15 



having come from spores blown b}^ the wind from the dead leaves of 

 the previous season. The olive green, velvety spots on the leaves and 

 fruit produce great numbers of spores, which continue to spread the 

 scab broadcast. In a wet season the flowers and ver}^ young fruit and 

 its pedicels are attacked. The fungus grows in this manner through- 

 out the summer and autumn. In late autumn and winter the Venturia 

 or perfect stage is produced on the dead apple leaves on the ground. 



The relative severity of the disease is influenced by a number of 

 factors, chief of which is the weather, A low temperature and abun- 

 dant moisture favor the development of the fungus, and consequently 

 scab is worse in cool, damp seasons. 



Cultural conditions in the orchard influence the scab fungus as 

 much as they do the codling moth. Neglected, unpruned, and uncul- 

 tivated trees are more subject to scab, and careful attention to the 

 general condition of the orchard in connection with spraying will 

 always be profitable. 



Varieties of apples differ in their susceptibility to scab, but sus- 

 ceptible varieties often possess counterbalancing desirable qualities 

 which lead to tjieir extensive use. 



HOW TO MAKE AND USE BORDEAUX MIXTURE. 



For spraying apples, the following is a formula which has given 

 good results: 



Copper sulphate (bluestone) pounds. . 4 



Liine do 5 



Water gallons. . 50 



When the apple ^cab is bad and the season wet, 6 pounds of the 

 copper sulphate should be used. 



The following paragraphs on making and using Bordeaux mixture 

 and on types of spray outfits are quoted from a recent bulletin pre- 

 pared in the Bureau of Plant Industry:'^' 



Method of Making- Bordeaux Mixture in Small Quantities. 



Where only a small quantity of Bordeaux mixture is required — from a bucketful 

 to a barrel — the method described by Dr. B. T. Gallov^'ay in Farmers' Bulletin 

 No. 38 gives excellent results. Two half-barrel tubs are made by sawing a barrel 

 through the middle. One tub is used for the bluestone solution and the other for 

 the milk of lime, and each tub should contain 23 to 25 gallons. One man 

 dips the bluestone solution with a bucket and pours it into a barrel or other 

 vessel, and another man simultaneously dips up and pours in bucketfuls of the 

 milk of lime (fig. 3). The lime solution should be kept well stirred. If only 

 a single barrel is to be made, the materials may be dissolved in the dilution tubs; 



« Farmers' Bulletin No. 243. — Fungicides and Their Use in Preventing Diseases of 

 Fruits. By M. B. Waite, pathologist in charge of investigations of diseases of fruits. 



247 



