EXPERIMENT STATION EEPORT. 583 



groiiiul and will be more quickly fatal to young maggots and stimu- 

 lating to the plants. I prefer the tobacco to the kerosene and sand 

 because of the double value. 



A good preventive measure is to avoid the use of manures and de- 

 caying vegetalile material generally, so far as possible. j\Iaggots are 

 essentially feeders and inhabitants of vegetable decay, and moist, soft 

 soil attracts them. The advice is, therefore, depend upon mineral 

 fertilizers so far as possible and so far as the crop will be favored. 



In the way of destructive measures, fertilizers also have a place 

 on the light soils of Southern New Jersey. As soon as infestation is 

 noted, tarn a shallow furrow from the row, as close to it as is safe. 

 Apply a liberal dressing of nitrate of soda, with kainit or muriate of 

 potash, and turn back the soil. Use nitrate at the rate of 300 pounds 

 per acre and kainit or muriate at about the same rate. The application 

 acts best made just before a rain, and is, of course, a stimulant as 

 well as a remedy. 



On heavy land this ap})lication does not work as well, but its effect 

 as a stimulant is useful, and, in any event, the growing onions should 

 always have an abundance of available plant food. 



x\nother method of prevention is to avoid all accumulation of rub- 

 bish, or to allow the accumulation in fall, with the object of burning 

 during the winter, to destroy hibernating insects. So the sheds and 

 luirns where baskets, trays and other paraphernalia necessary to the 

 handling of the crop are stored should be thoroughly cleaned, and, if 

 possible, fumigated with sulphur during the winter. Baskets, trays 

 and the like can be put into a tolerably tight building and thoroughly 

 cleaned of all hibernating forms. Open sheds are more difficult to 

 deal with, and for these a thin whitewash, to which carbolic acid has 

 been added, may be used by spraying the material with as much force 

 as possible into all cracks and crevices in which the flies may find 

 shelter. 



About the only insecticide that seems to have been at all effective 

 is the carbolic acid emulsion, prepared as follows : Dissolve one pound 

 of soap, shaved fine, in one gallon of boiling water; add one pint of 

 crude carbolic acid and make into an emulsion with a force pump; 

 dilute with thirty parts of water and apply lilx^rally to infested plants. 

 A modification of this formula, given by Mr. Chittenden, doubles 

 the amount of carbolic acid and suggests a dilution with from thirty- 

 five to fifty parts of water. Here, also, it is important that the appli- 



