Monday, July 30, 2012

Bacterial Culturing at the U of I Plant Clinic

(Blog written by U of I Plant Clinic Student, Sean Mullahy)

When dealing with a plant sample, the first step is generally to determine the causal agent of the problem: abiotic factor, fungi, bacteria, or a virus. Once this is determined, each agent has a different method of approach. Today we will be dealing with a bacterial pathogen, so the first step is going to be the search for the illustrious bacterial ooze. Plant pathogenic bacteria have an interesting property in that they will “ooze” out of tissue when sliced. With a large enough (and well infected) sample, this can actually be seen in a beaker or glass of water. With a smaller sample, a small section of infected tissue is sliced, preferably at a transition zone, and then mounted onto a slide. Under the scope, along the edges of the cut tissue, bacteria can be seen streaming out in what can be best described as a mist or a cloud. Once this is found, we can move onto the next step, the best step, the culturing step.
 Bacterial ooze!

The transition zones mentioned previously are next going to be used to make up our nasty and kind of creamy bacterial broth. These zones are selected, cut, and then surface sterilized with a quick dip in a 10% bleach solution. Following this is a quick dip in distilled water, they are then left to dry in the crease of a paper towel in our flow hood. Once air dried the sample material is placed in a test tube of sterile water, shaken up, and left to sit for at least 30 minutes. This is when the bacteria start streaming out into the water, making what can be best described as a “broth” of bacteria. This nasty little tube of liquid is what will be used to culture out our bacteria.

 In this case, we suspect a Pseudomonas bacteria, so we have chosen Kings B or Pseudomonas Agar. This medium is pretty cool in that most bacteria will grow just fine on it, but if a Pseudomonas bacteria is cultured on it. This agar will glow under UV or blacklight, once there has been adequate bacterial growth. The Plant Clinic cultures its bacteria in two ways, either by spread plates or streak plates. Both techniques are quite easy, with each having its own benefits. In one technique, an inoculating loop (a small wire loop) is used to grab a droplet of bacteria solution which is then “streaked” over the agar plate.  The other technique is called a spread plate. In this a larger amount of the liquid bacteria solution, 1/10 of a mL, is pipetted onto the plate. A bent glass rod is then used to “spread” it evenly over the surface of the media. 

Hopefully you found this quick look behind the scenes at the U of I Plant Clinic to be informative (and hopefully somewhat interesting too).

Monday, July 23, 2012

Todd Gleason's Sunday Drive to Determine Illinois #Corn Yields

On Sunday, a member posted the following on a private agronomic Facebook page:

"Do you follow Todd Gleason (University of Illinois Farm Broadcaster) on Twitter? @commodityweek. He just did a big loop today from C-U to Jacksonville and south and back east through Litchfield to Dalton City. They were driving 20 miles, stopping at first corn field @ first culvert and walking in 50 paces and pulling 3 ears in so many steps."

After seeing this post on Facebook, I quickly checked out Todd's posts on Twitter.  If you are interested in corn yields around the state of Illinois, I suggest that you check it out too!

Thanks to the magical world of social media, Todd saw that I was following his "Sunday corn yield journey" and sent me an email with further information and pictures. 

Above is the route and actual field stops.

The above photo is taken near Pana, Illinois, my home county, and can give us some hope that some areas in Illinois may actually have some fair yields.  My Dad farms not too far away from this location, but I don't know that our corn looks this good.  The rains were "hit and miss" and very spotty this year in our area.

Above are Todd's photos of corn ears from each field visit from left to right.  He got an actual "0" in Carlinville, Illinois.  

Monday, July 16, 2012

Why did my maple die so suddenly?

Every day I receive calls about plant problems.  It is often very, difficult for me to determine what the problem may be over the phone.  So, I ask for plant samples or pictures, depending on the description of the problem.
In this case, this maple died very suddenly.  This does not sound like a disease or insect problem to me.  Yes, maples can have problems with Verticillium wilt, but let's not be too quick to blame this disease.  Further investigation should be done.   First of all, the drought and heat this summer have been very, harsh on tree health.  Unfortunately, if that tree has any preexisting decline problems, this stressful weather will not help! 

I usually ask for a picture of the tree base.  Here I can see that this tree is suspect for being planted to deeply.  It is hard for someone to believe, but yes, a tree can survive for many years being planted to deeply; however, when harsh growing or site conditions arrive, the tree can quickly decline.  It is also possible that this tree could have had a girdling root on it's left side.  Deep planting and girdling roots can cause the tree to decline.  But, could the hot/dry weather and incorrect planting cause the tree to die suddenly?

If a root rot or wood decay fungus infects the declining tree.....yes, that can cause a sudden death. The symptoms of the maple in the above pictures are very symptomatic of Armillaria root rot. For more info, you can check out this link:

There are some species of this fungi that are just saprophytic (survive on dead wood), but there are some that can be parasitic (cause disease). I can’t tell you which came first. It is still possible that that the girdling root/deep planting killed the plant and then Armillaria invaded later. But, Armillaria root rot could have caused the tree to die too.

Friday, July 6, 2012

Waterhemp Herbicide Resistance Testing in Illinois

The U of I Plant Clinic has receive many questions in the last week about testing waterhemp for herbicide resistance.  The U of I Plant Clinic is not the lab that is performing this testing, but here is the information needed below.

In case you are not sure what a waterhemp looks like, here are some pictures:

With continued support from the Illinois Soybean Association, U of I can offer free screening of waterhemp populations for herbicide resistance again this growing season.
To submit samples, follow these directions:
  • After applying glyphosate, select five waterhemp survivors in the field.
  • Remove the top inch or two from each plant (containing young, newly emerged, healthy leaves), and seal it in a sandwich-sized zip-top plastic bag. Use a separate bag for each plant.
  • Place the bags in an envelope and send by overnight delivery to Dr. Chance Riggins, 320 ERML, 1201 W. Gregory Dr., Urbana, IL 61801. Ideally, samples should be sent the same day they are collected, but if necessary, they can be stored for a day or two in a refrigerator (but do not freeze). Do not send samples on a Friday or Saturday.
  • Print the following submission form (Adobe PDF) and complete a copy for every field sampled.
Not every waterhemp plant that survives an application of glyphosate is resistant to it. If the following conditions all apply, however, you might suspect that a waterhemp population is indeed glyphosate resistant:
  • The appropriate rate of glyphosate (plus proper adjuvants) was applied at the appropriate weed growth stage.
  • Environmental conditions during and after application were conducive for good glyphosate activity.
  • Plants that survived the glyphosate application are found next to plants that did not.
  • The field has a history of glyphosate use.
They will not charge for the screening, but please understand that they cannot promise how soon results will be available. Also, because of the way they conduct the resistance tests, a result of "sensitive" does not rule out the possibility that the plant actually is resistant, but by a mechanism different from what we are testing for. Finally, be assured that they respect the privacy of those sending samples: they will not make the exact location of any sample or name associated with them available to anyone without your permission. If you have any questions, feel free to contact Pat Tranel (217-333-1531, Tranel and Aaron Hager

Pat Tranel
Aaron Hager