298 ANNUAL REPORT, OF THE Off. Doc. 



found the disease germs and insects that caused the death of the 

 wood, and if the branches be cut and burned at once, the causes of 

 the trouble are destroyed, and future difficulties prevented. 



In clean farming, one might also include clean soil, not only free 

 from weeds, but also free from disease germs and insect pests. It 

 is well known, for example, that potato scab, which causes the 

 scabby appearance of potatoes, is a disease due to definite germs 

 or organisms that live in the soil for years. AVhen a field is once 

 badly infested a potato grower should avoid planting upon this 

 again until after he is assured there is no danger of infection. 



(6.) Killing pests while they are few in numbers is not only a tem- 

 porary remedy, but is also a permanent means of preventing their 

 occurrence in disastrous outbreaks. Many persons think that when 

 insects are few they may be neglected without serious consequences. 

 The evils of such negligence often become too plainly emphasized. 

 For example, a grower of pickles came to see us a few years ago, say- 

 ing that the large stinking squash bugs were destroying his entire 

 crop of many acres for the third time that year. He said that they 

 had been less abundant in previous years, but this was the first 

 season in which they had occurred in such great numbers. He said 

 that he had written to the United States Entomologist at Washing- 

 ton, and had been told that the chief cause of their prevalence during 

 that particular year in that region was the failure of growers to 

 attack and exterminate them while few in number during previous 

 years. All insects are likely to increase until an outbreak occurs 

 as a result of lack of check upon them. Prevent this by destroying 

 all that are obnoxious, letting no guilty bug escape. At the same 

 time one should know which are his friends and not exterminate 

 them. 



Many insects may be prevented by planting trap crops for them, 

 as in planting a strip of wheat the last of August in order to re- 

 ceive the eggs of tlie Hessian fly, and destroying it later. This is 

 a means of preventing the pests from laying their eggs in the 

 regular crop, which is to be planted soon, and for which they might 

 wait a short time. Another example of the trap crop to prevent 

 insects from injuring the desired crop is beans scattered through 

 the field where cucumbers, melons and squash are to be planted 

 in order to attract the flea beetles and serve as preferred food for 

 these pests while the desired plants may be so small as to be seri- 

 ously injured by them. Yet another example of trap crop is 

 mustard, permitted to grow in the vicinity of cabbage plants, cauli- 

 flower, radishes, etc., to catch the lice and root maggots, destroying 

 it as soon as it is found to be infested. 



(7.) A variation of the previous method, is sowing a little lettuce 

 among cucumber plants. This has been duly reported to us as 



