ODC (tm): Is This "Stuff" for Real and How Does It Work?

Originally posted 4.12.10, this post is from the Kansas State University Department of Entomology Newsletter, March 26, 2010 authored by Raymond A. Cloyd, Professor and Extension Specialist in Ornamental Entomology/Integrated Pest Management.  Dr. Cloyd is affiliated with the Department of Entomology at KSU in Manhattan, KS.

The entire publication can be found at http://www.entomology.ksu.edu/DesktopDefault.aspx?tabid=756, look for issue #1, March 26, 2010. 

"We have received numerous inquiries regarding the product Organic Disease Control or ODC (tm), and its supposed effectiveness against insects and diseases.  This product contains chitosan (0.25%) as the active ingredient and is being marketed by AgriHouse, Inc., (Berthoud, CO) with claims that the product protects trees from attack by pine beetles and blue stain mold.  First of all, it is important to discuss the characteristics of the active ingredient.  Chitosan (poly-D-glucosamine) is a common polymer present in nature in the cell walls of certain fungi and insects, and the commercial formulation is prepared from chitin that is found in the shells of crustaceans (e.g., crabs and shrimps). Chitosan is supposed to enhance, stimulate, or boost the plants immune (or defense) response.  Well, how does it do this?  It has been proposed that chitosan is active on the octadecanoid pathway.  What happens in this pathway is that linolenic acid is converted to jasmonic acid resulting in the transcriptional activation of genes associated with defense that "turns on" compounds and/or enzymes  such as proteinase inhibitors and polyphenol oxidase.  In other words, chitosan may elicit or activate plant defense responses.  However, the mechanisms affiliated with this process are not clearly understood.   

Currently, there is no quantitative information (based on scientific studies) on the efficacy of ODC (tm) against the mountain pine beetle (Dendroctonus ponderosae) in lodgepole or ponderosa pine.  Furthermore, the publications (#672 and #5322) referred to in the in-house blog (http://agrihouse.wordpress.com/) do not contain any conclusive data to substantiate the claims being made associated with this product.  In fact, one of the publications presented only one years' worth of data (1996) and did not even test for activity against bark beetles.  Additionally, the methodology or procedures used (inoculation) are questionable.  I have listed four publications at the end of this article that discuss the potential role of chitosan; however, none of these are studies that have conducted or include evaluations against wood-boring beetles."

Dr. Cloyd goes on to talk about the claims made regarding ODC (tm) and his questions to each of the claims.  If you are interested in reading the rest of the article, I encourage you to click on the KSU link above to access the full story.  The bottom line, according to Dr. Cloyd, is that "overall, this appears to be an example of an 'aggressive marketing' strategy, which may cause confusion among homeowners/consumers.  As such, this supports the value of extension at land-grant universities because it is our responsibility as extension personnel to provide un-biased information to homeowners/consumers so they can make sound pest management decisions based on the results from 'sound' science.....not mis-information." 

Good Advice on Winter Watering

These articles come from two posts on another blog that I follow, and I thought I would post them here as well.  Along the Front Range, we are in a moderate to severe drought, depending on where you live.  With no appreciable moisture since the end of July, it's a challenge to keep our plants healthy.  Winter watering can help.  Check out these posts on Gardening After Five. 

http://gardeningafterfive.wordpress.com/2010/12/14/give-your-trees-a-drink/

http://gardeningafterfive.wordpress.com/2010/12/20/winter-water-is-for-lawns-too/

Updated MPB Information

I thought a recent post by Dave Leatherman, retired CSFS Entomologist, regarding Mountain Pine Beetle would be beneficial as an update on the behavior of the beetle along the Front Range and questions we are receiving regarding when to spray.  

"If less than a full compliment of beetles hits an urban tree (i.e. an 'unsuccessful' attack from the viewpoint of the beetle), two patterns have been common the last several years:  
  1.  a band of pitch tubes at mid-trunk, with very few on the basal and upper parts of the trunk, or
  2.  a gradation of pitch tubes, heaviest at the base, fizzling out about 10 feet above the ground.

