THE MONTHLY BULLETIN. 613 



gummosis. The results of inoculations with the grey fungus, into 

 the bark of lemon, sweet orange and sour orange trees, appear to show 

 that the lemon is affected readily, the sweet orange much less readily, 

 and the sour orange scarcely at all. This appears to furnish an explana- 

 tion for the well known fact that sour orange trees are the least of all 

 subject to gummosis under unfavorable orchard conditions, the sweet 

 orange trees next and the lemon trees most of all. This may possibly 

 be one explanation why lemons can not well be grown on their own 

 roots in California. 



Treatment of Gummosis. 



Experiments discussed: Having found that two forms of lemon gum- 

 mosis were infectious and that the causative agents were fungi, experi- 

 ments were begun in co-operation with several of the lemon growers, not 

 only to prevent the infection, but to find means of remedying those trees 

 already infected. The requirements of a mixture to be used for this 

 purpose seemed to us to be effectiveness in killing out the fungi, lasting 

 qualities, inexpensiveness, and lack of injurious effect on the bark. The 

 concentrated Bordeaux mixture was one of the most effective fungicides 

 known, had lasting qualities that scarcely any other fungicide had, was 

 inexpensive, and had been known to give good results when used for the 

 treatment of similar troubles in Florida. Bordeaux mixture paste at 

 various strengths, as well as a number of other fungicides, were tried 

 out by the Limoneira Ranch. Bordeaux paste was also used by the San 

 Diego Fruit Company at about the same time.* The experiments with 

 the Bordeaux paste, which were begun over a year ago, appear to show 

 that it is the most promising of any preparation yet tried. These 

 investigations are yet in an experimental stage, and other growers 

 may find something ju.st as good. It seems certain, however, that the 

 Bordeaux paste will prevent infection from these fungi when applied 

 to bark not yet infected, and will kill out any of the fungus it is allowed 

 to come in contact with, and will last a long time. So far the mixture 

 has shown no injurious effect on the bark. It should be kept in mind 

 that small patches of bark may be infected and have the fungus in 

 them when there is yet no evidence of gum on the surface, and giim 

 may exude after applying the mixture. Results from treatment of trees 

 already diseased must not be expected too soon. The inoculation experi- 

 ments before described show that the fungus may at times be in the 

 bark for over a year before large areas are finally killed, and it will 

 probably take as long, or longer, to work out all the infection. 



Applying the Bordeaux paste: It seems from our present knowl- 

 edge that the bark that is dead to the wood should be removed before 

 applying the paste, in order to allow the mixture to kill out the infec- 

 tion. In grey fungus gummosis the outer bark is often infected and 

 dead over large areas while the inner bark with cambium is still alive. 

 In this case the outer dead part may be scraped off with a curved sharp 

 tool made by a blacksmith on purpose for this work, leaving the inner 

 part of the bark still attached (Figure 350). The idea of scraping the 

 outer bark was conceived by Mr. J. D. Culbertson, and the instruments 



•Only recently the writer has learned of three or four other growers having used a 

 similar mixture each independently of the knowledge of the other, two years or more, 

 for gummosis and scaly bark with good results in all cases. 



