Diseases of Field Crops: Corn Diseases


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Pub 811: Agronomy Guide >Diseases of Field Crops> Corn Diseases

Order OMAFRA Publication 811: Agronomy Guide for Field Crops


Corn Seedling Diseases

Seed Rot, Seedling Blight, Root Rot

Incidence and Management Strategies: See General Seed Rots and Seedling Blights.

Disease Cycle: In corn, the most common diseases are caused by Pythium, Fusarium, Gibberella, Trichoderma and Penicillium, but other fungi such as Diplodia and Rhizoctonia can also be involved. Seed, seedling and roots infected by Pythium are most often soft (wet) and dark coloured, as opposed to roots infected with Fusarium, Gibberella, Diplodia and Rhizoctonia, which are firm or leathery. The colour of the roots most often provides a good indication of which organism(s) are present:

  • greyish-white indicates Diplodia
  • tan to pink indicates Fusarium or Gibberella
  • reddish to brown indicates Rhizoctonia
  • blue-green indicates Penicillium or Trichoderma

Pythium, Fusarium, Gibberella, Diplodia, Rhizoctonia, Penicillium and Trichoderma all live and thrive in the soil. In most cases, they can affect other crops besides corn. Except for Pythium, all of these organisms also have the ability to live on or in corn seed.

Corn Leaf Diseases

Anthracnose Leaf Blight (Colletotrichum graminicola)

Incidence: Anthracnose may become severe in warm, wet years and is often the first corn leaf disease that is noticed. It begins on the lower leaves, working its way up the plant. Symptoms often disappear as the corn plant begins its rapid growth phase. The fungus that causes anthracnose leaf blight is also responsible for anthracnose stalk rot (see Anthracnose Stalk Rot ). Record where anthracnose leaf blight symptoms developed early in the season and return to those areas to scout for stalk rots a few weeks before harvest. Tillage systems that leave considerable amounts of anthracnose-infected debris on the soil surface may lead to greater severity of the disease and an increased presence.

Anthracnose may affect both leaves and stalks. The main symptoms are leaf spotting, top dieback and stalk rot. Leaf spots are oval, up to 15 mm (6 in.) long, with a tan centre and reddish-brown border (See Plate 108 ). Individual lesions may join, forming streaking along the margin or midrib. A general yellowing of the tissue surrounding the infected areas often develops. With the aid of a hand lens, small black spots can be seen in the centre of the lesions. Under close examination, black hairs may be seen protruding from these spots. The disease is first observed on the lower leaves and later on the upper leaves. Top dieback can occur late in the season as diseased leaves wilt and gradually die, taking on the appearance of frost damage.

Disease Cycle: Residue is an important component in anthracnose development, since the fungus survives (overwinters) as mycelium or sclerotia within corn residue or seed. Rain splashes spores from the corn residues onto the lower leaves and stalk. For this reason, second-year corn is the most prone to anthracnose infection, especially when the weather is warm and wet.

Management Strategies: Planting hybrids that are resistant to anthracnose leaf blight can help to manage anthracnose leaf blight. However, resistance to anthracnose stalk rot is separate from resistance to anthracnose leaf blight. Hybrid resistance to anthracnose stalk rot does not guarantee resistance to early-season anthracnose infections on leaves. In conventional tillage corn fields, removal of corn residues through tillage will lower the risk to the disease, especially when corn follows corn. In no-till or reduced tillage fields, management of anthracnose leaf blight is best achieved with rotations (avoiding second-year corn) and planting of resistant corn hybrids. Fungicide applications are not economical in field corn situations, because more than one application is necessary to control the disease. However, in seed corn fields, fungicide applications may be cost effective.

Plate 108. Anthracnose affects both leaves and stalks. The main symptoms are leaf spots, top dieback and stalk rot.

Photo showing  how anthracnose affects both leaves and stalks. The main symptoms are leaf spots, top dieback and stalk rot.

Northern Leaf Blight (Setosphaeria turcica)

Incidence: Northern leaf blight has traditionally been one of the most damaging corn leaf diseases. Use of resistant/tolerant hybrids has limited yield losses from this disease in commercial corn. However, in recent years the disease has increased, which may suggest a decline in tolerance levels. Significant losses continue to occur in seed corn production when highly susceptible corn inbreds are planted.

