338 



INJURIOUS AND RKNEFIf'TAI, INSECTS OK CALIFORNIA. 



Distribution. — This fly is quife common in the San Francisco Bay 

 region, having been collected by E. M. Ehrhorn in August, 1901. 243 

 The writer lias found it abundant in Berkeley, in August and Sep- 

 tember, 1914. Professor 1\. W. Doane reports it at Carmel, Monterey 

 ( Jounty. 



Food Plants. — The author has reared this maggot from the follow- 

 ing plants: cabbage, cauliflower, radish, rutabaga and turnips. To this 



list J. A. Hyslop adds lupines 

 and field peas. 244 



Control. — The control of 

 such a pest is extremely diffi- 

 cult and relief measures are 

 usually employed as preventa- 

 tives. Among the most effec- 

 tive remedies used for the cab- 

 bage maggot, a very close rela- 

 tive, are the placing of sand, 

 soaked in kerosene, around the 

 bases of each plant as soon as 

 transplanted or well up in the 

 field. This is to prevent egg- 

 laying by the female. A weak 

 solution of carbolic acid emul- 

 sion sprayed repeatedly over 

 the plants will keep the flies 

 away. Fertilizers, such as 

 kainit, nitrate of soda and 

 superphosphate, applied at the 

 rate of from 1,000 to 1.500 

 pounds of kainit, 100 pounds 

 of nitrate of soda, or 200 

 pounds of superphosphate per 

 acre are recommended. Gas 

 lime, applied around each 

 plant, is claimed to afford 

 some protection. 



Carbon bisulfid, though an 

 expensive remedy, is effectual. 

 A special tarred card, placed 

 around the base of cabbage and 

 cauliflower plants, prevents the 

 flies depositing their eggs upon 

 the stem. 



Plowing and thorough cultivation arc recommended as giving excel- 

 lent results in the control of this pest. A badly infested field should be 

 thoroughly plowed and cultivated as early as possible to destroy the 

 pupa'. 



Natural Enemies. — Of the internal parasites bred from this species 

 there are reported Aphareta sp., Polypeza sp. 243 and Holaspis sp. 244 The 

 author has reared as many as eleven individuals of an undetermined 

 parasite from a single pupa. 



No. fi6. pt. VII, Bur. Ent, U. S. Dept. Agric, p. 95, lQO'J. 

 '•"Uiil. No. 95, pt. VI, pp. 105-108, 1!U2. 



Fig. 336. — Longitudinal section of cauliflower 

 plant and young cabbage plant showing work 

 and maggots of the Western radish maggot, 

 Phorbia planipalpis (Stein). Natural size 

 ( Original) 



