Plants as Affected by Fungous Parasites. 185 



Continue to test and add lime until the reddish-brown 

 color no longer appears. Then add a little more lime; 

 as a slight excess of lime is desirable. A bright, clean 

 knife blade may also be used as a test, but is less sat- 

 isfactory. If a slight film of copper forms upon it 

 when placed in the mixture, more lime is needed. The 

 Bordeaux mixture is preferably strained before use, 

 and should be kept well stirred during its application 

 (304). It may be applied with any good spray pump. 

 The arsenical compounds (283) may be added to the 

 Bordeaux mixture, and thus a single treatment will 

 serve for both insects and fungi. 



330. The Diseases Preventable by Bordeaux Mixture 

 are the apple and pear scab (328), the downy mildew 

 and black rot* of the grape, the earlyf and late blight| 

 of the potato, the gooseberry mildew, § the leaf -blight 

 of the pear** and some others. 



In all these diseases, however, the treatment is pre- 

 ventive rather than curative. The first application 

 should be made before the disease appears and should 

 be followed occasionally by others as new foliage is 

 formed or as the material is washed off by rains. 



331. Ammoniacal Solution of Copper Carbonate 

 possesses nearly the same fungicidal properties as Bor- 

 deaux mixture, but adheres less strongly to foliage. 

 Being a solution, it requires no straining or stirring, 

 and it leaves less stain on drying than Bordeaux mix- 

 ture, which makes it preferable to the latter for use 

 upon plants of which the fruit is nearly mature. To 

 make this solution, dissolve one and one-half ounces of 



* Oingnardia BidwelU. t Alternaria Solani. t Phytophthora in- 



festans. § Svtioerotheca Mors-uvoe. ** Entnmosvoriiim maculatum. 



13 



