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Clubroot is a soilborne disease caused by the biotrophic protist Plasmodiophora brassicae. The infection causes the formation of large galls on the roots which look like clubs. These formations impede nutrient and water uptake and can cause plant death, wiping out important money generating canola crops.
Lesions may enlarge and coalesce to kill the entire leaf. Symptoms are observed on all above-ground parts of the plant. [17] Lesions can be seen on the leaf collar, culm, culm nodes, and panicle neck node. Internodal infection of the culm occurs in a banded pattern. Nodal infection causes the culm to break at the infected node (rotten neck). [18]
These tumors exert significant pressure on the surrounding plant tissue, which causes this tissue to become crushed and/or distorted. The crushed vessels lead to reduced water flow in the xylem. Young tumors are soft and therefore vulnerable to secondary invasion by insects and saprophytic microorganisms.
Most bacteria associated with plants are saprotrophic and do no harm to the plant itself. However, a small number, around 100 known species, cause disease, especially in subtropical and tropical regions of the world. [15] [page needed] Most plant pathogenic bacteria are bacilli. Erwinia uses cell wall–degrading enzymes to cause soft rot.
It is responsible for a disease (commonly called milky spore) of the white grubs of Japanese beetles. The adult Japanese beetles pupate in July (in the Northeast United States) and feed on flowers and leaves of shrubs and garden plants. During this adult stage, the beetles also mate and the females lay eggs in the soil in late July to early August.
Infected tissue is removed from white pines and strict quarantines of Ribes spp. are maintained in high risk areas. [citation needed] Puccinia graminis is a macrocyclic heteroecious fungus that causes wheat stem rust disease. [citation needed] The sexual stage in this fungus occurs on the alternate host – barberry – and not wheat. The ...
Many phytoplasma-infected plants develop a bushy or "witches' broom" appearance due to changes in their normal growth patterns. Most plants exhibit apical dominance, but infection can trigger the proliferation of axillary (side) shoots and a reduction in internode size. [8] Such symptoms are actually useful in the commercial production of ...
The disease can be spread through the use of unfiltered water as well as unsterilized tools. Also leaving previous dead roots in soil can increase the risk of stem rot. Spores can also enter the plant through injured stem tissue on the plant including from insect attacks. The fungus impedes stem functions like transporting nutrients.