Degrade Causing Increased Lodging And Harvest Problems

Authors: Patrick Lipps, Dennis Mills

Full grain bins, lack of adequate storage facilities and slow movement of this years record yielding crop to grain processors have caused corn farmers to halt harvest leaving corn in the field. Although little can be done to quicken the movement of harvested grain, corn left in the field at this time continues to be vulnerable to losses due to stalk rots that result in lodging and lost ears in the field. Stalk rot diseases have been widespread in Ohio due to the weather conditions favoring infection of stalks and early root rot that occurred during the summer months. As the harvest season started anthracnose and Gibberella stalk rots were detected as primary causes of stalk diseases, but up to about two weeks ago stalk lodging was at a minimum due to drier weather and the lack of wind storms.

In recent weeks, wet weather and high winds have begun to cause plants with stalk rots to lodge. Wet weather has promoted increased fungal growth within stalks resulting in continued degradation of stalk tissues. As the harvest season progresses, corn growers can expect increased stalk lodging and ear loss that will obviously reduce profits. Although the seed corn companies have done an excellent job in breeding corn hybrids with stiff stalks that will stand in the field over a period of time after maturity, the amount of stalk diseases and weather conditions this year are impacting the standability of even the best hybrids. It is just as important now as it was at the beginning of the harvest season to prioritize fields for combining so that fields with the weakest stalks are harvested next.

Sludge and Waste Application on Production Fields

Authors: Robert Mullen

Sludges and wastes generated from municipal, agricultural, and industrial activities can be excellent sources of nutrients for crop production, and land application is an excellent way to recycle these materials. Due to the variability of waste materials and their nutrient contents (primarily depending upon how it was treated), lab analysis of the material is extremely important. Typical lab analysis should reveal nutrient concentrations of nitrogen, potassium, and phosphorus as well as some micros and heavy metals.

Nitrogen

Keep the following rules in mind when determining sludge and waste material rates based on nitrogen need. Nitrogen applied as nitrate is readily plant available, so allocate it appropriately in your N budget. If the sludge (or waste) is surface-applied between November and February, assume that 50% of the N applied as ammonium will be available next spring. If the manure is injected below the soil surface or incorporated immediately after surface application, assume that all of the N will be available next spring. Assume that of the organic N applied 30% will be plant available next spring. Below is an example calculation:

Yield potential – 160 bu/acre
N recommendation (Tri-State Guide) – 190 lb N/acre
Sludge analysis (aerobically digested)
Ammonium-N – 683 ppm
Organic N – 18,500 ppm
Moisture – 35%

To determine the amount of ammonium-N available (assuming the waste is surface applied in November), convert from ppm to lb NH4-N/ton of sludge by multiplying 683 by 0.002. Because the material is surface applied only 50% is assumed to be available next spring thus only 0.7 lb NH4-N/ton of sludge will be available (683 * 0.002 *0.5). Convert the concentration of organic-N from ppm to lb organic-N/ton of sludge using the same 0.002 conversion factor. Assuming that 30% of the organic-N applied will be plant available next year, 11.1 lb N/ton of sludge will be plant available from mineralization of the organic-N fraction (18,500 * 0.002 * 0.3). Combining both plant available pools of N (ammonium-N and mineralized organic-N), a total of 11.8 lb N/ton of sludge will be plant available next growing season. Because 190 lb N/acre is needed, 16.1 dry tons of sludge per acre must be applied (190/11.8). The water contained in the sludge must be accounted for when determining the total amount of material to apply. The rate of material that must be applied to provide 190 lb N/acre is 24.8 ton/acre (16.1/(1-0.35)). Estimated mineralization rates for sludges and waste materials differ, so make sure to identify the material you want to apply. For additional mineralization rate estimates consult Ohio State University Bulletin 879-99 at http://ohioline.osu.edu/b879/.

Phosphorus

Assuming the above material was applied at 24.8 ton/acre, how much P was applied? Lab analysis reveals that the sludge material contained 800 ppm P. Converting the concentration from ppm to lb P/ton of sludge is done using the same conversion factor as before, thus there 1.6 lb P/ton of sludge (800 * 0.002). Fertilizer P is typically presented as P2O5, so the P concentration should be converted. Thus the sludge contains 3.7 lb P2O5/ton (1.6/0.436). If 24.8 tons of sludge is applied per acre, 91.8 lb P2O5 is applied per acre (24.8 * 3.7). Depending upon soil test levels this rate may exceed the agronomic rate, so make certain to account for P when making sludge applications.

