660 EXPERIMENT STATION RECORD. 



Observations on the propagation of apple-tree canker, Descours-Desacres 



{Compt. Rend. Acad. Sci. Paris, 132 {1901), No. 7, pp. 438, 439; abs. in Gard. Chron., 

 3. ser., 89 {1901), No. 745, p. 2^). — The author reports on observations made on the 

 apple-tree canker in nurseries containing several thousand trees, and prolonged for 

 a considerable period. He asserts that the appearance of canker, caused by Nectria 

 ditissima, is almost invariablj^ preceded by the occurrence of a woolly aphis on the 

 branches or roots of the trees. The presence of the woolly aphis is almost invariably 

 followed by the appearance of canker, if diseased trees are in the immediate vicinity, 

 otherwise there is no canker. The appearance of canker followed punctures of the 

 aphis when the insect had been transferred from a contaminated region, and all the 

 cankers examined on the apple tree contained the fungus N dlli.^sima. Experiments 

 were conducted in which colonies of woolly aphis were transferred from a diseased 

 tree and placed upon a sound one near wounds which had been intentionally made, 

 and soon after the canker growth was observed in these wounds; while colonies 

 taken from sound trees and transferred to other trees, under identical conditions, 

 seldom developed any cankerous growth. These experiments were repeated a num- 

 ber of times with similar results. It seems that the woolly aphis is an active agent 

 in the transmission of apple canker, not only in preparing the way for the fungus, 

 but in actually transporting the mycelium and spores to wounds which had been 

 accidentally made. As means for preventing the occurrence of this disease, nicotin, 

 tannin, and tannic acid have been found very efficient, the solution being employed 

 after thorough cleansing of the diseased part and cutting away the cankerous growth. 

 The use of tannic acid gave particularly favorable results. 



The canker fungus {Jour. Bd. Agr. [London'], 8 {1901), No. l,pp. 12-16, pi. 1).— 

 A popular description is given of the apple-tree canker of Europe {Nectria ditissima). 

 In addition to attacking apple trees, some varieties of which are more susceptible 

 than others, this fungus has also been noted on pear, plum, oak, beech, ash, hazel, 

 alder, maple, and linden. Young branches of trees which are attacked should be 

 cut off as soon as the fungus shows itself, and older branches may have the wounded 

 parts cut away and the cut surface coated with gas tar or some similar substance. 

 If the disease spreads from the original point of infection the branch should be cut 

 off. The fungus may be held in check by applying a strong solution of sulphate of 

 iron to the diseased parts of the trees. 



Root rot of peaches, sugar prunes, and apricots, H. von Schrenk {Pacific 

 Rural Press, 61 {1901), No. 21, p. 324). — A brief account is given of a disease which 

 attacks the roots of peaches, prunes, and apricots. The fungus attacks the younger 

 roots, growing through the bark into the inner bark and the cambium layer. As the 

 disease progresses the newer wood Ijecomes affected, and pockets filled with gum 

 appear here and there. At first these pockets are very small, lint rapidly increasing 

 m size and fusing form large cavities separated only by thin layers of pith rays. The 

 gum exudes from the l^ark, where it can be readily detected in roots still alive. With 

 continued growth of the fungus the cambium layer and inner bark are killed near 

 the point of infection, and the fungus spreads toward the base of the tree. In trees 

 which are in a dying condition the bark readily separates from the diseased roots. 

 In the specimens submitted to the author there were no signs of fruiting bodies, so 

 that the nature of the fungus could not be definitely determined. Koot diseases, 

 caused by Agaricus melleus and Peniophora parasitica, which destroy many fruit trees, 

 are described; and based upon other investigations the author recommends combat- 

 ing the diseases by trenching a"bout diseased trees, sterilizing the soil where possible, 

 and planting resistant varieties. 



Pear blight on the Pacific coast, N. B. Pierce {California Fruit Groiver, 26 

 {1901), No. 675, p. 4). — The occurrence of pear blight among the orchards of poma- 

 ceous fruits is noted, and the cause of the disease and methods of infection are 

 described, being essentially those given by Waite (E. S. R., 8, p. 796). 



