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Volume 9, Number 6 - June 2003

This Month in Ag Connection

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Seedling Diseases of Soybeans

Several diseases can affect the emergence and establishment of soybeans. These diseases cause seed decay, seedling blights and root rots of soybeans. Most of these early-season diseases are caused by fungi in the soil. Pythium, Phytophthora, Rhizoctonia and Fusarium are the most common of these early-season pathogens.

Pythium diseases are generally associated with wet soil conditions. Symptoms include seed decay before germination and seedlings being killed before emergence. Areas of brown discoloration and soft, watery rot develop on infected hypocotyls, and cotyledons. Infected seedlings wilt, collapse and shrivel up. Diseased plants are easily pulled from the soil as few roots have developed and the hypocotyls are shriveled and deteriorated.

Phytophthora sojae is another soil-inhabiting fungus that causes seed decay, preemergence or postemergence damping-off and seedling blight of soybeans. Phytophthora can rot soybean seed before germination and it can also kill young seedlings either before or after they emerge. Dark, reddish brown to black, water-soaked lesions are evident on the hypocotyls. Cotyledons and hypocotyls turn brown to black and have a wet, rotted appearance. Another symptom of phytophthora is the seedling blight phase of the disease in which young seedlings that appear to be established turn off-color yellow, wilt and die. The stems of these plants may show a brown discoloration that begins at the soil line and extends up the stem. Phytophthora root rot is more severe in areas that are low or poorly drained, in compacted areas or in clay and heavy soils.

Rhizoctonia solani is another common soil inhabiting fungus with a wide range of hosts. Rhizoctonia can cause seed decay and preemergence damping-off. The infected seed or seedling root is discolored and decayed. The discoloration is usually a red to reddish-brown color and the decay may be a dry type of rot. More typically, symptoms are found on seedlings, young plants and even older plants. Localized red to reddish brown lesions develop on the hypocotyls near the soil line. The red color is a good symptom, but it is best observed immediately after plants are removed from the soil because the color fades as plants are exposed to air. Crusting, hard pan layers, herbicide injury, deep planting, poor seed quality, hail damage, insect damage, mechanical injuries, poor fertility or other factors that delay germination and emergence favor the development of Rhizoctonia root rot.

Fusarium seedling blight can be caused by Fusarium oxysporium or Fusarium solani. In fields with Fusarium seedling blight, stands may be uneven. The pathogens cause a rot of lateral roots, taproot and lower stem. Lesions developing on the taproot range from an nondescript brown to a dark purple brown or black. These lesions may increase in size until they girdle the taproot. The lower part of the taproot and the lateral root system may be rotted or destroyed. A proliferation of secondary roots may develop above the damaged main taproot giving the plants a shallow, fibrous root system. The above ground portions of infected plants may have an off-color to yellow cast. Foliage may dry and plants wilt and die during periods of drying winds or warm to hot weather. Fusarium root rot can occur at any time during the growing season, but is most common on seedlings and young plants. Any factor that delays germination and emergence favors the development of Fusarium seedling blight and root rot.

Phomopsis seedling blight is most likely to be a problem if infected seed is planted. The fungi can survive in the seed, infested crop residues and in the soil. Infected seed may fail to germinate or it may germinate slowly. Severely infected seedlings may collapse and die. Phomopsis seedling blight tends to be more severe if weather conditions after planting are cool and wet.

(Author: Wayne Crook, Agronomy Specialist)

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Take-All Of Wheat


With the wet weather this year, we have seen a few instances of take-all in wheat. Take-all is a root and crown disease of wheat that is most obvious near heading time. As it nears maturity, the most obvious symptom is white heads on wheat plants. Entire heads on infected plants may be bleached and sterile. As the plants near maturity the heads on diseased plants may be darkened by sooty molds. Infected plants are also stunted, slightly yellow, have few tillers and ripen prematurely. Roots are sparse, blackened and brittle. If there is sufficient moisture present, a black-brown dry rot may extend into the crown. This black discoloration of the crown may be evident if the lowest leaf sheath is scraped. Diseased plants may lodge, and fields may appear uneven in height and irregular in maturity.

