1624 



ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 



Bartlett Pear Tree Showiu^- the Blight Eradi- 

 cated from the Body. It was necessary to 

 cut part of the root system away. This tree 

 is capable of bearing a normal crop. (Orig- 

 inal.) 



prove that insects* cause some of the in- 

 fections of some of the twigs, it is not 

 absolutely certain that they do all the 

 inoculating. Twigs are sometimes found 

 with blight started in the axils of the 

 leaves or in the tender bark where no 

 punctures can be found on careful exam- 

 ination. It is possible that the germ may 

 enter in damp weather through growth 

 cracks where the cuticle is ruptured, ex- 

 posing the tender tissues. 



Means of Infection 



That insects really carry pear-blight 

 germs on their feet and mouth parts, I 

 have proved by capturing these insects 

 in infected orchards and allowing them 

 to walk about on prepared culture plates 

 known as Petri dishes, which contained 

 a substance in which germs might make 

 growth. In from 24 to 48 hours colonies 

 of germs would be found growing from 

 the points where the insects walked upon 

 the culture medium. By inoculating 

 growing shoots from these cultures, typi- ' 

 cal cases of blight were produced. 



Numerous experiments have been made 

 by atomizing the germs on trees. These 

 have been failures, except where punctures 

 through the cuticle have been made by 

 a pin point, or where by the breaking of 

 the leaf or some slight abrasion the skin 

 has been ruptured, allowing the germ to 

 enter. 



There are, therefore, two main meth- 

 ods of entry by the germ. First, in the 

 nectaries of the blossoms, and second, the 

 tender tips of growing twigs or water- 

 sprouts on bodies and roots. Blight 

 occasionally enters by the third method 

 — directly into the tender, growing, 

 fleshy bark, through growth cracks. 

 Sapsuckers or woodpeckers become in- 

 fected by puncturing cases of holdover 

 blight, and afterwards visiting healthy 

 trees produce blight infection in them. 

 We have several observations along 

 this line, and doubtless many more occur 

 in nature. It is even possible for the 

 whiffletrees or implements used in culti- 



A Bad Crown Infection on Spitzenburg Apple, 

 Due to Water-Sprouts. Poor attempt at 



working out the infection. Note ooze running 

 down the body above the part cut out. 

 (Original.) 



