Damping-off and rot problems on newly planted roofs

I have heard that several newly planted roofs are experiencing damping-off and rot this Spring.  Damping-off is a condition that causes the plant to lose vigor and die, in some cases almost overnight.  This is caused by several fungi.  Plants are vulnerable to attack by these fungi during periods of unfavorable growing conditions.  Species of Pythium, Sclerotinia, and Phytophthora are more likely to cause damping-off in cool, wet soils; whereas species of Rhizoctonia, Fusarium and Sclerotium rolfsii may cause damping-off under warmer and drier conditions. This type of injury often damages the leaves and upper stem before the roots are affected.  True damping-off may be confused with plant injury caused by planting too deep, high soluble salts, drowning in wet soil, desiccation in dry soil, and death of plants from excessive heat or cold.  Rhizoctonia and Pythium do not have an airborne stage. The spread of both fungi depends primarily on the mechanical transfer of resting spores in infested soil. As with most fungi, the spores are spread by the splash of rain water or infected tools.


Typical symptoms of damping-off are rotting stems at or near the soil line and root decay.  You generally notice brown stems at or just above the soil line.  Infected plants are shriveled, brown, collapsed or stunted. Moldy fungal growth may be seen on affected plants at the soil line. Phytopthera, Rhizoctonia, Fusarium, Sclerotinia, and Sclerotium generally caused damping-off by killing the plant at the soil line. Pythium attacks below the soil line, often at root tips.


The best control of damping-off is to avoid it altogether. Once damping-off has started in a plant bed, it may be difficult to control.  Proper soil treatment with heat or chemicals to reduce the level of fungi that cause damping-off is very important.  The compost added to the growing mix needs to be properly "Composted" to rid it of any pathogens.  The compost added to the growing mix needs to be from a trusted source.  The composting time needs to be a minimum of four months with proper aeration, then covering while it cures for four weeks.  Proper temperatures of 150F or above must be maintained for eight weeks for sterilization.  Chemical control is an effective tool you can use once damping-off is suspected.  Check with your University's Agricultural Extension Service for their recomendations. 


Damping-off can be avoided if you take into account that a Greenroof planting is just as suceptable to issues that most gardeners face on the ground.  We need to remember that plants aren't just another layer on the roof, they are but living organisms.

Replies to this Topic

As a grower like Wayne, I have had intermittant problems with fungus.  My problems start primarily due to high temperatures (92 degrees plus) stressing the plants especially during the lengthy severe drought we are having in NC.  What I have found best for treatment is to apply 1 teaspoon per gallon of Ortho Garden Disease Control (Chlorothalonil) or Daconil (which is the same). 


Bob Long   Carolina Stonecrops, Inc. 

I am so glad that Wayne brought this topic up especially as we are beginning to enter into the season when our "dew points" start to rise and the humidity becomes a factor in the health of many of the succulents that we use on our roofs.

Normally, in early August we apply a lightweight fungicide on projects where crown rot is most likely to occur. Buildings that are in low lying areas where there tends to be a lot of early morning fog and are partially shaded in the afternoons tend to become a hot spot for a variety of diseases especially if the sun can not get in and dry out those areas. Most buildings over 6 stories in height might not have any problems unless the greenroof assembly is constantly inundated with rainwater or a drains backs up or clogs causing an area to become to wet. We had a problem with that earlier this spring when some filter fabric clogged up around a drain inlet causing water to pond. We are now going with "fiberglass" based filter fabrics around our drains to allow for better drainage.

Also, I believe that Tectaclor is another chemical that is good for controlling "crown rot" and if you suspect that your roof might be suffering from either a disease or poor drainage I would recommend having the system checked out immediately by a professional.

With fall on the horizon and cooler nights, scouting for and finding pockets of fungus now will help with control and eradication, avoiding potentially serious problems this winter. As I've said before, we need to treat these plantings just like the landscapes we have on the ground, constantly watching for problems. It isn't a bad idea to treat your greenroof plantings with a preventative fungicide drench of Subdue, Terrachlor or Zero-Tol now to stop potential outbreaks.    Check the label on the above products for application rates and apply in the morning when wind and other environmental conditions permit.  If you need any help with finding these products, give me a call or drop me an e-mail.  Remember Ben Franklin;  "A stitch in time saves nine".

April showers bring May flowers (right?) but what happens when it rains 20+ days in May and continues into early June? Well, we have been noticing more fungal outbreaks of many soil bourne pathogens  like Rhizoctonia and Fusarium which Wayne has mentioned above. The problem with crown rot and other fungus is that by the time you notice that you have a problem it could already be too late to begin treatment. So, we have been encouraging our clients to let us use a preventative biological control produced by BioWorks that we incorporate into our maintenance program when conditions are right for this fungus to grow. Right now would be an excellent time to apply this biological fungicide because of the prolonged rain events that we have recieved and given that the temperatures and humidity are on the rise. Here is a little information about this product.

Microbial fungicide and bactericide
EPA Registered

Controls of a wide array of both fungal and bacterial pathogens, while providing outstanding plant, human and environmental safety.  CEASE controls disease using multi-site modes of action for superior resistance management, and leaves virtually no residues on plants or flowers.  

