444 EXPERIMENT STATION BECORD. 



Where the scab is due to the action of fungi the author recommends the 

 forniiilin treatment of seed [iotatoes. 



Wart disease of potatoes, T. II. Middleton (Bd. Agr. and Fisheries [Lon- 

 don], Ann. Rpt. JJort. Brunch, l[)13-lJf, pp. 38-55). — An account is given of 

 investigations on control measures undertaken under the Wart Disease of 

 Potatoes Orders of ini3 and 1914. It has been demonstrated for at least five 

 years that certain varieties of potatoes, if true to type, are wholly I'esistant 

 to this disease, and that under ordinary conditions these varieties will yield 

 a sound cro]) while susceptible varieties will give a number of warty potatoes. 



Potato spraying, Dukk ok Redkord and S. U. Pickering (Wohurn Expt. 

 Fruit Farm Rpt., J4 (lOU,), pp. 1-32; ah-i. in Gard. Chron., 3. ner., ,56 {191^), 

 No. lJ/60, p. JfOl). — A report is given of experiments on spraying potatoes, the 

 initial object of which was to ascertain the proportion of Woborn Bordeaux 

 l)aste which is equivalent in fungicidal action to ordinary Bordeaux mixture. 



The paste is prepared by precipitating a solution of copper sulphate with 

 clear limewater sutficient to render the mixture barely alkaline and then sepa- 

 rating the precipitate. When used this is simply mixed with water and the 

 jjreparation is complete. Some difficulty has been met with in preparing a com- 

 mercial mixture of this sort, but the authors consider that this has been 

 overcome. 



As a result of the experiments it was found that on potatoes sprayed for the 

 prevention of late blight 15 or 16 lbs. of the paste was as efficient as Bordeaux 

 mixture made with 8 lbs. of copper sulphate and 8 lbs. of lime to 100 gal. of 

 water. The Bordeaux mixture as prepared by the ordinary method would 

 contain five or six times as much copper as the paste. 



A trial was made of soda Bordeaux, but it was found not to compare favoi'- 

 ably either with the paste or with ordinary Bordeaux mixture, even wlien the 

 amount of copper in it was very large. 



Control of potato diseases in Wisconsin, L. K. Jones {T^isconsin Sta. Circ. 

 52 (1914), pp. 19, figs. Jf). — A popular description is given of a number of the 

 nonparasitic and pai'asitic diseases of potatoes, with suggestions for their con- 

 trol. 



Studies on the relation of certain species of Fusariuni to the tomato blight 

 of the Pacific Northwest, II. B. Humphrey (Washington Sta. Bui. 115 {191-i\. 

 pp. 22, pis. 5). — The I'esults are given of an extended study of the liistory, dis- 

 tribution, cause, and methods of control of the disease commonly known as 

 yellow blight in the States of the Pacific Northwest. 



This disease is generally characterized in its incipient stage by twisting of 

 the leaf accompanied by a purpling of the leaf veins. Later the leaves are 

 twisted and rolled inward, followed by a drooping, but not a wilting, of the 

 leaflets and leaves. The fruits develop poorly and often seeds are not pro- 

 duced. With the appearance of the blight there is a marked cessation of 

 growth, and all plants assume an erect habit excepting those cases in which 

 the root systems have been invaded late in the season. 



The studies show that the cause of the disease is in part at least two specie.^; 

 of Fusarium, F. orthoceras and two varieties of F. ojpysporum. Chlamydn- 

 spores of the fungi are said to be produced abundantly in the soil, and it is 

 possible that they may also be propagated by a perennial mycelium formed in 

 the roots of blighted plants. 



Among the factors which limit the disease are soil temperature and moisture, 

 wind movement, air temperature, and light intensity. Crop rotation and plant- 

 ing in virgin soil are thought to be of doubtful preventive value, the greatest 

 freedom from the disease being obtained where the practice of tran.splauting 

 from hotbed to cold frames or field is abandoned. 



