Canker

A plant canker is a small area of dead tissue, which grows slowly, often over years. Some cankers are of only minor consequence, but others are ultimately lethal and therefore of major economic importance in agriculture and horticulture. Their causes include such a wide range of organisms as fungi, bacteria, mycoplasmas and viruses. The majority of canker-causing organisms are bound to a unique host species or genus, but a few will attack other plants. Weather and animals can spread canker, thereby endangering areas that have only slight amount of canker.

Butternut canker is a lethal disease of Butternut trees, and has no cure.

Although fungicides or bactericides can treat some cankers, often the only available treatment is to destroy the infected plant to contain the disease.

Examples
Tree cankers (right) are caused by injuries to the bark that allow pathogens or insects in to infect the tree. Compared above is a healthy tree and segment (left) to a tree infected and containing a canker.
  • Canker on a birch
  • Canker on a beech tree.
  • Canker on an ash tree in North Ayrshire, Scotland.
gollark: Please also give me write access to the repo.
gollark: Oh, right, array indexing.
gollark: ```python# parsita-based pseudocode syntax parserfrom stmt import *from parsita import *from parsita.util import constantdef compose(f, g): return lambda x: f(g(x))def map_expr(x): start, end = x if end == "": return start return Op([start, end[1]], end[0])def map_unop_expr(x): return Op(x[1], x[0])def aliases(name, aliases): p = lit(name) for alias in aliases: p |= (lit(alias) > (lambda _: name)) return pclass ExprParser(TextParsers): ε = lit("") IntLit = reg("\-?[0-9]+") > compose(IntLit, int) StrLit = "'" >> reg("[^']*") << "'" > StrLit # TODO escapes (not in "spec" but could be needed) FloatLit = reg("\-?[0-9]+\.[0-9]+") > compose(FloatLit, float) Identifier = reg("[a-zA-Z_]+[a-zA-Z_0-9]*") > Var BracketedExpr = "(" >> Expr << ")" UnaryOperator = lit("NOT") Start = FloatLit | StrLit | IntLit | BracketedExpr | (UnaryOperator & Expr > map_unop_expr) | Identifier # avoid left recursion problems by not doing left recursion # AQA pseudocode does not appear to have a notion of "operator precedence", simplifying parsing logic nicely BinaryOperator = aliases("≤", ["<="]) | aliases("≠", ["!="]) | aliases("≥", [">="]) | lit("DIV") | lit("MOD") | lit("AND") | lit("OR") | reg("[+/*\-=<>]") End = (BinaryOperator & Expr) | ε Expr = (Start & End) > map_exprparse = ExprParser.Expr.parsex = parse("1+2+3 != 6 AND NOT 4 AND x + y")if isinstance(x, Failure): print(x.message)else: print(x.value)```
gollark: <@332271551481118732> Expression parsing is done, I think.
gollark: I wonder if AQA pseudocode *does* have operator precedence. We may need to harvest exam papers.

See also

References
  1. Gardan, L.; Shafik, H.; Belouin, S.; Broch, R.; Grimont, F.; Grimont, P. A. D. (1 April 1999). "DNA relatedness among the pathovars of Pseudomonas syringae and description of Pseudomonas tremae sp. nov. and Pseudomonas cannabina sp. nov. (ex Sutic and Dowson 1959)". International Journal of Systematic Bacteriology. 49 (2): 469–478. doi:10.1099/00207713-49-2-469. PMID 10319466. Archived from the original on 15 April 2013.
  2. Southwest Canker
  • Canker Diseases of Trees
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