INSECTS AND PREVENTIVES 



This view points us to the main remedy or pre- 

 ventive of all disease and more particularly the 

 chief preventive against every form of vegetable 

 parasite: 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. Hurtful conditions may 

 be noted and avoided. It may reasonably enough 

 be assumed that plants are liable to forms of dis- 

 ease attributable neither to vegetable nor animal 

 parasites, but arising much like disorders in 

 animals, as from imperfect nourishment, exces- 

 sive cold or heat, lack or superabundance of 

 moisture and the like unhealthy conditions. Mis- 

 management of heat, or moisture, on a forced crop 

 frequently entails a blight; or promotes mildew, as 

 elsewhere described in treating of the culture of 

 lettuce. A succession of dark days, depriving the 

 plant of sunshine, exerts a similar influence; unless 

 relieved by aid of the electric light, now beginning 

 to be used. 



So, too, some harmful element may exist in the 

 soil or fertilizer, causing the plants to languish; 

 and thus again the spores of fungi may be enabled 

 to fasten upon them. It is good policy, alike as 



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