f)50 EXPERIMENT STATION RECORD. 



The Bordeaux mixture did not injure either the leaves or the flowers, while 

 the other liquid sprays were all more or less destructive of the flowers, aud 

 some injured the foliage as well. Nonnit destroyed a portion of the tlowers 

 and burned the leaves to a considerable extent. None of the fungicides used 

 in a dry form i)roved injurious. 



Gum disease of citrus trees in California, R. E. Smith and O. Butler 

 {California tita. BuL 200, pp. 235-272, figs. 14). — According to the authors, the 

 most common and characteristic citrus tree diseases in California are included 

 under the general term gum disease, and the present bulletin considers various 

 citrus troubles, showing the features which they have in common and dis- 

 cussing their nature, together with means of prevention and cure. 



Gum disease, or gummosis, is a term applied to a condition in which an 

 exudation of a gummy sap takes place through the bark. The disease is at- 

 tributed to various causes, but so far as known it is not infectious. A common 

 form in California to which the term gummosis is applied occurs on the lemon, 

 although the characteristic trouble is not confined to these trees. An examina- 

 tion of diseased trees showed that the gum does not originate in the bark, but 

 breaks out through the latter by mechanical pressure from within. The af- 

 fected area may be large or small and may spread until the trunk is completely 

 girdled. In severe cases the bark of the affected portions dies and the tree 

 may do likewise. The relation of soil and location of orchards to this disease 

 is discussed, and it is shown that almost invariably gummosis is found in trees 

 growing in poorly drained situations, such as the lower slopes of orchards, or 

 where the orchard is on heavy soil or poorly drained due to hardpan or other 

 causes. The effect of the disease upon the tissues is described and methods 

 of control are suggested, among them the avoidance of unfavorable conditions 

 in planting, the use of sour-orange roots as stock, high budding, cultural pre- 

 vention, improvement of soil conditions, slitting and stripping the bark on 

 diseased areas, etc. Where the bark is cut it has been found advantageous 

 to cover the wounds with a form of grafting wax to prevent the entrance of 

 fungi. Attention should be paid to soil improvement aud pruning, and it ha^ 

 been found that good drainage and the proper aeration of the roots by boxing 

 or digging away about the trees and placing sand about the trunks are on the 

 whole practical means for the prevention of gummosis. 



Another citrus tree disease described is. that known as scaly bark, or psorosis, 

 which is primarily a disease of the orange and which apparently rarely occurs 

 on other citrus trees. This disease is distinguished from gummosis by its 

 occurrence at any point on the trunk or branches of a tree, and there is ap- 

 parently no direct connection between the soil and the location of the affected 

 area. The appearance of the disease is well described by the name scaly bark. 

 The authors say that there seems to be a connection between the irregular 

 water supply and the occurrence of scaly bark, and an extreme case is cited 

 which seems to prove their claim. The relation of scaly bark to gummosis 

 is discussed, and for the control of the former the authors say that treatment 

 does not promise very satisfactory results and that precautions for the pre- 

 vention of the disease are more to be sought than methods for its treatment. 

 The methods of treatment ai'e essentially the same as those described for 

 gummosis. 



Brief notes are also given on the gumming of nursery trees, foot rot, Florida 

 die back or exanthema, and twig blight. 



Phoma abietina, a parasitic disease of the fir, E. Mkr (Rev. Eaux et Forets, 

 41 (1908), JSlo. 20, pp. 609-621).— In 1890 the author published an account of a 

 disease of fir trees in which a kind of canker was formed by P. abietina. Dur- 

 ing a recent outbreak of a disease of firs in the .Jura Mountains, he was led to 