The great, great majority of such trees survive, at least the initial attack.  These sorts of trees, however, do seem prone to re-attack, sometimes later in the same season, sometimes the following summer.  If the trees have high value, rigorous inspection to determine the success of the attack is in order.  IF the tree will not die from the attack in question, preventive spraying is warranted.  The historical spray timetables have become problematic and spraying anytime during the April to early November period might be warranted, depending on the specific circumstances and wishes of the consumer. 

Three things seem clear:  1) the flight season of the beetle is not just late July thru early August anymore (more like April thru early November, with two peaks, one in July-early Aug, and the other mid Oct-early Nov),  2) with the flying beetle population being diluted at any one time over a period of month, successful attacks resulting from a single attack are fairly rare among urban trees, and 3) foliage fading in relation to when observers first see pitch tubes is all out of whack.

For urban areas in CO, NE, and WY and the MPB attacked trees I have seen of late, the following statements apply: 

• The hosts are overwhelmingly either Scots or Ponderosa pine, the pitch tubes are often large and 'runny' (as would be characteristic of unsuccessful, 'pitch-out' type tubes);
• IF the attacked trees die, they didn't die of a single attack; most attacked trees display pitch tubes of varying hardness (indicating initial and later attacks);
• IF the attacks are successful and result in a big emergence of beetles, the trees are usually still green-needled (at least not obviously brown) when this occurs;
• Emergence is usually in October or November (but sometimes 'on schedule'  in July-August);
• Relying solely on external evidence is more dangerous than ever because of the above;
• A hatchet/under-bark-peek is more needed than ever to make a proper diagnosis (and because of the preponderance of strip attacks, looking under the bark on more than one side of the tree is a wise move).

In urban areas, assuming the trees are of suitable diameter (6 inches or more at breast height), I would put pines into three categores:  Likely to be attacked, sometimes attacked, and rarely attacked.  The likely to be attacked pines are Scots, Ponderosa and Lodgepole.  The sometimes attacked would be Limber and Bristlecone.  The rarely attacked pines are Austrian, Mugo, Pinyon, Spruce and other pines."

Another Tree Problem

Dr. Ned Tisserat, Extension Plant Pathologist, was asked by the city forester in Boulder to come take a look at some Red Oak trees that were declining in one of the parks in the city.  The symptoms are branch dieback with borer holes in the trunks of the trees.   After further investigation, it appears that the branch dieback may be associated with Kermes scale, but the borer holes in the trunk caused by a flat-headed borer were unusual.  Dr. Tisserat isolated Fusarium solani from an area surrounding the borer galleries, but also noticed a gummosis on the branches.  This gummosis was in close proximity to the Kermes scale.  Isolations were done and the gummosis was the result of a bacteria which was identified as Brenneria (Erwinia) quercina.  This bacterium has been previously associated with 'Drippy Nuts Disease' on oaks in California and with an oak decline in Europe.  More investigation is needed to understand if the Kermes scale is contributing to the bacterial infection, where the bacterium is originating from and how the flat-headed borer is involved in the infection process, if at all. 

Tomato/Potato Psyllid

This year along the Front Range of Colorado has been devastating for fresh market potato producers and home gardeners alike.  The culprit this year is an insect, the tomato/potato psyllid, which comes to us courtesy of the southern states and Mexico.  They arrive via the southerly air currents that bring us other pathogens like wheat rust.  This insect injects a toxic saliva into the plant that causes the potato to turn yellow with curled leaves.  Potatoes are smaller or non-existent, reducing harvest yields considerably.  Dr, Whitney Cranshaw, CSU Extension Entomologist, was interviewed recently by 9News reporter Adam Chodak.  The video link is attached. 
http://www.9news.com/video/default.aspx?bctid=603977271001

Update on Thousand Cankers Disease

The following is an excerpt from an email sent to several listservs by Whitney Cranshaw regarding a new confirmation of Thousand Cankers Disease in Tennessee.
"Thousand cankers disease of walnut has been confirmed from Tennessee.  This was first identified about 10 days ago with a sample we received from Knoxville, but a formal announcement has been pending per the Tennessee Department of Agriculture's wish to delay announcement for further confirmations.  As this has been done, and I see an AP report on the internet, I think that we can now let it be generally known. 

