Any Reports of Areas or Entire Corn Fields (V5-V7) that are Completely Purple?

Well, a month ago, we were received reports of white in corn fields.  Some Southern Illinois growers were "spotting" white on leaves (Holcus spot), while others were trying to solve the mystery of white corn plants in Central Illinois.  For more on this you can refer to my May 19th blog: Everyone is Talking about White Corn

Now, Northern Illinois (Ottawa and Southeast of Mendota) must need " have a turn" to have a corn, color issue, but this time, their color is purple.  Today, I was asked if there had been any reports of areas or entire corn fields (V5-V7) that were purple.  I had no additional information, nor pictures, but I asked some of the U of I Crop Science Extension Specialists if they had heard of any reports of "purple corn fields" and I asked what, in their opinion, could cause a large area of corn, growing in moderate to high temperatures, beyond a growth stage of V5, to become purple?

Dr. Mike Gray, U of I Crop Sciences Extension Entomologist:

"I have not heard of any reports.  Because of the clumped distribution of insects within a field -- it is unlikely that an entire field showing purple discoloration is insect related. However, some insect feeding (e.g. grape colaspis and/or white grubs) that prune root hairs on seedling corn plants can lead to purple discoloration on plants. The mechanism -- poorer absorption of nutrients (especially phosphorus) by the root systems."

Corn Insects - A Diagnostic Guide

Dr. Fabian Fernandez, U of I  Crop Sciences Soil Fertility and Plant Nutrition Extension Specialist

"I have not had any reports. Would it be possible to get a picture of the field and a close up on the plant? Purpling of corn leaves is typical for phosphorus deficiency, but often the problem is observed with younger plants when it’s very wet or cool. I suspect if they are seeing this at V5-7, and is due to phosphorus, the field is either very deficient in phosphorus, or something terribly wrong is going on with the root system that is not allowing plants to take up phosphorus. Both situations seem very unlikely to me because 1)it is not very common to see entire fields completely phosphorus-deficient and 2) if the problem is related to the roots there are other nutrients that would show deficiencies too, making for very sorry-looking plants. Again, if you can get a couple of pictures, that would be beneficial."

Nutrient Deficiency Symptoms in Corn (Identification) 

Dr. Aaron Hager, U of I Crop Sciences Weed Science Extension Specialist

I was lucky enough to have Dr. Hager looking at 7 crop samples, with potential herbicide injury, today at the U of I Plant Clinic.  In passing, in the hallway, I quickly asked him his thoughts on purple corn.  He said that some herbicides can cause corn to turn purple.  However, it is very, unlikely for an entire field to show symptoms for very, long.  For example, glyphosate may cause purple leaves in corn, but it will not stay purple, in time, it could become "smoked".   

Purple Corn May Indicate Herbicide Injury

As noted by Dr. Nafziger, in his comments below, other herbicides can cause injury by limiting root growth, but they just are not used that much anymore.

Dr. Emerson Nafziger, U of I Crop Science Agronomic Extension

"The “proximate cause” of purple corn is sugar accumulation. This can arise from P deficiency, since P is needed for sugar transport. In young plants, though, it usually results from inability of the root system to grow out into the soil around the base of the plant. Sugars accumulate when roots can’t grow, and the anthocyanin pigment then forms.

We’ve heard of some of this in areas where the surface soil is dry this year (I wrote about it in this week’s Bulletin) -The Bulletin: What Crops Need Now If it’s only in parts of the field, it will often be in places where the surface soil dried out before nodal roots could penetrate. Sometimes it can be in heavier soils as well, where the sidewall that forms during planting dries to form a barrier.

So I’d suggest looking first at root growth. In some cases the seminal roots will have grown more than normal, but at some point they just can’t support the plant anymore. If the field recently had rain, the problem will likely go away very quickly. If the crop is still purple several days after rainfall, then other possible causes need to be looked at. But since we don’t use many herbicides that limit root growth anymore, there aren’t that many causes to consider."

The Agronomist that is dealing with the issue of corn turning purple made the following comment after receiving the above information and consulting further with  Dr. Fabian Fernandez:

"We have been extremely wet, and I wonder if this problem is related to saturated soils. I am beginning to think so. Dr Fernandez also mentions extremely low P levels. In one area that I see the purpling, this is a possibility, in another, it is a field that is extremely HIGH in P."