Lime

Some sludges or waste materials are lime stabilized and actually have some neutralizing power. Care should be taken when applying these materials. Annual applications of such materials can increase soil pH levels well above 7, so make sure to account for the neutralizing ability of the materials that are applied as well as monitoring soil pH levels determined by soil test.

Heavy Metals

Depending upon the source of the sludge or waste material and how it was treated, heavy metal levels may be of concern for land application. Current EPA levels restrict the amount of heavy metals that can be applied to production land. Laboratory analysis should reveal the metal content of the sludge/waste material which can be used for determining application restrictions. For additional information on EPA restrictions regarding sludge materials and heavy metals consult Ohio State University Bulletin 879-99.

Diplodia Damaged Corn Grain: Assessing Feed Value

Authors: Bill Weiss, Peter Thomison, Patrick Lipps

Reports of corn damaged by Diplodia ear rot are widespread this year in Ohio. Relatively cool and wet weather conditions during the later whorl through silking growth stages were favorable for Diplodia infection. The symptoms and impact of Diplodia ear rot have been described in a recent newsletter article http://corn.osu.edu/story.php?setissueID=56&storyID=295. Diplodia ear rot is recognized as a thick mat of gray mold generally covering the lower part or the entire ear. Infected kernels are usually dark brown and moldy in shelled corn samples. Diplodia ear rot causes damage by causing lightweight kernels that reduce yield and by reducing the nutritional value of affected grain. Unlike fungi that cause Gibberella ear rot and Fusarium kernel rot, the Diplodia fungus does not appear to produce mycotoxins in the grain under field conditions usually occurring in Ohio. Additional, information on Diplodia diseases of corn can be obtained on the Ohio Field Crop Disease web site at http://www.oardc.ohio-state.edu/ohiofieldcropdisease/corn/diplodia.htm.

The high incidence of moldy grain caused by Diplodia has resulted in dockage at some elevators. Large discounts on Diplodia affected grain, as high as 50 cents per bushel, have led to questions about using moldy grain on farm as animal feed. While there is considerable information available on managing moldy corn containing mycotoxins, less is know about using varying levels of moldy, mycotoxin-free corn grain in animal feed.
Grain contaminated with mycotoxins is of less value, or of no value, than grain with a mold that just reduces nutritional value of the grain. Although it appears that Diplodia is the fungus primarily responsible for many of the moldy corn problems in Ohio this year, moldy corn should be evaluated for mycotoxins before it is used as animal feed. Relying on a visual assessment to determine the fungus causing moldy grain is not sufficient, and could be dangerous. A directory of labs that provide analysis of grain for mycotoxins is available online at http://www.oardc.ohio-state.edu/ohiofieldcropdisease/Mycotoxins/mycopagedefault.htm

A past evaluation suggests that moldy corn (not defined but with greater than 1,000,000 cfu/g) had about 10% less nutrient value compared with clean corn (<10,000 cfu/g). This is based on crude protein, amino acids, starch, fat, and estimated energy. In an unpublished study from Wisconsin, cows fed moldy (no detectable mycotoxin) high moisture corn (1 to 5 million cfu/g) produced about 8% less milk than cows fed clean corn (<10,000 cfu/g). In that experiment corn made up about 25% of the diet.

Although the mold level in grain in this study was characterized by colony forming units per gram of grain (cfu/g) this is not a precise measure of the quality of grain or of the amount of fungus in the grain. Evaluating grain using cfu/g is only an indication of the number of viable fungal spores in a gram of grain and this value can vary greatly depending on the fungal species present. Moldy grain should be subjected to chemical tests for the presence of specific mycotoxins (e. g. deoxynivalenol, zearalenone, T-2 toxin) to determine their presence and level before using moldy grain for feed. The reason for this is that several different fungi are capable of causing moldy grain and they frequently occur in the same field. Also, distinguishing among the different ear and kernel rots is not easy. In addition to a mycotoxin test, appropriate analysis of the nutritional value of the grain should also be conducted. The proper mycotoxin analysis and nutritional value will provide the livestock producer with the appropriate information needed to utilize the grain as a feed.

The bottom line, if the moldy corn will be fed to beef cows or to other animals at less than 25% of diet, the economic loss in reduced performance would probably be less than the 50 cent/bu (25%) discount. If fed to finishing animals in which 60 to 80% of the diet will be the moldy corn, loss in animal performance will probably equal or exceed the 50 cent discount.

