Friday, June 21, 2013

Phytophthora root and crown rot ALERT!

Recently, the U of I  Plant Clinic, has diagnosed many different plants with Phytophthora root or crown rot. Phytophthora is a genus of soil borne, fungal-like organisms that cause root, stem, and/or crown rot on many, susceptible plants including field crops, fruits, vegetables, trees, and shrubs. Different species of Phytophthora will prefer cool or warm weather, but all of them like it wet, which is one reason they are commonly referred to as water molds. This season has been especially, conducive to Phytophthora infection with an extended spring bringing excessive rainfall. Below are a few examples of different plant samples that have been received and diagnosed with Phytophthora crown and root rot at the Plant Clinic.  Management and links to more information on Phytophthora root/crown rot on trees and shrubs, fruits and vegetables, and soybeans are below.

Phytophthora root and crown rot on a Juniper from a nursery.

Phytophthora root and crown rot on soybean.

Phytophthora crown and root rot on red raspberry.
There is no simple "cure" for Phytophthora root and crown rot disease. Prevention and proper cultural practices are the best way to avoid or minimize losses. It's better to develop an integrated disease management to conquer this disease. Many methods are available, such as site selection, resistance species selection, fungicide application, etc.

1.  Exclusion - Buy healthy plants.  If possible only buy plants that come directly form the greenhouse and have not been grown in nursery fields before sale.
2.  Good Health - Place plants in proper location, plant properly, and keep in good vigor
3.  Drainage - Avoid overwatering, low lying areas, or plant in raised beds
4.  Resistance - Choose plants that are not as susceptible or tolerant to Phytophthora sp.
5. Fungicide/seed treatment - gives partial control and is only used in commercial growing situations

Phythophthora on Trees and Shrubs:

Phytophthora on Fruits and Vegetables:

Phytophthora on Soybeans:

Tuesday, June 11, 2013

U of I Plant Clinic June Crop Disease Report

The crop samples have finally started to arrive from across the Midwest to the U of I Plant Clinic after very, late planting dates, thanks to the rain.

I had a "Deja vu" moment last week, because I realized that we were diagnosing some of the same corn diseases, such as holcus spot and anthracnose leaf blight at this same time during 2011. I have also recently heard some reports of purple corn.  This problem was also seen and discussed in this 2011 blog:

Here are some of the diseases or problems that we have been diagnosing on corn and soybeans at the U of I Plant Clinic:

Soybean cyst nematode (SCN) egg counts in soil samples
For more information on SCN and sampling:
Pythium root rot of corn
 For more information on pythium root rot of corn:

Rhizoctonia root rot of soybeans
 For more information on Rhizoctonia root rot of soybeans:

Holcus spot of corn
 For more information on Holcus spot of corn:

Anthracnose leaf blight of corn
 For more information of Anthracnose leaf blight of corn:

Symptoms are very similar to those that can be caused when a soil applied PP0-inhibiting herbicide receives precipitation at about the time when soybeans are emerging - Dr. Aaron Hager

For more information on the U of I Plant Clinic:

Monday, June 3, 2013

U of I Tree Disease and Pest Update: June 1, 2013

Monthly Summary
(Courtesy of Kelly Estes, State Survey Coordinator)

Average Temperature and Precipitation

Modified Growing Degree Days (Base 50⁰ F,  March 1 through May 30)
Station Location
Actual Temperature
Historical Average   (11 year)
One-Week Projection
Two-Week Projection
St. Charles
Rend Lake
Dixon Springs

Update from the U of I Plant Clinic 
 (Courtesy of Stephanie Porter, Diagnostician and Outreach Coordinator and 
Travis Cleveland, Pesticide Safety Education Specialist)
U of I Plant Clinic Website:
U of I Plant Clinic Facebook Page:
Follow Stephanie Porter on Twitter @skporter

Similarly to previous springs, we are seeing many different issues with various species of spruce.  The problems that we often see at the U of I Plant Clinic are outlined in our Spruce Problems Fact sheet:

