INSECT PESTS 83 



(i) direct measures which may be adopted when an 

 attack is expected or is actually in progress; (2) in- 

 direct measures which will tend to reduce the numbers 

 of the various pests in the beds and so prevent further 

 attacks. 



(i) Direct Measures. As a matter of general prin- 

 ciple, when the foliage of any plant is being eaten by 

 beetles or caterpillars, the first measure to be considered 

 is some form of poisonous spray which will leave a 

 coating of poison on the leaves and so kill the insects 

 as they feed. The poison most commonly used for 

 this purpose is lead arsenate, but it should be noted 

 that in the case of the basket willows grown in this 

 country, spraying with lead arsenate has proved a 

 complete failure, probably on account of the fact that 

 the leaves have such a smooth surface that the poison 

 cannot stick on. If this explanation is correct, the 

 difficulty should be easily overcome; but until a 

 formula has been proved successful by experiment, it 

 is suggested that in the case of all attacks by leaf- 

 eating beetles, caterpillars, or grubs, a wash containing 

 nicotine and soap should be used. Insecticides of this 

 nature have been found efficient in practice, and 

 their application is treated below in connection with 

 aphides. 



When plants are attacked by aphides or other 

 insects which feed by sucking up the juices of the 

 plant and not by eating the solid parts, it is necessary 

 to use a contact insecticide, that is to say, an insecti- 

 cide which kills those insects which are touched by it. 

 There are several such washes, but the only one which 

 seems to have been properly tested on willows is 

 nicotine, which is undoubtedly the best contact insecti- 

 cide known. It has also the additional advantage of 



