101D] DISEASES OF PLANTS. 251 



of workmen during the process of culling watermelon fields. Evidence pre- 

 sented seems to Indicate that the disease Is borne by the seed, and also that the 

 fungus overwinters In diseased vine debris burled in the soil. 



Experiments with sprays have shown that Bordeaux mixture checks but 

 does not prevent the spread of the fungus, as the lower epidermis of the sprayed 

 leaves is usually unprotected. It is believed that disinfection of the seed by 

 means of immersion for 5 minutes in mercuric chlorid solution (1:1,000) 

 will destroy all surface infection. The use of disease-free seed and a proper 

 crop rotation to insure clean soil are recommended as control measures. 



The effects of potato leaf roll on product, C. S. Wennink (Tijdschr. Planten- 

 zicktm. „'>} (1918), Nn. 1, Bijbl., pp. 1-J h figs. 5).— Four potatoes affected with 

 leaf roll which were used [or seed gave an output about equal in weight to the 

 original seed tubers, control plants on the same healthy ground producing 

 normally. 



A carrier of the mosaic disease, M. Nishimura (Bui. Torrey Bot. Club. 45 

 (1918), Xo. 6. pp. 219-23S, pi. 1). — In experimentation here described, the author 

 found that Physalis alkekengi may act as a carrier of the mosaic disease at- 

 tacking tobacco, tomato, and other plants without itself showing any symptoms 

 of the disease. 



Latest information on fruit diseases and their control, H. H. Whetzel 

 (West. X. Y. Hort. Soc. Proc, 6S (1918), pp. 63-7/).— This report relates chiefly 

 to diseases of fruit as affecting interests of New York growers. 



Apple scab, which was favored by conditions during the season of 1917, was 

 found to be as effectively controlled by dusting as by spraying. Prevention of 

 the first infection still appears to be a measure of primary importance. Black 

 root (collar) rot of apple has been found in practically constant association 

 with Xylaria spp. The infection persists in the soil for a number of years, and 

 Is also said to attack pears. 



Cherry leaf blight, one of the most serious cherry diseases, is not controlled 

 by the dormant spray. Lime-sulphur or dust sulphur applied just before bloom- 

 ing may prove to be an important measure in a rainy season. An application 

 Just before the petals fall, another 10 to 14 days later, and a third just after 

 the fruit is picked give practically clean foliage throughout the average season. 

 Bordeaux mixture is apt to injure the foliage of sweet cherries. Sour cherries 

 may be protected by use of Bordeaux mixture at 5: 5: 50, lime-sulphur 1: 50, or 

 ground sulphur with lead arsenate 9:1. 



Peach brown rot, while seldom serious in New York, is controlled by the 

 treatment for scab — that is, the sulphur-lead arsenate dust, which also deepens 

 the red color of the fruit. Leaf curl is effectively controlled with copper sul- 

 phate 2 : 50 or lime-sulphur 1 : 15 or 1 : 20. 



Plum fruit gumming has been reported from several parts of the State as 

 causing a loss amounting to 50 per cent in one instance. 



Tests of lime-sulphur for the control of apple mildew, A. Osterwaldeb 

 (Landw. Jahrb. Scluceiz. SI (1917), No. 5, pp. 442-4-U). — Tests of lime-sulphur 

 during 1915 to 1917 at a strength of 1 : 30 after a dormant treatment at a 

 strength of 1:2, showed no effective control of apple mildew in case of sus- 

 ceptible varieties. The fungus (Podosylncra Iritcotricha) appears to winter in 

 the buds, attacking the inclosed parts before they begin to open in the spring 

 and spreading the infection by means of spores soon after the blooms open. 



Bacterial and fungus diseases of the pear, <:. P, WELDOR (Mo. Bui. Cal. Com. 

 Hort.. 7 (1918), No. 5, pp. 848-370, figs. 21).— In this paper, the author gives a 

 condensed account of information at present available regarding pear blight 

 (Bacillus (imylovvrus), canker (SpJiaroysis mabirum and Xectria spp.), crown 



