Friday, June 24, 2011

Spruce and Pine damage- {Herbicide (Imprelis -DuPont) or Evironmental Factors}?

Several States have now reported evergreen injury (mainly spruce and white pine) due to either, herbicide or environmental factors. 
Symptoms include: wilted, necrotic, yellow, needles; needle death, wilting of new shoots; desiccated and drooping candles; twisting and distorted shoots

These are pictures of a spruce sample where a lawn herbicide was applied on the property; however we never received confirmation of exactly what chemistry was used; therefore, we could not make a definite diagnosis.

One of the main topics of discussion is the injury of spruce and white pine, in some cases, which has been linked to to the herbicide, Imprelis (DuPont). Imprelis is a newly, released lawn herbicide with excellent soil activity. It is also important to note, that not all spruce and white pines have been injured in areas where Imprelis herbicide has been applied.
Be aware that all herbicides with good, soil activity could be a potential danger to evergreens and broadleaf ornamentals, if root uptake occurs.

 DuPont Imprelis Label:
The Imprelis label states:  “Do not apply this product directly to, or allow to be under, ornamental ground covers, foliage plants, flowers, nearby crops or other desirable plants; or to the soil where potentially sensitive plants will be planted during the same season.  Do not exceed specified application rates for any area and particular care should be taken within the dripline of trees and shrubs.”  In addition, the Imprelis label states that grass clippings are not to be used as mulch or put into compost piles.

DuPont has made a statement. See more in the link below:
Here are some other links to fact sheets, blogs, and pictures with further information on this topic.
There have been several other reports of evergreen injury (spruce) linked with herbicides that contain (2, 4-D, Mecoprop and Dicamba) as well as "auxin" or phenoxy herbicides.

Why is this herbicide injury happening this growing season?  Could environment or weather be a factor?  There is speculation that spruce may be stressed from the drought of last fall and could be more susceptible to injury of all kind (diseases, insects, and herbicides). There was alot of rain this season that could move chemicals to roots of plants for uptake. In addition, was it a coincidence that symptoms started to occur when there was a sudden temperature fluctuation from low 40 degrees F to 90 degrees F? 

Lastly, there have been reports of some of these same evergreen symptoms in areas where NO HERBICIDES have been applied.  Late freezes can cause death of new growth. It possible that hot, dry winds or "tornado like winds", as well as a cold to hot temperature extreme can cause evergreens, such as spruces, to have uniform candle dieback or dessication of needles.

Since the environment could be to blame for some of the same symptoms described on spruce, you have to very, careful before you jump to the conclusion of herbicide injury.  However, it appears that the "twisting" and "distortion" of evergreen seems to be a common symptom of suspected herbicide injury cases.

Friday, June 17, 2011

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."

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."

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".   

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."

Friday, June 10, 2011

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:

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:

Saturday, June 4, 2011

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:

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.