25 



tion thickens on cooling, and should be used at the rate of 1 

 part of the stock solution to 30 parts of water. This emulsion 

 has also been used successfully for the control of the cabbage 

 root maggot when attacking radishes and turnips. 



The best method of controlling the onion maggot is by the 

 application of a poison bait to the plants during May. This 

 will attract the adult flies, which feed upon the poison and are 

 killed before egg-laying takes place. In order to obtain good 

 results the bait should be applied to the plants and other 

 vegetation, checker-board fashion, at weekly intervals, from 

 the time the onions appear above ground until the first or 

 second week in June. During exceptionally rainy seasons it 

 is advisable to apply this bait at shorter intervals. This 

 poison bait is made as follows: — 



Sodium arsenate, i ounce. 



Water, 1 gallon. 



Cheap molasses, 1 pint. 



Dissolve the sodium arsenate in boiling water, and after 

 cooling add the molasses. 



Attacking Potatoes and Tomatoes. 



1. Cutworms (see page 9). 



2. White grubs (see page 9). 



3. Wireworms (see page 10). ■ 



4. Flea beetles (see page 12). 



5. Blister beetles (see page 12). 



6. Stalk borer (see page 20). 



7. Potato plant louse, Macrosiphtnn solonifolii Ashm. 



This plant louse caused severe losses during the summer of 

 1917 in nearly all potato-growing districts. As these small 

 sucking insects usually infest the lower surface of the potato 

 foliage, the contact spray used should be directed so that it will 

 hit them. Thorough application is essential for the successful 

 control of this pest. Nicotine sulphate, as recommended on 

 page 6, is a reliable contact insecticide, and should be applied 

 as soon as infestation is noticed. Whale or fish-oil soap, 1 

 pound in 6 gallons of water, is also effective (see page 6). 



