48 CALIFORNIA CITRUS CULTURE. 



placed under the trees, and to a lesser degree a cover crop, helps to keep 

 the spores from reaching the fruit. The usual strength of the bluestone 

 water for brown rot is one and one half pounds to one thousand gallons. 

 This fungus, as we have seen, causes one kind of gum disease of 

 lemon, see page 44. 



Cottony Mold or White Rot (Sclerotinia libertiana). 



This is much like the brown rot, except that it coats the fruit with 

 white. It attacks and often kills the twigs a foot or two from the end. 

 In this mold develop black bodies (sclerotia) , another stage in the 

 growth of the fungus. This fungus also - develops in the soil, and is 

 more likely to attack lemons that are bruised. It is thought that cover 

 crops, especially vetch, which is also a host plant, favors this fungus. 

 Bluestone will aid in its control, but it must be stronger than for brown 

 rot. Professor Smith suggests that it may not be safe to use it strong 

 enough to be effective on account of injury to the fruit, in which case 

 the remedy must be to destroy it in the field. This fungus has been 

 found recently attacking the orange roots of full grown lemon trees, 

 entirely killing the trees in many instances, at the same time causing 

 more or less gummosis. 



Gray Mold (Botrytis vulgaris). 



This is the dark colored decay of lemons in which a gray fungus 

 develops. The fungus in the packing-house is not usually very serious, 

 but as we have seen, it is a cause of gum disease. (See Monthly Bulle- 

 tin, Vol. 2, No. 8, page 601, August, 1913.) 



Wither-tip (Colletotrichum gloeosporioides). 



This fungus kills the twigs at their ends, spots the fruit and leaves, 

 and fells the latter to the ground. Mr. C. C. Teague says that this pest 

 has cost the Limoneira lemon grove more than all injurious insects 

 combined. I saw the plague in Mr. N. W. Blanchard's orange orchard 

 so bad that the foliage looked as if it had been blighted by fire. This 

 disease is becoming more and more common in many orchards, and many 

 are now fighting it with no little success. It seems to be erratic, depend- 

 ing on seasons. Bordeaux mixture and lime-sulphur spray are the 

 specifics to use in its control. Care must be taken in the use of the 

 Bordeaux or injury may result. This is the more true if fumigation 

 follows soon after the spraying. 



Damping Off (Rhizoctonia and Fusarium). 



Two fungi seem to be responsible for damping off. The first named 

 fungus attacks the young seedlings at or just above the ground, causing 



