DISEASES OF PLANTS. 959 



It is thought to be due to the too extensive forcing of the plants and 

 consequently can be very easily avoided. 



The plum rot and its effect on plum culture in Rhode Island, 

 L. F. Kinney (Rhode Island 8ta. Ept. 1896, pp. 191, 192). — Brief notes 

 are given on the occurrence of black knot, curculio, and the plum rot 

 fungus. The first 2, according to the author, may be more or less suc- 

 cessfully combated, but his conclusions relative to the treatment for the 

 prevention of plum rot indicate that the disease ean not be controlled 

 by spraying the trees with Bordeaux mixture. It is stated that plum 

 trees heavily sprayed with strong Bordeaux mixture were severely 

 attacked by piuin rot. The varying susceptibility of different varieties 

 toward disease is mentioned. This seems to be due in part at least to 

 a difference in the texture of the skin of the fruits, although early vari- 

 eties are reported as more commonly injured than those which ripen 

 their fruit later. At present it is thought that the Japanese varieties 

 are more resistant than the European, but further discussion of them is 

 deferred. 



The root rot of tobacco caused by Thielavia basicola, V. Peg- 

 lion (Centbl. Bait. u. Far., 2. AM., 3 (1897), No. 21-22, pp. 580-583).— 

 This disease, which consists of the rotting away of all secondary roots 

 from the main root of the plants, is said to attack some varieties of 

 tobacco more severely than others, Kentucky Burley and to a less extent 

 Seed Leaf being especially susceptible. The rotting away of the sec- 

 ondary rootlets is soon followed by the rapid yellowing of the plant. 

 Adventive roots are put out and the plants sustained for a time, but 

 usually all diseased subjects dry up and perish. 



Microscopic examination showed the presence of Thielavia basicola, 

 a fungus already known to attack the roots of various cultivated plants, 

 among them Lupinus luteus, L. angustifolius, L. albus, Trigonella cayrulea, 

 Onobrychis crista-galli, Pisum sativum, etc. The relationships of the 

 fungus and its description are given in considerable detail. 



Until more is known concerning rational methods of soil disinfection 

 and relative resistance of different varieties, those varieties known to 

 be least liable to disease should be planted. 



The periods favorable for treatment against black rot, A. 

 Prinet (Gompi. Rend. Acad. Sci. Paris, 125 (1897), No. 22, pp. 889-891).— 

 The author gives a brief account of experiments made to determine the 

 proper time for spraying grapevines to secure immunity from attacks 

 of the black rot fungus. 



In the region where the experiments were conducted it was found 

 that the first important appearance of the disease was noted on May 

 18. Those vines which had received a single spraying about April 20, 

 when the young shoots are 15 to 20 cm. long, were almost wholly free 

 from disease. Single sprayings made April 12 or 13 were less efficient, 

 and after April 29 were of little effect. Two sprayings, April L'O and 

 May 12, were about equal to the single application at the first date, 

 16733— No. 10 5 



