What is 'Dutch elm disease' and what causes it?
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A
A bacterial wilt spread by aphids that kills elm within weeks
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B
A lethal vascular wilt disease caused by the fungus Ophiostoma ulmi, spread by elm bark beetles
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C
A root rot disease caused by Phytophthora species affecting elms in wet soils
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D
A defoliating disease caused by a caterpillar specific to American elm