72 Second Report on Economic Zoology. 



Natukal Enemies. 



I have never come across a single natural enemy of this pest in 

 England, but Dr. Carpenter records a small insect belonging to the 

 Gall Flies {Eucoela) as having been reared from cabbage maggots 

 found in County Down some years ago. Slingerland refers to 

 Euccda anthomyise working in a similar way in America and also 

 to a small Rove Beetle (Aleochara nitida) preying upon them. Thi.s 

 latter occurs commonly in dung, haystack refuse, etc, all over Great 

 Britain, and may do the same good work, but has not been observed 

 to do so. I have found several mites (Acari) in company with these 

 maggots. 



Prevention and Treatment. 



This pest is undoubtedly worst where cabbage, etc., are grown 

 year after year on the same land. When land becomes fouled by 

 this pest it can to some extent be cleaned by the application of gas 

 lime, but so uncertain is this substance in its action that it is 

 scarcely advisable to recommend it. In some cases it works 

 admirably, in others it is a complete failure. If it is used it must 

 be allowed to stand on the land after being spread for at least a 

 month. The quantity depends on the nature of the soil, but from 

 3 to 6 cwts. to the acre may safely be used anywhere. 



It would be far better to deeply plough or dig two spits deep 

 land that had been infested and grow no cabbage on it for two years, 

 but some crop other than of a cruciferous nature. 



All cabbage stumps and other roots after an attack should be 

 burnt. This is seldom done, and as many larviie pupate in the 

 stalks which are left about in heaps, they can only tend to help 

 forward the advances of the pest. 



Broadcasting soot and lime after planting out has met with some 

 success, but I have seen fields and gardens badly attacked later in 

 the year when this has been done. A small amount of soot and lime 

 may also be put in with the plants when dibbled out. In America 

 a plan which is the best we have is being adopted by growers of 

 " discing " the plants when they are set out. It is not very trouble- 

 some, nor costly, and it is certainly very successful. It consists of 

 placing discs of tarred paper or card around each plant. They can 

 be cut out by machinery at little cost, and are so easily applied to 

 the plant that no objection can be raised in regard to cost of extra 

 labour. 



