SUMMARY.1This investigation proves that lightning is a factor of the first importance in the causation of disease on coconut palm plantations in Malaya.2The “bud‐rot” symptoms occurring in Malayan coconut palm plantations are produced entirely by lightning or the after‐effects thereof. No evidence of the presence of aPhytophthorahas been obtained.3Lightning has been proved to be of some importance in the causation of disease on rubber plantations.4The typical effects on rubber plantations are described, and attention is specially directed to the association of claret‐coloured bark canker at the collar of trees slightly affected by lightning.The writer wishes to acknowledge the considerable help rendered by his colleague, Mr H. Gunnery, in the preparation of photographs and recording of field work. Thanks are also tendered to Mr H. T. A. Biddle‐combe for great assistance in the coconut investigations and to Mr G. Shelton‐Agar for similar assistance in connection with the work on rubbe