Field Crop News

Website Address: http://fcn.agronomy.psu.edu/

October 7, 2008    Vol. 08:31

IN THIS ISSUE:

• Weather Outlook
• It’s Time to Revisit Fall Herbicide Applications for No-Till Corn and Soybean
• Reducing the Potential of Prussic Acid Poisoning
• Slug Management in Reduced-Tillage Systems
• Corn Ear Molds
• Consider Label Guidelines before Using Milestone or Forefront
• Commodity Market Update

Weather Outlook — Paul Knight, Pennsylvania State Climatologist

After the first frost of the autumn in many northern tier counties, the pendulum will swing back to what should become a period of near record warmth by this time next week. After a dry, chilly start to Wednesday, milder breezes will develop along with increasing clouds. Showers will arrive by dusk in the western counties and will migrate across the state Wednesday night and Thursday. Rainfall will vary from about a third of an inch in the northwest third to less than a tenth of an inch in the southeast third. Noticeably milder weather will be noticed starting on Friday (especially at night). An air flow from the east and southeast during the weekend should contribute to persistent low clouds, fog and patches of drizzle in the southern counties and central mountains.

A push of slightly cooler, but noticeably drier air early next week should suppress the clouds and allow more sunshine for the state. Temperatures will likely climb well into the 70’s and perhaps into the low 80’s from October 12-15. A cold front will approach the region at mid-week with a few showers possible in the northern tier. The Tropics will come alive next week with a possible storm threat for the Southeast between October 16-20.

Despite the cool start to October, it is still likely to average warmer than normal (though not as warm as last year) and this will be followed by a chilly November which may translate into an early and vigorous start to the lake effect snow season in the northwest and Laurel highlands. Indications point to a rather cold and snowy December.

It’s Time to Revisit Fall Herbicide Applications for No-Till Corn and Soybean — William Curran, Crop and Soil Sciences

Fall herbicide treatments have gained some ground in parts of the eastern Corn Belt for some no-till producers. Target weeds include chickweed, the winter annual grasses, purple deadnettle, marestail, wild carrot, dandelion, and others. These weeds overwinter and regrow in the spring, interfering with crop establishment and early-season growth.

Herbicides labeled for this practice include the non or short residual products such as glyphosate and 2,4-D as well as several residual herbicides that will provide some control well into the spring. Of course the major benefit to this approach is controlling certain tough winter weeds that are difficult to manage in the spring and potentially providing a weed-free seedbed at spring planting. Disadvantage includes the cost of the herbicide and the application and hoping that what you do is worth the time and money. Residual herbicides will also lock you into either corn or soybeans, depending on the product.

With the strong emphasis in our region on protecting water resources and improving soil quality, another consideration includes potentially losing the opportunity to plant a fall cover crop and/or leaving fields more exposed over the winter. As a compromise, consider using a non or short residual herbicide in the fall to kill emerged vegetation (if necessary) and follow it with a small grain cover crop such as wheat or cereal rye. There’s nothing better at suppressing winter weeds and providing soil cover than a vigorous winter cover crop.

If you decide to use a herbicide program, apply herbicides anytime after early October and by mid-November if possible. If you include a residual herbicide, our research over the last 5 or 6 years has any chlorimuron-containing product (Canopy EX, DF, etc.) at the top for soybeans and simazine at the top for corn. Glyphosate + 2,4-D is most effective for control of perennials and most biennial weeds. Control with fall applied glyphosate alone is often similar to the combination of glyphosate + 2,4-D (especially for dandelion), but the 2,4-D is needed for glyphosate-resistant marestail and can help on certain other broadleaf weeds. If seeding a small grain cover, use only glyphosate or Gramoxone (2,4-D is not labeled ahead of small grains, although lower rates and adequate lead time would reduce the potential for injury). Application of 2,4-D alone controls many winter annual weeds, but 2,4-D will not control chickweed and is less effective on dandelion than when in tank mixture with other herbicides.

Reducing the Potential of Prussic Acid Poisoning — Marvin Hall, Crop and Soil Sciences

(With widespread frost in the state, it is worthy of repeating this article from October 2007.)

The Sudangrass, forage sorghums and sorghum-sudangrass crosses (all in the genus Sorghum) contain a non-poisonous chemical called dhurrin. If these plants are damaged by freezing, chewing or trampling), the dhurrin is converted into prussic acid (cyanide) which is potentially very dangerous for animals eating these crops.

