296 THE MONTHLY BULLETIN. 



Having proved that this fungus was the cause, experiments were 

 started to see what could be done in controlling it. Some of these 

 cankers which had been produced by inoculation w^ere cut out so as to 

 remove all the diseased bark, as well as the black killed wood under- 

 neath, and the wounds were treated with strong lime sulphur solution, 

 and with Bordeaux paste, the same that had been used for the treat- 

 ment of citrus gummosis. The results showed that the cankers could 

 be stopped in this way and prevented from enlarging any further. 

 (Fig. 63). Other cankers not treated enlarged until the limbs were 

 killed by girdling. During the past summer (1914) control work on a 

 larger scale has been carried out to learn, if possible, .just how well the 

 cankers need to be dissected out in order to stop their spread. Mr. 

 C. W. Beers, Horticultural Commissioner of Santa Barbara County, 

 has given much assistance in this work. A large grower in Santa Bar- 

 bara County has started cutting out these cankers and dead limbs on a 

 rather extensive scale, having treated more than 100 acres. The w^ork 

 was })egun in August of last j^ear. The results are so far quite prom- 

 ising, but it will be a year or two before it will be known definitely 

 how fa r this control is practical. Mr. Beers, who has seen the orchard 

 recently, says that all except a very few of the wounds where cankers 

 have been cut out are healing perfectly without further spread of the 

 disease. 



In August of last year, cankers identical with those on walnut trees 

 were discovered on a common species of native willow in Santa Barbara 

 County. On microscopical examination, the same fungus appeared to 

 be present on the willows. Cross inoculations were made by placing 

 diseased tissue from a willow canker into the healthy bark of a walnut 

 tree and from a walnut canker into the healthy bark of a willow tree, 

 with the result that typical cankers were produced in each case. 

 Cankers were found on willow trees not only on the edge of walnut 

 orchards but on trees removed from walnut orchards. It is believed 

 that the disease may have originally come from the native willows to 

 the walnut trees. The transmission of the disease in many eases was 

 probably hastened by the common practice of propping the lower limbs 

 with poles cut from the nearby willows. 



In conclusion, it may be said that this disease, as far as known, has 

 not assumed a serious proportion in any sections except Santa Barbara 

 County, and as far as known does not appear to attack the younger 

 trees readily, but is found mostly on larger, older trees. The causal 

 agent has been proved to be a fungus. It appears from our experi- 

 ments, so far carried out, that if the disease has not gone too far on 

 a tree it may be successfully checked by carefully cutting out the 

 cankers and dead limbs and treating the wounds with a good fungicide, 

 such as strong lime-sulfur or Bordeaux paste. 



The formula for Bordeaux paste is as follows: 12 pounds of blue- 

 stone (copper sulphate) dissolved in 8 gallons of water in a wooden, 

 earthen or glass vessel; and 21 pounds of quick-lime slaked in 8 gal- 

 lons of water. When the lime is cool, stir together about equal parts 

 by volume of each for making enough mixture to last for one day only. 

 The bluestone is easiest dissolved by suspending it in a sack at the 

 top of the water over night. If the bluestone is pulverized and sus- 

 pended in warm water it dissolves rapidly. Good lime that is not air 



