Monday, January 31, 2011

Problem Pythium?

Have you been having a problem with Pythium root rot at your facility? Do you think that you may have resistant isolates? If so, you can contact the Plant Disease and Insect Clinic (link below) for more information about sample submission procedures.  I am going to be actively sampling North Carolina greenhouses for Pythium isolates.  If you would like us to sample your greenhouse or test your plants for mefenoxam resistance we might be able to add your facility to our list.  Please contact the clinic for more information. 


Friday, January 28, 2011

Plants, Pests, and Pathogens Webinar

The next Plants, Pests, and Pathogens session is scheduled for February 22,  2011.  The Plant, Pests, and Pathogen session is a free two-hour interactive webinar broadcast via Elluminate.  

For more information and how to sign up visit the website at:

Tuesday, January 25, 2011

A Little Bit About Pythium

About Pythium

Pythium species are  “water molds” that produce swimming spores called zoospores. There are many species of Pythium.   Some species are saprophytes or weak pathogens that mostly decay dead root tissue.  Often, Pythium nibbles on feeder roots of plants. Under the right environmental conditions, however, some Pythium species become destructive pathogens that rot and kill the roots of plants, resulting in stunted growth or death.  The pathogen is favored by wet conditions, such as when media does not drain properly or when weather events prevent the soil from drying out completely.  Pythium can also be more problematic when the host plants are stressed.

             Pythium can be a problem on many annual and perennial hosts and is extremely destructive to greenhouse production of poinsettias and geraniums. Pythium can be introduced into greenhouses on infected plugs or infected plant material.  It can also be a year-round “resident” hiding on dirty plant containers, equipment, benches, or even in irrigation water, waiting for the conditions that favor the pathogen and disease development. 

Leaf curling associated with Pythium root rot on poinsettia

Stunted growth symptom of Pythium root rot on poinsettia

Managing Pythium Problems

Sanitation is very important in managing root rot because Pythium produces survival structures, called chlamydospores, that are able to survive for long periods of time on infected plant material or dirty benches and pots.  There are some fungicides that are effective against Pythium and other water molds (oomycetes).  Some of the most popular oomycete fungicides contain the active ingredient mefenoxam.  In recent years, greenhouse growers have seen an increase in oomycete resistance to mefenoxam, resulting in poor disease control.  Some good practices that limit the occurrence of fungicide resistance include:

  • Time spray applications when the pathogen is weakest or most vulnerable to application
  • Use a fungicide registered for your pathogen that is proven to be effective in controlled settings
  • Alternate active ingredients in your spray programs
  • Use only the labeled rates listed on the container and do not over-apply the fungicide
  • Incorporate new fungicides into your spray program as they become available

Unfortunately, even when using good application practices, sometimes the pathogens still develop resistance. 

Research Goals

The purpose of my research is to determine which Pythium species are present in North Carolina greenhouses and to evaluate their abilities to be effective pathogens in the greenhouse environment.  This will involve morphological and molecular species characterization, pathogenicity assays, growth chamber studies, and checking for mefenoxam sensitivity.  

At the plant disease clinic, we routinely run root assays to determine the presence of Pythium.  Currently, we are not able to determine which species of Pythium is present and whether it is pathogenic or just saprophytic.  My research will allow the diagnosticians at the disease clinic the opportunity to expand their Pythium diagnosis to be more beneficial to the grower.  We will be able to tell the grower whether the Pythium we isolated from their plants is resistant to mefenoxam and if so, offer alternative control options.  

Fungicides are expensive.  Routine mefenoxam screening will help growers develop effective fungicide programs so they are not spraying money down the drain.  

Monday, January 24, 2011

About Me

Hello! My name is Emma Lookabaugh and I wanted to start off our new blog by telling you all a little bit about myself.  I am a graduate research assistant at the Plant Disease and Insect Clinic at North Carolina State University.  I worked at the PDIC for several years as an undergraduate student and fell in love with the dynamic field of Plant Pathology.   

Clinic Responsibilities
Some my responsibilities as an undergraduate included performing routine assays, running ELISA virus screening assays, using BIOLOG to identify bacterial pathogens, making slide mounts to observe pathogen structures under the microscope, invoicing and clerical work, and basic lab maintenance.  As a graduate research assistant, I have worked towards expanding my diagnostic abilities considerably.  One of my main responsibilities is tomato disease diagnosis under the direction of Dr. Frank Louws.  I have worked with Dr. Louws to learn how to recognize most of the major tomato diseases we see here in North Carolina.  In addition to tomato diagnosis, I am also working on a research project under the direction of Dr. Barbara Shew.  Currently, my research is focused on Pythium root rot in greenhouse ornamentals.  

Friday, January 21, 2011


The Plant Disease and Insect Clinic at North Carolina State University welcomes you to our blog. The purpose of this blog is to bring you information about some of the samples we receive in the PDIC and to post links to interesting news about plants, plant diseases, insects, gardens, agriculture and science.