36 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



ing in a square, thus forcing them to the centre and catching large 

 numbers of them in the furrows. 



Early plowing and thorough harrowing in the spring are of 

 value against cutworms by keeping the ground fallow and thus 

 starving them out before a crop is planted. The same method 

 may be used against other pests with similar habits. 



Thorough cultivation in the summer has been found to be of 

 value against many insects, affecting them differently according to 

 their habits. Many which pupate in the soil during the summer 

 are destroyed while making their pupal cells, or these cells are 

 broken and they are subjected to abnormal moisture and tem- 

 perature conditions and are thus killed. This has been shown to be 

 the case with the cotton bollworm or corn ear-worm, and is true 

 of the plum curculio, against which thorough cultivation has 

 proved to be one of the most effective means of control in apple 

 orchards. Thorough cultivation is also of importance in breaking 

 up the nests of ants which care for such aphids as the corn root- 

 aphis. Summer fallowing is used to starve out some pests; for 

 example, the clover root-borer may be eradicated by plowing up 

 infested clover immediately after it is cut and exposing the roots 

 to the sun and wind which will soon dry them out and thus destroy 

 the food of the larvae. 



Trap Crops. Trap crops are those which are planted as a bait 

 or lure to attract the early insects so that they may be destroyed 

 upon them before the crop to be protected is available. Doubt- 

 less the reason that trap crops are not more frequently used by the 

 farmer is because their successful use requires more or less of a 

 knowledge of the life history and habits of the pest to be fought. 

 But that is easily acquired and will make the fight against them 

 more interesting and successful. 



South of Mason and Dixon's line the harlequin cabbage 

 bug frequently becomes the most serious pest of cabbage and 

 related plants. When a cabbage patch has become well infested 

 it is an exceedingly difficult matter to prevent injury, for the adult 

 bugs cannot be killed by insecticides which will not injure the 

 plant. If, however, a crop of kale be planted the previous fall 

 the bugs which hibernate over winter will attack it in the spring, 

 and may then be killed by spraying them with pure kerosene, and 

 the danger to the cabbage crop be thus largely averted. 



