SPRING PRACTICE IN ECONOMIC ZOOLOGY 17 



ROTATION OF CROPS. 

 In the case of field and garden crops, not only is rotation neces- 

 sary as a means for conserving- soil fertility, but it is of the utmost 

 importance as a means to control injurious insects and fungous 

 diseases. It is unwise to grow the same specific crop for two suc- 

 cessive years on the same soil, and it is even unwise to grow two 

 different but closely related crops following each other; for example, 

 rape or turnips should not follow cabbage, lest they be attacked by 

 some of the yarious cabbage worms or by root maggots; also egg- 

 plants or tomatoes after potatoes are apt to be attacked by flea- 

 beetles. It is likewise bad practice to plant crops following each other 

 that are badly attacked by the same insects, though the two crops are 

 not closely related in a botanical sense. When the common Stalk 

 BORER, Pafaii>ema nitela, is abundant in corn, it will in all probability 

 destroy a crop of tomatoes immediately following the corn. All 

 things considered, a systematic and regular rotation, properly 

 planned, is probably the most effective means for controlling the 

 majority of insect pests which attack field crops. 



FERTILIZERS. 



Plants that are badly attacked by insects can often be stimulated 

 to outgrow the injury by a liberal application of fertilizer. From 

 the entomological standpoint, commercial fertilizers are in many 

 cases more desirable to use than barnyard manure; for instance, 

 root maggots flourish in organic matter, but are discouraged or 

 killed by such commercial fertilizers as kainit and nitrate of soda. 

 As a matter of course, all soil, to produce well, must have a certain 

 amount of humus in it and barnyard manure must sometimes be 

 applied in liberal quantity. The increased vigor of plants growing 

 in a well manured soil, generally more than counterbalances the dam- 

 age caused by the greater number of insects which are sometimes 

 thereby developed. 



CLEAN FARMING. 



Chintz Bugs, Sqttash Bugs, and hundreds of others hibernate in 

 grass and weeds, or beneath rubbish, such as old boards, during 

 winter, and may be destroyed in early spring by burning. Many 

 insects feed upon common weeds in the spring before crops of value 

 are planted or have appeared above ground. An illustration is found 

 in the Corn Root Louse which feeds upon the roots of smartweed 

 until the corn appears. The free use of the weeder in early spring 

 is one of the preventives of insect damage. "Whenever any crop has 

 been harvested, grub out and destroy all remnants of stems, roots 

 and leaves by burning, or by deeply burying them. 



