478 INSECTS AFFECTING VEGETATION 



the spores. This insect may render spraying for brown-rot partially 

 ineffective by breaking the sprayed skin of the fruit, thus exposing 

 the flesh to attack. In the treatment of the disease it is, therefore, 

 important to combine an insecticide with the fungicide so as to de- 

 stroy the beetles. 



Experiments conducted by the Bureau of Plant Industry during 

 the past four years have shown conclusively that this disease can be 

 controlled by the use of self-boiled lime-sulphur mixture. (F. B. 

 440.) 



Peach Scab. Of the diseases affecting the fruit of the peach, 

 scab is second only to brown-rot in economic importance; in fact, 

 it is more destructive than brown-rot in some of the mountain dis- 

 tricts. It dwarfs the fruit and causes premature dropping, thereby 

 reducing the yield; it ruptures the skin, opening the way for brown- 

 rot attacks; and it mars the appearance of the fruit, thus lowering 

 the grade and reducing its market value. The disease is common 

 wherever peaches are grown east of the Rocky Mountains, scarcely 

 an orchard being entirely free from it. In some cases, especially in 

 a dry season, only a small percentage of the fruit may become affected 

 and with only a few small harmless spots, while in other cases the 

 entire crop may become so badly affected as to be unmarketable. If 

 the loss in the orchard and the reduction in market value are both 

 considered, it seems evident that a loss of 10 per cent of the total 

 value of the peach crop in the eastern United States is caused by 

 peach scab. 



The name commonly applied to this disease is "peach seal?," 

 but it is also known as black spot and freckles and in some districts 

 it is often improperly called mildew. It is caused by the fungus 

 Cladosporium carpophilum Thum., which grows in the skin of the 

 fruit, producing small, circular dark-brown spots. When numerous, 

 these spots give the fruit a smutty or blackened appearance and 

 cause the skin to crack. Fruit badly affected does not reach normal 

 size and often drops prematurely. 



The fungus also attacks the twigs, producing brown spots, in 

 which it passes the winter. These spots are very common in peach 

 orchards, but they apparently do little damage to the twigs. During 

 the spring or early summer the fungus growing in the spots pro- 

 duces olive-brown spores which serve to infect the young peaches. 

 Similar spores are also produced on the fruit spots. (F. B. 440.) 



There is a considerable difference in varieties as to their suscept- 

 ibility to peach scab. In general, the late varieties are much more 

 susceptible than the early varieties. This is due, in part at least, 

 to the fact that the fruit of the late-maturing varieties is exposed to 

 infection over a longer period and the opportunity for the develop- 

 ment of the disease is greater. Of the commercial varieties, the 

 Heath is perhaps the most susceptible ; in fact, the disease has almost 

 prohibited the growing of this variety except in a small way. The 

 Bilyeu variety is also badly affected and the disease has restricted 

 its culture to high, well-drained locations. The Salway, Smock, 

 and most of the other varieties that ripen after the Elberta usually 



