1904.] 



The Cabbage Root Fly. 



355 



bend it slightly to open the slit, then slip it on to the centre, 

 the stem entering the slit, after which spread the card out flat 

 and press the points, formed by the star-shaped cut, round 

 the stem. A tool has been devised to cut these cards so that 

 five to six hundred can be cut in an hour. The card must be 

 put on carefully so as to lie on and prevent the fly from creeping 

 under to lay her eggs. 



3. In garden cultivation, a cupful of paraffin may be added 

 to a pailful of sand, and the sand sprinkled once a week round 

 the stems of cabbages. This would act as a deterrent to the fly 

 in her egg-laying. 



4. In cultivation on a small scale, picking the maggots by hand 

 from the plants, which have been taken up for the moment for 

 the purpose, can be practised. 



5. Badly infested plants should be removed and burnt, the 

 stumps being uprooted and burnt after attack so as to keep 

 down the pest. 



6. Slingerland mentions carbolic acid emulsion and bisulphide 

 of carbon as successful insecticides for destroying the eggs, or 

 killing the maggots, once they have got to work. The formula 

 for the carbolic acid emulsion is 1 lb. of hard soap or 1 qt. of soft 

 soap, dissolved in 1 gall, of boiling water, into which 1 pt. of crude 

 carbolic acid is poured. Stir well till an emulsion is formed. 

 For use, dilute with thirty equal parts of water. This may be 

 put on the plants so as to reach the eggs or maggots. 



In the treatment with bisulphide of carbon (its fumes are 

 poisonous, and no light must be brought near the substance) a 

 little of it is injected into the soil near the plants, care being 

 taken that the liquid does not touch the roots. The vapour 

 diffuses through the soil and quickly kills the maggots. 



7. Where the attack has been bad, neither cabbages or 

 beet should immediately follow, nor any cruciferous crop. 

 Whatever rotation of crop be practised to evade the pest it 

 must be accompanied with the destruction of cruciferous weeds 

 which play the part of nurseries for the cabbage maggot. 



F F 2 



