2016 Corn Ear Moulds and Mycotoxin Update
Oct 182016 Corn Ear Moulds and Mycotoxin Update
The fall of 2016 is shaping up to have more corn ear mould challenges and increased vomitoxin levels than we have experienced in the past few years. In many cases, Western Bean Cutworm damage is giving the ear mould a foothold and in other cases, poor pollination or tight husks are providing a place at the ear tip for moulds to develop.
The OMAFRA 2016 Vomitoxin Survey is complete and can be found here.
The survey indicates that 26% of the samples collected had a vomitoxin level over 2.0 ppm.
Growers are encouraged to scout fields so as to prioritize harvest and get mouldy fields harvested early to reduce the chance of vomitoxin increasing in concentration. Combines should be set to screen or blow as many of the smaller tip kernels as possible out of the sample as they are often higher in mycotoxin concentration.
Additional information on corn ear mould can be found on the Grain Farmers of Ontario site.
The following pictures and descriptions can assist in identifying ear moulds in this year’s corn crop. Appreciation is expressed to Albert Tenuta, OMAFRA for assistance with compiling photos and details.
Gibberella Ear Rot
- The most common and important ear mould in Ontario is Gibberella zeae which is the sexual reproductive stage of Fusarium graminearium.
- Infection often begins at the ear tip and moves down towards the ear base.
- Although the fungus can produce a white-coloured mould which makes it difficult to tell apart from Fusarium Kernel Rot, the two can be distinguished easily when Gibberella produces its characteristic red or pink colour mould.
- Toxins produced by Gibberella include Deoxynivalenol (vomitoxin or DON), Zearalenone (ZEN) and T-2 toxin. If grain is to be used for feed, a mycotoxin test is recommended.
- Reducing toxin levels by combine adjustment and grain cleaning is difficult.
Fusarium Ear Rot
- Unlike Gibberella, Fusarium infected kernels are often scattered around the cob amongst healthy looking kernels.
- In most cases, Fusarium does not fuse the husk to the ear unlike Gibberella.
- 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 which produces the toxin, Fumonisin.
Diplodia Ear Rot
- The characteristic ear symptom of Diplodia maydis infection is a white mould that begins at the base of the ear and will eventually cover and rot the entire ear.
- Mould growth can also occur on the outer husk which has small black bumps (pycnidia) embedded in the mould.
- No known mycotoxins produced.
Penicillium Ear Rot
- Penicillium oxalicum produces a light blue-green powdery mould which grows between the kernels and cob/husk surface.
- Can be a serious problem if corn is stored at high moisture levels (greater than 18%).
- Ochratoxins are produced by other Penicillium species (P.oxalicum does not produce ochratoxin and is rarely detected in Ontario)
Cladosporium Ear Rot
- Cladosporium was particularly prominent in 2009.
- Delayed maturity, frost events and wet conditions contributed to the Cladosporium development.
- Cladosporium produces a black mould on the ear and kernel surface. Cladosporium grows mainly on the kernel surface or between kernels and are not great colonizers. They are often referred to as “surface contaminants” and therefore the mould (mycelium) they produce rubs off easily. Basically, as the corn dries the Cladosporium mould often dries as well and some friction (such as combining) will remove it to some degree.
- Cladosporium does not produce any known toxins and if properly stored or ensiled, mould growth should stop under anaerobic (oxygen-free) conditions.
Maizex Seeds Agronomy Lead
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