Appearance: The disease appears as long, elliptical, 2-15 cm (1-6 in.), greyish-green or tan streaks. Lesions most often begin on the lower leaves (See Plate 109). As the disease develops, individual lesions may join, forming large blighted areas. In some cases, the entire leaves may become blighted or "burned"(See Plate 110). Losses due to northern leaf blight are most severe when the leaves above the ear are infected at or slightly after pollination. The disease is often confused with Stewart's wilt (see Bacterial Leaf Blight or Stewart's Wilt).

Disease Cycle: The fungus survives in corn residue as either spores or fungal strands (mycelium). The spores of the fungus are spread from the ground residue to the developing corn plant through wind or rain "splashing." Plants that become infected act as a secondary source of infection and may spread to other fields. Disease development is favoured by moderate temperatures (18°C-27°C) with prolonged periods of humid or rainy weather.

Management Strategies: There are various races of northern leaf blight. Most of the commercial corn hybrids have resistance or tolerance to the common races. An increase in northern leaf blight symptoms in an area could indicate the potential for a new race developing and should be reported. Crop rotation and tillage will reduce inoculum levels in surface residues. In reduced tillage systems, rotation and the use of resistant hybrids is necessary. Foliar fungicides are not usually economical in field corn but may be warranted if a susceptible hybrid is planted and disease develops early in the season.

Plate 109. Northern corn leaf blight showing long, elliptical, greyish-green or tan streaks.

Photo showing northern corn leaf blight showing long, elliptical, greyish-green or tan streaks.

Plate 110. Northern leaf blight on a susceptible variety (left) and a resistant variety (right), showing fewer symptoms.

Photo showing northern leaf blight on a susceptible variety (left) and a resistant variety (right), showing fewer symptoms.

Eyespot (Aureobasidium zeae)

Incidence: Although eyespot normally causes only minor losses in corn, the disease has been increasing in Ontario with the shift to higher corn residues remaining in the field.

Appearance: The disease produces characteristic round or oval spots, 1-4 mm (1/16-1/8 in.) with a tan/brown centre and a brown or purple margin (See Plate 111). A translucent yellow halo forms around the margin, and when held to the sun, the lesions resemble an eye. Leaf blighting may occur when these lesions join, killing large portions of leaf tissue. The disease may be confused with non-infectious physiological leaf spots or insect damage.

Disease Cycle: The disease is more prevalent under continuous corn and reduced tillage systems, since the fungus overwinters in corn residue. Disease development is favoured by cool, wet conditions.

Management Strategies: Resistant varieties, crop rotation and clean plowing of crop debris help to reduce disease severity. Foliar fungicides are rarely recommended for the disease.

Plate 111. Eyespot causes round or oval leaf spots with a tan/brown centre, a brown or purple margin, and a translucent yellow halo when held up to the sun.

Photo showing how eyespot causes round or oval leaf spots with a tan/brown centre, a brown or purple margin, and a translucent yellow halo when held up to the sun.

Bacterial Leaf Blight (Stewart's wilt )(Pantoea stewartii)

Bacterial leaf blight occurs throughout Ontario, but the disease is only of concern in Southwestern Ontario. Essex and Kent Counties, where the majority of seed corn production fields are located, tend to be especially affected by bacterial leaf blight. Warmer-than-normal winters in this area have allowed the corn flea beetle, which is a vector of bacterial leaf blight (Stewart's wilt), to survive in higher numbers.

Appearance: There are two distinct phases of the disease: the wilt phase and the late wilt phase. The wilt phase primarily affects highly susceptible seed corn inbreds and sweet corn hybrids early in the year (V2-V4). The first noticeable sign of the disease appears as long, yellow streaks that extend along the length of the leaf (See Plate 112). These streaks will take on a water-soaked appearance and eventually become brown, dead streaks. The bacteria interrupt the water and nutrient movement in the plant by plugging the vascular system of the plant. The result is a rapid wilting and even death. Since the new growth is affected, the wilting and death occur from the top down. Cutting the plant lengthwise will reveal a discoloured, rotted or hollowed-out growing point.

The leaf blight phase or late-infection stage often occurs after tasselling and is the most common phase. Symptoms include pale-green to yellow streaks with irregular or wavy margins that run parallel to the veins. These streaks may run the full length of the leaf. Infected leaves eventually become dry and brown. The marks of corn flea beetle feeding are often visible within the lesions. Premature leaf death can result in reduced yield and an increase in stalk rots, since weakened plants are more susceptible to stalk rots.

