CEREAL-SMUTS.

New Zealand Journal of Agriculture, Volume XXX, Issue 6, 20 June 1925, Page 374

CEREAL-SMUTS.

AN ILLUSTRATED KEY TO THE NEW ZEALAND SPECIES.

G. H. CUNNINGHAM,

Numerous requests have been made for the publication of an illustrated key to the cereal-smuts present in New Zealand, so as to facilitate recognition of each species. It is necessary for the farmer to know each species, for on account of certain differences in their life-histories the smuts are divided into two groups, and each group requires a different control treatment. This article has been prepared accordingly. It has been found necessary to supplement the illustrations with certain descriptive matter, calling attention to the salient features of each species, so as to facilitate diagnosis. Six species of smuts are present on cereals in New Zealand. These may be most conveniently arranged according to the host, (the plant attacked by the smut) as follows :■ — On wheat- — Ustilago Tritici Jens. —loose smut. Tilletia levis Kuehn and Tilletia Tritici Wint.- —stinking smut. On barley— - ' Ustilago Jensenii —covered smut. - 1 Ustilago Tritici Jens.* —loose smut. On oats Ustilago Avenae Jens, and Ustilago levis Magn.—oat-smut. By grouping the smuts in this manner these ' six species are conveniently divided into three groups. These in turn may be further subdivided according to macroscopic and microscopic characters. For example, the sori (the spore mass of a smut is known as a

Mycologist, Biological Laboratory, Wellington.

“ sorus ”) may be powdery, forming a black mass covering the entire inflorescence (as Ustilago Tritici} ; or may be compact and covered with a transparent. membrane, yet visible (as Ustilago Jehsenii) ;] or may be confined to individual ovaries and difficult to detect on account: of being covered by the external opaque seed-coat (as Tilletia Tritici). According to these differences in appearance the smuts may be grouped as under :- On wheat Sori powdery, evident.. Ustilago Tritici— loose smut. • Sori compact, in evident Tilletia levis and Tilletia Tritici —• stinking-smut. On barley— , ; ■ Sori powdery, evident. . . Ustilago Tritici loose smut. . .. Sori compact, evident.. Ustilago Jensenii —covered smut.

On oats

Sori powdery, evident .. Ustilago levis ai d Ustilago Avenae

■ —-oat-smut.

This grouping serves to separate Ustilago Tritici from U. Jensenii and to separate these two species from the others, but does not separate either Tilletia levis from T. Tritici or Ustilago levis from U. A venae, It has been claimed that these are separable on macroscopic characters, but after extended examination of numerous specimens the writer is

of the opinion that separation may be effected only by the use of the microscope, as follows :

Spores smooth . : On wheat .. ... .. ' .. Tilletia levis. On oats .. .. .. .. Ustilago-levis. ' Spores rough— ■ On wheat .. .. .. .. Tilletia Tritici. On oats .. .. .. . . Ustilago .Avenae.

Fortunately, from the control point of view it is unnecessary to separate these species, for all are controlled by the same treatment,

Control measures are dependent on the life-history of the species,, and are divisable into two groups according to («) whether the species is disseminated by spores adhering to the exterior of the seed, or (6) whether the species is disseminated by hibernating mycelium within the seed.

Smuts disseminated by seed-borne spores are controlled by steeping the seed in a fungicide, or by dusting with a fungicide in powder form ; those disseminated by internal mycelium are controlled by steeping the seed in hot water.

The species may therefore be grouped according to the method of treatment as under :

Hot-water treatment —

Ustilago Tritici —-loose smut of wheat and barley. Steep or dust treatment —

Tilletia levis and T. Tritici —stinking-smut Ustilago. Jensenii — covered smut. Ustilago levis and ’ U. Avenae — oat-smut.

All the species may be treated by the hot-water method, as this treatment would destroy all seed-borne spores in addition to the internal mycelium; but this treatment, owing to the difficulty of application, is usually restricted to those species not controlled by steeping or dusting.

The reader will find full particulars regarding treatments in a series of articles by J. C. Neill published in the Journal (see below).

- ' LITERATURE CITED. (i.) Cunningham, G. H. The Ustilagineae, or “Smuts” of New Zealand. Trans. N.Z. Ins/., vol. 55, pp. 397-433 ; 1924- ■ (2.) Neill, J. C. Stinking-smut of Wheat : The Effect on Germination of some' Seed-disinfectants. N.Z. Jour. Agr., vol. 27, pp. 159-67 ; 1923. (3.) Loose Smut of ..Wheat: I, Seed-disinfection by Hot Water. Ibid., ' vol. 29, pp. 177-187 ; 1924. (4.) Loose Smut of Wheat : 11, Field Experiments on Seed-disinfection by Hot Water. Ibid., vol. 30, pp. 167-74 ; 1925. . ' . (5.) Stinking of Wheat : 11, Fields Experiments on Control. Ibid.,

vol. 30, pp. 302-13 ; 1925

* This form on barley is in literature usually named Ustilago nuda, but as it is morphologically identical with U. Tritici it cannot be considered other than as a synonym, or at least a biologic race. See (i) in “ Literature cited ”at end of article.