Factors Affecting Prussic Acid Content In Plants

Species. The vegetative portion of all sorghums contains prussic acid. Generally, however, prussic acid content in sudangrass is about 40 percent less than in most other sorghums. As a group, the sorghum-sudangrass hybrids have more prussic acid than sudangrass. Crosses have now been developed that contain extremely low quantities.

Plant Parts. In the sorghums, young leaf blades normally contain higher prussic acid levels than old leaf blades or leaf sheaths or stems. The seedheads are low in prussic acid, and the seeds contain none.

Maturity. Highest prussic acid levels are reached before the boot stage. As plants mature, the stalks make up a greater proportion of the plant, causing prussic acid content in the total forage to decrease.

Drought. Severe drought is probably the most common cause of prussic acid poisoning. Drought-stricken plants are hazardous to feed because they are mostly leaves.

Freezing. Forage is usually considered safe to pasture or feed as green chop 5–6 days after a killing frost.

Fertilizer. If high N rates are applied to soils deficient in phosphorus and potassium, prussic acid levels usually increase.

Safe Feeding of Potentially Hazardous Forages

Pasture. Sorghum that has wilted and dried 5–6 days after being killed by frost is considered safe for grazing. The risk of prussic acid poisoning can be reduced by feeding ground cereal grains to the animals before turning them out to graze. The chance of problems on pasture can be further reduced by using heavy stocking rates (4–6 head per acre) and rotational grazing to avoid cattle selectively grazing the leaves. If new shoots develop after a frost the crop should not be grazed until this new growth is 2 feet tall.

Green Chop. Green chop forage is usually safer than the same material used for pasture because it is not selectively grazed. Whereas in the case of pasture only the leaves may be eaten, with green chop material the total plant is consumed. Stems act as safety devices ‘diluting’ the high prussic acid content of leaves.

Silage. Sorghum silage is generally safe for feeding. Although it could contain toxic levels of prussic acid while in storage, much of the poison escapes as a gas during fermentation and when being moved for feeding. However, as a precaution, do not feed new silage for at least 3 weeks after harvesting and storing.

Hay. The prussic acid content of sorghum hay decreases as much as 75 percent while curing and is rarely hazardous when fed to livestock.

Slug Management in Reduced-Tillage Systems — John Tooker, Entomology

Extension agents around PA have been hearing about slugs. These pesky mollusks have been particularly troublesome in no-till fields as winter crops emerge (e.g., rye, wheat, and barley). Slugs are most active when it is cool and moist and they thrive in fields with surface residue and high organic matter, accurate descriptors of most no-till fields.

Most slugs have a single generation per year with overwintering eggs hatching in spring and slugs developing through the spring, summer, and into the fall. Some slug species feed on decaying matter in leaf litter and soil, but others also feed upon green tissue and these, of course, are the ones that feed upon crop seedlings in the spring and fall causing headaches for farmers. Unfortunately for farmers with slug problems this fall, many management tactics need to be implemented in spring.

In most cases, slug have become pests following a switch to no-till farming, so one option for managing slugs is change tillage practices to a reduced-tillage or conventional tillage program, which will reduce amounts of food and shelter available in fields. This option of course is not feasible for many, so other options must be considered. Dr. Galen Dively, long-time extension entomologist at the University of Maryland, has suggested the following options for farmers who do not wish to alter their tillage practices:

• Plant when soil temperatures are higher (later in the spring; earlier in the fall). Warmer soil will allow crops to germinate and grow more quickly and perhaps “outrun” slug damage which is harder on younger plants. If this tactic is implemented in the spring, lower slug populations may be expected in the fall.
• Similarly, farmers can use starter fertilizer at planting to give seedling a “jump start.”
• Use row cleaners (a.k.a. residue managers, trash whippers, trash wheels) when planting. These devices push residue to the side leaving a band of relatively clean soil for planting. This clean soil will warm up faster and provide habitat that is less suitable for slugs.
• Metaldehyde in various formulations is one of the only chemical options available. It is often used as a bait, which poisons slugs if ingested at high concentrations and can also kill on contact by forcing slugs to produce more mucus, drying them out. Dr. Dively has recommended as a cost effective option using 10 lbs/acre of a product called Deadline M-Ps, banded over the row.
• For heavy infestations, urea-based nitrogen can be used as rescue treatments. Studies have demonstrated that 30% urea-based nitrogen applied in the evening can cause significant slug mortality. It is not clear if this nitrogen also becomes available for plant growth.

