326 SCHOOL ENTOMOLOGY 



and good culture may give a crop such favorable conditions 

 as to enable it to withstand insect injury which would be 

 fatal to plants of weaker growth. 



(e) Clean Farming. The insects peculiar to a crop often 

 feed and multiply in the refuse left on the land after the crop 

 is harvested and then hibernate over winter beneath it. All 

 remnants of a crop, such as stubble, vines, leaves or stumps, 

 should be removed from the field or turned under as soon 

 after harvest as possible. Numerous examples have been 

 cited in the preceding pages of insects which hibernate in 

 stubble or under the remains of the crop. 



(/) Burning. Stubble and refuse may often be gathered 

 into piles in which the insects will congregate and then be 

 burned. The burning of grass land is often resorted to for 

 the control of army-worms, chinch-bugs, and grasshoppers, 

 but should only be practiced where they occur in sufficient 

 numbers to warrant it. Strawberry beds are sometimes 

 burned over to destroy the eggs of the root-aphis, and the 

 aphides affecting small grains may sometimes be controlled 

 when they occur in small spots by covering them with straw 

 and burning. 



(</) Plowing. Deep plowing and thorough harrowing 

 are often exceedingly effective in the control of many insects 

 which pass some one stage in the soil. Late fall and winter 

 plowing is particularly beneficial, as the cells in which the 

 insects pass the winter are so broken up that they are 

 exposed to freezing and thawing and excessive moisture. 

 Thus cutworms pass the winter in the soil in the larval 

 stage; the cotton bollworm or corn earworm in the pupal 

 stage; May beetles and click beetles hibernate as newly 

 transformed beetles; and grasshoppers' eggs pass the winter 

 just under the soil; but all are largely destroyed by thorough 

 plowing and harrowing, as has been described. 



