204 Market Gardening. 



which causes the "blight" in celery; but I do not 

 agree with that view. I know an insect does appear 

 on the leaves when they begin to decay; but on almost 

 every different kind of decaying vegetation some one 

 insect peculiar to it is apt to appear — being invited 

 by the decay, but not the occasion of it. 



And often when the insects have made their appear- 

 ance and the leaves are already yellow, if there is a 

 sufficient application of water, either by the occurrence 

 of a heavy rain or artificially supplied by irrigation, 

 the insects will disappear, the yellow leaves will drop 

 away, and the plants will grow healthy again, with a good 

 crop as the result. The renewed vitality of the plant 

 enables it to cast off the parasitic enemies which would 

 otherwise have joined forces and eaten it up. 



This view points us to the main remedy or preven- 

 tive of all disease, — and more particularly the chief pre- 

 ventive against every form of vegetable parasite, viz. : 

 clean and nourishing culture. In the outset this is the 

 means, and the only means, to be relied upon. This is 

 the first requirement ; of course there are others. Hurt- 

 ful conditions may be noted and avoided. Mismanage- 

 ment of heat (or moisture) on forced crops frequently 

 entails a blight. Some harmful element in the soil or 

 fertilizer may cause the plants to languish for a time, 

 and so allow the fungus spores to get a foothold. It 

 is good policy, alike as against the fungi and the insect 

 pests, to put all the vigor v/e can into the growing 

 plants. We should also remember the great impor- 

 tance of prompt treatment when disease "is apparent. 



Fumigation has already been spoken of [see p. 124.] 