Anthracnose Leaf Blight on Corn: Crop Disease of the Week at the U of I Plant Clinic!!

The sample of the week was Anthracnose leaf blight of corn!  The U of I Plant Clinic confirmed this fungal leaf blight on several corn samples.  As you can see in the pictures below, this disease is being observed at various corn growth stages. The fungus, Colletotrichum graminicola that causes Anthracnose requires wet and cloudy weather, which is just what the weatherman has ordered for the past several weeks.

Anthracnose leaf symptoms will vary among corn hybrids.  The lower leaves are usually affected first because this disease is lurking in corn residue, which means corn on corn is more at risk.  However, RESISTANCE is the key with this disease.  If you are seeing this in your field, I would check your hybrid's susceptibility to Anthracnose.  No need to worry too much at this time, if you are seeing this disease in your fields now.  Research has shown that this disease should not extend to far up the plant beyond the V6 growth stage.  Also, just because you are seeing Anthracnose leaf blight now, does not necessarily mean your corn has been sentenced to a stalk rot death.  So, fungicides are not warranted at this time.  For more information on Fungicides at Early Growth Stages, go to this link: http://bulletin.ipm.illinois.edu/article.php?id=1284

So, I think the underlying question on some of our client's mind was if this disease was killing corn seedlings, because many of our clients included a blighted corn seedling with their sample...just like the one below

Each of these blighted corn seedlings (like the one above) had roots that consisted of oospores, which tells me that our friend (or enemy), Pythium made it's debut on these roots and caused seedling blight or even death on many of the corn seedlings that were examined at the U of I Plant Clinic.  So, Anthracnose was not the culprit of the demise of corn seedlings.  In other cases, corn death occurred because corn roots were under water for a long enough period that caused root tissue to became oxygen deprived. 

Some of the older corn plants that I examined did show signs Pythium on primary roots, but I am very happy to report that new, healthy roots had grown and the corn was quickly "growing out" of the root rot, thanks to the recent onset of better growing conditions!

For more information on Anthracnose leaf blight, you can check out the following links:

http://bulletin.ipm.illinois.edu/article.php?id=1337
http://bulletin.ipm.illinois.edu/pastpest/articles/200211m.html

Organic Pesticide Toxicity Problems

The U of I Plant Clinic recently received 2 tomato samples with injury from organic fungicide and insecticides. 

The first sample was from a Commercial organic grower with a hoop house operation.  A copper product (not specified), which is often used an organic fungicide, was applied.  If the copper product is applied improperly or in cool, wet conditions (the copper product is not allowed to dry) plant injury can result.  Here is a link for more information:
http://www.oardc.ohio-state.edu/fruitpathology/organic/grape/organic.html

In this picture, you can see the plant injury that resulted from the application of the copper product.

The next sample was submitted from a home grower.  When, his sample was found to be free of disease and had no signs of insect injury, I gave him a call to get more information.  I told him that his tomato leaves had symptoms (interveinal necrosis) that looked very similar to that of chemical phytotoxity; however he had not indicated that he had used any chemicals on his plants, on the information provided with the sample.  But, on the phone he told me that he had "thew down" an organic pesticide on the soil that consisted of Eugenol and Thyme oils.  This could also cause injury to plants if not applied correctly.  Only the lower leaves of his tomato plant were affected, which led me to believe that the injury had come from the application of the organic pesticide.

My purpose of this blog, is to bring awareness when applying pesticides. No matter if it is an organic or conventional pesticide, you still should always read the label and follow use directions.  Often times, pesticides that are considered organic have a greater potential to cause plant injury.  Luckily, if plants are not severely injured, new growth will come, and the plant will "grow-out" of these symptoms.

Have You Ever Wondered How We Culture and Isolate for Oak Wilt?

This week the students at the U of I Plant Clinic learned how to culture and isolate the fungal pathogen, Ceratocystis fagacearum, that causes oak wilt in oak trees.

When someone suspects that their oak tree is dying from oak wilt, they can send a sample to the U of I Plant Clinic. We usually suggest that they sample from areas of the trees that are showing symptoms typical of oak wilt as well as wood that may show streaking or darkening of vascular tissue (see pictures below). We would like the sample to consist of several 1 to 2 foot long branches with at least the diameter the size of a thumb. 

Some oak leaves showing a symptoms of oak wilt.

Dark streaking of the wood caused by the oak wilt fungal pathogen.

