PLANT DISEASES 419 



potato crop or any other crop is harvested, the stubs, vines or 

 other remains should not be left in the field to harbor insects and 

 diseases They should be plowed under or raked up and piled 

 into composts where they will rot and destroy the enemies. 



Seasonal Plowing. It is much cheaper to plow a field well 

 and to plow it at a season when the insects are at rest, than to spray 

 the crop or otherwise fight the insects after they have developed. 

 Plow deep. This will kill many a larva and pupa. It will also 

 turn up many for the attacks of birds, poultry and ''Jack Frost." 

 Plowing late in the fall after insects have hibernated for the 

 winter will thus destroy countless numbers of them. The farmer 

 finds this practice one of the best methods of treating the soil, 

 to say nothing of its effect upon insect life. Grub worms, cut worms, 

 corn ear-worms, stalk-borers, chinch bugs, grasshoppers and numer- 

 ous others attempt to pass the winter in the ground and most of 

 them will be destroyed by the late fall plowing. Early spring harrow- 

 ing also destroys insects. Frequent harrowing and cultivating of the 

 corn crop, potato crop and most garden crops are recommended. 



Trapping the insects is also practiced with much benefit in 

 particular cases. The trap crop may be a natural weed, or may 

 be planted as a bait crop to attract the insects so they will avoid 

 the main crop. The brood of insects may be poisoned or otherwise 

 killed before the attack of the main crop. In the case of the 

 cotton boll-worm, which also attacks the ears of young corn, the 

 cotton crop is often protected by making successive plan tings of corn 

 in narrow strips through the cotton field. As the corn matures it is 

 used for stock feed, and the cotton is grown without much injury. 



Plant Diseases. In the fighting of plant diseases, "preven- 

 tion is better than cure. " If the gardener or farmer is aware of 

 what diseases are likely to appear, he can always prevent them by 

 proper methods. These should be intelligently carried out with- 

 out interruption. A common mistake is to hope that the diseases 

 may not appear, and preventive measures are not practiced. 

 Nearly all spraying for insect diseases should be in advance of the 

 attack and not after it (Fig. 293). When a disease starts in one 

 part of the field a large part of the crop is sometimes saved by the 

 quick application of remedies. In nearly all cases, however, the 

 infection is so general and so complete before the outbreak is 

 noticed that remedial measures are of no avail. It is perhaps for 

 this reason that spraying for plant diseases is so often discredited 

 by the uninformed. 



