Life cycle of the ramorum fungus
Introduction
A ramorum fungus is a plant pathogen that causes diseases like sudden oak death and the death of the affected plants. Ramorum fungus is a water mold that spreads through infection of the host plant and the subsequent production of spores. These spores are spread through the wind and rain, and they require a cool, moist environment to develop and flourish. The spores are bisexual, meaning that two types of spores, the zoo-spores and the chlamydospores, are required to be present in order for an infection to occur. When the spores land on the foliage, the zoo-spores are released. The zoo-spores swim within the chlamydospore and hence, germination occurs. This process produces the ramorum fungus.
Life cycle of ramorum fungus
Birth
Ramorum fungus use spores for reproduction. The mature fungi release the spores which divide to form a hyphae which are threads like roots made of haploid. When this hyphae meets with two other different spores, they intertwine to form one cell that has two distinctive nuclei.
Growth
The egg that is produced forms a fungus that continues to feed and grow. Fungus extract nutrients from the environment and can often be found growing on the decaying organic matter.
Anamoprhic stage
Anamorphic stage means that the fungus is asexual, and it reproduces by dropping spores with distinctive hyphae that bond and grow into new fungus. This process is faster than sexual growth and results in clonal environments. At this stage the fungus is highly dependant on the environment.
Telemorphic stage
At this stage, two individual fungi meet and fuse, creating a gametangium which is a structure designed to form gametes. It then forms into a zygospore that germinates and undergoes meiosis to form a new hyphae which later forms a spore.
Spore dispensing
Fungi contain specialised structures that eject the spores into the air. Some will drop the spores into the soil. Though the use of build-up fluids, the ramorum fungi eject the spores to about 0.02 cm which is far enough for the to beginning the reproduction process again.
Tree species that are attacked by ramorum fungus
Broadleaved trees: The broadleaved trees that are mostly infected by ramorum fungi are the sweet chestnut and the beech. It affects the bark and the leaves. The affected barks look like large brown black cankers an the lower portion of the trunk that seep dark red sap.
Conifers: This mainly affects the larch. Its symptoms are needle like infections, shoot die back and cankers on the trunk and branches. The infected shoot tips wither and wilt as the infected needles appear black.
Bilberry: The ramorum fungus infected areas have necrotic brown stem lesions that look like bands on the stem. Affected leaves have black lesions that sometimes extend from the petiole into the leaves.
Rhododendron: The twigs, leaves and the shoot are affected. The affected plant appears wilted with black brown discolouring and a distinctive dagger pattern that spreads from the petiole to affect the leaf tips.
Treatment and control of ramorum fungus
As of now, there is no cure for ramorum fungus. Prevention of further infections is the best thing that can be done to reduce its damage to the plants. Fosetyl-AL and metalaxyl are used to treat new plants and to prevent spreading of the ramorum fungus. Fungicides are applied on the host plant during the seasonal conditions that predispose the development of the infection.
