244 CALIFORNIA FRUITS I HOW TO GROW THEM 



and its prevention by washes of fungicidal character demonstrated. 

 The treatment will be described in the chapter on tree diseases. The 

 facts of its occurrence may be stated as follows : 



Curl-leaf is much more prevalent in some sections than others, and 

 in one place than another in the same section, and some sections are 

 practically free from it. Some varieties are much more subject to 

 curl-leaf than others ; generally speaking, some curl nearly everywhere, 

 others curl in one place and not in another, others are practically free 

 from curl in all situations. 



Curl-leaf occurs in various degrees. Mild cases do not seem to 

 injure either tree or fruit; severe cases destroy the fruit and sometimes 

 the tree itself. The disease is almost always at its height when the 

 young fruit is about the size of small peas. If the curl is "bad," the 

 fruit will fall to the ground, there not being healthy leaves enough to 

 afford the required support. If, however, the curl is moderate and 

 partial, only a part and sometimes none of the fruit will be lost. The 

 disease, as is well known, is of brief duration, say twelve to twenty 

 days, after which the trees resume a healthy appearance in every 

 respect, and if the fruit has been able to survice the ordeal, it also 

 appears to grow and become as perfect as if no check had been given 

 to its growth. But it is better to save the tree the burden of a new 

 foliage growth. 



Mildew. This disease, which occurs in the form of whitish 

 felted patches on leaf and twig early in the spring, and finally affects 

 the fruit, has long been troublesome in this State, and occurs on certain 

 susceptible varieties in many localities from the coast to the Sierra 

 foothills. Observation in this State has fully affirmed the statement of 

 Downing, that the serrate, glandless-leaved varieties are liable, and 

 those with good glands on the leaf stems are free. 



The conclusion would be that where mildew prevails, varieties with 

 serrate, glandless leaves should be avoided. But it has been found that 

 some glandless-leaved varieties, although subject to mildew, resist 

 curl-leaf. Therefore it may be worth while to combat the mildew. 

 This has been done effectually by treatment which will be described in 

 a later chapter. 



As with curl-leaf, mildew is prevalent some years and slight in 

 others. 



The most serious disease which has thus far stricken the peach in 

 California is locally known as the "peach blight," the work of a shot- 

 hole fungus (coryneum). This also has been satisfactorily checked by 

 spraying, as will be described in the Chapter on Diseases of Trees and 

 Vines. 



A common trouble of the peach known as "split-pit," has recently 

 been studied by the California Experiment Station and the tentative 

 conclusion has been reached that split-pits are physiological phenomena 

 and not caused by disease germs. Whether this abnormal growth is 

 due to weakness of variety or to cultural conditions is not determined. 

 It is true that varieties differ in amount of splitting, and selection is 

 being made to some extent on that basis. 