Here students at the U of I Plant Clinic:
1.  Take notes on the condition of the oak sample.
2.  Label agar plates with sample number, date, type of agar, and OW (Oak Wilt)
3.  The bark is peeled back from the end of the branch, so that the wood is exposed under a sterile hood.
4.  They flame their knife and notch the wood into tiny wood chips, which remain attached to the branch.
5.  Then, they flame their tweezers and pick off wood chips.
6.  These wood chips are placed, very quickly, (to avoid any unwanted contamination) into PDA -Potato Dextrose Agar, plates under a sterile hood.

The agar plates are stored on a shelf in our lab, with their paperwork.  They are kept there for up to 7 to 10 days to allow time for the fungal isolates to grow.

If we were successful at isolation of the oak wilt fungus, the above pictures show what it would look like growing in our PDA culture plates.

Lastly, we take clear tape and place it on top of the fungus to "catch spores".  This clear tape is placed onto a microscope slide with a drop of water on it.  If the oak tree is infected with oak wilt (oak wilt positive), we will see the chains of spores that is seen in the picture above.  If none of these spores can be found, the oak sample will be considered "oak wilt negative". (Picture above taken by Travis Cleveland)

For more information on oak wilt, you can refer to: http://ipm.illinois.edu/diseases/rpds/618.pdf

Everyone is Talking about Corn that has Turned White......

There have been several reports of corn turning white in different parts of Illinois. 

One of those reports from Southern Illinois (not yet confirmed at the U of I Plant Clinic)  refers to the possibility of Holcus spot in corn.  Holcus spot is caused by a bacterial pathogen and can be easily confused with paraquat (herbicide) injury.  Holcus spot is difficult to diagnose because the bacteria may not be readily found within the lesion.  Holcus spot has a wide host range and can infect foxtail millet, pearl millet, Sudan grass, broom corn, Johnson grass, wheat, and sorghum.  This disease is not a major problem in corn, but it is not commonly found.  For additional information, you can go to:   http://cropdisease.cropsci.illinois.edu/corn/holcusspot.html

These are pictures of suspect Holcus spot or paraquat injury from another sample that was previously submitted to the U of I Plant Clinic:

Now, the next issue that is causing "quite the buzz" among agronomists and consultants is the issue of corn turning white in the field.  I was lucky enough to find a case of this and I did take pictures.  I am not sure what may be causing this and I am unable to investigate further on this particular case, as I do not have any information on what chemicals (herbicide or insecticide) that have been applied to or near this corn field.  This picture was taken in a field south of I-72.  There does not seem to be a pattern.  As you can see in the pictures below, these plants were found in areas of the field that had been waterlogged.

 

Dr. Aaron Hager,

Associate Professor of Weed Science, has had a few reports of this, but is not sure there has been anything consistent in each instance.  Some wonder about herbicide injury (which is possible), although there have been reports of this occurring in fields where no herbicide as yet been applied.  He suspects the weather/wet soils might also be contributing to this.

You are always welcome to submit a sample to the U of I Plant Clinic, where we and Dr. Hager will fully examine the white, corn plants.  We will also need a very extensive history of the field, which includes all chemicals applied to the field.

So, You Want to Grow Grapes..........

I have recently had some grape questions. Luckily, Dr. Elizabeth Wahle, Horticulture Specialist has some advice, for those wanting to start growing grapes. 

"All grapes have numerous disease and insect problems and there should be a commitment to a spray program. If you plan on managing the pruning and pest management for good fruit quality, then grapes would be an attractive addition to any home.  If not, it can turn ugly fast!"  

http://ohioline.osu.edu/b919/index.html (Midwest Grape Production Guide)

 Here are a few grape diseases that affect fruit quality:

Powdery Mildew of Grape (Picture by NC Jones)

Grape Black Rot and Anthracnose

Just wanted to let you know about the great, commercial and home grape production as well as other fruit resources available, thanks to Dr. Elizabeth Wahle, Horticulture Specialist, located out of Edwardsville, IL.  These links are taken directly from her website.  They are as follows:

COMMERCIAL GRAPE GROWERS

Commercial Grape Nurseries

Commercial Vinyard Suppliers

All you need to know to grow grapes!
Midwest Grape Production Guide

HOME FRUIT PRODUCTION

Growing Fruit for Home Use

Midwest Home Fruit Production Guide


Other U of I Extension information on Grapes:
http://urbanext.illinois.edu/hortanswers/plantdetail.cfm?PlantID=284&PlantTypeID=7


