.8 



Methods of Controlling Insect Pests. Measures for 

 keeping insect pests in check may be divided roughly into 

 Indirect, which tend to make conditions unfavourable to 

 pests in general, and Direct, which are designed to destroy a 

 certain definite pest. 



Indirect Measures. From what has been said above it is 

 clear that insects in their various stages are adapted to certain 

 special conditions the caterpillar to living and feeding on a 

 leaf, the butterfly to breeding, and so on. The object of all 

 indirect measures is to make the conditions unsuitable to pests 

 in one or more of their stages and so cut the cycle. An 

 instance or two will show what is meant. Certain beetles 

 (Scolytus rugulosus, S. pruni, &c.) which burrow into the 

 twigs and branches of plum and other fruit trees, find a 

 difficulty in beginning an attack on a tree of which all the 

 branches are in vigorous health, probably because the sap flow 

 blocks up the tunnels and hinders the beetles from working. 

 A branch dying, however, or recently dead, suits them exactly 

 and enables them to begin their attack. If an orchard is well 

 pruned so that all dead and weakly branches are removed, and 

 if the soil is kept reasonably fertile, the trees will never be in 

 the condition to suit boring beetles and a serious infestation 

 is rendered most unlikely. 



Again, certain pests spend the winter in one of the active 

 stages and so are compelled to find protection of some sort 

 .as, for instance, in heaps of rubbish, in moss and lichen on 

 tree trunks, or in rough growth in ditches. If trees are kept 

 clear of moss and lich'ens, heaps of rubbish are burnt, and 

 hedgerows and ditches are cleaned out, the winter shelter is 

 at once much reduced with the result that, however favourable 

 to pests the orchard may be at other seasons, they will always 

 be kept in check by the lack of suitable winter quarters. 



These instances show the possibility of influencing the 

 numbers of insect pests by making conditions unfavourable 

 during a period of their life-history. 



Finally, reference may be made to the temptation to defer 

 too long the removal of worn-out pest attacked trees or 

 bushes. It is true that they can often be cleaned up to some 

 extent and their productive life in this way prolonged, but 

 from the commercial point of view it is better policy to grub 

 or burn them substituting young stock in their place. In 

 this way possible centres of infestation are got rid of and the 

 productive capacity of the whole plantation will be kept at a 

 high level. 



Direct Measures. Chief among direct measures for the 

 control of fruit pests is spraying which is very efficient when 

 done thoroughly and with understanding. Haphazard work 

 carried out witli no clear idea as .to what is required is usually 

 waste of money. Sprays may be divided into (a) Cleansing 



