A rickettsia‐like organism associated with diseased white clover

SUMMARY Diseased white clovers (Trifolium repens) , with symptoms similar to clover club leaf, were found in England. Electron microscopy of thin sections revealed rickettsia‐like organisms, 1–2 μm long by 0–2‐0‐3 μm diameter, in the phloem cells of these diseased plants. They were not present in healthy clover plants. At 23–30 °C the organisms multiplied rapidly and symptoms became more severe. After treatment with penicillin the organisms degenerated and plants showed remission of symptoms.