1919] DISEASES OF PLANTS. ^749 



lent in 1918. It was found difficult to control tliis trouble with formaldehyde 

 solution without injuring the eyes. Mercuric chlorid solution at 0.1 to 0.2 per 

 cent injured the tubers (without killing the fungus), causing at each lenticel a 

 spotting appearance resembling pit rot, which is itself supposed to be caused 

 by the entrance of some poisonous gas, vapor, or liquid. Experiments with 

 heat showed that an exposure of cultures to temperature of 43-43.5° C. (109.4 

 to 110.3° F.) for 18 to 24 hours kills the fungus. However, tests with infected 

 potato tubers showed that these are not able to endure treatments by heat 

 sufficient to kill the fungus of silver scurf. 



Leaf roll was not produced by heating seed tubers to 42 or 43° for .5, 12, 20, 

 or 40 hours after a preliminary heating of 2 hours. 



' Pit rot is described. It is thought to be due neither to the fungi generally 

 associated with the pits nor to bacteria, and it does not appear to be hereditary. 

 A very similar or identical rot has been produced artificially. It is thought 

 that some gas may be the cause of this rot, which, as above noted, starts at the 

 eyes of the tubers. Ventilation of the pit and exclusion of diseased tubers are 

 recommended. 



Potato-spraying experiments at "Wye College Fruit Experiment Station, 

 East Mailing, Kent, E. S. Salmon and H. Wormald {Jour. Bd. Agr. {London'], 

 26 (1919), No. 1, pp. 71-77, pi. 1). — Although the practice of spraying the main 

 crop varieties of potatoes is almost invariable, that of spraying such second 

 early varieties as British Queen has not become general, notwithstanding the 

 fact that such varieties frequently suffer severely from blight. Field experi- 

 ments were carried out during 1918 with this variety. It was found that, 

 under certain seasonal conditions, one application of Bordeaux or Burgundy 

 mixture resulted in loss on account of its lengthening the period of ripening 

 without protecting the crop from blight ; while, under the same seasonal con- 

 ditions, two sprayings increased the yield 2| and' 1^ ton per acre for these 

 two mixtures, respectively. 



Blast of paddy, W. McRae (Agr. Jour. India, I4 (1919), No. 1, pp. 65-70).— 

 An account is given of the shortage of the 1918 second rice crop of the variety 

 of rice (Orysa sativa) called Korangu Samba. This disease is described as 

 being due to the fungus Piricularia orysce, which is noted as causing much 

 damage to rice in certain other countries. The consensus of opinion connects 

 the susceptibility of rice to this disease with the employment of nitrogenous 

 fertilizers. 



A disease of the yam, B. M. Wakefield (Roy. Bot. Gard. Keio, Bui. Misc. 

 Inform., No. 6 (1918), pp. 199-201. fig. 1). — A disease affecting Dioscorea 

 prehenmlis in the southern provinces of Nigeria is described. The disease at- 

 tacks the stems, rarely the w'hole vine, preferring poor or swampy situations, 

 and confining itself to the round-stemmed yams. The fungus is considered 

 a new species of Bagnisiopsis, and is described under the name B. dioscorece. 



Vegetable diseases and their remedies, G. B. Hoeener (Minn. Hort., ^6 

 (1918), No. 4, PP- 1^8-15^ figs. If). — ^This is an address to Minnesota vegetable 

 growers, having in view the needs associated with the war conditions then 

 existing. 



Preventing winter injury to fruit trees, J. C. Whitten (Minn. Hort., 46 

 (1918), No. 10, pp. 364-367). — In Missouri, as contrasted with Minnesota, winter 

 injury to fruit trees is ordinarily due rather to the occurrence of warm, sunny 

 days in winter than to extreme or continued cold. On such days thermometers 

 inserted in a fruiting twig of a peach tree often registered from 15 to 20° 

 higher than in the air around them, the result of this condition being that 

 the buds swelle<l, became tender, and were thus liable to be killed during the 

 cold nights which followed. 



