J. 'I\ Wadswoktii 87 



cut and marketed up to the end of September. This number agrees 

 closely with the number of plants (761) unaffected with maggots on 

 July 8th. A few plants had evidently recovered and made marketable 

 plants by the end of September, as predicted by the market-gardener. 



Table showing the numbers of Gauli flower j^lcnls destroyed by Cabbage- 

 root Maggots ivhen 'protected by tarred felt discs, and ivhen unprotected. 

 Each of the four rotvs contained 233 plants. 



Results in percentages 



protected unprotected 

 Row IV rows rows 



protected unprotected (I and III) (II and IV) 



10 — 15-4 



5G 1-5 40-3 



85 3-2 48-5 



120 5-1 630 



Results with Cabbages. Each row contained 102 plants. 



Results in percentages 



Rows Rows Rows Rows protected unprotected 



Dates when II and IV I and III Viand VIII V and YII rows II, rows I, III, 

 counted protected unprotected protected unprotected IV, VI, VIII V, VII 



The cauliflower plants were also counted on July 8th but no further 

 losses had occurred since the previous count (July 4th). The effect of 

 the infestation produced by the first brood of flies had reached its 

 maximum about this date. 



From July 15th onward the losses increased very considerably as 

 w^ll be seen by reference to the table. This increase was attributed to 

 a secondary attack of maggots produced by the second generation of 

 flies. At this period also a spell of three weeks of very hot, rainless 

 weather prevailed ; these weather conditions rendered the cauliflowers 

 more susceptible to maggot attack and less able to recover therefrom. 



On August 1 2th the plants were again counted but no further losses 

 were observed ; on August 16th some of the cauliflowers were ready for 

 cutting and counting was discontinued. 



The results obtained prove very conclusively that the tarred felt 

 discs are a very effective means of protection from cabbage maggot 

 attacks. Only twenty-four cauliflower plants were lost out of a total 

 number of 166 protected by discs, whereas 294 plants were lost out of 



0—2 