Do you want to take grapes or other fruits to the market?
http://web.extension.illinois.edu/edwardsvillecenter/foodcrophort2801.html

PLANT: CSI (How Plant Problem Investigation Works at the U of I Plant Clinic)

When I first started, I have a couple of tough, plant samples that I was working on.  Now, my definition of a "tough, plant problem" can mean one of following:
A.  It's not a disease (I am a plant pathologist) Suzanne Bissonnette is a plant pathologist too; however she plays the role of an entomologist on TV! Ha ha!
B.  The plant is exhibiting symptoms that could be attributed to a variety of problems (we just have to rule of some of these problems out).
C.  The plant has a variety of problems that is contributing to the symptoms that are exhibited.
D.  I don't know what the "heck" is going on!

I was helping to consult with Richard Hentschel, Extension Educator Horticulture, on a difficult plant issue (that could be an entirely different blog in itself), and in the flurry of emails back and forth between myself and his client, he mentioned that this whole process of plant diagnosis was much like, "Plant CSI".  I liked that analogy and Richard, you inspired me to write this blog : )

Plant Crime Scence Evidence: Dead or yellowing plant parts/not normal plant symptoms <invision yellow crime scence tape placed around the plant sample>

Unfortunately, we are unable to come to the "plant scene", but alot of times, we want you to send us pictures of the "plant scene".  Then, we recommend that you send the "Plant Crime Scene Evidence" to the lab: U of I Plant Clinic

First, we do an "initial walk-through" to get an overall feel for the injured plant scene.  Luckily, we don't have to worry about touching things!  Now, we can make some theories of diagnosis based on visual plant symptoms.

Here we don't swab or collect fingerprints, hair, or dried blood (that is why I am a plant doctor, not a medical doctor).  We look for signs of fungal diseases, nematodes, chemical injury, environmental injury, or insects.

We do try to document all of this "evidence".  And, of course, we are very careful to preserve this plant evidence in it's current form by using refridgeration or even watering (if we have an entire plant).  Sometimes, we even document the "plant crime scene" by taking pictures, sketches, but no video walk throughs are necessary.

Next, we take the plant sample to the scopes (dissecting scope and microscope) to collect potential evidence.  We don't use a swab, but we do use tweezers, as well as other tools such as pruners, knives, and razor blades.  Here are some things we may find on the plant sample in question:  fungal structures, fungal spores, bacterial oozing, nematodes, insect exoskeletons, insect frass, insect webbing, insect feeding, or even nematodes.   Depending on the plant symptoms, we could also use assays or quick strip tests involving ELISA or PCR!  Then, I guess you could say we tag, log, and package it!

If we can't find any of these things above (signs of disease or insect), now that is when it can get tricky!  It could be an environmental, nutrient, or pesticide injury situation.

In this case, we may need to rely on documents such as soil tests, water analysis, or pesticide application log.

Don't forget, once we have a plant sample in hand, we reserve the right to call or email a grower, and perform a full interrogation!  No, we don't ask them were the plant was on the night in question, but we may ask them questions such as:
When was it planted?
What pesticides have been applied?
When were the pesticides applied?
Have you had a soil test?
What fertilizer has been applied?
What was the rate of fertilzer applied?
What has the weather been like?
How long have you had this problem?
In what kind of site is this plant growing?
Was it planted correctly?
What is planted in this area before?
What is the soil type?
What is the condition of the nearby plants?
How old is the plant?
What is the pattern of the affected plants?
What is the name of the plant species?
Are you a homeowner or a commercial grower?
Just to name a few.................................................

When all of the evidence is collected and research has been done (books and internet), it goes straight to the lead detective or in our case, the head diagnostician (that's me).  If I need too, I can also consult with experts.  Now, I don't deal with experts in blood pattern spatter, trajectory determination, serology (blood and bodily fluides), but rather deal with campus specialists that can help me in more specific areas such as crop, fruit, and vegetable pathology or entomology. 

Some Plant CSI's only work in the field - these are Extension Educators or Consultants.  They help to collect the evidence and they pass it to our forensic lab - The U of I Plant Clinic!

Based on these procedures, we can hopefully, MAKE A PLANT DIAGNOSIS!