Take-all of wheat is caused by the fungus Gaeumannomyces graminis. The fungus survives in infected host plants (wheat, barley, rye and weed grasses such as smooth bromegrass, quackgrass and bentgrass) and in infected host debris. The fungus is more active in wet soils. Infection can occur throughout the growing season but is more severe when the temperature is between 54 and 64 degrees. Take-all is favored by continuous cropping of wheat. It is also more severe in soils that are lighter, alkaline, infertile and poorly drained. Soil pH also affects the development of this disease. Disease damage is usually worse as soil pH approaches 7.0.

Wheat varieties resistant to take-all are not available. Plant nutrients offer increased resistance to take-all and a greater capacity to tolerate infections by producing more roots. It is important to maintain good levels of available nitrogen, phosphorous and potassium. Crop rotation is one of the best means of managing take-all. Rotating to a non-host crop such as forage legumes, corn or milo for one to three years is usually sufficient for disease control. Eradicating wild grass hosts, volunteer wheat and improving field drainage may also help reduce take-all on wheat.

For more information on wheat take-all, see UMC Guide G4345.

(Author: Wayne Crook ,Agronomy Specialist)

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Algae Pond Management With Barley Straw?

It is called management because barley straw does not control algae the same way Roundup controls grassy weeds. It acts more like a pre-emergent herbicide stopping new algae from growing. As a natural method, do not expect it to act immediately. If a pond already has an algae problem, the algae will have to die of old age and not be replaced.

As barley straw rots in water it gives off lignin from the plant cell walls. Lignin oxidizes in the water to form humic acids which sunlight turns into hydrogen peroxide. Hydrogen peroxide appears to inhibit algae growth. The key word is "appears". Other things may go into this process, as it has not been absolutely defined.

Enter the backyard garden pool or pond. A popular addition to many home gardens is the decorative garden pool. Just like larger farm ponds and lakes, lots of algae are unattractive and unwelcome visitors. One-half pound barley bales have become a popular sales item for garden pools. Every farmer wishes they could sell hay by the half pound for what these mail order companies charge. Also, there are little barley bags, balls and even barley hay tea.

Enter the EPA. If a product label claims to prevent, destroy, repel or mitigate any living thing, it is a pesticide. Then the product has to be registered with EPA and they approve what goes on the label before it can be legally sold. No one has attempted to register barley straw or submit the research data proving it works. University research has produced variable results. Variable results are not enough for an approved label. EPA has classified barley straw as a "home remedy". It cannot be labeled or sold for the stated or implied purpose of algae control. Barley straw can be marketed as a water clarifier. Clearing pond water by inhibiting algae growth may allow more sunlight to penetrate increasing submerged aquatic plant growth. Wheat, oat and other straws do not work like barley straw.

Suggestions for using barley straw in bodies of water include placing it loosely in net bags in the upper layer of water where the sunlight penetrates. A commonly stated dosage is 225 pounds per acre. Small backyard pools should use the dosage accompanying the barley straw or at 0.8 ounces per 10 square feet of surface area. These are approximate amounts but do not go over 900 pounds or less than 90 pounds per acre and 3.3 ounces or less than 0.3 ounces per 10 square feet. Too much straw can rob the water of oxygen as it breaks down and cause a fish kill. Treatments should begin early before the algae begins to grow. It can take as long as a month for enough barley straw to break for any results. Recommended aquatic herbicides may be used for initial control. Aquatic herbicides may cause enough aquatic weeds to die that their rotting can rob oxygen from the water causing a fish kill. Using barley straw and an aquatic herbicide at the same time may combine to make a fish kill more likely. Use caution especially during the hot summer months when oxygen levels are at their lowest.

Excess algae and other aquatic plant growth may be caused by nutrient runoff from animal waste, fertilizer and septic systems. To get the level of control desired, more than one management technique may be necessary. Although private landowners can use barley straw as a home remedy on bodies of water they own, it is illegal to put barley straw in public waters.

Several states have information describing the use of barley straw. The following are web links on use of barley straw for algae management:

(Author: Jim Jarman, Agronomy Specialist)

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Labor Tax Tidbits

Generally, social security and Medicare must be withheld and matched on wages paid to your employees of your business. Wages subject to social security and Medicare taxes are also subject to income tax withholding. However, there are some exceptions to these rules.

The $150 or the $2,500 Test Wages paid during the year for farm work are not subject to social security and Medicare taxes and income tax withholding if either of the following two tests is met:

Wages Paid-in-Kind
Commodity wages are not considered cash wages and are therefore not subject to social security and Medicare taxes or income tax withholding. Several i's must be dotted and t's crossed in order to insure commodity wages are not reclassified by the IRS as cash wages. Work with a tax specialist if you desire to utilize commodity wages in your employee compensation package.

