U. S. D. A., B. E. Bui. 85, Part IV (Revised). C. F. I. I., April 18, 1911. 



PAPERS ON CEREAL AND FORAGE INSECTS. 



THE SORGHUM MIDGE. 



( Contarinia [Diplosis] sorghicola Coq . ) 

 By W. Harper Dean, 



Agent and Expert. 

 INTRODUCTION. 



Sweet sorghum, aside from its use in making molasses, ranks as 

 one of the most important forage crops grown in the United States. 

 It is highly prized as a green food for cattle and horses and is well 

 adapted to entering the composition of silage. Several crops are 

 sometimes produced during the season, the last fall crop generally- 

 being cured as a dry winter fodder. In Louisiana and Texas, while 

 this crop is grown practically over the entire States, no large areas 

 are cultivated, but it is found in small, isolated blocks ranging in 

 extent from one-fourth acre upward. 



In parts of a great many sorghum-growing States the seed do not 

 mature a profitable crop, and while this may be attributed, and 

 rightly, too, to a number of causes, it is safe to say that in the majority 

 of cases the sorghum midge, Contarinia sorghicola Coq. (figs. 24, 25), 

 is directly responsible for the damage to the seed. 



Such destructive agencies as various pathological diseases, the 

 English sparrow, the moth Nigetia sorghiella, and the rice weevil 

 (Calandra oryza L.) all help to curtail the number of sound, mature 

 seed produced, but by far the most destructive agency that has been 

 observed by the writer is this minute fly, the midge, which breeds 

 in swarms from the time the first heads have bloomed until the last 

 have been killed by cold. 



An examination of damaged seed in sections where the midge is 

 known to occur will reveal the minute larvae of this fly lying close 

 alongside the ovary, which is blackened and shriveled (fig. 20, b), 

 while the ovary in healthy mature seed is plump and white (fig. 20, c) . 



Injury by the English sparrow can be readily distinguished upon 

 examination from injury by other agents. Such heads have a shat- 



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