Disease Cycle: The bacteria overwinters in the gut of adult flea beetles, which hide through the winter in protected areas (See Corn Flea Beetle). Mild winters can result in higher beetle numbers. Overwintering adult flea beetles feed on corn in the seedling-to-whorl stage, and susceptible varieties will develop a stem wilt, resulting in complete plant loss. This occurs rarely in hybrids but occasionally in susceptible seed corn parents. The next generation of adult beetles emerges after corn silking and causes leaf wilting symptoms, which are commonly seen in many hybrids. Seed transmission is rare. Most often, late infections after silking are associated with high beetle populations. Sweet corn is often more susceptible than field corn and can serve as a reservoir for the bacteria. The disease is often found in the best fields, and fertility seems to play a part. Susceptibility to the disease increases in fields that have high nitrogen and phosphorous levels.

Management Strategies: Field corn has good tolerance to Stewart's wilt and therefore no control is required. Certain seed corn inbreds are susceptible and are rated for disease tolerance. This disease is controlled by managing the corn flea beetle. See Corn Flea Beetle.

Plate 112. Stewart's wilt (bacterial leaf blight) occurs after tasselling. Wilt phase occurs at V2-V4 growth stage. Corn flea beetle is a vector of Stewart's wilt.

Photo showing how Stewart's wilt (bacterial leaf blight) occurs after tasselling. Wilt phase occurs at V2-V4 growth stage. Corn flea beetle is a vector of Stewart's wilt.

Grey Leaf Spot (Cercospora zeae-maydis)

Grey leaf spot is a destructive and economically important disease that has been increasing over the past 10 years in the states surrounding the Great Lakes. Significant losses can occur from this disease under warm, wet and humid conditions.

Appearance: Soon after tasselling, the symptoms develop on the lower leaves. The disease has unique, elongated, 2-7 cm (1-3 in.) long, narrow, light-tan, rectangular lesions. These lesions run parallel to the leaf veins. As the lesions mature, they become grey and join, killing or blighting entire leaves.

Disease Cycle: Grey leaf spot is most problematic when corn follows corn in fields with a considerable amount of corn residue. The fungus survives as fungal strands (mycelium) in corn residue. Spores produced on the residue are dispersed by wind and rain splash. Warm, humid weather favours spore and disease development.

Management Strategies: Crop rotation and tillage will reduce inoculum levels in surface residues. In reduced tillage systems, rotation and use of hybrid resistance may be necessary. Chemical control is not usually needed but if a highly susceptible hybrid is planted and disease development begins early in the season, it may be warranted.

Common Rust (Puccinia sorghi)

Common rust does not overwinter in Ontario. It originates from infected corn in the southern U.S. and Mexico. Rust spores are blown into Ontario. In most years, rust is of minor economic importance. However, sometimes spring storm fronts bring in spores and cause early-season infection. The disease is favoured by high humidity with cool evening temperatures (14°C-18°C), followed by moderate daytime temperatures.

Appearance: Early symptoms of rust infection are yellow flecks or spots on either side of a leaf. These develop into small, brick-red pustules that break through the leaf surface (See Plate 113). The brick-red colour is the result of spores being released from these oval or elongated 2-10 mm (1-4 in.) lesions. Yellowing of the leaf occurs around these lesions. Dead, brown areas of the leaf develop. In severe cases, the entire leaf dies. The brick-red spores mature and turn black as they mature, causing the lesions and leaf surface to appear black.

Management Strategies: Since common rust does not survive in Ontario, cultural practices such as reduced tillage and crop rotation do not influence disease development. Commercial corn hybrids have good tolerance. However, many seed corn inbreds, sweet corn and specialty corn hybrids are very susceptible to the disease. Foliar fungicides in field corn are not usually needed but can be economical in highly susceptible corn hybrids, seed corn inbreds or specialty corn hybrids.

Plate 113. Common rust symptoms range from yellow flecks to red pustules.

Photo showing common rust symptoms range from yellow flecks to red pustules.

Common Smut (Ustilago zeae)

Head Smut (Sporisorium holci-sorghi)

Incidence: Two corn smut diseases, common and head smut, occur in Ontario. Common smut occurs most frequently. In severe cases, over 25% of the plants in some fields can have smut galls.

