34 DISEASES OF CROPS. 



following season. Pupation may also take place on the 

 leaves. The beet-fly attacks the plants in the following 

 manner : " After the beet plants have been singled and 

 begin to show vigorous growth, with broad leaves, they 

 suddenly droop, and have a withered appearance. Upon 

 examination it will be found that there are white blotches, 

 like blisters, upon the leaves, caused by maggots lying 

 snugly within their tissues, from which they have ex- 

 hausted the juices and extracted the chlorophyll, or green 

 colouring." "The perfect insect is about the size and 

 shape of a common house-fly. It is dark-grey, with black 

 hairy legs, having yellow antennae with black tips. The 

 femora (thighs) of the female are yellow.'' 



Prevention. — (1) Before growing a crop of beetroots 

 plough in a green manure of buckivheat. This destroys 

 the pupae of the beet-fly. (2) An observer in the 

 Agricultural Gazette (Aug. 18th, 1884) writes: "Any 

 fertilizing application will do good which will act at once 

 in furnishing nourishment to the plant, and thus keep it 

 continually replacing by new growth the leafage which 

 is destroyed by the maggots. Nitrate of soda appears to 

 do best ; but as the action of fertilizers depends on having 

 rain at the time to wash them down to the roots, it is 

 better to have previous good treatment of the land to 

 trust to." (3) " Many weeds (thistles, sow-thistles, dande- 

 lion, etc.) serve as breeding-places for this insect, and 

 should therefore be kept from the neighbourhood of dung 

 heaps and beet or mangel fields." 



Cure. — Wash the plants with mixtures of mineral oil 

 and a solution of soft soap. The proportions of this mix- 

 ture are 5 lbs. of soft soap and from 1^- to 2 gallons of 

 paraffin oil to 100 gallons of water. This should be " put 

 on with the ordinary hop-washing machine, like a garden- 



