Aspergillis ear rot and Aflatoxin in Corn as well as other ear rots that cause mycotoxins

Aspergillus ear rot, as well as other ear rots were an issue in some areas of Illinois in 2011. Some areas experienced hot and dry weather or STRESS after silking, which are favorable conditions for Aspergillus ear rot as well as Fusarium ear rot.  Other areas, which were lucky enough to get some rain after flowering, may have had a risk of Diplodia ear rot, especially if it was a problem in previous years. In most cases, injury by birds or insects (as seen in the pictures below), allow entry of ear rot fungal pathogens.  Often times, fields that are corn on corn and have reduced tillage allow for the build up of and survival of the ear rot fungi, where it awaits for the right conditions to flourish on a injured or stressed corn crop.

Picture taken by Angela Peltier, U of I Extension Commercial Crop Educator.  Kernals infected with Aspergillus (greenish fungus) as well as Diplodia (white fungus) and possibly Fusarium (starburst pattern on kernal) are present.

Picture taken by Angela Peltier, U of I Extension Commercial Crop Educator.  Kernals infected with Aspergillus (greenish fungus) as well as Diplodia (white fungus) and possibly Fusarium (starburst pattern on kernal) are present.

Picture taken by Angela Peltier, U of I Extension Commercial Crop Educator.  Kernals infected with Aspergillus are present.

In response to this outbreak, Angela Peltier authored the following article:  Corn ear molds make an appearance in western Illinois


 Aspergillus flavus and Aspergillus parasiticus, the fungal pathogens that causes Aspergillus ear rot, produces a very, dangerous mycotoxin that is considered to be a  major carcinogen!  The FDA regulates the allowable amount of this toxin in grain for food or feed and less than 20 ppb (parts per billion) is the allowable amount of the toxin in grain intended for human consumption and immature animals. At the U of I Plant Clinic, one of the diagnostic tests that we use to detect the fungal growth of Aspergillus flavus, is put a black light over the corn ear in a dark room.  The black light will cause corn kernals infected with Aspergillus flavus to glow in the dark.

 

 Some other diagnostic techniques used to diagnose ear rots involve "plating" infected corn kernels on agar to allow the fungal ear rot pathogens to grow.  Identification can be made by spore and fungus morphology.

Aspergillus sp. are not the only fungal ear rot pathogens to produce mycotoxins in corn. For more information on Aspergillus ear rot, see the following link: http://cropdisease.cropsci.illinois.edu/corn/Aspergillusearrot.html

Other ear rots that can cause mycotoxins:

• Fusarium ear rot, often characterized by a starburst pattern on corn kernals, caused by Fusarium moniliforme, F. proliferatum, and F. subglutinans can also produce a mycotoxin called Fumonisin. For more information, see the following link: http://cropdisease.cropsci.illinois.edu/corn/Fusariumkernelandearrot.html
• Gibberella ear rot, often characterized by a reddish mold first on the ear tip, then spreads downward, caused by Gibberella zeae (=Fusarium graminearum) also produces multiple mycotoxins.  For more information, see the following link: http://cropdisease.cropsci.illinois.edu/corn/GibberellaRedearrot.html

In Illinois, to get an accurate test for the concentration of mycotoxins in grain, you can send samples to the Illinois Department of Agriculture CENTRALIA ANIMAL DISEASE LABORATORY

Please call them for further instructions and information.

For more information, contact:
Illinois Department of Agriculture
Centralia Animal Disease Laboratory
9732 Shattuc Road
Centralia, IL 62801-5858
618.532.6701
TDD: 217.524.6858
FAX: 618.532.1195

Need some information on ear rots and grain storage?
Check out this link to another 2011 article written by Dr. Suzanne Bissonnette:   Look at Your Ears-Crop, Stock and Ledger

Seed collecting, Treatments, and Storage

This weeks University of Illinois Plant Clinic blog was brought to you by:
Mike Kwiatek, University of Illinois Horticulture Student and Plant Clinic Student Worker

If you haven’t started collecting seeds yet, it may not be too late. Seed collecting is a fun pastime that provides you with plants for the following years to come, lets you share favorite varieties with friends, and saves you some money for the next season. Many home gardeners collect seed and some even participate in seed exchanges, which allow gardeners to meet and share some of their collected seeds with other gardeners. If you’re interested in participating in a seed exchange, look to community newsletters, local co-ops, and organic food stores; as they often play host to these events.

 When collecting seed, consider choosing from plants that looked their best this year.  Try to avoid collecting seeds from plants that are known to be hybrids.  Lastly, be aware, that for many plants, the plants that will grow from your collected seeds, may not look exactly like the plants that grew the previous year.

