1920 



ENTOMOLOGICAL SOCIETY. 



65 



II. Field Plots. 



Inekl tosl-s were coiulucted on 3,200 cabbagX'S (Danish Kound-headj. Tiieso 

 were the treatments showing most promise in tlie previous years' experiments. 

 The ])hints were set out on July 19th during the emergence of the 2nd brood flies 

 and wliile oviposition was actively proceeding. There was some infestation of tlie 

 plants in the seed bed, Avhich was mostly, but proba})ly not entirely, removed l)y 

 carefully washing the roots in water. Two applications at intervals of one week 

 were made in the case of corrosive sublimate. One application of the dust av;is 

 mndc and the earth was not removed from the discs after cultivation. 



Field Testk ox Late Cabkages (3,200 Plants). 



Plot 

 No. 



3 



Check 



Materials used. 



Tar paper discs 



Tobacco dust, soap powder and 



soot 



(equal parts.) 



Corrosive sublimate 



(1-1,000.) 



No. of 

 Plants. 



800 

 800 

 800 

 800 



No. 

 destroyed 

 by maggot. 



42 



104 

 11 



850 



No. with 



marketable 



heads. 



758 



450 



Per cent, 

 destroyed 

 by maggot, 



5.25 

 13.0 



1.375 

 43.75 



Per ceut. 



with 



marketable 



heads. 



94.75 

 87.0 

 98.G25 

 50.25 



Field Tests on Late Cauliflower (280 Plants). 



The accompanying table shows the treatments given and the results. It mII! 

 be seen that the corrosive sublimate is again superior to the other treatments, 

 the control being almost perfect. While the other two treatments were hardly 

 given a fair chance in comparison with the corrosive sublimate, the lesser cost 

 of the latter and the prospect of still greater reduction in tlie price of the material, 

 |)laces it definitely ahead as a method of control of the cabbage maggot. 



A similar experiment was carried out on a small adjoining block of cauli- 

 liowers, using sulphur in conjunction with the tobacco dust, iuvstead of Scotch 

 soot and soap powder. The results, as will be seen from the table, are companibh!. 



It was originally intended to make further tests using the main crop of late 

 cabbage, but this was not done as our investigations brought to light the fact that 

 duly planted cabbage suffer very little from the attacks of the maggot. 



5 H.S. 



