|
Phytophthora
Diseases and Sudden Oak Death in Tennessee Nurseries
Margaret T
Mmbaga
Institute of Agricultural and Environmental Research Seminar Series
Nursery Crop
Research Station
Tennessee State University, McMinnville, TN
March 9, 2005
More than 60 species of Phytophthora
are known, most are primary plant pathogens with very limited
saprophytic ability. Many are responsible for serious diseases of
economically important crops and natural plant communities. Many forest
trees and woody ornamental plants are hosts to different Phytophthora
species resulting in tree decline, dieback and tree mortality. Many
cause root rots, but some cause foliar blights, collar or crown rots
with no effect on roots. All Phytophthora have a soil phase and can
survive in the soil and spread easily with soil, water flow and farm
machinery. Phytophthora diseases are difficult to control and the best
control is preventative, to stop the introduction into non-infested
areas. Many Phytophthora species have deciduous propagules (sporangia)
that are dispersed by rain splash, and can spread long distances in
wind-borne droplets. Out of the root-rotting Phytophthoras, P.
cinnamomi, P. citrophthora (on citrus) and P. nicotianae
(parasitica), P. cactorum (citricola) P.
cryptogea, etc. are common in ornamental plants. Recent emergence of
P. ramorum causing Sudden Oak death Syndrome has caused a lot of
concern in that it has a wide host range that includes important trees
plants that are widespread in forest and urban areas. P. ramorum
affects mostly “above ground” plants parts. Sudden Oak death Syndrome
threatens the nursery industry because 90% of nursery stock is shipped
out of their area of production and involve soil movement. The disease
is known to affect 59 different hosts and many other associated host
species. As part of the disease detection and management program, the
U.S. Department of Agriculture’s Animal and Plant Health Inspection
Service (APHIS) is regulating the interstate movement of P. ramorum
hosts and associated host plants from all California nurseries effective
March 26, 2004. Such regulation has significant economic impact to the
nursery industry. A new project funded by USDA Capacity Building grants
was initiated n Oct 2004 to conduct a systematic and intensive survey
for Phytophthora diseases including Sudden Oak Death Syndrome in
Tennessee nurseries. The project will establish a disease monitoring
system for rapid detection and containment of Phytophthora species in TN
nurseries. Specific objectives of this project are: (1) to identify and
d characterize Phytophthora diseases in nurseries and around nurseries,
(2) Confirm their pathogenicity, on different hosts, (3) Documentation
of Phytophthora species, their incidence, hosts and infection severity
in TN nurseries, and (4) Develop an educational tool on Phytophthora
diseases for nursery growers.
Return
to Seminar Series
|
