354 INSECTS AFFECTING VEGETATION 



The vigor and healthfulness of plant growth has also much to 

 do with freedom from insect injury. Strong, healthy plants seem to 

 have a native power of resistance which renders them, in a measure, 

 distasteful to most insects, or at least able to throw off or withstand 

 their attacks. A plant already weakened from any cause, however, 

 seems to be especially sought after, is almost sure to be the first 

 affected, and furnishes a starting point for general infestation. 

 Anything, therefore, which aids good culture in keeping plants 

 strong and vigorous, such as the judicious use of fertilizers, will 

 materially assist in preventing injury. 



The constant cropping of large areas of land year after year 

 to the same staple is largely responsible for the excessive loss from in- 

 eects in this country as compared with European countries, because 

 this practice furnishes the best possible conditions for the multipli- 

 cation of the enemies of such crops. A most valuable cultural means, 

 therefore, is a system of rotation of crops which will prevent the 

 gradual yearly increase of the enemies of any particular staple by 

 the substitution every year or two of other cultures not subject to 

 the attacks of the insect enemies of the first. 



With such insects as the Hessian fly, the squash borers, and 

 many others which have regular times of appearance, much can be 

 done by the planting of early or late varieties or by deferring seed- 

 ing so as to avoid the periods of excessive danger. Wherever pos- 

 sible, varieties should bo selected which experience has shown to be 

 resistant to insect attack. Familiar illustrations of such resistant 

 varieties in all classes of cultivated plants will occur to every prac- 

 tical man, and a better instance of the benefit to be derived from 

 taking advantage of this knowledge can not be given than the 

 almost universal adoption of resistant American vines as stocks for 

 the regeneration of the vineyards of France destroyed by the phyl- 

 loxera and for the similarly affected vineyards of European grapes in 

 California. 



In the case of stored-grain pests, particularly the Angoumois 

 moth, or so-called fly weevil, the chief danger in the South occurs 

 while the grain is standing in shock or stack, after harvesting, dur- 

 ing which period the insects have easy access to it. This source of 

 infestation may be avoided by thrashing grain promptly after 

 harvesting and storing it in bulk. (Farmers' Bui. 127, U. S. D. A. 

 B. E.) 



MECHANICAL METHODS OP CONTROL. 



In many cases it is impossible to capture some species of insects 

 before they have caused much damage, and if this can be done at the 

 right time it will not require much labor to check future damages. 



Catching Insects by Nets, Jarring and Beating. The few white 

 Cabbage-butterflies that succeed in passing our winters safely and 

 which appear on the wing in spring near the young cabbage plants 

 can be readily caught by small boys and girls with a butterfly net, 

 which anybody can easily make. By preventing these early butter- 

 flies from laying eggs none of the later brood can appear. The dif- 

 ferent species of snout-beetles that infest our plum trees hibernate 



