Blight
Blight is a rapid and complete chlorosis, browning, then death of plant tissues such as leaves, branches, twigs, or floral organs. Accordingly, many diseases that primarily exhibit this symptom are called blights. Several notable examples are:
Highland Potato Famine
Blight returned year after year, but never to the same extent as in 1846. As late as 1854, the complete loss of the potato crop was being reported for local blackspots such as the Hebridean communities of Barra and Harris (where the blight was said to be more prevalent than in 1846). In subsequent years blight was usually reported in various localities, but it was always only partial and never as bad as first feared: "There is some clamour about the potato blight but ... the fear is greater than the hurt". On Lewis, Sir James Matheson had spent £33,000 in three years to support his tenants; in six of the next thirty years he had to provide similar help, but on a much smaller scale and with a greater likelihood of being repaid: 
Most landlords worked to lessen the effects of the famine on their crofting tenants; forgoing rent, donating to the relief committees, running their own parallel relief operations, funding the introduction of new crops and industries or reviving old ones. However, as it became apparent that crofting at current population levels had long-term problems, they feared that the government would impose some system of permanent relief charged against their estates (either directly or through Poor Law reform). They instead sought to solve or remove the problems by inducing their poorer tenants to migrate to the Lowlands, or emigrate overseas.