186 INSECTS AFFECTING VEGETATION 



the time being a very healthy appearance. The leaves are also 

 broader, but the upright central stems are wanting, having been 

 killed by the fly. Later, the infested plants turn yellow or brown and 

 die in part or altogether. 



The excessive stooling, or tillering, of wheat attacked by the fly 

 is doubtless due to the natural tendency on the part of the plant to 

 offset the injury by forming new lateral stems, and therefore a wheat 

 that has a natural tendency in this direction is less apt to be seri- 

 ously damaged by the fly. Other things being equal, also, wheat with 

 stiff, flinty stems is less damaged by fly attack, chiefly because the 

 straw does not bend or break so readily at the point weakened by the 

 spring brood of larvas. 



It is practically impossible to save a field once severely attacked 

 by this fly, and under such circumstances it is better to plow the 

 wheat under deeply and plant to corn or other spring crop. A crop 

 of wheat may be partly saved, but in the main the measures of really 

 practical value against this insect are, of necessity, chiefly in the di- 

 rection of preventing future injury. These are all in the line of 

 farm methods of control, and are arranged in the order of importance 

 as follows: 



As already indicated in the paragraphs on habits and life his- 

 tory, late planting of winter wheat is undoubtedly the best and most 

 practical means in normal seasons of preventing damage in regions 

 where infestation is to be anticipated. The most that can be advised 

 under this head, however, is to give a general statement covering 

 normal years and climatic conditions. The actual date after which 

 planting may be safely made must necessarily be fixed for each local- 

 ity separately, and be subject to yearly modification to meet varying 

 seasonal conditions. In a general way, to avoid fly injury, planting 

 should be made in the northern winter-wheat districts after the 15th 

 or 20th of September, and in the more southern districts between 

 October 1 and 15. If the right time be selected, neither early enough 

 to be attacked by the fly nor vet so late as to cause danger of winter 

 killing, much of the damage in normal seasons to winter wheat from 

 this insect may be avoided. 



The fact has been noted in the life history that the second brood 

 develops in the lower joints of the wheat and is left, for the most 

 part, in the field in the flaxseed state at harvesting. All these indi- 

 viduals may be destroyed by promptly burning the stubble. Burning 

 may be more easily effected if a rather long stubble be left, and 

 especially if it be broken down by rolling. If the burning of the 

 stubble be neglected until the rank growth of weeds has sprung up 

 which usually follows harvest, it will be well to run a mower over the 

 fields, cutting off the stubble, weeds, and grass as close to the ground 

 as possible, and burning over as soon as the weeds and grass dry suffi- 

 ciently. Careful burning will very largely prevent an abundant fall 

 brood of flies, and may be supplemented by burning all screenings 

 of the wheat if thrashing precedes the fall appearance of the fly. 



In line with burning, and of nearly equal importance, is turn- 

 ing the stubble under by deep plowing, and afterwards rolling the 



