DISEASES OF CULTIVATED PLANTS 525 



about the first of October. Any considerable dropping of fruit from a 

 tree calls for immediate careful inspection. If the characteristic 

 anthracnose lesions are found on the fruit, prompt and thorough 

 spraying with ammoniacal solution of copper carbonate is demanded. 

 If this work is done in a desultory manner, it might as well be left 

 undone. Spraying with fungicide should be the last resort. Use 

 eight ounces of pure copper carbonate in a wooden or earthen jar, 

 and add enough water to make a thin paste. Then add three pints 

 of twenty-six degree ammonia. This will make a deep blue liquid. 

 Pour this liquid into fifty gallons of water. Spray the fruit thor- 

 oughly so as to moisten every part of it, but avoid using so much 

 fungicide as will cause it to run off, which is worse than wasteful. 

 Keep the spray from the leaves and trunks of the trees as much as 

 practicable. Repeat the spraying in ten days or two weeks. It will 

 take from two to four weeks before the beneficial effect of the spray- 

 ing can be noticed. 



Chemical Injuries. These may arise either from a too large 

 application of readily soluble fertilizers, or from sprays. An over- 

 large application of fertilizers will cause a severe dropping of the 

 fruit. This fruit will show a dark brown to black discoloration and 

 depression of the rind in irregular patches. The fruit as a whole 

 will finally turn black and become mummified. Fruit thus affected 

 differs from the rots in the more rapid development of the affection 

 and in that it does not become soft. 



Weakened and diseased fruit are the first to become affected 

 and fall. The old leaves will show the same sort of discoloration 

 and will fall. If the injury is not great enough to kill the branches 

 back, the new leaves on the tree will escape injury for the most part. 



The chemicals and fertilizers most commonly used that will 

 cause this sort of injury are nitrate of soda, nitrate of potash, sul- 

 phate of ammonia, and copper sulphate. 



Direct chemical injury to fruit frequently happens from the 

 use of sprays that have been improperly mixed, or are used in a too 

 concentrated condition. In general, the injury from the different 

 chemical sprays is about the same. They produce a killing and de- 

 pression of the tissue in the spots affected. These spots will resemble 

 those produced by anthracnose, but are usually located at the blos- 

 som or lowest end, from the collection of the spray at this point. 

 These spots once produced may become infected with fungi that 

 grow inward and produce a rotting of the fruit. 



Another form of spotting that is entirely different sometimes 

 occurs where improperly mixed oil sprays have been used. This 

 consists of a mere discoloration of the skin that shows as a circular 

 spot of light green against the deep green of the unaffected portion 

 of the fruit. 



Sometimos a form of chemical injury occurs on young fruit 

 from the use of sprays, which, when the fruit has matured, re- 

 sembles mechanical injury. This is due to the fact that the chemi- 

 cal injury was slight, and the formation of the new skin and the 

 development in size were identical with what occurs in mechanical 



