30 SUCCESSFUL FARMING 



moisture, thus reducing the yield and sometimes causing absolute failure, 

 but they entail additional labor in the process of cultivation. Many 

 weeds grow best in certain kinds of crops. For example, mustard is a 

 common weed in the small grain crops in the prairie states. The seeds 

 ripen a little earlier than the grain, and in the process of harvesting are 

 freely shattered and seed the land for the succeeding year. Where small 

 grain is grown continuously this weed becomes a serious pest. Its 

 extermination calls for an inter-tilled crop following the small grain. 

 Pigweed, bindweed, foxtail and crab-grass are common in corn and 

 potato fields, but they seldom become serious in small grain fields or in 

 grass land; consequently, cultivated crops followed by grasses and small 

 grains make for extermination of these weeds. Daisies, wild carrot and 

 buckhorn are common weeds in hay fields, and generally grow worse the 

 longer the land remains in hay. Such weeds, however, give no trouble 

 in cultivated fields devoted to corn, potatoes, etc., and the cultivation 

 helps to exterminate them. 



Lessen Insect Depredations. — Most insect pests live upon some 

 particular crop or a few closely related crops. A crop or related crops, 

 grown continuously on the same land, affords an opportunity for the 

 associated insects to multiply and become very numerous. The remedy 

 is to plant the infested fields with a crop which will not be injured by the 

 pest in question. Unless these insects have the power of migration they 

 will perish for the want of suitable food or for lack of conditions suitable 

 for multiplication. 



However efficient the rotation of crops may be in the extermination 

 of insects, some rotations may prove not only ineffective but actually 

 disastrous. For example, land that has been long in grass sometimes 

 becomes so infested with wire-worms as to cause a practical failure when 

 devoted to corn. Grass affords conditions favorable to the multiplication 

 of wire-worms, and they may live in the soil sufficiently long after the 

 grass is| plowed up to destroy a crop of corn which follows. Under such 

 conditions fall plowing or bare fallow should precede the planting of the 

 corn. The bill bug breeds freely in the bulbous roots of timothy, and 

 when timothy sod is plowed late in the spring and planted to corn, this 

 insect transfers its attention to the corn with disastrous results. Such 

 trouble may be avoided by destroying the existing vegetation some time 

 in advance of planting the corn. The insect under such conditions will 

 either be starved or forced to leave the field before it is planted to corn. 



Cutworms are a great menace to newly planted tobacco and many 

 other crops, but their presence depends largely on the preceding crop. 

 Cutworms multiply extensively only in grass land where the eggs are laid 

 by the moths. Many similar examples could be cited, and success in 

 preventing insect depredation by crop rotation calls for a knowledge of 

 the life history and habits of the insect pest concerned. (See Chapter 

 76: "Insect Pests and Their Control.") 



