THE PEAR 131 



of the tree to their liking. The most destructive of these 

 enemies are the tiny bacterial germs that cause the 

 dreaded Fire BHght which ];ias done so much damage 

 to Pear trees that it has long been called Pear Blight, 

 though it also affects apples, quinces, and various other 

 trees. This commonly shows its presence by the sudden 

 blackening of leaves or blossoms or both, the whole twig 

 appearing as if scorched by fire. It affects also the 

 fruit and the bark. 



On the bark of the trunk and larger branches Pear 

 BHght produces dead cankered spots, around the mar- 

 gins of which the germs often develop in the exuding 

 sap in enormous numbers. Wasps and flies are at- . 

 tracted to this sap; they get the germs upon their 

 mouth-parts and feet so that when they visit the flowers 

 they leave some germs upon the sticky stigma or in the 

 liquid nectar in the nectar cup. Either situation is 

 favorable to the increase of the blight bacteria; they 

 multiply enormously and go down from the blossom to 

 the branch, destroying the live tissues as they go. 



When the BHght germs have thus begun to develop 

 in some blossoms they are very likely to be carried to 

 others by the bees that visit the flowers. So these 

 insects may serve to spread infection while engaged in 

 their useful work of pollen distribution. Plant lice or 

 other sucking insects that develop upon a blighting twig 

 or leaf may also carry the germs when they move to new 

 feeding places. Even man may unwittingly spread the 

 disease with his pruning tools, unless he is careful to 

 disinfect them after using them on diseased branches. 



The prompt cutting and burning of all diseased parts, 

 with weekly inspections during May, June, and July, and 



