146 Control of Parasites 



out borers, to prevent egg masses from hatching, and to 

 kill scale insects. 



The insects which can be controlled by such bands are 

 all those whose caterpillars are hatched out below the region 

 of the band, but it is also useful with those which wander, 

 seeking for new supplies after having defoliated one tree. 



It is, of course, necessary to apply the band in season, 

 before the caterpillars begin to wander. 



The application of a lime wash (whitewash) to the trunks, 

 has been very frequently practised, and it is without ques- 

 tion a good protection against several insect pests, especially 

 scales. It acts merely as a repellant, not as an insecticide. 

 But the unsightliness should rule this remedy out for orna- 

 mental trees, wherever other methods are available. If 

 used at all, the addition of flowers of sulphur ' (making 

 '^ bisulphide of lime), or else the addition of crude carbolic 

 acid (one pint to a hundred pounds of lime) will increase its 

 efficiency. 



Like all such coatings, the Hme wash must be renewed 

 to remain effective, since it is washed away by rains. 



Borers and Bark-beetles. While there are many ways of 

 combating the insects which attack the leaves and which 

 li^'e within reach, the various borers and bark-beetles are 

 much more difficult to deal with since they are hidden from 

 direct access during much of their life and especially during 

 their dangerous stage. If their holes can be found, which 

 is not always easy, the injection of carbon bisulphide into 

 • the tunnel and plugging the outlet tight with putty or hard 

 soap will kill them, the bisulphide developing a gas injurious 

 to the boring larva. Or else, they may be reached by a wire 



' Five pounds of sulphur and five pounds of lime boiled together in a 

 small quantity of water until dissolved, making a brownish liquid, to be 

 diluted in a hundred gallons of water. 



