What is this mystery orange structure on this grass species found this afternoon on the Phase 1 grassland? It is about 2.5cm long and surrounds the grass stem. Look out for the answer soon....
This orange substance is actually a fungus and is a common disease of various plants (both monocotyledons and dicotyledons), known as rust disease. There are various species of fungus involved, but most commonly they are of the genera Puccinia or Uromyces. The colour can vary depending on the species of fungus, but is usually yellow or orange, but occasionally can be black, especially later on in the year.
The fungus usually appears in late-summer or autumn and at first is just yellow/orange coloured flecks on the grass leaves, enlarging to eventually surround the grass stalk as in the photo. This is the fruiting body of the fungus and produces thousands of spores, that can be carried large distances by the wind.
The fungi require several hours of damp conditions on the leaf's surface in order for them to germinate, therefore infection can be worse in wet summers (like this year!) and often more prominent in the autumn.