Unfortunately, we can commonly able find several diseases, spider mite, or abiotic issues on a single branch sample.  Thus far, we have had only one sample that was diagnosed with SNEED or Sudden Needle Drop (Setomelanomma holmii).  This sample was declining from other problems.  I fear that last summers drought stress, in addition to the recent above average, wet weather will be the perfect recipe for an infection of SNEED.  Field diagnosis of SNEED is not recomended. This disease should be confimed by a diagnostic laboratory. There are many other spruce problems (disease, spider mite, environmental, and cultural) that cause symptoms that may lead to confusion.  In addition, we often find many other black, fungal saprophytes on spruce branches that can be easily confused with the fungal structures of SNEED.  I have not heard of any new SNEED research, but the latest information on disease management is being reported from the Missouri Department of Conservation:

SNEED – Sudden Needle Drop (Setomelanomma holmii) found on Spruce
Stigmina needle blight is often found on spruce needles and can be easily confused with that of Rhizosphaera needle cast.  We do not yet know whether Stigmina is a pathogen on spruce. We do know that this Stigmina is associated with needle blight symptoms on stressed spruce.  It appears that North Dakota has been doing some preliminary research of Stigmina needle cast.  In their fact sheet,, they recommend the following:  "Timing of treatment for Stigmina needle cast is similar to Rhizosphaera, except preliminary data suggest that the trees should be treated indefinitely, with at least two properly timed fungicide applications per year."

We have recently diagnosed Verticillium wilt on elm.  Hundreds of plant species, including trees, shrubs, groundcovers, vines, vegetables, fruits, herbaceous ornamentals, and flowers may become infected. Some trees that are frequently infected by this disease are maple, ash, and elm. Symptoms can be seen throughout the growing season and include wilt, branch death, and quick decline of plants. Peel off some of the bark on a symptomatic branch and look for staining of the wood in distinct streaks of brown, dark green, or yellow-green wood. Verticillium-infected ash trees do not always show staining. There is no cure for Verticillium wilt. Still, there are many cultural and preventive strategies to manage the disease and help infected trees live with the fungus. Because the fungus remains in the soil even after removal of an infected plant, replanting with resistant varieties is a desirable control option.  Always start with healthy plants and avoid susceptible species. Supply balanced fertilization and provide adequate irrigation to improve the health of stressed plants.  If you have any questions on sampling or sample submission, please contact the U of I Plant Clinic at 217-333-0519.

Verticillium sp. isolated from an elm sample on PDA agar at the U of I Plant Clinic
As many of you already know, there has been an epidemic of fungal leaf blight diseases on many trees across the state, thanks to the conducive, weather conditions.   The majority of the leaf blight reports have been on maple.  For more information on the U of I Plant Clinic diagnosis of leaf blights of maple, you can refer to the recent Home, Yard, and Garden article, Maple Blight Mania:

Invasive Species News from the Illinois Cooperative Agriculture Pest Survey (CAPS) Program
Monthly Summary (Courtesy of Kelly Estes, State Survey Coordinator) 

Storm Damage? Friendly Reminder about Moving Firewood 
The recent storms that have swept across the state have left destruction in their wake – including downed trees and limbs. I’m sure there will be lots of activity in across much of the state in the coming days. But, don’t forget the dangers associated with invasive species and moving this debris. There are many invasive insects and diseases that are found in firewood-gypsy moth, emerald ash borer, Asian Longhorned beetle, and thousand cankers disease are just a few. While they may not move far on their own, when people move firewood and debris, they can move hundreds of miles. This aided movement can spread these pests to areas where they were not present before.  If you are cleaning up fallen ash trees, please keep in mind there are federal and state regulations limiting the movement of ash and ash products in Illinois. Don’t forget to take a look for signs and symptoms of the emerald ash borer. Adults generally begin emerging from ash trees at the end of May. EAB activity will soon begin in many areas of the state; degree day accumulations indicate that emergence should be beginning.  Visit the Illinois CAPS blog for all the latest news on invasive pests in Illinois or contact Kelly Estes ( with any questions.