Slugs are a challenge to control and a single tactic may not be successful; therefore, a combination of these tactics provides the best chance for success. Reliance on metaldehyde alone may be tough because it can be expensive.

Corn Ear Molds — Del Voight, Interim Grain Crop Specialist

This article includes pictures of ear molds, a description of their mycotoxin potential and some management ideas.

Just because there is the mold does not mean that a mycotoxin will result. There is still much that needs to be learned regarding these molds and their relationship to the toxin formation. Both fusariums can be an issue and have been researched the most intensively in silage.

The following information is from Ontario Ministry of Agriculture.

Gibberella Ear Rot

The most common and important ear mold in Ontario is Gibberella zeae which is the sexual reproductive stage of Fusarium graminearium. This fungus not only infects corn but also small grains such as wheat and can survive on soybean roots. Although, the fungus can produce a white colour mold which makes it difficult to tell apart from Fusarium Ear Rot, the two can be distinguished easily when Gibberella produces its characteristic red or pink colour mold.

Scout fields which have a susceptible hybrid planted. If you are not sure how your hybrid rates for Gibberella, contact your seed supplier.

Gibberella Ear Rot is economically important not only because of the potential yield and quality losses but because Gibberella zeae and Fusarium graminearum produce two very important mycotoxins that occur in Ontario, deoxynivalenol (vomitoxin or DON) and zearalenone.

These mycotoxins are especially important to swine and other livestock producers since they can have a detrimental affect on their animals. Feed containing low levels of vomitoxin (1ppm) can result in poor weight gain and feed refusal in swine. Zealalenone is an estrogen and causes reproductive problems such as infertility and abortion in livestock, especially swine. If you have Gibberella ear rot (5 % or more) and are planning to feed the grain, you should have the grain tested for these toxins.

Fusarium Ear Rot

Unlike Gibberella, Fusarium infected kernels are often scattered around the cob amongst healthy looking kernels or on kernels that have been damaged (for example by corn borer or bird feeding). Fusarium infection produces a white to pink or salmon-coloured mold. A “white streaking” or “star-bursting” can be seen on the infected kernel surface. Although many Fusarium species may be responsible for these symptoms, the primary species we are concerned about in Ontario is Fusarium verticillioides (formerly Fusarium moniliforme). The significance of this fungus is that it produces a toxin called fumonisin.

Diplodia Ear Rot

The characteristic ear symptom of Diplodia maydis infection is a white mold that begins at the base of the ear and will eventually cover and rot the entire ear. Mold growth can also occur on the outer husk which has small black bumps (pycnidia) embedded in the mold. These reproductive structures are where new spores are produced. Unlike Gibberella and Fusarium, Diplodia does not produce any known toxins.

Penicillium Ear Rot

Penicillium rot (Penicillium oxalicum) produces a light blue-green powdery mold which grows between the kernels and cob/husk surface. Infected kernels could become bleached or streaked. Can be a serious problem if corn is stored at high moisture levels (greater 18%). Although other Penicillium species have been shown to produce Ochratoxins, Penicillium oxalicum does not and this toxin does not occur in Ontario.

Table 1 — Common Ear Rots and Molds That Occur in Ontario and The Primary Mycotoxins They Produce

Corn Ear Rot	Description	Primary Mycotoxins
Gibberella (Gibberella zeae also called Fusarium graminearum (asexual stage))	Red/pink mold Begins on ear tip Bird, insect injury increases damage	Deoxynivalenol (vomitoxin or DON) Zearalenone T-2 toxin
Fusarium (Fusarium verticilliodes)	White, pink or salmon colored Can occur anywhere on ear Often begins at the sites of insect damage	Fumonisins
Diplodia (Stenocarpella maydis)	White mold Begins at baseof ear but often entire ear covered Black pycnidia (bumps) on husks and kernels	None
Penicillium (Penicillium oxalicum)	Blue-green mold Mold between kernels and on cobs/husk	Ochratoxns (other Penicillium species) P. oxalicum does not produce ochratoxin; not detected in Ontario

Ear Mold Management

From: Iowa State University Extension

The best option for moldy grain is to feed it or sell it instead of storing it. However, it should be tested for toxins before feeding. Testing for mycotoxins can be done before putting the grain in storage.

