In The Death of Grass by John Christopher, a virus kills all grasses plunging the world into famine and chaos. It is a darker work than Day of the Trifids because the protagonists’ enemy is well pretty much everyone else who is struggling to survive. There is no general incapacity inflicting the population. No monsters to helpfully empty the land of inhabitants and moral dilemmas. It’s ‘them or us’ where morals take second place to survival. If you brought this one home to your mother it would hold her at gun point while it emptied the larder.
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 - John Christopher)