Many herbaceous and woody ornamental crops are susceptible to root rot when exposed to wet, warm soil. Diseased roots prevent nutrients from reaching all areas of the plant, resulting in its diminished appearance and possible death.

Maintaining a clean, dry growing environment, along with regular scouting is the best way to keep root rot out of your operation. Additionally, adding effective products labeled for root rot control to your disease management program helps to not only treat affected crops, but also prevent future infections.

Primary Pathogens

Root rot is caused by a variety of different pathogens that harm susceptible plants in different ways.  Types of root rots to watch out for include:

Phytophthora Root Rot

Causal agent: Phytophthora nicotianae, P. cryptogeae, P. cactorum, P. cinnamomi

Early symptoms of Phytophthora root rot include wilting and smaller than normal foliage. Plants will appear drought stressed and will lose lower leaves depending on the amount of infection. Diseased plants exhibit signs of slow growth and reduced vigor. It’s important to scout the roots and crown of susceptible plants as the fungus attacks there first.

Rhizoctonia Root & Crown Rot

Causal agent: Rhizoctonia solani

Rhizoctonia pathogens often infect roots and lower stems of the plant when plants are transplanted too deeply. When scouting, look for dry, sunken cankers on the lower part of the stem at the soil line. Infections often causes the plant to collapse, leading to an unsalable crop.   

Rhizoctonia stem rot on poinsettia
Nancy Rechcigl, Syngenta photo. 2016

Pythium Root and Crown Rot

Causal agent: Pythium spp. (Pythium aphanidermatum, P. ultimum, P. irregulare)

When scouting for Pythium root and crown rot, look out for plants with leaves that have lowered and turned yellow. The roots will be soft and brown, with a water-soaked appearance. Removing the outer portion of the root is a simple test to see if roots are infected. If it comes off easily, leaving behind the stringy vascular core of the root, the plant is likely infected. Infected seedlings will collapse shortly after germination or will appear severely stunted and nutrient deficient.

Pythium root rot on poinsettia
Nancy Rechcigl, Syngenta photo.

Take Control with Proven Treatment Options

If you’ve spotted Pythium root rot in your operation, consider adding Subdue Maxx^® fungicide into your disease management program. As a soil treatment, Subdue Maxx provides systemic protection for roots and stems from invasive oomycete pathogens. It can be tank mixed with many other products, delivering comprehensive control to all forms of soilborne pathogens.

Heritage^®  or Mural^® fungicides are excellent tank-mix or rotation partners with Subdue Maxx, providing proven control of Rhizoctonia solani as well as additional protection against Pythium and Phytophthora root and stem rots. Both fungicides are xylem mobile, allowing them to move into and upward throughout the plant, inhibiting disease progression for better control.

View our fungicide disease guide to discover all the available solutions to control root rot in your operation.

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