Thursday, August 25, 2011

Insecticidal Soaps

This past week in the Diagnostic Clinic, we received some photos of a Japanese Maple whose younger leaves were exhibiting curling at the edges.  No insects were found and so the search began for the cause of the damage.  As more information was forthcoming, it was also noted that the new buds on some of the blue spruces were turning brown as well.  We also learned that a nearby plum tree had recently been sprayed with an insecticidal soap.  Since the symptoms on the Japanese Maple and the Spruce were associated with new growth, not the older growth and no insects were found, it appeared that there was most likely an abiotic issue.  So we did some research and discovered that insecticidal soaps can cause phytotoxicity damage to certain plants if sprayed at the wrong time, and that newer growth on Japanese Maple is extremely susceptible to damage from insecticidal soaps.  An excellent fact sheet from Cornell University provided the information that we based our diagnosis on, which also indicated that if the insecticidal soap was applied when temperatures were above 90F, it could increase the incidence of phytotoxicity damage.  The link for the fact sheet can be found at 

The take-home message from all this is that reading the label is important to make sure your plants won't be unnecessarily harmed by the use of any product.

Friday, July 8, 2011

Update from the Clinic...........

This year we have seen a variety of diseases that usually don't happen frequently in Colorado.  We have confirmed anthracnose on Ash from Aurora, and just this morning, found anthracnose on Oak here at the CSU campus. is a link to the fact sheet on Sycamore Anthracnose, but control measures would be similar for Ash and Oak.  

We are also seeing samples of Oak Leaf Blister on a regular basis this year. is a fact sheet from U of Mass on oak leaf blister that shows some really nice pictures of the blisters on oak leaves. Older blisters can often be confused with anthracnose. 

We are also still seeing effects of the prolonged fall/winter (2010-11) drought on trees and shrubs.  Winter watering is critical in our area for survival of trees and shrubs. is a fact sheet that talks about healthy trees and tree roots and provides insight on what can affect the growth of a tree via the roots.     

There may be some residual effect of the cool temperatures in May and June on vegetable production in the home garden.  The coolness has pushed back fruit set on a lot of the warmer season vegetables, so be patient with your plants.   

Lastly, there are a lot of aphids out there.  A blog post from Gardening After Five has some recommendations on control,

Thursday, June 9, 2011

Wheat Virus's not too late!

If you are a Colorado wheat grower and your wheat is looking a little yellow or sickly, we are offering again this year (at no charge to the grower/submitter) to test wheat samples for five different viruses (virus screen).  We test for Cereal Yellow Dwarf Virus-rpv (CYDV-rpv), Barley Yellow Dwarf Virus-pav (BYDV-pav), High Plains Virus/Disease (HPV), Wheat Streak Mosaic Virus (WSMV) and Triticum Mosaic Virus (TriMV).  It's not too late to submit your samples to the Diagnostic Clinic this season.  Samples should contain at least 4-5 symptomatic plants so that we have enough leaf material to test.  Information included with the sample should include location of the field, county, variety of wheat (if known) and contact information of the grower or submitter so that we can let you know what the results were.  Our mailing address is Plant Diagnostic Clinic, E215 Plant Sciences Bldg, Colorado State University, Fort Collins, CO  80523-1177.  If you would like to call and let us know a sample is on the way, our phone number is 970-491-6950. 

Tuesday, June 7, 2011

Wind vs Tree.........

Yesterday here in Fort Collins, about 3 p.m., we experienced a microburst wind event with a bit of rain.  Didn't think too much of it, as this happens quite frequently as temperatures start to warm up and high and low pressure areas collide.  However, it did some damage on campus.  A mature linden tree, approximately 40 feet in height was apparently blown over by the wind.  On closer inspection, it appears there may have been some pre-disposing factors that contributed to the demise of the tree.  It looked like it was planted incorrectly and there was some butt rot involved.  I'm posting photos of the trunk and the entire tree for you to decide. 
 Luckily no one was hurt nor was any property damaged, i.e. cars, etc.  Above photo is of the complete fallen tree as taken from the east side of NESB.

