Phytophthora Tentaculata

New disease warning!

---

Imagine a world without oregano. Or celery. Or sage. Or chrysanthemums. It could happen.


There is a new plant disease and its name is Phytophthora tentaculata. [Wait! Come back!]


​Just because this disease is tricky to pronounce (Fie-TOF-ther-uh), doesn’t mean you can ignore it. Its name is from the Greek phytón (plant) and phthorá (destruction), so the name phytophthora means “the plant-destroyer”. (The tentaculata part of the name refers to the tentacle shape of these particular  pathogens.)


First noted in Germany in 1993, Phytophthora tentaculata hitched a ride on contaminated nursery stock and made its way to Central California and Monterey County in 2012. It is spreading rapidly and is deadly to many of your garden and landscape plants.


​According to the Retail Nursery and Garden Center IPM News, Phytophthora tentaculata poses long term potential environmental and economic threat to many native and non-native plants, as this pathogen can stay in the soil for many years and there is currently no known treatment.


What is Phytophthora tentaculata?

Phytophthora tentaculata is a member of the water mold family. In the world of scientific classification, water molds fall between fungi and algae. These pathogens attack stems and roots and frequently kill their host plants. There are several types of phytophthora, including those that cause potato blight, crown rot, and sudden oak death. You cannot see these organisms with the naked eye, but it is important that you keep a look out for the symptoms and know which plants are currently considered susceptible.


Host plants

Many California native plants are highly susceptible to Phytophthora tentaculata. The most recent list includes:

• Buck brush (Ceanothus cuneate)
• California coffeeberry (Frangula californica)
• California sagebrush (Artemisia californica)
• Coyote mint (Monardella villosa)
• Mugwort (Artemisia douglasiana) 
• Toyon (Heteromeles arbutifolia)

Non-native plants that are at risk include:

• Celery (Apium graveolens)
• Costus root (Saussurea costus)
• Hickory (Cichorium intybus)
• Chrysanthemum species (hybrids, marguerite, and oxeye daisy)
• Rocket larkspur (Consolida ajacis)
• Sage (Salvia species)
• Tarragon (Artemisia dracunculus)
• Barberton daisy (Gerbera jamesonii) 
• Oregano (Origanum vulgare)
• Lavender cotton (Santolina chamaecyparissus)
• Verbena species (vervain hybrids)

Symptoms of Phytophthora tentaculata

• stunted growth
• chlorosis (yellowing leaves)
• stem cankers
• root lesions
• stem collar lesions
• root rot
• reduced root growth

Preventing Phytophthora tentaculata infestation

Contaminated nursery stock is the most likely way this pest will reach your garden and water management is the best way to prevent infestation. Phytophthora tentaculata are soil borne, which means they spread by sticking to plants, tools, containers, and shoes. Phytophthora tentaculata spores can also travel through the movement of water. This means that spraying an infested plant can transfer the water molds to nearby plants. Since symptoms do not appear right away, it is in your garden’s best interest to stay away from unhealthy-looking plants until you know for sure what is going on. These tips can help you protect your garden:

• Only install healthy-looking plants
• Do not plant plants too deeply or water excessively
• Allow soil to dry out between waterings
• Ensure proper drainage
• Avoid buying infected plants or their neighbors
• Quarantine all new plants for at least 4 to 6 weeks, and that includes water that may drip from the container
• Wash tools, boots, and hands after handling potentially contaminated plants
• Sanitize shoes with bathroom cleaner after walking through an infected area
• When possible, plants seeds rather than plants
• Ask nursery or garden store staff if they are aware of this new problem and how they are preventing its spread (You may be the first person to bring it to their attention!)
• Do not add contaminated plants to the compost pile

If Phytophthora tentaculata appears in your garden or landscape, contact your local Cooperative Extension Office right away. They may have helpful advice that will protect your plants and they need to know how far this disease is spreading.