Insects and Disease 



growing one kind of crop over large areas have made 

 the spread of plant pests much more easy than it 

 formerly was, and something in the way of breaking 

 up these areas by interposing other crops will impose 

 a check to their spread. In the same way changing 

 the ground occupied by one crop in succeeding years 

 will render the attack of pests which lurk in the soil 

 more difficult. 



9. Destruction of " hosts " of garden enemies. In 

 paragraph 4 above we advocated the destruction 

 of diseased weeds and the hke, but it is as import- 

 ant to remove this chance of propagating disease- 

 producing fungi. Where possible the alternate host 

 of the rust fungi (where there is one) should be 

 destroyed. Hedge plants should differ from the 

 cultivated crops as riiuch as possible. 



10. The fruits of the large fungi which attack 

 timber and ornamental trees should be removed as 

 soon as they appear, so as to prevent the formation 

 and spread of the spores. 



11. Certain insects, such as woolly aphis, are 

 concerned in the spread of certain plant diseases 

 and should be destroyed. 



12. An acid condition of the soil encourages the 

 growth of certain fungi such as club-root, and should 

 be remedied by the appHcation of quicklime at the 

 rate of 3-4 tons to the acre (f-1 bushel to the square 

 rod) spread over and forked in. It is, however, 

 better to avoid the need for this drastic dressing by 



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