New York Agricultural Experiment Station. 927 



appear and are busy laying their eggs. From these the larvae 

 hatch in a few days so that when the young plants should be mak- 

 ing their best growth the maggots are most abundant and most 

 busily at work. In consequence, entire plantings of early cabbage 

 sometimes present the appearance of the check rows shown on the 

 title page and in Plate XX; and the roots, upon examination, are 

 found to be as pictured in Plate XXIV. 



Against this pest, only two methods of control 



insecticides. " re P racticable — tne young maggots may be 

 killed by injecting into the soil some contact 

 insecticide, or the flies may be prevented from laying their eggs 

 about the plants. Many materials have been tested for the pur- 

 pose of destroying these larvae, but, in the main, without thor- 

 oughly satisfactory results. If strong enough to kill the mag- 

 gots the materials employed have also been strong enough to 

 injure the delicate roots of the plants and to so stunt them that 

 the crops have been little better than they would if tne insects 

 had been allowed to work undisturbed. 



The experiments made by other entomologists, some of them 

 dating back thirty years, and preliminary tests made- at the Sta- 

 tion seemed to indicate that carbolic acid emulsion was most 

 promising of all the insecticides suggested, and it was decided to 

 make a series of thorough tests with it in both laboratory and 

 field. 



In the laboratory, direct immersion of eggs of 

 Tests of caroblic ,, , n . . ,, , . , 



acid emulsion maggot flies m the emulsion, even when as 



strong as l 1 /} per ct. of carbolic acid, did 



not affect them; but when the eggs were covered with soil and 



treated with emulsion, so that the exposure was more prolonged, 



as it would be in the field, few of the eggs hatched and the larvae 



that did hatch died near the eerffs. This was true even when 



the emulsion contained only one-third of one per ct. of the acid. 



Field tests with the emulsion were made during two different 



years on cabbage seed beds near Seneca Castle, but it proved 



wholly ineffective, though not injurious to plants five to seven 



