Phytophthora Root Rot
Purpose of our research:
- To determine the causes of Phytophthora root rot in the Pacific Northwest nursery industry.
- To determine why disease control methods for Phytophthora root rot sometimes fail.
- To develop and refine disease control methods for Phytophthora root rot that actually work.
What is Phytophthora root rot?
Phytophthora root rot is a plant disease that is caused by several different species of Phytophthora. These organisms are closely related to
Phytophthoras are a type of oomycete, or water mold. Although they look like microscopic fungi, they are actually more closely related to algae. These pathogens grow by producing hyphae (long thin, threads that grow through the soil or inside plant tissues). Phytophthora species also produce several types of spores. Some spores, like chlamydospores and oospores, are survival structures that help the pathogen survive for long periods of time. When conditions improve, these spores can germinate and infect plant roots. There is another spore type, called a zoospore. Zoospores are produced within a saclike enclosure called a sporangium.
Plant roots become infected by Phytophthora when the hyphae penetrate the
They also produce swimming spores, called zoospores, that can swim through moist soils to infect plants. Symptoms of the disease generally start with stunting, yellowing (chlorosis), or reddening (anthocyanosis). Belowground, the are growing through the plant's roots, killing the root tissues as they go.
Diseased plants often occur in groups (disease pockets) within a field or block of container plants.
Phytophthora root rot is a plant disease that is caused by several different species of Phytophthora. These organisms are closely related to
Phytophthoras are a type of oomycete, or water mold. Although they look like microscopic fungi, they are actually more closely related to algae. These pathogens grow by producing hyphae (long thin, threads that grow through the soil or inside plant tissues). Phytophthora species also produce several types of spores. Some spores, like chlamydospores and oospores, are survival structures that help the pathogen survive for long periods of time. When conditions improve, these spores can germinate and infect plant roots. There is another spore type, called a zoospore. Zoospores are produced within a saclike enclosure called a sporangium.
Plant roots become infected by Phytophthora when the hyphae penetrate the
They also produce swimming spores, called zoospores, that can swim through moist soils to infect plants. Symptoms of the disease generally start with stunting, yellowing (chlorosis), or reddening (anthocyanosis). Belowground, the are growing through the plant's roots, killing the root tissues as they go.
Diseased plants often occur in groups (disease pockets) within a field or block of container plants.
Background:
Phytophthora root rot has been a serious problem in the nursery industry for almost 100 years. The disease affects many plant species in the nursery industry, including boxwood (Buxus), juniper (Juniperus), Pieris, rhododendron and azalea (Rhododendron), among many, many others. Honestly, sometimes it feels like what ISN't affected by root rot. Our research focuses on rhododendron because this crop is important to Oregon and because it has the longest history of research (below). Richard White was the first person to officially diagnose the disease on rhododendron plants in New Jersey nurseries back in 1927. He isolated the species Phytophthora cinnamomi from . For decades
Phytophthora root rot is caused by a number of different soilborne Phytophthora species, such as P. cactorum, P. cambivora, P. cinnamomi, P. citrophthora, P. cryptogea, P. drechsleri, P. lateralis, P. megasperma, P. nicotianae, P. niederhauserii, P. occultans, P. pini, P. plurivora, P. pseudocryptogea, and P. tentacula. There is another set of Phytophthora species, that primarily infect aboveground leaves and stems are often very different set than the Phytophthora species that cause foliar blights and stem cankers, . There is a different set of Phytophthora species that cause foliar and stem cankers are often different than those that cause Phytophthora root rot, with some overlap. Species that infect above-ground portions of the plant include P. syringae, P. ramorum. However, some species, such as P. plurivora, are capable of infecting foliage, stems, AND roots ().
So, why is all of this discussion important? Because
Phytophthora root rot has been a serious problem in the nursery industry for almost 100 years. The disease affects many plant species in the nursery industry, including boxwood (Buxus), juniper (Juniperus), Pieris, rhododendron and azalea (Rhododendron), among many, many others. Honestly, sometimes it feels like what ISN't affected by root rot. Our research focuses on rhododendron because this crop is important to Oregon and because it has the longest history of research (below). Richard White was the first person to officially diagnose the disease on rhododendron plants in New Jersey nurseries back in 1927. He isolated the species Phytophthora cinnamomi from . For decades
Phytophthora root rot is caused by a number of different soilborne Phytophthora species, such as P. cactorum, P. cambivora, P. cinnamomi, P. citrophthora, P. cryptogea, P. drechsleri, P. lateralis, P. megasperma, P. nicotianae, P. niederhauserii, P. occultans, P. pini, P. plurivora, P. pseudocryptogea, and P. tentacula. There is another set of Phytophthora species, that primarily infect aboveground leaves and stems are often very different set than the Phytophthora species that cause foliar blights and stem cankers, . There is a different set of Phytophthora species that cause foliar and stem cankers are often different than those that cause Phytophthora root rot, with some overlap. Species that infect above-ground portions of the plant include P. syringae, P. ramorum. However, some species, such as P. plurivora, are capable of infecting foliage, stems, AND roots ().
So, why is all of this discussion important? Because