GUMMOSIS AND ROOT KNOTS 491 



Gummosis. This is a convenient term to designate the gumming 

 which is seen on many kinds of trees. As has been said of die-back, 

 gumming may result from excess of water or of drouth in the soil. 

 Gumming is, therefore, not always to be considered in itself a disease, 

 but rather an indication of conditions unfavorable to the thrifty growth 

 of the tree. It has been usually found by investigation that trees in 

 perfect condition of health, with the moisture just enough and not 

 excessive, are not troubled with gumming ; but there are cases in which 

 this statement does not wholly apply. Prof. H. S. Fawcett has dem- 

 onstrated that in some cases it is communicable because of a fungus 

 cause. Full accounts of this may be expected in University publica- 

 tions. 



When there is an outbreak of gum where it can be treated it is 

 desirable to cleanly remove all the unhealthy bark cutting clean to 

 sound bark and covering the wound with paint or wax to exclude the 

 air. Prof. Fawcett gives these detailed suggestions : 



The treatment for the gummosis caused by fungi is still somewhat in the 

 experimental stage. All that can be said at present is that in several lemon 

 groves where the Bordeaux paste was used over a year ago the results appear 

 very promising. 



Before applying the paste on lemon trees the bark that is dead to the wood 

 should be removed to allow the Bordeaux to get in to kill out the infection. 

 In case the outer bark is infected over a large area and the inner or cambium 

 is still alive, the outer layer may be scraped off with a curved sharp tool made 

 on purpose for this work, leaving the cambium covered by inner bark still 

 attached. In this way the infection is killed and a new bark is built up under 

 the Bordeaux. One must expect the gum to run out freely for several weeks 

 or months after treatment. One should watch for the formation of new, healthy 

 tissue, rather than the amount of gum that may run out after treatment. The 

 gum that has formed under the bark beyond where any fungus has gone will 

 continue to drain out. The gum itself does not as a rule have any infectious 

 principle in it. The fungus is in the diseased bark at the junction of the live 

 and dead tissue. The fungus does not manufacture the gum, but causes the tree 

 to produce it from its own products. 



The formula for the Bordeaux paste is as follows: 



One pound of bluestone dissolved in 1 gallon of water in a wooden or earthen 

 vessel by hanging it in the top in a sack. Two pounds of unslaked lime, slaked 

 in about one-half gallon of water. Stir together when cool, making a light blue 

 mixture about the consistency of whitewash. Apply with a brush. This may 

 also be applied to healthy bark as a preventive against new infections. 



Root Knots. These are excrescences upon the roots or at the 

 root crown of various trees and of grape-vines, and they have been 

 a serious trouble in this State for a good many years. Some of the 

 knots have been studied by experts in plant pathology and the cause 

 of the trouble demonstrated to be a fungus and the disease infectious. 

 A satisfactory treatment has, however, been discovered. If the knot 

 has not increased in size sufficiently to seriously interfere with the 

 growth of the tree it can be smoothly removed, the wound treated with 

 the Bordeaux Mixture, and the knot will not reappear at the same 

 place. Success has also been had with boring a hole into the knot and 

 rilling the hole with bluestone solution, but some trees have been killed 

 in this way. Bluestone can be used with least danger when the tree 

 is dormant. 



