FORTIETH ANNUAL REPORT. 167 



diicing 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 produces olive-brown 

 spores which serve to infect the young peaches. Similar spores are also 

 produced on the fruit spots. 



THE SUSCEPTIBILITY OF VARIETIES. 



There is a considerable difference in varieties as to their susceptibility 

 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 development 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 Avay. 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 

 lipen after the Elberta usually suffer rather severely from this disease, 

 while the Elberta may be considered somewhat less affected, although 

 the crop of this variety often becomes badly diseased. The varieties 

 that ripen earlier than Elberta are as a rule only slightly or moderately 

 affected. This is especially true of the Carman, Hiley, Champion, and 

 Belle. On the other hand, the Mountain Kose and Early Rivers are 

 quite susceptible to tlie disease. 



TREATMENT. 



The development of the self-boiled lime-sulphur mixture as a fungi- 

 cide has made possible the control of the scab without injury to the 

 fruit or foliage. The injury produced by this disease may be almost 

 entirely prevented at a small cost. This has been abundantly dem- 

 onstrated through experiments conducted by the Bureau of Plant In- 

 dustry during the past three or four years.^ 



THE PLUM CURCULIO. — WHAT THE CURCULIO IS. 



The curculio is a small snout beetle of the family Curculionidfe, which 

 contains many species of economic importance. The adult insects vary 

 somewhat in size, but will average about three-sixteenths of an inch in 

 length. In the course of its growth the insect passes through 

 four stages, namely, the egg, larva, pupa, and adult. The larva, or grub, 

 is the small whitish worm frequently found in ripe peaches, plums, and 

 cherries and is well known to lovers of these fruits. 



There are many common names for this insect, such as the "plum 

 curculio," "plum weevil," "peach curculio," "peach worm," "fruit 



'Circulars 1 and 27 and Bulletin 174, Bureau of Plant Industry, U. S. Dept. of Agriculture. 