There are two main types of seeds: dry seeds and those that come from moist fruit. Vegetables such as beans and ornamental plants such as cosmos or zinnias will produce dry seeds, which can be treated for disease, dried, and stored. Seed should always be harvested when dry.  Those seeds that come from moist fruit, can be scooped out once the fruit has fully ripened, washed in a strainer, or sieved to remove any mucilage; then can be treated, dried, and stored. If dealing with squash or pumpkin seeds, a strainer alone will likely not be sufficient to remove the stringy mass that surrounds seeds.

After the collecting seed, it is very important to treat the seeds in order to reduce seedling infection or death caused by bacterial diseases like Xanthomonas and fungal diseases such as Alternaria. Seed treatments will vary by plant species. Plants like eggplant, tomato, pepper, carrot, spinach, lettuce, celery, cabbage, turnips, radishes, broccoli, and related vegetables should be treated with hot water. (See the following link for more details http://en.wikipedia.org/wiki/Cruciferous_vegetables).  Vegetables like squash, gourds, pumpkins, watermelons, asparagus, as well as flowers like zinnias, should undergo a chlorine treatment.

Hot water treatment

Place washed seed in a cotton bag, nylon bag, or wrap it in cheesecloth.  Warm the seeds for about 10 minutes in a 100F (37C) degree water.  Drop the bag into water that is 118-125 degrees Fahrenheit (47-51C) for 15-30 minutes, depending on treatment (See the following link for more details: 

http://ohioline.osu.edu/hyg-fact/3000/pdf/3085.pdf ) .  Place the bags of seed in cool water for about 5 minutes after the set period of time and then, place them on a screen or newspaper to dry.

Bleach Treatment

Make a solution of 20% bleach, 80% water, and surfactant (dish soap will be adequate). A simple way to do this is by mixing 1/4 cup bleach to 1 cup water, and then add a drop or two of dish soap to this mixture. Place the seeds in this solution for one minute and mix. Then pour this mixture through a strainer and rinse the seeds well with water. Place the seeds on newspaper or a screen and allow them to dry.

Storage

When your seeds have completely dried, place them in paper bags or envelopes, label them properly, and store them in a cool, dry place. Adding a piece of paper towel or a napkin to the envelope or bag will help ensure dryness. You may choose to store the bags in the bottom drawer of your refrigerator. If you do this, you may wish to place all envelopes or paper bags in a plastic bag with 1-2 pieces of paper towel. This will ensure that if any spills occur, your seeds will be safe.

Another helpful web Source:

http://web.extension.illinois.edu/cook/downloads/8584.pdf

Related links:

http://www.seedsavers.org/

http://www.heirloomseedswap.com/

A Trip to Muir Woods and the Effect of Phytophthora ramorum (Sudden Oak Death)

Thanks to the National Plant Diagnostic Network (NPDN) meeting, I was able to make my first trip to California.  In addition to some awesome, diagnostic workshops and meetings, we were able to choose one of four field trips/tours.  It was a very, hard decision, but I chose: Phytophthora ramorum-Redwoods Tour-
Marin County.

Basically, on the this tour, we were taken to the site where Sudden Oak Death (P. ramorum) was first discovered in the United States.

"Since the early 1990s, oaks and tanoaks have been dying in the coastal counties of California. Since then, other types of plants have been found to be infected or associated with this disease, referred to as Sudden Oak Death (SOD), ramorum leaf blight or ramorum dieback. Phytophthora ramorum is the pathogen that causes these diseases. Sudden Oak Death was first reported in 1995 in Mill Valley (Marin County) on tanoak. Since that time, the pathogen has been confirmed on various native hosts in fourteen coastal California counties (Marin, Santa Cruz, Sonoma, Napa, San Mateo, Monterey, Santa Clara, Mendocino, Solano, Alameda, Contra Costa, Humboldt, Lake, and San Francisco), and in Curry County, Oregon. Through ongoing surveys, APHIS-PPQ continues to define the extent of the pathogen’s distribution in the US and limit its artificial spread beyond infected areas through quarantine and a public education program." -USDA-APHIS

Case Study: Sudden Oak Death /ramorum blight caused by Phytophthora ramorum

This tour included a visit to Muir Woods!

There is an abundance of information and stories that could come from Muir Woods, but the one I would like to share is that of the trees located there.  The large live trees located at Muir Woods mostly consist of coastal redwoods; however, there are some scattered Douglas Firs there.  The tallest coastal redwood stands 258 feet tall ("A six foot person stacked 45 times").  The average coastal redwood is 600 to 800 years old and the oldest is 1200 years old. -Now, that is old!  In the understory of these magnificent trees are tanoaks.

Unfortunately, many of the tanoaks in Muir Woods are infected with Phytophthora ramorum or SOD (Sudden Oak Death). Most of the trees are dying. To a plant pathologist the story may end here.  We took many pictures, so that we would have record of the symptoms of tragedy, in the hope that we can catch it before it enters our State, like Illinois.  What I did not realize, is how much this disease is affecting the ecosystem of Muir woods.