Soybean Cyst Nematode – Sampling, HG Type Testing And Plans For Next Year

Authors: Anne Dorrance

Soybean cyst nematode continues to take yield from Ohio soybean crop and now is a good time to take assessment of your fields. Fields where the drainage was good, but the yield monitors had low readings or the “chatter” from the beans took a dip are the places to sample for soybean cyst nematode. This nematode has a tendency to sit in pockets. If you were walking your fields, these were the areas where the bean height drops from knee high to mid-calf high or waist high to knee high depending on your field. These areas are getting bigger. I walked some fields and what used to be a car size circle has now expanded to a football size area. Because cysts do sit in pockets, it is possible to miss them when collecting soil samples. For every 10 to 20 acre field, collect soil cores as you would for fertility samples. Many folks use the zig-zag pattern. When sampling, aim your soil probe for the root zone. If you probe between rows, you will have a lower likelihood of hitting a cyst pocket. If you have GIS information and can go back to the spot where the yields took a hit – this would also be good. Take all of the soil cores and mix them thoroughly – and then send a good healthy quart of soil to the SCN testing lab.

Do you need to determine which HG type (Heterodera glycines), formerly called race type, of SCN populations are in your field. My answer is the same as it is for Phytophthora sojae, NO. For SCN we have one primary source of resistance that is currently in commercial varieties, PI88788. There are a few varieties with Hartwig or Peking sources of resistance. The management of these sources of resistance and SCN in general is to rotate. Rotate your crops, so when planting SCN resistant beans, the SCN populations are low (<2,000 eggs or 4-5 cysts per cup of soil) and follow this by rotating sources or resistance. SCN is also notorious in that it can also adapt to these sources of resistance. So we need to rotate sources of resistance by rotating soybean varieties. What is bad, is that this is all the resistance we have available and many of you know of the yield drag associated with the early releases. With Phytophthora, there are a few more tools in the tool box such as partial resistance and fungicide seed treatments.

USDA Confirms Soybean Rust in United States

CORN Newsletter Specialist will keep you updated on developments related to this find and needs for the 2005 production year throughout the upcoming winter.

WASHINGTON, Nov. 10, 2004 ­ The U.S. Department of Agriculture’s Animal and Plant Health Inspection Service today confirmed the presence of soybean rust on soybean leaf samples taken from two plots associated with a Louisiana State University research farm Saturday.

While this is the first instance of soybean rust to be found in the United States, the detection comes at a time when most soybeans have been harvested across the country. As a result of the harvest, the impact of the fungus should be minimal this year. Soybean rust is caused by either of two fungal species, Phakopsora pachyrhizi, also known as the Asian species, and Phakopsora meibomiae, the New World species. The Asian species, the one found in Louisiana, is the more aggressive of the two species, causing more damage to soybean plants.

USDA will dispatch its soybean rust detection assessment team, composed of scientific experts and regulatory officials, to the site within 24 hours. The assessment team will work closely with Louisiana State Department of Agriculture representatives to assess the situation and conduct surveillance around the detection site to determine the extent of the disease spread.

Soybean rust is spread primarily by wind-borne spores capable of being transported over long distances. At this point in time, based on predictive models, APHIS believes that the detection in the U.S. is related to this year’s very active hurricane season. While the harvest for this year is complete, during next year’s planting season, producers will need to watch for symptoms of the fungus such as small lesions on the lower leaves of the infected plant that increase in size and change from gray to tan or reddish brown on the undersides of the leaves. USDA and the soybean industry have been cooperating on awareness efforts and will amplify those efforts now that the disease has been found in this country. Lesions are most common on leaves but may occur on petioles, stems, and pods. Soybean rust produces two types of lesions, tan and reddish brown. Tan lesions, when mature, consist of small pustules surrounded by slightly discolored necrotic area with masses of tan spores on the lower leaf surface. Reddish brown lesions have a larger reddish brown necrotic area, with a limited number of pustules and few visible spores on the lower leaf surface. Once pod set begins on soybean, infection can spread rapidly to the middle and upper leaves of the plant.

Soybean rust can be managed with the judicious use of fungicides. However, early detection is required for the most effective management of soybean rust. Monitoring soybean fields and adjacent areas is recommended throughout the growing season.