DISEASES OF PLANTS. 1053 



Investigations on a leaf curl of mulberry trees, M. Miyoshi 



{Bof. Ci-nthl., SJ {1900), No. 11, pp. dJ^G, .4'/).— This disease, which 

 seriously threatens the iiiulberr}" trees of Japan, is characterized by a 

 marked increase in tiie nunil)erof lateral twigs and leaves through the 

 development of adventitious ])uds. At the same time the develop- 

 ment of the leaves l)ecomes abnormal. They arc greath^ reduced in 

 size, crumpled with a less developed mesophyll, while upon the upper 

 side numerous blister-like elevations occur between the veins. The 

 leaves liecome yellowish in color and hard in texture, and the twigs 

 are but little developed. In the older l)ranches, where the disease has 

 l^een severe, leaf and twig growth is stopped and the whole branch 

 ultimate!}^ falls to the ground. 



The cause of this disease is believed to be not parasitic, but is due 

 rather to the impaired functions of the twigs and leaves, brought 

 about by the common practice of removing them for silkworm feeding. 



The "mal nero" of grapes, D. Cavazza (Vlgne Amer., 2J^ {1900), 

 Has. 5, pj)- l-'>-'>-l-'>^ j ^1 i'l>- i'VJ-i'S'fi'). — This grape disease, which the 

 author says is also known as "bacterial gummosis,'' the California vine 

 disease, gelivure, chyti'idiose, etc., is said to be a very polymorphous 

 disease caused b}- BacUhi^ vitironis. It attacks all parts of the plant, 

 producing variable symptoms which seem to l)e somewhat dependent 

 upon external conditions. The season, time of appearance, and develop- 

 ment of the parts attacked influence the color of the diseased leaves, 

 making them yellow, red, reddish brown and violet, etc., as the case 

 may be. The bacillus attacks the camliium and extends into the wood 

 of the vine, producing irregidarly triangular l)rown spots. As means 

 for the partial prevention of the disease, which the author believes 

 attacks the plants from the soil, the fumigation of the soil with car- 

 bon bisulphid and thorough drainage are recommended. 



Copper sulphate as a remedy for grape vnildie-vT {ScL Amer. Sup., 

 Jii) {1900) No. 1200, p. ,'0.101). — A report is given of investigations 

 with copper sulphate for the prevention of grape mildew. On account 

 of the solul)iiity of this substance it is claimed that it does not adhere 

 readily to the foliage, and numerous attempts have been made to 

 secure a more adhesive as well as cheaper mixture. The results of 

 some investigations by Trabut are given, in which the dry resin 

 exuded from pines in Algeria, as well as the mucilage which is extracted 

 from the stems of the Barbar^' lig tree, were used with excellent 

 results. The resin mixtures were prepared liy heating 1 kg. Avith 500 

 gm. of soda or potassium carbonate. To this was added 500 gm. 

 copper sulphate and I(»() liters of water. A second preparation was 

 obtained by extracting l>y maceration the mucilage from 3 to 5 kg. of 

 the Barbary tig tree and adding simple solution of copper sulphate. 

 B}' the use of either of these fungicides it is claimed that from 50 to 

 80 per cent of the copper sulphate is saved and the prevention of the 

 mildew secured. 



