Lebanon Crop Management Video

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02 August 2016

Corn Ear Molds


Del Voight – Penn State Extension
Two Items to be reviewing as the corn season progresses. Ears are rapidly forming and growers are applying fungicides presently to fields that the hybrid may be susceptible to leaf diseases.. Knowing the characteristics of the molds are helpful in management. Also many fields of corn were planted late and are showing some leaf diseases. This is important also in determine early harvest prior to complete infection of the plants.
Here are some pictures of ear molds and a description of their mycotoxin potential as well as some management ideas.  As in other cases just because there is the mold does not mean that a mycotoxin will result.  There is still a lot that needs to be learned regarding these molds and there relationship to the toxin formation.  Both fusariums can be an issue and have been researched the most intensively mainly in the silage portion for dairy.  As you get out on farms in the coming weeks it might be wise to have this or some other reference in your truck to use as a discussion.  Also keep an eye on the nitrate situation(silage after rains return) and stalk lodging due to stalk rot. Many times with a drought the plant robs leaves, stalk and roots to feed the ear and during this time stalk rots invade since the plant is weakened.  A squeeze test of the lower stalk can reveal the management of the field for early harvest. 
I have viewed mostly corn smut. at differing stages of development.  This is not a fungus that can cause any harm to livestock contrary many folks will consume it as a delicacy.


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 cause 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.
Figure 2 - Gibberella Ear Rot





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.
Figure 3. Fusarium Ear Rot

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.
Figure 4. Diplodia Ear Rot

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 dos not and this toxin does not occur in Ontario.
Figure 5. Penicillium Ear Rot

Table 1 – Common Ear Rots and Molds That Occur in Pa 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 verticillioides)
  • White, pink or salmon coloured
  • Can occur anywhere on ear
  • Often begins at the sites of insect damage
  • Fumonisins
Diplodia
(Stenocarpella maydis)
  • White mold
  • Begins at base of 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
  • Ochratoxins (other Penicillium species)
  • P. oxalicum does not produce ochratoxin; not detected in Ontario
Management – Iowa State University.
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, see Iowa State University Extension publications PM 1800, LEAF DISEASESAflatoxins in Corn (free), and PM 1698, Corn Ear Rots, Storage Molds, Mycotoxins, and Animal Health ($1.50 plus shipping).

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