DISEASES OF PLANTS. 1C)5 



Numerons footnote references are given, which constitute a very extensive l)il)li- 

 ography of the literature of the sulijects treated. 



Phthiriosis, a disease of grapes, L. Mangix and P. Viala {C'onipt. Rend. Acad. 

 ScL Paris, 136 {1903), No. 6, pp. 397-399; Prog. Agr. et Vit. (Ed. L'Est), U {1903), 

 No. 10, pp. 316-318; Rev. Vit., 19 {1903), Noh. 431, pp. 269-311; 483, pp. 329-335; 

 484, pp. 357-363; 485, pp. 385-388, pji^. 2, figs. 16).— An account is given of a disease 

 of grapes which has caused considerable injury in the vineyards of Palestine and 

 adjacent countries. The disease is due to the combined attacks of Dnrli/lojriiis rilis 

 and Bornetina coriurn, n. sp. The attack is made ujion the roots, and specimens of all 

 ages show a peculiar thickening of the root which is more or less cylindrical, liaving 

 when fresh a decided elasticity, l)ut in (h-ying becomes hard and brittle. If these 

 enlargements which surround the root be examined thej^ will show a tlocculent mass 

 made up of a mass of insects and the mycelium of the fungus. The root itself will 

 be found to be in various stages of disorganization. The insect punctures the roots, 

 and from the exuding sap is formed a substratum in which the fungus readily 

 develops. In this way a sort of symbiosis is established between the two, resulting 

 in the destruction of the plant. Experiments have been conducted which indicate 

 that the injection of carbon bisulphid about the plants during the early stages of 

 the disease, before the mycelium has made an impenetrable felt about the roots, will 

 destroy the insect. If the treatment be put off too late in the season the Dactylopius 

 within the mass of mycelium will not be reached by the insecticide. 



A disease of chestnut, L. Maxc;ix {Jour. Agr. Prat., n. ser., 5 {1903), No. 9, pp. 

 278, 279) . — For a numljer of years the author has had under observation a disease of 

 chestnut trees which seems to be widely distributed throughout France and which has 

 caused the destruction of many trees. Two forms of the disease seem to be recog- 

 nized, the first of which is due to the weakening of the trees by injury, removal of 

 forest cover, lack of fertility in the soil, etc. The second type, which is the one 

 described, is due to a fungus, and is found in all soils and exposures equally affecting 

 young and old trees. It seems to spread from definite centers, on which account it 

 has been called phylloxera from its resemblance to the spread of that disease in the 

 grape. The aerial parts of the trees seem to be unaffected, but the roots are more or 

 less discolored by the fungus which seems to attack the mycorrhiza, which is sym- 

 biotically associated in the growth of the chestnut tree. The parasite consists of a 

 very delicate mycelium which attacks the mycorrhiza, causing its destruction. A 

 study has been made of the fungus, and the author states that it apparently consti- 

 tutes a new genus associated with Oomyces, and he has given to it the name Mycelo- 

 phagus casfanew. Although experiments do not seem to have been made, the author 

 recommends the destruction of tlie parasite by injecting carbon bisulphid about the 

 trees and the destruction of those which show evidence of attack. The use of carbon 

 l)isul])hid can' be recommended only in case of exceeding]}' valualtle trees which are 

 planted in soils where that material can be used to an advantage. 



A disease of conifers {Jour. Bd. Agr. [London], 10 {1903), No. 1, pp. 17-21, pi. 

 1). — A descrijition is given of a rather serious disease of coniferous trees, which is 

 caused by attacks of the fungus Botrytis cinerea. So far this fungus has been observed 

 occurring on the larch, silver fir, spruce, and sequoia seedlings. The disease has been 

 under observation for 2 years and has proved very destructive to seedlings of larch 

 and Scotch pine. The fungus causes the diseased slioots to curve down or l)ecome 

 twisted, the leaves die and separate themselves from the branches, but are frequently 

 prevented from falling by the formation of a web-like mat of mycelium. So far as 

 the observations in England are concerned, this disease is quite abundant in nurser- 

 ies and seed beds, and particular attention should be given to prevent the growth of 

 weeds which would result in keeping the seedlings damp and shaded. Where the 

 disease is prevalent it is suggested that the seedlings should be sprayed with a mix- 

 ture called the "violet" mixture. This consists of copper sulphate, 2 lbs.; copper 



