42 



THE MONTHLY BULLETIN. 



of our state, that whatever strikes at the pear industry of California 

 strikes at the prosperity of the whole state. This is why pear blight is 

 a subject of paramount importance to California pomology. 



We know positively that pear blight is a bacterial disease. The 

 specific germs live and multiply in the sap and so are protected and 



Fig. 10. 



-Pear tree treated for pear blight. (After Gam- 

 mon, Mo. Bui., Cal. Hort. Com.) 



are beyond the reach of medication. More than this, whatever brings 

 this infected sap to the surface is a menace to healthy nearby trees, 

 for if carried by insect, bird, pruning knife or shears, even tiniest 

 droplets, the contagion is very sure to spread. These infectious germs 

 may live and thrive and kill in blossoms, leaves, twigs, branches, trunks 

 and roots. Thus we have to fight twig or "fire" blight, trunk blight 

 and root blight. The last is most obscure and insidious and so most 

 to be dreaded. In the branches, trunk and roots it grips to stay, and so 

 we have "hold-over" blight. As we know, the crude sap rises from 

 roots to leaves in the sap wood an appreciable distance from the sur- 



