Sugar cane is attacked by a number of diseases and insects which are transferred from country to country with seed canes. Of the more than 60 diseases, 9 cause serious losses in susceptible varieties though fortunately none of them are distributed world-wide. Apart from this, the incidence of certain weeds is so severe that crop values are seriously reduced.
Viruses cause mosaic, Fiji disease and ratton stunting disease; bacteria cause gummosis and leaf scald; fungi cause red rot, smut, downy mildew and root rot. The highly destructive mosaic disease at one time threatened to destroy entirely the sugar cane industry in such places as Java, Puerto Rico, Argentina and Louisiana. Gummosis is widely distributed, occurring in Brazil, Australia, Mauritius and several other countries. Fiji disease and leaf scald are both prevalent in the Pacific area. Insect pests include various moth borers and beetles, froghoppers, the woolly aphid and sapsucking leafhoppers. In the western hemisphere and to some extent in India, Java and the Philippines, moth borers have been especially destructive. In the Pacific area, particularly Australia, the grubs of several species of beetles have also caused severe damage. Of the weed pests, the most severe and widespread are Cyperus rotundus, Cynodon dactylon, Digitaria sanguialis, Portufaca oleracea, Eleusine indica and Echinochloa colonum. Of these the most important is Cyperus rotundus which is a principal weed of sugar cane wherever it is grown.