CEASE can be used on ornamentals (container or field), trees, shrubs, potted and cut flowers, annual and perennial bedding plants, tropical foliage plants, seedlings, conifers, covered vegetables. 
CEASE can be used in the field, greenhouse, nurseries - open or enclosed, shade house environments, interiorscapes, seedling production sites, forest seedling production sites, agricultural, residential and commercial landscapes, and reforestation.

For Foliar Diseases
BotrytisCEASE is an effective alternative to synthetic chemicals for fungal pathogens such as Botrytis gray mold and powdery mildews, and to coppers for bacterial diseases, such as Erwinia and Xanthomonas. With a 4-hour re-entry interval and a 0-day preharvest interval, CEASE provides growers flexibility and labor costs savings.

For Soil Diseases
CEASE is also a broad spectrum root biofungicide for the control of soil borne diseases on a wide range of ornamentals and vegetables. CEASE enhances germination and plant growth by suppressing diseases caused by Rhizoctonia, Pythium, Fusarium and Phytophthora.

Mode of Action
Based on a naturally occurring patented strain of Bacillus subtilis (strain QST 713), CEASE contains a group of natural antifungal and antibacterial compounds with multiple modes of action to destroy pathogens. CEASE is a valuable addition to any disease control program where resistance development is a concern.

CEASE, a liquid formulation, easily goes into suspension. It is compatible with a wide range of pesticides, fertilizers and adjuvants. The use of a spreader/sticker or wetting agent is strongly recommended to improve canopy penetration and coverage. Use CEASE immediately before or after a B-Nine application without the phytotoxicity concerns
common with coppers.


Problems with Pythium and other Diseases on Green Roofs

We are hearing about problems with Pythium and other fungal diseases on Green Roofs.  To try and avoid these problems, start with an organic healthy base.  There is no need for harsh synthetic chemicals to cure these problems.  At install use VermaPlex and Pure Castings along with your fully decomposed Compost.

VermaPlex is an all in one shot: a source of micro-organisms and humates that suppress disease and improve the soil-plant relationship.  Pure Castings is a special high quality organic fertilizer, high in minerals and free of weed seed, nematodes, E-coli & Salmonella.  It contains natural soil microbes with high bio-diversity.

Funguses start on decaying organic matter and capitalize on weakened plant material This begins in the roots.  VermaPlex is loaded with native micro-organisms that proliferate in the soil, thereby completely out-competing the pathogens.  You are adding the balance back by offering competitive organisms which will result in disease suppression.  This can help to solve the problems that we are seeing of failing roofs and dead plants after a year.  You are creating a sustained ecosystem and healthy strong plants.  Add Pure Castings and VermaPlex at install and you will see lasting results.  If you are dealing with an established Green Roof exhibiting signs of disease, then a maintenance program with VermaPlex and Pure Castings can help to rebuild the plant-soil eco-system, re-strengthening the plants and out-competing the bad bugs to restore and re-enliven your Green Roofs.


Recently, Circle Organics supplied Pure Castings and VermaPlex for the new Yankees Stadium Rooftop Garden on their Parking Garage.   We will keep you posted.

website: www.circleorganics.com

For more information contact  diane@circleorganics.com


Edited Thu, Jul 30, 2009 9:20 AM

I have heard that some of our suppliers and growers are using more biological controls like Root Shield and Actino-Iron in the plant propagation process. They believe that you can obtain the same level of control with biological treatment which features Streptomyces lydicus and Trichoderma harzianum. Normally, they will mix the granules into their potting mix as a preventative measures during the growing season when outbreaks would be more likely to happen. Has anyone thought of using these same controls as part of a larger integrated pest management program or as a standard practice for maintaining vegetated roofs. I would think that this treatment would be useful on newly planted "intensive" roofs where plug plantings would be the most vunerable until the root zone becomes more established.

We are especially interested in the Actino-Iron product due to it's ability to be easily broadcast on a roof (normally at an application rate between 8-10lbs./1,000 sq. ft.) and that it will remain active in the soil for around three months. We think that this level of prevention would be adequate for a preventative treatment a whole sort of soil bourne diseases like Fusarium, Pythium, Rhizoctonia, Phytophthora, Phytomatotricum, Aphanomyces, Monosprascus, Armillaria, Sclerotinia, Postia, Verticillium, Geotrichum and other root decay fungi. Has anyone perscribed and used Actino-iron as a preventative control for fungus in their projects. It looks like a fantastic product and many nurserymen swear by it. I would be curious to hear anyones feedback on this product or similar products like Cease and RootShield.

Back in 2008, Wayne Mills wrote on this topic:

With fall on the horizon and cooler nights, scouting for and finding pockets of fungus now will help with control and eradication, avoiding potentially serious problems this winter. As I've said before, we need to treat these plantings just like the landscapes we have on the ground, constantly watching for problems. It isn't a bad idea to treat your greenroof plantings with a preventative fungicide drench of Subdue, Terrachlor or Zero-Tol now to stop potential outbreaks.

Is this considered a best practice for Fall?  What are others doing to prevent fungus and eradicate other soil-based pathogens prior to entering winter dormancy?

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