Appearance: Common smut overwinters in the soil and in corn residue. The spores are spread by wind and rain through splashing. All above-ground plant tissue is susceptible, but infection occurs most often in areas of actively growing tissue. Common smut incidence increases in fields where the plants have been wounded by hail, frost, drought, mechanical injury, detasselling, herbicide injury, insects or sandblasting. High levels of nitrogen and manure promote this disease.

Greyish smut galls up to 10 cm (4 in.) in diameter develop on the stalks, ears and tassels, while smaller galls often appear on the leaves (See Plate 114). The galls initially have a white membrane cover that eventually breaks and releases dark-brown or black powdery spores. On the leaves, galls develop into a hard, dry growth. Smut galls can replace kernels. Unlike common smut, head smut occurs only on the ears and tassels (See Plate 115).

Disease Cycle: Spores released from the galls are well adapted for Ontario conditions. They survive in soil and crop residues for many years. In the spring, these spores germinate to produce new spores that will infect the rapidly growing areas or injured areas of the plant. The resulting galls will release spores that infect other plants. Disease development is favoured by rain showers, high humidity and warm temperatures in conjunction with physical plant injury.

Management Strategies: Most commercial corn hybrids have sufficient resistance to smut to prevent serious outbreaks. However, some smut is present in most fields and is still very problematic in many seed corn fields. Risk is reduced by minimizing mechanical and herbicide injury, while maintaining a balanced fertility program. Rotation and cultivation have little effect on the disease, since spores can survive for a long time in the soil.

Plate 114. Common smut incidence increases where plants have been wounded.

Photo showing common smut incidence increases where plants have been wounded.

Plate 115. Head smut can occur on the ears or tassels of corn.

Photo showing how head smut can occur on the ears or tassels of corn.

Stalk Rots

Incidence: Fungi cause corn stalk rots. The amount of damage they cause increases when the crop is under stress, such as prolonged wet or dry conditions, cool temperatures, cloudy weather, leaf diseases (such as rust and Stewart's wilt), leaf and ear damage from hail, birds and frost, incomplete pollination, unbalanced fertility, insect damage (e.g., European corn borer), high plant populations, hybrid susceptibility and poor soil conditions.

The distribution and prevalence of stalk and ear rot diseases vary from year to year. However, the diseases are present in most years even though it may be at low levels. The majority of stalk rot damage in Ontario is caused by three fungi, namely Anthracnose, Gibberella and Fusarium. However, Diplodia and Pythium have also been observed in Ontario.

Impact of Stalk Rot: Although these fungi cause different symptoms, their ultimate effect on the corn plant is the same. They reduce grain fill and stalk integrity and accelerate senescence. Stalk rot fungi affect the nutrient movement of the corn plant in three main ways:

  • Sugars produced through photosynthesis and carbohydrates in the root and stalk are diverted to the fungus and not to the ear. These nutrients allow stalk rot fungi to grow and flourish.
  • There is a reduction in stalk integrity. To meet the nutrient needs of both the developing ear and the stalk rot organisms, the corn plant will begin to cannibalize itself by moving soluble carbohydrates from the root and stalk. Problems arise when the plant is unable to meet the nutrient requirements of the developing ear. The result is a weaker stalk (prone to lodging) and less resistance to stalk rot fungi.
  • Finally, the infection and colonization process inhibits or blocks many of the pathways that the plant would ordinarily use to move nutrients. Yield losses (generally 10%-20%) arise from poorly filled ears and harvest losses from lodging.

General Stalk Rot Management Strategies: Management begins by reducing crop stresses through:

  • planting hybrids that have good resistance or tolerance to leaf diseases and stalk rots
  • managing insects such as European corn borer
  • good weed control
  • appropriate plant populations
  • a balanced N and K fertility program
  • crop rotation
  • tillage

Scouting for Stalk Rots

Two methods are used to scout for stalk rots.

The Push Test
1. Randomly select 20 plants from five different areas of the field, for a total of 100 plants.
2. As the name implies, push the top portion of the plant 15 to 20 cm (6 to 8 in.) from the vertical.
3. Note whether the plant lodged or not.

The Pinch or Squeeze Test
1. Randomly select 100 plants in the field (20 plants from five different locations).
2. Remove lower leaves and pinch or squeeze the stalk above the brace roots.
3. Record the number of rotted stalks.

If 10%-15% of plants lodged, or are rotted, harvest the crop early. The extra drying charges that may result will be covered by increased harvest efficiencies with less corn left in the field.