Left photo:  Looking southeast from NESB


Monday, June 6, 2011

Colorado Wheat Update

The wet, cool weather most of the eastern part of the state experienced the past week or more was very conducive to stripe rust development. Yet, I still have not had any confirmation of stripe rust in the state. However, Dr. Bob Harveson, U. Nebraska reported stripe rust in an irrigated wheat field from western Scotts Bluff Co (south of Morrill). Therefore, it is entirely possible there are ‘hot spots’ of rust out there. If you have seen stripe rust, please email me with some images or send me some samples. The weather outlook for the next week isn’t that favorable for stripe rust development so I am hoping we are in the clear. Remember if you decide to make a fungicide application (which I am not advocating), make sure you follow the label concerning plant harvest intervals.

We have received a smattering of virus disease samples. Barley yellow dwarf is fairly common with some wheat streak mosaic. But we certainly don’t have the virus problems of some previous years.

Ned Tisserat

Extension Specialist and Professor

Wheat Disease Update from Oklahoma

Wheat Disease Update –06-Jun-2011

Bob Hunger, Extension Wheat Pathologist

Department of Entomology & Plant Pathology

Oklahoma State University

Oklahoma: Harvest is occurring or starting across all of Oklahoma, so observations and reports of disease occurrence are about at an end. The only disease observations that have come to my attention are a number of samples from the OK panhandle that came into the diagnostic lab last week and tested positive for various combinations of wheat streak mosaic virus, wheat mosaic virus (high plains virus), Triticum mosaic virus, and barley yellow dwarf virus. This is similar to the panhandle of Texas where Dr. Jacob Price (Plant Pathology Research Associate, Texas AgriLife Research, Amarillo, TX) has reported that, “During this wheat season 214 samples were submitted to the GPDN diagnostic lab in Amarillo from counties in the northern Texas Panhandle. Of these, many were found to be infected with single and multiple infections of Wheat streak mosaic virus (WSMV), Triticum mosaic virus (TriMV), Wheat mosaic virus (WMoV), and Barley yellow dwarf virus (BYDV). The most prevalent viruses found were WSMV and BYDV at 31 and 21%, respectively. Thirteen percent of samples were found to be infected with TriMV and of these samples 93% were also infected with WSMV, as has been seen in previous years. Only 4 and .01% of the samples were found to be infected with WMoV and CYDV, respectively. These results are similar to previous years.”

Thursday, May 19, 2011

Clinic Update

Since the weather has not been cooperating, we have not received many samples in the clinic so far this season.  It's still pretty cool and moist.  We have received several samples of turfgrass with Necrotic Ring Spot already this spring.  As soon as soil temperatures start warming up, we expect to see more.  Information on control can be found here:  There are both cultural and chemical controls, but be advised that NRS is a difficult disease to cure.

We have also received a couple of samples of wheat with Tan Spot (Pyrenophora tritici-repentis).  This disease can show up anytime April-June and appears as small brown, oval lesions with tan centers usually with a yellow halo around the lesion.  It is always a good idea to get confirmation of this pathogen before deciding to spray as magnesium and chloride deficiencies can mimic tan spot.  This disease overwinters in old wheat stubble and germinates in early spring after a prolonged wet period (usually 24 hours or more).  Asexual spores are spread by wind and keep the disease cycle going, infecting new leaves.  North Dakota State University has an excellent fact sheet on control measures that can be found at   

With the recent moisture we can also expect to see Gymnosporangium rusts, most often Juniper-Hawthorn rusts.  This disease will manifest first as orange, gelatinous masses on juniper causing some discomfort for homeowners.  These brightly colored galls often look like some alien being has landed in the landscape.  After they dry, the galls become dark brown and will stay on the junipers but will not generally harm the plant, only causing aesthetic damage.  Cooperative Extension Plant Talk has a script on this disease that can be found at

Recently planted vegetables will be set back a bit with this cooler weather.  Be patient with your landscape as the roots need some warm soil temps to really get your plants going. 

Monday, February 7, 2011

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, 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 ( 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."