476 INSECTS AFFECTING VEGETATION 



equally as good results, but for the blight alone the more easily pre- 

 pared Bordeaux is usually preferable. We have not laid great stress 

 on the exact formula for the Bordeaux mixture to be used. Where 

 the mixture was properly prepared very little difference in the re- 

 sults has appeared, whether it was 20-20-200, 30-35-200, or very 

 much stronger as some have used it. Ordinarily the 20-20-200 

 formula is probably strong enough and affords some saving of ma- 

 terial over a heavier application. A mixture containing more cop- 

 per and lime remains longer on the tree, however, is not as quickly 

 washed off by rain, and shows more plainly on the tree just how 

 thoroughly it has been covered. We would therefore advise the use 

 of the lesser strength only when materials are very high and scarce 

 or where the workmen are particularly adept in applying the spray 

 perfectly. For average conditions we prefer the 30-35-200 for the 

 early application. (Cal. E. S. B. 191.) 



Brown-Rot. This is a fungous disease which affects the stone 

 fruits, such as the peach, plum, and cherry, and to a less extent some 

 of the pome fruits, such as the apple, pear, and quince, producing a 

 so-called rot of the fruit and blight of the twigs. It is caused by a 

 fungus known to botanists as Sclerotinia fructigena. Brown-rot is 

 the common name usually applied to the disease, but monilia, the 

 generic name of the imperfect stage of the fungus, is often used by 

 some of the older fruit growers. 



The disease appears on the fruit as a small circular brown spot, 

 which under moist, warm conditions enlarges rapidly, soon involv- 

 ing the entire fruit in decay. The spots do not usually become 

 shrunken, and the fruit remains plump until almost entirely de- 

 cayed. The fungus growing in the tissues of the fruit breaks 

 through the skin, forming small, grayish tufts of spore-bearing 

 threads. These tufts, although few on young spots, soon become so 

 numerous as to give the diseased area a grayish, moldy appearance, 

 which is responsible for the term peach mold sometimes applied to 

 the disease. The spores which are produced in great abundance by 

 these fungous- tufts are blown by the wind and carried by insects 

 and birds from fruit to fruit, tree to tree, and orchard to orchard. 

 Finding lodgment on the fruit under favorable conditions of tem- 

 perature and moisture, these spores germinate, producing a fungous 

 growth, which ramifies and kills the tissues. These dead tissues turn 

 brown, and the fungus breaks through the surface, producing an- 

 other crop of spores. The process is very rapid, only a few days in- 

 tervening between one generation of spores and another. 



Although the young fruits soon after the petals are shed may 

 become affected, as a rule no marked outbreak occurs until the fruit 

 is half grown or larger, and the greatest destruction is wrought at 

 harvest time. The fruit crop may reach maturity in perfect condi- 

 tion and yet be destroyed before it can be picked. Moreover, the 

 fruit may become affected in transit or after reaching the market. 

 It is no uncommon experience among peach growers to have a car- 

 load of peaches leave the orchard in apparently good condition and 

 arrive on the market specked and practically worthless, owing to the 



