No. 7. DEPARTMENT OF AGRICULTURE. 292 



farming by various modified methods. One should be able to pro- 

 duce good crops, aud at the same time avoid pests. This is the most 

 important method of preventing insects, but it is so complex that 

 it in turn must be treated in several sub-heads. 



(1) Rotation of Crops. Every farmer knows that this means avoid- 

 ing the continued growth of one kind of crop upon the same land. 

 We have invariably found pests to be most abundant in those fields 

 where the same crop had been tried more or less continuously for 

 years. The worst infested timothy field I ever saw was one that 

 had been kept constantly in this kind of grass for sixteen years. 

 Clover fields generally die out in a comparatively short time, since 

 the various kinds of pests that attack them become so abundant as 

 to effect their destruction. The rotation of crops is especially de- 

 sirable for such insects as root lice, and flea beetles, and others that 

 do not travel any great distance. The flea beetle, which is often so 

 injurious to both the leaves and tubers of potatoes in its adult and 

 larval stages, respectively, is an example of an insect that should be 

 prevented by rotation of crops, rather than remedied by any means 

 that may be suggested. The necessity of rotation of crops is also to 

 be emphasized in considering other insects, such as wireworms and 

 cutworms, that live in the soil. This kind of rotation is important, 

 for example, where corn is to follow sod. One should anticipate 

 the attacks by cutworms and wireworms and thus prevent their oc- 

 currence. In knowing that such attacks are likely to occur he may 

 prevent them by certain farming methods, which we shall give 

 presently. 



Parallel with rotation of crops, we should call attention to the 

 necessity of planting crops upon some portion of the farm not imme- 

 diately adjacent to a field in which the same kind grew during the 

 previous year. Many insects, such as the Hessian fly, are able to 

 travel the short distance, but do not readily travel a great distance 

 unless unusually favorable conditions occur. The practice of grow- 

 ing large areas of one kind of crop is also tending toward the in- 

 crease of diseases and enemies of that kind of crop. For example, 

 w^here peas have been grown in great quantities, there both pea lice 

 and other pests of this particular plant have multiplied and proven 

 especially destructive as a result. Where asparagus has been grown 

 upon an extensive scale, the asparagus beetle and rust have been 

 found most disastrous, and where much celery is cultivated there 

 are to be seen celery caterpillars or striped worms, also rust, blight, 

 etc. This applies to the enemies of most other crops, especially to- 

 bacco, potatoes, tomatoes, etc. Thus by rotation of the kind of 

 crop, and by planting in a region where pests of that particular kind 

 of crop have not occurred abundantly, such pests may be avoided. 



(2) A careful selection of stock for growth is very important, 



