102 TREATISE ON 



dry up. But it's better to forestall this stage by cutting off the entire enlarged portion of 

 the shoot & removing all of the leaves as soon as they appear to be affected. Keep only 

 those needed to shelter the fruit until the tree grows new ones, & burn or discard the 

 others in water to destroy the insects. With this effort the tree is freed of the diseased 

 parts that debilitate it, & breeding of the aphids, or at least their proliferation, is 

 prevented. 



4°. There is another disease that M. de Combes describes very well: " it is 

 incurable", he says, "and so far it has no specific name. All of the tree's branches, its 

 leaves, and even its fruit, become black & sticky. It's a kind of contagious mildew that's 

 transmitted to everything around it. Care must be taken to pull up the tree as soon as it's 

 afflicted and to coat with lime the wall that, in a manner of speaking, has contracted the 

 disease and blackens just like the tree. If you don't, all of the plants on your espalier will 

 die one after the other. I'm unable to say what the source of this infection is. The 

 common view that it's a bug doesn't seem likely to me. If there is one somewhere, it's 

 combined with some other cause: a malevolent mist that prevails in one place rather than 

 in another, a gust of contaminated air, some unhealthy characteristic within the tree itself, 

 or lastly, scorching by the sun after a fog. [Translator's note: the germ theory of 

 infectious disease, developed by Pasteur and Koch, came more than a century later.] 

 Regardless of its cause, the disease is a certainty, & since it's absolutely incurable, one 

 must be content to arrest its progress by promptly sacrificing the sick tree". This disease 

 is not at all unique to peach trees. Vines, plum, apricot, & even apple trees are by no 

 means free of it. I've seen it appear on a south-facing espalier vine branch. In two months 

 it spread extensively on one side of the vine, & on the other side it overran three lattice 

 squares of the trellis, & got as far as 



