INSECTS INJURIOUS TO MISCELLANEOUS CROPS 377 



flies hibernate while many of the pupae remain in the soil over 

 winter and the flies issue from them in the spring. This com- 

 plicates remedial measures. 



Control. Liberal applications of commercial fertilizers such 

 as nitrate of soda, which will assist to rapid growth, are of great 

 value in overcoming injury by all root-feeding pests. Thorough 

 culture is of value. Rotation of the onion plot to a point far 

 distant from that of the previous year, the cleaning up of old 

 beds, and plowing them deeply in the fall, will aid in the control. 

 Pull up and destroy the young plants affected as soon as noticed, 

 being careful to dig up the maggots with the roots. The appli- 



FIG. 316. Tne barred-winged onion-maggot (Chcetopsis cenea Wied.): a, 

 larva, with spiracular opening highly magnified at left; 6, puparium; 

 c, adult fly all enlarged. (After Riley and Howard, U. S. Dept. Agr.) 



cation of carbolic emulsion as for the cabbage-root maggot has 

 been advocated and will doubtless lessen the injury by repelling 

 the adult flies. 



A more recent method of control is based on the fact that 

 the flies are on the wing and feeding for several days before they 

 lay their eggs and that they may be attracted to sweet sub- 

 stances. A poisoned syrup, sprinkled about the field and on 

 weeds nearby, will attract the flies and kill large numbers before 

 they lay their eggs. The syrup is poisoned as follows: 



One pint of syrup is mixed with a gallon of water and to this 

 is added one-fifth ounce of sodium arsenite dissolved in a small 

 quantity of hot water. This is sprinkled where it will do the 

 most good at intervals of about a week.*, 



* See Severin and Severin, Journal Econ. Ent., Vol. 8, pp. 342-350, 1915, 

 and Howard, ibid. Vol. II, pp. 82-85, 1918. 



