Phytophthora tentaculata: A New Exotic and Invasive Disease new plant pathogen in the genus pathogens of agricultural, ornamental, species and one additional genus have A Phytophthora (pronounced Fie- and forest plants. been found infected, all common in the TOF-ther-uh) has recently been found native plant nursery trade and in wild- Similar to other members of the Phy- in several California native plant nurser- lands. These include Artemisia dougla- tophthora genus, P. tentaculata releases ies and habitat restoration sites. The siana (mugwort), A. dracunculus swimming spores that move through pathogen, Phytophthora tentaculata, (tarragon), A. californica (California water and are attracted to plant root poses a risk of disease in wildlands, gar- sagebrush), Salvia species (sage), Ceano- exudates. Once infected, the pathogen dens and landscapes that use susceptible thus cuneatus (buck brush), Frangula can cause disease in susceptible plant California native and non-native plants. californica (California coffeeberry), roots. If susceptible stems are contacted, Once introduced in these areas, the Monardella villosa (coyote-mint), and infection can occur there following pathogen can generate disease for years Heteromeles arbutifolia (toyon). water movement or splash, and stem to come, potentially causing lasting envi- disease can also result from the patho- In California, P. tentaculata was first ronmental and economic impacts. gen growing into the stem from the isolated from Diplacus aurantiacus Because both native and non-native roots. Phytophthora tentaculata cannot (orange bush monkeyflower) where it California plants from nurseries can be seen with the naked eye unless grown was observed causing aboveground carry new pathogens and other pests, it in a laboratory. However, it usually pro- symptoms (Fig. 1a) that included is important to remember that only duces visible symptoms – stem cankers stunted growth, sparse and chlorotic healthy plant material should be used and root rots – on host plants. foliage, stem collar lesions (Fig. 1b) and for planting. plant death. Root system symptoms Hosts, symptoms and detection included necrotic, sunken lesions, and What is Phytophthora? few roots (Fig. 1c). Soon after, P. tentacu- The pathogen was first described in 1993 Phytophthoras are microscopic, fungus- lata was detected in the nursery trade in from a nursery in Germany. In the like organisms called water molds that the U. S., the pathogen was recovered in United States, it was first found in 2012 produce spores and hyphae. Many are central California wildlands, presumably in a nursery in Monterey County, and to soilborne, attack plant roots and stems, having been released into the landscape date is present only in central California. and spread by the movement of infested via contaminated nursery plants used in Currently, seventeen plant species and soil, including soil stuck to tools, con- restoration plantings. It has now been two additional genera worldwide are tainers, or shoes. The genus Phytoph- found in Alameda, Butte, Monterey, thought to be susceptible to P. tentacu- thora is large, with over 100 described Placer, and Santa Cruz Counties. lata, but the list may expand as we learn species, including the Sudden Oak more. In California, eight native plant Death pathogen and other destructive ... continued on page 4 Page 3 | DecemberPage 2016 A B C [IMAGES: (A) L. SIMS; (B-C) S. ROONEY-LATHAM, CDFA] Figure 1. (a) Dying and dead Diplacus aurantiacus (orange bush monkeyflower) with advanced above ground symptoms, typical of Phytophthora disease. The infected plants has chlorotic (yellowing and browning) foliage. (b) The inner stem and root crown of a diseased D. aurantiacus was discolored and advanced up the stem from the roots. (c) Artemisia douglasiana (mugwort) plant infected with P. tentaculata had a sparse root system a result of severe root rot. P. tentaculata ...continued from page 3 Germany, Italy, Spain, and China have Avoidance: Avoid buying known host- If possible, check root systems for abnor- reported disease from P. tentaculata on plant container stock and do not pur- mally large numbers of dead and dying several plant species including Apium chase plants that appear unhealthy or roots, few healthy new roots, and graveolens (celery), Saussurea costus otherwise potentially contaminated. At necrotic spotting on roots that are still (costus root), Cichorium intybus (chic- more advanced stages of disease, plants living. If the roots appear to be infected, ory), Chrysanthemum species (hybrids, may exhibit symptoms as outlined above, do not move soil from the garden bed marguerite, and oxeye daisy), Consolida but nearby plants may still look healthy and nearby infected plants to other parts ajacis (rocket larkspur), Gerbera jameso- even though they have been contami- of the garden. nii (Barberton daisy), Origanum vulgare nated through soil or water movement. Change irrigation practices to reduce the (oregano), Santolina