Plant diseases can be infectious (transmitted from plant to plant) or noninfectious. Noninfectious diseases are usually referred to as disorders. Common plant disorders are caused by deficiencies in plant nutrients, by waterlogged or polluted soil, and by polluted air.
Such refinements in the images of Betelgeuse's atmosphere has been helping to resolve the mystery of how massive amounts of dust and gas are expelled from red supergiant stars, an important source of enrichment for the interstellar medium.
Our Sun is a reasonably average star. Its surface temperature of 9,900 degrees F results in a yellowish light, just as Planck's equations predict. Betelgeuse, a bright star in the constellation of Orion, is much cooler, about 6,900 degrees F, and so even to the naked eye has an easily identified red hue.