Summer Meeting. 47 



Of all the woes that confront the pear grower, the one that 

 outweighs all others is fire blight; yet I would not advise any one 

 who would expect to give them serious and careful attention to be 

 deterred from growing pears on account of it. 



The blight is the work of a microscopic plant, and that plant 

 does not grow except where it is planted. You will have no blight 

 in your orchard, then, unless the blight plant is planted there. 

 The blight plant does not bear seed, has no roots, branches or leaves, 

 and does not fly; it goes only where it is carried. It is simply a 

 little oval mass of soft vegetable tissue, mostly water. If the 

 water once thoroughly dries out of it, it is dead. It is nourished 

 by absorbing food into itself, and only liquid matter can be so 

 absorbed. So far as known, except under artificial conditions, its 

 only food is the sap and juice found in the cambium, bark and 

 green buds, fruit, and shoots of the pear and allied plants. 



As the little blight plant lies in the sap and soaks it in, it be- 

 comes larger ; but, owing to well known mechanical laws, after in- 

 creasing but a little, it falls apart and becomes two separate plants, 

 each of which in turn grows and divides. Thus our one plant be- 

 comes a garden, which keeps on enlarging so long as conditions are 

 favorable. It takes a garden of millions of these plants, however, to 

 amount to a square inch in area. So long as a supply of sap flows 

 around and over this garden, it keeps on extending its borders; 

 but, if at any time the sap is all used up or ceases to flow to the 

 garden, every plant in the garden dies. 



Sa far, we see no means by which new gardens, or infections, 

 as we may call them, can be started. The only way is by the im- 

 mediate transfer of one or more of these living plants, or bacteria, 

 from one feeding ground to another before it has time to dry out 

 or starve. This is done sometimes, no doubt, by birds' claws, by 

 carelessly handled pruning knife or saw, or by other possible acci- 

 dents, but mostly, we are practically certain, by insects. 



The infection spots, or gardens of which we have been speak- 

 ing, are under the outer bark, in the green lower layers of bark and 

 the cambium. In a longer or shorter time, perhaps only a few 

 hours in the case of a green shoot, the circulation of the sap is ob- 

 structed by the infected spot, and some of the sap, with blight 

 bacteria floating in it, oozes out through the bark in sirupy drops. 

 Here it is found by the insects, some of which are very fond of it, 

 and they get it on their mouths and claws. Some of these insects 

 also visit the flowers, and some of the infected sap is wiped off 

 into the honey bowl of the blossom, in which the bacteria find ready 



