The spring brood of larvae attacks tillers or laterals that have escaped 

 the fall broods, dwarfing the stems and weakening them so that they 

 usually fall before ripening and can not be successfully harvested. 



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 seriously 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 f)f larva-. 



NATURAL ENEMIES. 



The Hessian fly in the larval and pupal periods is subject to the 

 attacks of important natural parasites — small four- winged flies which 

 develop within the bodies of their hosts. There are several native para- 

 sites, and in Europe there are many others, one of which is remarkably 

 prolific, and the Department has attempted its artificial introduction 

 into this country. This species, Entedon epigonus, has been liberated 

 in several States, and seems to have obtained a foothold, and consider- 

 able good may be expected from it. 



In general, the parasites are effective only in limiting damage and 

 are useful where other preventives are neglected, but can never take 

 the place of active measures where perfect immunity is desired. 



PREVENTIVE AND REMEDIAL MEASURES. 



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. In case of mild 

 infestation, the best procedure is the prompt use of fertilizers, which 

 may enable the wheat to tiller sufficiently to yield a partial crop. Pas- 

 turing in fall of early-sown fields is also recommended, and may do 

 some good by reducing the numbers of the pests. The measures 

 against this insect are, however, of necessity, chiefly in the direction 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 : 



Late planting of winter wheat. — Abundant experience has indicated 

 that in northern districts wheat sown late in September, say after the 

 15th or 20th, or in southern districts as late as October 1st, is compara- 

 tively uninjured by the fall brood, most of the flies having appeared 

 and deposited their eggs or perished before wheat sown at this time 

 will have sprouted. The actual date for safe planting will vary with 

 the season and with the latitude ; but if the right time be selected, 

 neither early enough to be attacked b}^ the t]y nor yet so late as to cause 

 danger of winter-killing, probably four-fifths of the injury to winter wheat 

 may be avoided. 



Burning stuhhle. — 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 individuals 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. This step will very 

 largely prevent an abundant fall brood of flies, and may be supple- 