Anthracnose Stalk Rot (Colletotrichum graminicola)

Anthracnose stalk rot is the easiest to identify. It appears as large, dark brown-to-black shiny areas or streaks on the outer stalk rind (See Plate 116). These shiny or discoloured areas are often found at the base of the stalk. Cutting the stalk lengthwise will reveal a discoloured and rotted pith. Another symptom associated with this disease is "top dieback." Typically, top dieback symptoms begin in late August or early September, as corn plants begin to wilt and die from the top down. This resembles premature death due to frost. Premature death occurs above the ear, with the plant tissue below the ear remaining green. Examination of the stalk in these dead areas will show the same shiny black areas that are found at the stalk base. Plants with top dieback symptoms correspond to areas of the field that had late-season stresses.

Disease Cycle: The fungus that causes anthracnose stalk rot survives in the previous corn crop residues and therefore is most often a problem in second-year corn. Warm, wet and humid weather favours anthracnose development.

Plate 116. Anthracnose stalk rot. Internal corn stalk tissue is often discoloured (black), and the pith is rotted.

Photo showing anthracnose stalk rot. Internal corn stalk tissue is often discoloured (black), and the pith is rotted.

Gibberella Stalk Rot (Fusarium graminearum/Gibberella zeae)

Fusarium Stalk Rot (Fusarium verticilloides)

Diplodia Stalk Rot (Diplodia maydis)

These fungi cause general stalk rot symptoms, including wilting and death. Affected leaves turn a grey-green colour that resembles frost damage. All three rots cause a dark external lesion or spots at the lower nodes. Diplodia stalk rot produces small black spots (pycnidia) that are embedded in the stalk rind. These spots are hard to remove. In contrast, gibberella stalk rot also produces small, round, black spots at the lower node, but these spots can be easily scraped from the stalk surface (See Plate 117). The pith is shredded and has a pink to red colour. Fusarium stalk rot symptoms appear as light-brown to black lesions near the nodes. The internal stalk symptom of fusarium stalk rot is a salmon-pink fungal growth in the pith.

Plate 117. Gibberella stalk rot. Inside of stalk is shredded and characteristically red.

Photo showing gibberella stalk rot. Inside of stalk is shredded and characteristically red.

Pythium Stalk Rot (Pythium aphanidermatum)

Appearance and Disease Cycle:
Pythium stalk rot gives the same general above-ground symptoms that are associated with the other stalk rot organisms. Pythium is in a unique group of fungi (that also includes Phytophthora) called "oomycetes" or "water moulds" because of their preference for wet conditions. The unique characteristic feature of this group of fungi is the production of mobile spores that can move through the water film in saturated soils. These spores (infection stage) are able to physically move to the corn plant roots and, once inside, cause disease. Unlike other stalk rots that produce overwintering structures (black dots) or mould, corn plants infected with Pythium have no visible signs of fungal growth at the base of the plant. When the plant is cut lengthwise through the stalk base and roots, Pythium-infected tissue will appear wet and soggy and will disintegrate ("a wet rot") at the root base.

Ear Rots or Moulds

Ear Rot Management Strategies: White moulded corn may or may not contain toxins, but pink or purple moulded corn will likely be contaminated. Any of the Fusarium or Gibberella rots can establish after pollination in wounds created by insects or birds. Warm rainy weather or long dews any time after pollination may lead to ear rots in these wounded cobs.

The green (Penicillium) and black (Cladosporium or Alternaria) moulds do not normally pose a problem. However, when found in great abundance, they may put livestock off feed. Development of ear rots is stopped when corn is dried or ensiled, but the level of harmful toxins already present will remain unchanged. The fungi will continue to produce toxin until corn moisture drops below 20%. More information on Fusarium mycotoxicoses can be found on the OMAFRA website at www.ontario.ca/crops.

Preventing ear rots and mould is difficult since weather conditions are critical to disease development. Although some tolerant hybrids are available, none have complete resistance. Crop rotation can reduce the incidence of diplodia ear rot. Cultural practices have been shown to have limited success in preventing ear and kernel rots. Minimize these diseases through timely harvest and proper drying and storage.

Harvest fields where 10% of the ears have some ear rot quickly to limit further disease development and potential mycotoxins production.

