344 EXPERIMENT RTATTON ■RECORD. 



Altliouyb the results were not satisfactory, it is suggested that greater rub- 

 ber returns may be procured from similar tests with other rubber-producing 

 species. 



DISEASES OF PLANTS. 



Report of the botanists, (J. E. Stone and G. H. Chapman (Massachunetts 

 Sta. Rpt. 1907, pp. 120-150). — An outline is given of the investigations carried 

 on during the season, jiarticular attention being paid to the study of mosaic 

 diseases of tobacco and other crops, the testing of banding substances for 

 trees, investigations of tomato rot, spraying experiments with potatoes, and a 

 study of the meteorological conditions affecting plant diseases and the develop- 

 ment of crops. A brief report of seed investigations is noted on page 3.3.5 of 

 this issue. 



Among some of the disea.ses investigated, attention is called to an appar- 

 ently new fungus trouble affecting asparagus. This is due to a species of 

 Fusarium, and when attacked the young slender shoots are rotted off near the 

 surface of the ground. A disease of peonies has been under oTjservation for 

 some time, but while microscopic examination of the material has shown fungi, 

 bacteria, and nematodes present, they are apparently secondary or accompany- 

 ing factors of decay. Further investigations are being conducted on this 

 disease. 



In experiments with fungicides for the conti'ol of diseases of potatoes, Bor- 

 deaux mixture and Paris green were tested in comparison with Bordeaux 

 mixture and Disparene, Bordeaux mixture and sodium benzoate, soda Bordeaux 

 mixture and Paris green, and copper phosphate and Disparene. Three applica- 

 tions of the fungicides were made to all the plats. The results showed that 

 soda Bordeaux and Paris green proved the best in reducing the amount of dis- 

 ease, with Bordeaux mixture and sodium benzoate a close second in effective- 

 ness. Bordeaux mixture and Disparene seemed to produce fairly good results 

 and held the blight and insects in check, but did not prove as efficient as either 

 of the other tw^o fungicides. Bordeaux mixture and Paris green did not seem 

 to hold disease in check as well as the others, but w^as productive of good 

 results, while copper phosphate and Disparene seemed to have no appreciable 

 effect on checking disease, so far as the results of this year's work were con- 

 cerned. 



The influence of various potnsli salts on potato scab was tested, potatoes being 

 fertilized with 7 different potash compounds and grown in plats previously 

 planted to potatoes and in which the scab organism had become more and more 

 troublesome. Of the forms of potash used, kaiuit, sulphate, muriate, nitrate, 

 and silicate of potash gave little increase in the development of scab, while the 

 plats receiving carbonate of ]iotash were badly affected liy the disease. As 

 the seed tubers in every case were treated with corrosive sublimate before 

 planting, the results obtained showed that this treatment is of little value 

 when the soil conditions are especially favorable for the scab fungus. 



Work on the mosaic disease of tomatoes and tobacco was begun at the sta- 

 tion in 1907, but it was too late in the season to observe the seed beds and the 

 transplanting of lield-grown tobacco, and the work was confined largely to 

 verifying the results of previous investigators. During the coming year the 

 work w'ill be renewed and the disease studied imder lield conditions. In con- 

 nection with field work, experiments will be carried on in the laboratory to 

 determine the effects which different enzyms have on the production of the 

 disease. 



Tomatoes are especially subject to the mosaic disease, particularly when 

 grown under glass, and healthy and diseased leaves of tomato plants grown 



