14 



Precautions to avoid poisoning. — At all times the greatest care should 

 be taken to prevent accident with these compounds, which are of the 

 most poisonous nature. All packag-es, boxes, or bottles containing 

 these materials should be plainl}^ labeled and kept under lock. The 

 utensils with which the mixtures are prepared should be thoroughly 

 cleansed after use. 



The method of application, spraying- dates, and the apparatus to be 

 used are discussed together for both the codling moth and the apple 

 scab on pages 18-23. 



APPLE SCAB. 



LOSSES DUE TO APPLE SCAB. 



Apple scab is perhaps the most destructive fungous enemy of the 

 fruit grower in the northeastern quarter of this country, occupying 

 among diseases a position ranking with that of the codling moth among 

 the insect foes of the apple. Its injuries are greater than are generally 

 appreciated, both in eiiect and extent. The 3deld of fruit per tree is 

 greatly lessened whenever scab is present: (1) By the premature drop- 

 ping of 3'oung apples, due to the attacks, soon after the blossoms fall, 

 of the scab fungus on flowers, stems, and fruits; (2) by the smaller size 

 of the scabby apples that mature, and (3) b}" the loss, just before pick- 

 ing, due to the fact that scabby fruit does not cling well to the tree 

 and is more easily blown off; (4) the value of the fruit harvested is 

 greatl}^ diminished, since spotted apples must be placed in a lower 

 grade and sold for less than clean fruit; (5) their keeping quality also 

 is impaired, as molds and other fungi which cause deca}' , such as the 

 pink-rot fungus, gain entrance through the scab spots and increase the 

 loss during storage. Nor is the damage confined to the fruit. The 

 leaves also are attacked by the fungus, and the resultant spotting and 

 distortion considerably lessen the vigor and general health of the tree. 



The aggregate loss from scab is enormous, amounting to many mil- 

 lions of dollars every year. This is a most oppressive tax on the 

 farmer, since it is unnecessary. An effective remedy is available in 

 Bordeaux mixture. The experience of many j^ears has demonstrated 

 that the loss from scab may be almost entirely prevented by thorough 

 and timely spraying, which is considered by the leading fruit growers 

 throughout the country to be an indispensable orchard practice. 



CAUSE. 



Apple scab is caused by the summer or conidial stage of a fimgus.* 

 This fungus attains its perfect form ^ on dead apple leaves. The disease 

 appears first on the leaves shortlj' after the}" unfold, the first infections 



247 



Fusicladium dendriticum (Wallr. ) Fckl. 

 ^ Venturia inccqualis (Cke.) Ader. 



