36 PROTECTION OF PLANTS, 1916-17 



wise have been the case. The caterpillar is about two inches long when full 

 grown, of a velvety black colour with two conspicuous yellow stripes on each 

 side of the body which are connected by narrow lines of the same colour. 

 (See fig. 5, page S3). 



Remedies. — Same as those recommended for Cabbage Butterfly. In 

 small gardens their numbers may usually be kept down by hand picking. 



The Cabbage Aphis, Aphis brassicce L. 



There are few kinds of plants which are free from injury by the various 

 species of plant lice which are also known as "Aphis" and "Green Fly." 

 Cabbage, turnip, potato and other vegetable crops are almost every year 

 injured seriously. The Cabbage Aphis is the chief destructive species of 

 the cabbage. (See Fig. 4, page 33). It is of a grayish colour and occurs 

 in conspicuous clusters around the bases of the stems and on the undersides 

 of the leaves. All plant lice are sucking insects and live solely on the juice 

 which they extract from their host plants. 



Remedies. — The Cabbage Aphis, as a rule is not noticed in destructive 

 numbers until late in the season. Much can be done to prevent the spread 

 of this insect, if the earlier colonies are destroyed. Any of the contact 

 insecticides mentioned for sucking insects, on pages 40-41, will destroy this 

 insect. It is important that whichever insecticide is used should be applied 

 so as to reach the places where the insects are clustered. Only the plant 

 lice which are actually hit by the spray will be killed. As the Cabbage Aphis 

 passes the winter in the egg state, the eggs being deposited on the leaves, it 

 is important that all remnants of crops be destroyed by ploughing down as 

 soon as possible after the heads are harv^ested. 



The Onion Thrips, Thrips tahaci Lind. 



The Onion Thrips is a very small insect about one-twenty-fifth of an 

 inch long and of a pale yellowish colour. In addition to the onion, the insect 

 feeds on the leaves of cabbage, cucumber, tomato, etc. 



Remedies. — Any of thejcontact insecticides mentio'ned on pages40 and 41 

 are useful in controlling this insect. Tobacco preparations are preferred by 

 many growers. 



The Cabbage Plusia, Autographa brassicce Riley. 



Occasionally in eastern Canada the caterpillars of the Cabbage Plusia, 

 are abundant enough to attract attention. When full grown the cater- 



