.The; Cabbage Root Maggot. 545 



implied that the radishes were to serve as a trap crop to entice the flies away 

 from the cabbages, and later the radishes were to be destroyed with their 

 accompanying maggots. Others, notably Mr. Hulst in 1888 and Mr. Fletch- 

 er in a recent letter to the writer, say that the pest is especially fond of cauli- 

 flowers, attacking them in preference to radishes or cabbages. No careful 

 experiments have been recorded in this line. Cabbages or cauliflowers could 

 not be profitably grown as trap crops. Radishes might in some cases, but 

 the evidence is not conclusive that the pest would attack this crop in prefer- 

 ence to either of the others .* 



Therefore, in the light of our present knowledge of the preferences of this 

 pest, gardeners cannot expect to save a crop of cabbages or cauliflowers by 

 growing radishes between the rows. Thus, while this suggestion of the use 

 of trap crops to combat this pest promises but little of practical value at 

 present, it should receive further investigation, for it would be interesting, 

 to know at least the preferences of the insect, if it has any. 



(d) Substances Applied to the Soil. 



Under this head come those substances which gardeners use, primarily to 

 increase the fertility of the soil, but which some have thought also acted as 

 preventives of the attacks of the maggot. 



Lime. 



This substance has doubtless been used to prevent the attacks of this pest 

 for half a century. Almost everyone who has written of the insect during 

 the past 40 years, has recommended lime as a preventive. And yet, the first 

 reference we have found of its use (a Maryland correspondent to the " Coun- 

 try Gentleman " for 1857, p. 47) gives negative results. In many accounts 

 of the use of the substance, it is not clear whether it prevents the ' ' Club- 

 root " or its supposed cause, the maggot ; thus this evidence is not of much 

 value. This is especially true of the many accounts of its use by Peter 

 Henderson. In fact, we have failed to find a single recommendation to use 

 lime as a preventive of the Cabbage Fly, which is based on careful experi- 

 ments from which definite conclusions could be drawn. 



On the contrary, there are some quite definite accounts which show neg- 

 ative results from its use. Mr. West ("Country Gentleman " for 1880, 

 p.470) applied, early in the spring, lime at the rate of 15 tons per acre to a 

 small bed ; this was dug in after a few weeks, and good cabbage plants then 

 set. In spite of this he lost }^ of his crop from the maggots. Equally con- 

 clusive results were obtained in 1887 by Mr. Goff" at Geneva, N. Y. He 

 mixed " a quantity of air-slacked lime with the soil of two rows of a small 

 plant of early cabbages at the time of setting the plants. As the season for 



*Prof. Cook and others have recommended that if radishes were grown between rows of 

 onions, the latter would be practically safe from the maggot. They probably would be 

 safe from the Cabbage Root Maggot, but would they from the Onion Maggot? As we have 

 shown on preceding pages, these insects iare distinct species, and it is doubtful if the lat- 

 ter ever attacks radishes or the former, onions. 



