LEAF-SPOT DISEASE OF THE TOBACCO-PLANT.

New Zealand Journal of Agriculture, Volume 41, Issue 1, 21 July 1930, Page 52

LEAF-SPOT DISEASE OF THE TOBACCO-PLANT.

Tobacco leaves from Rotorua affected by a leaf-spot disease were submitted to the Plant Research Station during the past season for examination. The numerous leaf-spots are at first brown in colour, later changing to almost white. In a number of instances the affected part falls away, giving the leaf a perforated appearance' The spots vary very much in shape and size, the shape being round and angular, and sometimes elongated, and the size from mere specks to J in. in diameter. Among growers , the disease is sometimes known as “ angular leaf-spot,” a term that is often rather loosely applied. After making cultures from these affected leaves, the Mycologist reports The specimens have now yielded an organism known as Macrosporium tabacinum, recorded in America and South Africa as the cause of a condition identical with that present on the specimens supplied. This disease is probably transmitted with the seed, as are most species of Alternaria and Macrosporium. Disinfection of the seed is advisable, and of the seed-bed prior to sowing. Seedlings showing signs of the disease should be removed, and the remainder of the bed sprayed with Bordeaux 5-4-50, which at this stage will not damage the leaf.” • . A disease-preventive treatment for tobacco-seed is being worked out by the Mycologist, and it is hoped that some definite information on this matter will be available before long. • —Horticulture Division. -