The known infestation is in and around Knoxville.  As this is a fairly recent find, the extent of the infestation has not been delimited.  But the extent of the infestation suggests that this disease (i.e., the walnut twig beetle and its associated fungus, Geosmithia morbida) has been there for a decade or more.

This is a disaster of tremendous proportion.  It had been my deepest hope - clearly a naive hope - that this problem would stay bottled up in the western states where black walnut, Juglans nigra, is planted but not native.  I had long ago given up that black walnut would survive in the West and that is a sad situation, but not tragic.  Now that it is irrevocably established in the center of the native distribution of Juglans nigra, there are no geographic/ecological barriers to prevent its ultimate spread throughout the US.  Furthermore, the fact that the disease appears to be progressing as a lethal tree killer in Tennessee as it has been doing for 10-20 years in the Rocky Mountain States answers the question as to whether this is a regional problem.

It also suggests that there may well be many other infestations in the Midwest that have gone undetected.  This is a very difficult disease to detect in early stages.  Apparently in Tennessee, as in our area, what attracted attention were plantings that showed symptoms of apparent drought stress.  But it is not drought stress nor related to drought.  For some help with this situation we have a web site:  http://www.colostate.edu/Depts/bspm/extension%20and%20outreach/thousand%20cankers.html.  There are sheets on diagnosis, Q & A, and a fact sheet (that needs a bit of updating).  Also available are links to pictures and powerpoint talks, including the version of "Nightmare on Walnut Street" that I presented at the ISA meeting last week in Chicago.

I am assuming that there will now be a scramble to have state quarantines become a reality.  As I understand it, following Missouri's lead, that Nebraska, Kansas, Michigan and Indiana have or are in the process of enacting state quarantines that restrict movement of certain Juglans material that originates from TCD-affected states.  And this disease is a deal breaker.  It is relatively slow to develop, at least compared to DED or EAB, but its progress will be inexorable.  My guesstimate from watching it in urban settings is that about 30 years after this is introduced into a city, all the black walnuts will be dead.  That is based on the disease taking 10-20 years to show symptoms after the initial point infestation and 10-15 years for it to progress across a city once the first symptomatic tree is detected.  How this disease will progress where there are native stands affecting the epidemiology will undoubtably change things in ways we will all have the unfortunate chance to see in the upcoming years. 

However, containment/slow the spread is still something we need to throw ourselves into.  The longer you can delay the introduction of the disease (by movement of fungus contaminated walnut twig beetles), the longer your black walnuts can survive.  Perhaps with dedicated effort we can push back the ultimate effects of this disaster for a generation or two in many areas, giving us valuable time to develop means of managing it and finding resistant cultivars."

Posted by Whitney Cranshaw, 8.2.2010

Wheat Virus Survey Results

Since wheat harvest is now finished and we are headed into corn season, I thought I would share the general results of the wheat virus survey.  In this survey we test for five known wheat-infecting viruses, Cereal Yellow Dwarf Virus (CYDV, formerly known as BYDV-rpv), Barley Yellow Dwarf Virus (BYDV-pav), High Plains Virus (HPV), Wheat Streak Mosaic Virus (WSMV), and Triticum Mosaic Virus (TriMV). A total of 368 ELISA's (enzyme-linked immunosorbent assay) were performed in the diagnostic clinic. Of all the ELISA's run, 252 of these were for the wheat breeding program.  There were a total of 116 wheat samples sent in to the clinic from growers, extension agents and crop consultants.  The results of those 116 samples were 79 virus positive and 37 virus negative.  The results reported here are the compilation of the 79 virus positive wheat samples from growers and do not include the results of the wheat breeding program.

• 39 samples had single virus infections; the sample was positive for only one of the five viruses tested.
• CYDV (3 positives)
• BYDV-pav (13 positives)
• HPV (6 positives)
• WSMV (14 positives)
• TriMV (3 positives)
• 40 samples had co-infections; meaning the sample was positive for two or more of the viruses tested.
• 32 samples were co-infected with 2 viruses
• 7 samples were co-infected with 3 viruses
• one sample was co-infected with 4 viruses
• there were no samples that tested positive for all five viruses
• Of the 32 samples that were positive for two viruses, 17 of those samples were positive for WSMV and TriMV.

Overall, WSMV is still the number one wheat virus in our state, either singly or co-infected with other viruses.