Corn is susceptible to a number of ear mould fungi that can reduce yield potential, grain quality, and feed value. Damage potential is greatest in the period from silking to harvest, when above average rainfall occurs. It is often coupled with kernel damage from insects, birds, hail, or early frost. Management of infected grain includes disease identification, attention to harvest, and storage considerations.
|Conditions Favouring Disease
|Aspergillus (Figure 1)
|Gray-green; light green
|Powdery mould starting at tip
|Damaged silks or kernels typically from insects or hail; dry weather with hot day and nighttime temperatures
|Aflatoxin: toxic to livestock and humans
|Diplodia (Figure 2)
|White to gray
|Usually begins at base of the ear and develops toward the tip; growing between kernels; often small black peppery spots will form on husks
|Cool wet weather during the 3 weeks following silking; corn debris on soil surface can harbour the disease
|Not known to produce any Mycotoxins
|Fusarium (Figure 3)
|White to pink
|Individual kernels with fungal growth and/or kernels with starburst pattern
|Infection points include kernel growth cracks and ear damage from insects; warm, wet weather during 2-3 weeks following silking
|Fumonisin: toxic to livestock, particularly horses
|Gibberella (Figure 4)
|Often bright pink; varies from red to white
|Usually begins at ear tip and progresses to base
|Cool, wet weather during the 2-10 days following silk initiation
|Vomitoxin and zearalenone: harmful to livestock
|Penicillium (Figure 1)
|Grows on and between kernels; powdery
|Damaged kernels by frost, insects, or hail
|Not known to produce any Mycotoxins
Corn ear and kernel rots. 1991. University of Illinois Extension. IPM RPD No.205. http://ipm.illinois.edu (verified 9/22/2011). OMAFRA. Diseases of field crops. Agronomy Guide. Publication 811.
Presence of disease, the proper host, and favourable environmental conditions are all needed for ear mould development. Disease pressure from common ear mould fungi found in the Province—Fusarium (verticillioides), Gibberella, and Diplodia—will vary from field to field. Weather during pollination, after pollination, and nearing harvest is a major factor in disease development as is kernel damage from birds and insects. Other less common fungi such as Penicillium and Aspergillus may also become established in some areas. Drought and heat stress is conducive to ear mould infection from Aspergillus.
Fields require scouting for ear moulds as some of these diseases—Fusarium and Gibberella—develop mycotoxins that are harmful to humans and livestock. Additional management is needed for storage and marketing grain infected with mould damage.
Weather and physical damage are often the leading factor in ear mould infection, and prevention is limited. Ears that mature in the downward position and are covered by husks may have less ear mould infection than open-husk, upright hybrids. This husk growth restricted by extremely dry weather may lead to exposed ear tips. Later rains and cooler weather re-initiate ear elongation in some cases causing ear tips to grow beyond restricted husk leaves and be susceptible to insect and bird damage.
Many pathogens that cause ear rots can also cause stalk rots. These fungi can remain viable in the soil for several years; therefore, carefully scout fields with a history of ear rots and stalk rots, even if management practices have been employed to decrease disease pressure. Some options to help decrease the risk of ear mould infection include crop rotation, heavy tillage, planting hybrids with insect protection traits, and good fertilization. Planting a package of hybrids with different maturities and heat unit requirements to flowering, as well as rotating germplasm planted in the same field from year to year, are also good practices to help reduce the impact of ear moulds.
Proper grain drying and storage are important when these diseases are evident. Here are some tips for harvesting and storing grain from fields with prevalent ear mould infection.
- Allow corn to mature in the field to 23 to 25% moisture content1. If lodging concerns exist, harvest early since down corn is more likely to mould.
- Consider tilling and rotating away from corn next year.
- Combines should be adjusted to minimize kernel damage and maximize cleaning.
- Corn should be dried to 13 to 14% moisture content prior to storage.
- Grain should be stored at cool temperatures 4 to 10° C (40 to 50° F) after drying.
- Grain should be checked periodically for temperature, wet spots, and insects.
Weather conditions and damage make disease pressure variable and nearly unpreventable across the Province. Scouting and identification are necessary as mycotoxins can be harmful for consumption and develop as a result of some corn ear moulds.
Because some moulds can be toxic to livestock, proper identification is important before using contaminated grain for feed. Always send a sample of suspect corn to a toxicology lab for analysis. If concentrations of a mycotoxin are present, a veterinarian or a qualified lab can help determine if it is safe to feed to livestock. Contact your local specialist for information on testing labs in your area.
Please check fields to identify the issues at hand. Take a close look at roots, stalks, and ears for disease, insect damage, and moisture. Each season can provide many weather extremes for crops and being aware of the crop situation in each field will help determine a plan for harvest.
Figure 1. Aspergillus flavus (left) and Penicillium (right) are less common in the area; however, hot and dry conditions favour Aspergillus and the development of aflatoxin
Figure 2. White to gray mould on ears infected with Diplodia.
Figure 3. Starburst pattern characteristic of Fusarium infection
Figure 4. Gibberella ear mould progressing from the tip to the butt of the ear.
1The Ohio State University. 2004. Corn disease managment in Ohio. Pub. 802. Munkvold, G. 2002. Corn ear molds and mycotoxins. Iowa State University. Integrated Crop Management Newsletter. IC-488(22) -- October 21, 2002 issue. (verified 9/5/2013).
Paul, P. and D. Mill. Corn ear rot: which one is it? Ohio State University. C.O.R.N. Newsletter 2009-35. corn.osu.edu (verified 9/5/2013).
Robertson, A. 2004. Corn Ear Rots. Iowa State University. Integrated Crop Management Newsletter. ICM > 2004 > IC-492(21) -- October 4, 2004. http://www.ipm.iastate.edu (verified 9/5/2013).
Tenuta, A. 2006. Identifying corn ear molds. OMAFRA Ridgetown. October 4, 2006. Corn ear and kernel rots. 1991. University of Illinois Extension. IPM RPD No.205. ipm.illinois.edu (verified 9/5/2013).