Employment of Family Members
Wages paid to your children under age 18 are exempt from income tax withholding, social security and Medicare taxes. If your child becomes 18 during the year, wages paid following that date are not exempt. These wages are included in calculating the $150 test and the $2,500 test.

Compensation paid to your parents are exempt from income tax withholding, social security and Medicare taxes, if the work:

Source: IRS Circular A, Agricultural Employer's Tax Guide. This publication is available online at

(Author: Parman R. Green, Farm Business Specialist)

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Weather Resources

Funnel Cloud

There are a number of weather resources that could assist you in your farming operation. On the Ag Electronic Bulletin Board, there are some useful links. Check it out at the following site:

We have just been through some very intense storms. We would encourage you to work with your families and employees to be prepared for emergencies from storms, earthquakes, etc. University of Missouri Extension has prepared information to assist you in this. Check out the following web sites:

(Author: Don Day, Natural Resource Engineer/Information Technology Specialist)

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Risk and Land Tenure Under Current Policy

Crop farms deal with risks from many sources, but two of the most important are the risks associated with prices and yields. FAPRI analysts were recently asked to quantify these risks on Missouri farms under provisions of the 2002 farm bill. Here are answers to a few of the questions.

Q: How risky are commodity prices?

A: The degree of price risk depends on how far into the future we want to look. One way to assess risk is to examine a period for which we currently have no physical information about the crop, but the outcomes and probabilities can be measured. For example, based on historical price-yield behavior, FAPRI models indicate a wide range of possibilities for the 2004/05 corn crop (chart 1).

The chart indicates that there is a 52 percent probability that the season average corn price will settle between $1.70 and $2.09. There is an equal chance (8 percent) that price will be below $1.70 or above $2.70. Alternatively, we can say there is an 84 probability that price will average between $1.70 and $2.70. That's a lot of variation or price risk. Within a given year, variation narrows as more information becomes available, but prices can still be quite volatile.

Chart 1

Chart 1

Q: Doesn't the farm bill provide downside price protection?

A:Not exactly. Farm bill provisions provide a safety net for returns in the event of low prices - if you actually raise a crop. In this sense price and yield risk are intertwined. The importance of having production to protect returns with low prices is illustrated in the charts below. Land leases come into play and are also a key element of the price-yield risk exposure a farm faces.

Q: How does land tenure affect price and yield risk under current policy?

A: To illustrate price and yield impacts on net returns under different leasing scenarios, consider the following example. The table outlines planning parameters for a central Missouri representative farm with 1700 acres of program crops.

Table 1. Carroll County Rep Farm, 1700 acres
  Planted Acres Expected Yields Expected Prices
Corn 825 150 bu $ 2.15
Soybean 825 40 bu $ 5.21
Wheat 50 40 bu $ 2.58

The example considers two ways of controlling land. Assume that the entire farm is either share leased (50-50) or cash leased at the share lease equivalent rate of $99 per acre. (Alternatively, this land charge is approximately equivalent to full operator tenure with principal and interest payments owed against 44 percent of the land at market value). The charts show how net returns respond when prices or yields deviate from the expectations-everything else held constant.

Price Impacts (Chart 2)

Chart 2

Chart 2

Production Impacts (Chart 3)

Chart 3

Chart 3

Q: How are Missouri farms structured to share price and yield risk?

A: While representative farm data does not necessarily align with the population of Missouri farms, it does provide some useful information about land tenure practices. Of the 30 rep farms with program crops in the FAPRI database, only two do not have share-lease arrangements on at least a portion of the cropland acres. For crop farms without livestock, the largest proportion of acres, on average, is shared leased. Farms with crops and livestock tend to do less share leasing - possibly because enterprise diversification alters the mix of overall farm financial risk exposure. The proportion of acres under share leases on individual rep farms ranges from 11 to 85 percent. Obviously, the specific terms of the agreement dictate how much risk each party bears.

Chart 4

Chart 4


(Author: Brent Carpenter, Research Associate, Food and Agricultural Policy Research Institute, UMC)

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Publishing Information

Ag Connection is published monthly for Central Missouri Region producers and is supported by University of Missouri Extension, the Commercial Agriculture program, the Missouri Agricultural Experiment Station and the MU College of Agriculture, Food and Natural Resources. Managing Editor: Kent Shannon.