INSECTS, DISEASES AND OTHER PESTS 247 



leaves and is first noticed as small pale green areas varying 

 in size and shape. On holding an infected leaf up to the 

 light the dots appear translucent. These spots become 

 more distinct and turn yellow, while the tissue beneath 

 collapses. The trouble is confined not only to the leaves, 

 but in badly infected plants, the branches and flower stems 

 may be covered with the yellow elongated spots. 



Apparently several distinct forms of yellows can be 

 recognized, which differ in general appearance and subse- 

 quent behavior. The early stages of the first type consist 

 of small translucent dots, scattered irregularly through the 

 leaf. At first they are a paler green than the surrounding 

 tissue, but distinctly delineated upon it. The spots in- 

 crease more or less rapidly until they reach a diameter of 

 I to 8 mm. Most of these spots are approximately circular, 

 but may be irregular in outline, rarely elongated. Few 

 of the spots coalesce in this form. This type is especially 

 noticeable on the White Enchantress. A single leaf may 

 have from one to two to fifty or more spots, depending on the 

 extent of infection. Another characteristic of this first type 

 is, that the spots do not tend to make the leaves brittle. 



The development of the second form is similar to the 

 one above, except that while still in the early stages the 

 spots coalesce and become very much elongated, so that a 

 single spot may be i in. to 2 in. or more in length. On 

 badly infected leaves these elongated areas run parallel 

 to the midrib and have a sort of flaky appearance. The 

 leaves become very brittle and are easily snapped off'. In 

 the later stage the cells beneath the infected areas collapse, 

 the spot becomes sunken and finally turns brown as the 

 leaf dies. This type of yellows is found in the Beacon and 

 Pink Enchantress and is as a rule much more destructive 

 than the first type. 



