Insects and Fungi 437 



pest, it is best in general to discontinue, for two or three 

 years, the growing of the crop on which they live. This 

 ordinarily is cheaper and quicker than to endeavor to de- 

 stroy the pest by direct means. This is well illustrated 

 in the case of the clubroot of cabbage and cauliflower. 

 The disease may be lessened somewhat by thoroughly dress- 

 ing the land with lime; but it is usually cheaper, and 

 always more effective, to cease the growing of cabbage, 

 cauliflower and turnips for a time, and to grow other 

 kinds of crops on the land. 



3. Make every effort .to secure strong, stocky, continu- 

 ous-growing plants. Even if they are attacked, they have 

 a better chance of coming through alive. Weak and soft 

 plants are poor for any purpose, but they are particularly 

 unsatisfactory when they must withstand the attacks of 

 insects and fungi. 



4. Destroy seriously affected plants, particularly those 

 attacked by fungi. If the vines are thrown on the man- 

 ure pile, the probability is that the disease will be dis- 

 tributed the next year in the manure. If the manure is 

 thoroughly rotted and composted, much of the danger will 

 be averted ; but even in that case it is wise not to take the 

 risk with such serious diseases as clubroot, potato blight 

 and rot, , and the blight of melons, cucumbers and toma- 

 toes. In autumn, all diseased plants and products should 

 be collected and burned. 



5. On infected seed-beds, use new or sterilized soil. Do 

 not add to the seed-bed soil from a field in which diseased 

 crops of the given kind have grown (page 413). 



6. Insects and fungi can be killed. Nowadays, spray- 

 ing is an economical means for many of the pests. Never- 