The best sampling method is to take a composite sample of at least 10 pounds from a moving grain stream, or to take multiple probes in a grain cart or truck for a composite 10-pound sample. If toxins are present, it is possible that the grain can be fed to a less sensitive livestock species, such as beef cattle, depending on the specific toxin and its concentration. A veterinarian or extension specialist can help with these decisions. If the grain is sold, there may be a reduced price due to mold damage.

Cleaning the grain removes fine particles that are usually the moldiest and most susceptible to further mold development. Good storage conditions (for example, proper temperature and moisture content, aeration, insect control, and clean bins) and regular inspection are essential in preventing mold and toxin development in any stored corn.

For additional information on sampling and other aspects of ear rots and mycotoxins:

• Iowa State University Extension publications PM 1800, Aflatoxins in Corn
• PM 1698, Corn Ear Rots, Storage Molds, Mycotoxins, and Animal Health (ordering information)

Consider Label Guidelines before Using Milestone or Forefront — William Curran

This week’s Lancaster Farming (Oct. 4, 2008) includes an article reporting some problems by commercial vegetable growers in the United Kingdom who experienced crop injury from aminopyralid residues that persisted in composted manure. Aminopyralid is the active ingredient in Milestone and Forefront, two products used in the Northeast for weed control in grass hay and pasture. Dow AgroSciences, the manufacturer of aminopyralid is very much aware of this potential problem and has included some very specific language on their product labels.

In our region, transporting manure onto fields that will be planted with sensitive crops or selling compost containing contaminated manure off the farm could cause serious crop injury. With the recent news abroad and even some suspected problems closer to home, be sure you and your farm customers are familiar with this herbicide’s restrictions and how they might impact sensitive crops.

The following language is taken directly from the Milestone label.

• Do not transfer grazing animals from treated areas to areas where sensitive broadleaf crops occur without first allowing 3 days of grazing on an untreated pasture. Otherwise urine and manure may contain enough aminopyralid to cause injury to sensitive broadleaf plants.
• Do not use aminopyralid-treated plant residues, including hay or straw from treated areas, or manure from animals that have grazed forage or eaten hay harvested from treated areas within the previous 3 days, in compost or mulch that will be applied to areas where commercially grown mushrooms or susceptible broadleaf plants may be grown.
• Do not spread manure from animals that have grazed or consumed forage or eaten hay from treated areas within the previous 3 days on land used for growing susceptible broadleaf crops.
• Manure from animals that have grazed forage or eaten hay harvested from aminopyralid-treated areas within the previous 3 days may only be used on pasture grasses, grass grown for seed, and wheat.
• Do not plant a broadleaf crop in fields treated in the previous year with manure from animals that have grazed forage or eaten hay harvested from Milestone-treated areas until an adequately sensitive field bioassay is conducted to determine that the Milestone concentration in the soil is at level that is not injurious to the crop to be planted.
• To promote herbicide decomposition, plant residues should be evenly incorporated in surface soil or burned. Breakdown in plant residues or manure is more rapid under warm, moist soil conditions and may be enhanced by supplemental irrigation.

Commodity Market Update — Andrew Frankenfield, Educator, Montgomery

Current cash prices for fall delivery are: Corn-$4.14; Soybeans-$8.37, down over $3.00 for corn and over $6.00 for soybeans. This leads many farmers to a lot of questions. What happened to $7.80 corn and $16.00 beans? Is this the bottom? Why didn’t I lock in some or more of my crop when the market was higher? Are fertilizer prices going to remain high or go down as we approach spring? We don’t know the answers to these questions, but by having a marketing plan you can take some of the emotion out of selling grain. There were excellent opportunities to market the 2008 grain crop over the past six months.

According to Mike Roberts, Commodity Marketing Agent for Virginia Tech, “The uncertainty in the financial markets is the leading factor currently impacting commodity futures markets and will continue to influence prices in a downward trend as long as financial instability persists. Harvest lows in crops are usually posted by August-September. The next USDA report due October 10 will show yield trends and therefore supply/use estimates. It may be expected that once the market gets clear of current financial stressors that commodity prices will rise.”

To read his full October 7th Market Report go to http://www.ext.vt.edu/news/periodicals/roberts/2008wp/Oct07_2008.html

Contributors: Extension Educators: Andrew Frankenfield (Montgomery), Jeff Graybill (Lancaster), Mark Madden (Sullivan), Tianna DuPont (Northampton), Delbert Voight (Lebanon), Grant Troop (Lebanon). Specialists: Crop and Soil Sciences: William Curran, Marvin Hall, Entomology: John Tooker.

Editor: Mena Hautau

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