When ear rot is present, the following harvest, storage and feeding precautions are advisable:

  • Harvest as early as possible.
  • If bird damage is evident, harvest outside damaged rows separately. Keep and handle the grain from these rows separately.
  • Adjust harvest equipment to minimize damage to corn. Clean corn thoroughly to remove pieces of cob, small kernels and red dog.
  • Cool the grain after drying.
  • Clean bins before storing new grain.
  • Check stored grain often for temperature, wet spots, insects and mould growth.
  • Control storage insects.
  • Exercise caution in feeding mouldy corn to livestock, especially to hogs. Pink or reddish moulds are particularly harmful. Test suspect samples for toxins.

See Appendix D, Feed- Mould- and Mycotoxin-Testing Laboratories, for a list of laboratories.

Fusarium Ear Rot (Fusarium verticilloides)

Fusarium ear rot is common in Ontario. Unlike gibberella ear rot, kernels infected with fusarium ear rot will be scattered around the cob among healthy-looking kernels or on kernels that have been damaged (by corn borer or bird feeding). Silks are susceptible to infection during the first 5 days after initiation.

Appearance: Fusarium infection produces a white-to-pink or salmon-coloured mould (See Plate 118). A "white streaking" or "star-bursting" can be seen on the infected kernel surface. Although many Fusarium species may be responsible for these symptoms, of concern in Ontario is Fusarium verticilloides.

Disease Cycle: Fusarium survives in corn debris. The significance of this fungus is that it produces a toxin called fumonisin that has been shown to cause cancer in humans. The environmental conditions that favour disease development are warm, wet weather, 2-3 weeks after silking.

Plate 118. Fusarium ear rot. Note the white fungal growth and the "starbursting" on the kernels.

Photo showing fusarium ear rot. Note the white fungal growth and the "starbursting" on the kernels.

Gibberella Ear Rot (Fusarium graminearum, Gibberella zeae)

The most common and important ear mould in Ontario is Gibberella zeae, which is the sexual reproductive stage of Fusarium graminearum. This fungus not only infects corn but also small grains such as wheat. Many plant pathologists believe that in years with a high occurrence of fusarium head blight in wheat, the potential exists for increased gibberella ear rot in corn.

Appearance: Although, the fungus can produce a white mould that makes it difficult to distinguish from fusarium ear rot, the two can be distinguished easily when Gibberella produces its characteristic red or dark-pink (purple) mould (See Plate 119).

Disease Cycle: Infection begins through the silk channel. Therefore, in most cases, it starts at the ear tip and works its way down the ear. In severe cases, most of the ear may be covered with mould growth. Corn silks are most susceptible 2-10 days after initiation. Cool and wet weather during this period is ideal for infection.

Caution: In addition to its economic importance due to yield loss, gibberella ear rot is also important because Gibberella zeae and Fusarium graminearum produce two very important mycotoxins - deoxynivalenol (vomitoxin or DON) and zearalenone. These mycotoxins are especially important to swine and other livestock producers since they can have a detrimental effect on the animals. Feed containing low levels of vomitoxin (1 ppm) can result in poor weight gain and feed refusal in swine. Zearalenone is an estrogen and causes reproductive problems, such as infertility and abortion in livestock, especially swine. Test feed grain that originates in a field with 5% or more gibberella ear rot for these toxins. See Appendix D, Feed- Mould- and Mycotoxin-Testing Laboratories.

Plate 119. Gibberella ear rot infection usually occurs from the tip down. Note the pink-to-red colour

Photo showing gibberella ear rot infection usually occurs from the tip down. Note the pink-to-red colour

Diplodia Ear Rot (Diplodia maydis)

Incidence: Of the three primary ear rots that occur in Ontario, diplodia ear rot is the least common. Diplodia ear rot is caused by Diplodia maydis and is favoured by cool, wet conditions through grain fill.

Appearance: The characteristic ear symptom is a white mould that begins at the base of the ear and eventually covers and rots the entire ear. Mould growth can also occur on the outer husk, which has small black bumps embedded in the mould. These reproductive structures are where new spores are produced. Diplodia ear rot does not produce any known toxins.

Disease Cycle: Diplodia ear rot overwinters in corn debris left on the soil surface from the previous crop. Spores that are produced during wet weather can infect silks and husks or enter through tissue damaged by birds or insects. Disease development is favoured when cool wet weather occurs during the first 21 days after silking.

For more information:
Toll Free: 1-877-424-1300
E-mail: ag.info.omafra@ontario.ca
Author: OMAFRA Staff
Creation Date: 13 May 2009
Last Reviewed: 13 May 2009