chamaecyparissus If a number of plants in the nursery potential for Phytophthora growth, as (lavender cotton), and Verbena species block show symptoms of infection, do outlined in the UC IPM Pest Note: Phy- (vervain hybrids). Many of the above not buy those plants or their neighbors. tophthora Root and Crown Rot in the species are grown in California and The host species list is a work in prog- Garden at ipm.ucanr.edu/PMG/PEST- should be considered at risk to disease. ress; be aware that other, unlisted species NOTES/pn74133.html. Clean your tools may also be susceptible. and boots before working another area Prevention and Management Quarantine: If you purchase host plants of your garden. You may wish to contact Prevention: By far, prevention is the best (or closely related species), consider your local Agricultural Commissioner or possible method for dealing with any setting them aside before planting. Give UC Cooperative Extension office to see Phytophthora pathogen. Consider plant- the plants time (4 - 6 weeks) to develop if they can offer updates or further ing from seed as Phytophthora in general symptoms before planting them in your advice. is rarely transmitted this way. If buying yard, and be sure soil and excess water For more information, including refer- container stock of any of the above plant from these plants does not flow into ences to original research and related species, find out if the nursery is follow- your garden soil. If symptoms develop, articles, see the pages covering this ing best management practices for pre- dispose of the plant, soil, and container pathogen at www.suddenoakdeath.org/ venting Phytophthora (for example: according to disposal guidelines for your diagnosis-and-management/nursery- tinyurl.com/zvmjyt3). Purchase plant area. Do not home-compost this patho- information/phytophthora-tentaculata/. material that has been grown in pasteur- gen, as it may not be killed. ized soil and under proper sanitation Remediation: If plants are already in the procedure. Do not use/buy plants or ground and exhibiting symptoms such material that has been in the nursery for as stunted growth and/or chlorotic foli- an extended time, these can become IPM Workshops for Retail age, check the root collar and stem for contaminated with Phytophthora and Nursery and Garden Centers necrotic sunken lesions and/or stem rots. other pathogens. Register now for one of these train- the-trainer workshops designed ~Laura Sims, UC Berkeley, [email protected]; Igor Lacan, UCCE San especially for retail nursery and Francisco and San Mateo counties, [email protected]; Steven Swain, UCCE garden center employees. Topics will Marin County, [email protected]; and Matteo Garbelotto, UC Berkeley, include invasive pests, Asian citrus [email protected] psyllid and huanglongbing disease, household pests, and pesticides. The University of California Produced by the University of California Statewide cost is only $30 and you’ll come back Statewide IPM Program IPM Program with partial funding from the USDA NIFA with materials and information to 2801 Second Street EIPM Coordination Program. To simplify information, Davis, CA 95618­7774 trade names of products have been used. No endorse­ better serve your customers! ment of named products is intended, nor is criticism Editor: K. Windbiel­Rojas implied of similar products not mentioned. For more information about managing pests, con­ Tuesday, January 24, 2017 tact your University of California Cooperative Exten­ Oakland, CA E-mail: [email protected] sion office listed under the county government pages Details at http://ucanr.edu/sites/ Online: ipm.ucanr.edu/RETAIL of your phone book, or visit the UC IPM Web site at ipm.ucanr.edu. retailipm2016oakland/ ANR NONDISCRIMINATION AND AFFIRMATIVE ACTION POLICY STATEMENT Tuesday, January 31, 2017 It is the policy of the University of California (UC) and the UC Division of Agriculture & Natural Resources not Sacramento, CA to engage in discrimination against or harassment of any person in any of its programs or activities. (Complete nondiscrimination policy statement can be found at ucanr.edu/sites/anrstaff/files/215244.pdf.) Details at http://ucanr.edu/sites/ Inquiries regarding ANR’s nondiscrimination policies may be directed to John Sims, Affirmative Action Contact, retailipm2017sac/ Page 4 | DecemberPage 2016 University of California, Agriculture and Natural Resources, 2801 Second Street, Davis, CA 95618, (530) 750­1397. WHAT IS IPM? Integrated Pest Management (IPM) programs focus on long-term prevention of pests or their damage through a combination of techniques including resistant plant varieties, biological control, physical or mechanical control, and modification of gar- dening and home maintenance practices to reduce conditions favorable for pests. Pesticides are part of IPM programs but are used only when needed. Products are selected and applied in a manner that minimizes risks to human health, beneficial and nontarget organisms, and the environment..