Note the dark, cankers on the tanoaks, which are symptoms of Sudden Oak Death caused the the fungal pathogen, Phytophthora ramorum.   For more information, go to:  http://www.suddenoakdeath.org/

If the tanoaks die-then there are no acorns...
If there are no acorns, then there will be no food for the forest rats.....
If the forest rats have no food, then they could possibly die, and then the endangered spotted owls will have no food....

And so, there are many ecological studies taking place to study the many ecosystems, like this one at Muir Woods.

In most of the pictures, the browning foliage belongs to dying tanoaks in Muir Woods.

I wish I could end my story here, but the horror of it is, this fungal disease pathogen,  P. ramorum, not only affects oaks, but also has been found to infect over 200 plant hosts and counting....
http://www.aphis.usda.gov/plant_health/plant_pest_info/pram/downloads/pdf_files/usdaprlist.pdf 

Here is how you can prevent the spread of this pathogen to your "neck of the woods": http://www.aphis.usda.gov/publications/plant_health/content/printable_version/SBR_StopTheSpread.pdf

Greenhouse Poinsettias with Pythium root rot

When these plants were examined, the roots appeared to be rotted.  When the root tissue was examined under the microscope, there were oospores present.  This is a sign of Pythium root rot.  The visual symptoms of the poinsettia roots also appeared to be those associated with Pythium root rot at various stages of infection.

Pythium can be introduced to plants by infested crop debris in the greenhouse, transplanting infected cuttings, or recycling potting mix or containers.  In addition, in some cases, this pathogen can be introduced by contaminated irrigation water.  The problem could also be that the potting medium is not draining properly.  Remember, environmental conditions can cause soils not to dry out properly. 

This disease is favored by high soil temperatures.  Another thing that seems to favor this disease is high soluble salts in the root substrate.  I also read where excess fertilization can promote the growth of Pythium.

Good sanitation is the best defense against this disease.  Make sure that the potting mix is sterile and disinfect work surfaces.  Unfortunately, once Pythium infection takes place, control of the pathogen can be very difficult.  Disease development can be reduced by lowering pH to 5.5 or below; however, this can cause nutrient disorders to develop in plants.

There are fungicides that can be used to help manage this disease.  In Illinois, the Commercial Landscape and Turfgrass Pest Management Handbook lists fungicides that can be used for root rot. You can also refer to the report on disease to find out which fungicides are used against Pythium: 
http://ipm.illinois.edu/diseases/rpds/615.pdf

A preventative fungicide application may be necessary the following year, in addition to improved sanitation.


Other very, helpful links:
http://ncsupdicblog.blogspot.com/2011_01_01_archive.html
http://www.negreenhouseupdate.info/index.php/diseases/296-poinsettia-pythium-root-rot
http://www.gpnmag.com/Don%E2%80%99t-Expect-Pythium-Root-Rot-to-Always-Act-the-Same-article2958
http://www.chasehorticulturalresearch.com/pages/ChaseArticles/45PythiumRootRotonPoinsettias.pdf

Downy Mildew on Impatiens in Illinois

In October, 2011, there were several reports of downy mildew on garden impatiens (Impatiens walleriana).  This disease was first reported in the U.S. in 1942, but recently several sources say this disease has been confirmed on impatiens in coastal southern California, northeastern Illinois, northern Indiana, Cape Cod in Massachusetts, Long Island and upstate New York. If you think that you experienced this disease in your garden, there are no worries of it infecting other plants.  However, it is very, important that you remove and destroy infected plants.  There is still a chance that this disease pathogen could overwinter and infect impatiens the following year.  I have read that New Guinea impatiens have resistance to this disease and can be a considered a choice that can be planted in an infected area.  End of the season fungicides are not recommended.  Watch for this disease next year! Keep a careful watch on impatiens and catch this disease in the early stages and remove infected plants immediately!  Fungicides can provide some protection, but will not protect impatiens for the entire season.


Several weeks ago, we received an email from from Diane Anderson saying that this downy mildew had infected most of the impatiens at the University of Illinois Trial Gardens.  In the next several pictures you can see just how devastating downy mildew can be, if impatiens have been infected.

Symptoms of downy mildew of impatiens have been described as: "yellowish or pale-green foliage, downward curled leaves, leaf distortion, white to light-gray fuzz on leaf undersides, new leaves that are small or discolored (yellow or pale green), flowers buds that fail to form and stunted growth".

 The plant pathogen that causes downy mildew is an oomycete and is spreads by oospores as seen below.

For more information on Down mildew of impatiens, you can check out the following websites:

Downy Mildew causing problems on impatiens in the Landscape

Check impatiens for downy mildew

It's Back

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